Article

Tree Species Suitability to Bioswales and Impact on the Urban Water Budget

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Abstract

Water movement between soil and the atmosphere is restricted by hardscapes in the urban environment. Some green infrastructure is intended to increase infiltration and storage of water, thus decreasing runoff and discharge of urban stormwater. Bioswales are a critical component of a water-sensitive urban design (or a low-impact urban design), and incorporation of trees into these green infrastructural components is believed to be a novel way to return stored water to the atmosphere via transpiration. This research was conducted in The Morton Arboretum’s main parking lot, which is one of the first and largest green infrastructure installations in the midwestern United States. The parking lot is constructed of permeable pavers and tree bioswales. Trees in bioswales were evaluated for growth and condition and for their effects on water cycling via transpiration. Our data indicate that trees in bioswales accounted for 46 to 72% of total water outputs via transpiration, thereby reducing runoff and discharge from the parking lot. By evaluating the stomatal conductance, diameter growth, and condition of a variety of tree species in these bioswales, we found that not all species are equally suited for bioswales and that not all are equivalent in their transpiration and growth rates, thereby contributing differentially to the functional capacity of bioswales. We conclude that species with high stomatal conductance and large mature form are likely to contribute best to bioswale function.

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... Barradas et al. [41] Puebla, Mexico Temperate, humid; 827 mm Stomatal conductance; leaf water potential Tirpak et al. [42] Knoxville, Tennessee Temperate; 1271 mm Sap flow Voyde et al. [43] Auckland, New Zealand Temperate; 1284 mm Evapotranspiration Scharenbroch et al. [44] Chicago ...
... Barradas et al. [41] Puebla, Mexico Temperate, humid; 827 mm Stomatal conductance; leaf water potential Tirpak et al. [42] Knoxville, Tennessee Temperate; 1271 mm Sap flow Voyde et al. [43] Auckland, New Zealand Temperate; 1284 mm Evapotranspiration Scharenbroch et al. [44] Chicago One way to evaluate the impact of ecohydrological consequences of climate change is by monitoring changes in the relationship between plant productivity and plant water use, i.e., water use efficiency (WUE). WUE has been defined as the amount of plant carbon uptake (as biomass produced) per unit of water used by the plant [40]; plants with a small biomass gain relative to water use would have a low WUE whereas plants with a high biomass gain relative to plant water use would have a high WUE (Figure 1). ...
... For instance, the stomatal conductance measurements suggest that physiological response and associated water use from the bioswale are species-specific ( Figure 6). Other studies have surmised that increases in stomatal conductance represent increased transpiration [44]. Observed differences in stomatal conductance between species were noted as suggesting that not all species will contribute equally to bioswale function [44,47]. ...
Article
Full-text available
Stormwater management is of great importance in large shrinking cities with aging and outdated infrastructure. Maintenance of vegetated areas, particularly referred to as green infrastructure, is often aimed at mitigating flooding and the urban heat island effect by stormwater storage and evaporative cooling, respectively. This approach has been applied in large cities as a cost-effective and eco-friendly solution. However, the ecohydrological processes and how the ecohydrology influences the function of green infrastructure and its potential to provide those ecosystem services are not well understood. In this study, continuous field measurements including air temperature, stomatal conductance, and phenocam images were taken in a 308 m2 bioswale retrofitted into a 4063 m2 parking lot on the Wayne State University campus in Detroit, Michigan over a two-year period. Our results suggest that plant characteristics such as water use efficiency impact the ecohydrological processes within bioswales and that retrofitted bioswales will need to be adapted over time to meet environmental demands to allow for full and sustained success. Therefore, projected shifts in precipitation regime change are expected to affect the performance of green infrastructure, and each bioswale needs to be developed and engineered to be able to adapt to changing rainfall patterns.
... This increased substrate depth returns to the original design guidelines of Clar and Green (1993), which recommended 1.2 m of substrate for adequate root development (Brown and Hunt 2011). Tree growth can increase by increasing the internal water storage of a SCM by producing a saturated subsoil volume via raised outflow or outlet control structures (Scharenbroch et al. 2016;Grey et al. 2018a). ...
... Xiao and McPherson 2011), and/or have a large storage volume (e.g. Li et al. 2009;DeBusk and Wynn 2011;Xiao and McPherson 2011) or outlet control structures (Scharenbroch et al. 2016). Where streetscapes are being redesigned, trees could make use of runoff stored in reservoirs beneath the pavement surface; in structural soils (Bartens et al., 2009) Regardless of SCM design, runoff needs to be captured as simply and efficiently as possible from the impervious catchment that supplies it so as to maximise system performance and minimise maintenance requirements (Szota et al. 2019). ...
... Where streetscapes are being redesigned, trees could make use of runoff stored in reservoirs beneath the pavement surface; in structural soils (Bartens et al., 2009) Regardless of SCM design, runoff needs to be captured as simply and efficiently as possible from the impervious catchment that supplies it so as to maximise system performance and minimise maintenance requirements (Szota et al. 2019). Bioswales that collect runoff from parking lots can avoid inlet restrictions by completely removing the kerb, such that runoff is delivered along the length of the system as a relatively uniform overland flow, rather than through an inlet (Xiao and McPherson 2011;Scharenbroch et al. 2016). Kerb cuts have also been used to effectively maintain inflows for bioretention cells (Brown and Hunt 2011) and street tree pits (Grey et al. 2018a). ...
Chapter
Impervious surfaces in urban areas generate substantial volumes of polluted surface runoff, resulting in flooding and degradation of waterway ecosystems. Urban trees can help to mitigate the adverse effects of runoff by restoring key hydrological processes, including canopy interception, throughfall, stemflow, and transpiration. Understanding how trees contribute to these processes can guide tree species selection and the design of green infrastructure elements. Climate, specifically the distribution of precipitation and evaporative demand, will ultimately determine the extent to which trees contribute to each process. In general, canopy interception, throughfall, stemflow, and transpiration will be greater where the rainfall distribution is dominated by smaller events separated by longer inter-event periods with higher evaporative demand. However, in any given climate, different tree species, and more importantly the traits which define them, can significantly alter their role in the urban hydrological cycle. For example, species with large, dense canopies (high leaf area) are likely to show greater canopy interception loss, resulting in lower throughfall and stemflow and reduced surface runoff. Additionally, larger trees with high leaf area can potentially transpire a significant amount of captured runoff when combined with stormwater control measures. However, selecting species to maximise retention and detention of runoff must do so without compromising other highly valued ecosystem services provided by trees. This chapter reviews the studies which contribute to our current understanding of how different species contribute to hydrological processes in the built environment. We discuss how this understanding has been integrated into urban hydrological models as well as opportunities for future studies to continue their development.
... In the context of existing drought stress, however, which is likely to be exacerbated by warmer, drier climates under predicted climate change scenarios (Hoegh-Guldberg et al., 2019;Zhang et al., 2019b), such efforts may be unsuccessful if trees do not have adequate soil moisture (Gebert et al., 2019;Widney et al., 2016). To address the challenge of vegetation drought stress, and excessive stormwater runoff concurrently, researchers and practitioners are increasingly advocating the use of stormwater as a resource to passively irrigate vegetation in cities (Berland et al., 2017;Fenner, 2017;Scharenbroch et al., 2016). ...
... Even higher maximum water use was measured by Litvak et al. (2012) in arid Los Angeles, ranging from 70 to 250 L d À1 depending on species. However, few studies to date have measured transpiration from trees passively irrigated by stormwater control measures (Scharenbroch et al., 2016;Tirpak et al., 2019). Hence, our understanding of the volume of water that trees could transpire from SCMs, and therefore their potential to increase volumetric retention of stormwater, is limited. ...
... Both these studies had small SCMs and tree canopy relative to the impervious catchment area, which meant the volume of stormwater runoff far exceeded transpiration. Conversely, Scharenbroch et al. (2016) suggested trees could play a much greater role in the water balance, estimating that trees could transpire up to 58% of stormwater runoff in bioswales fitted with an outlet control structure. When transpiration is high relative to the runoff received and retained by an SCM, evapotranspiration can play a greater role in the water balance of SCMs. ...
Article
Evapotranspiration is an important aspect of the hydrological cycle in natural landscapes. In cities, evapotranspiration is typically limited by reduced vegetation and extensive impervious surfaces. Stormwater control measures (SCMs) seek, among other objectives, to move the urban hydrological cycle towards pre-development conditions, promoting processes such as infiltration and evapotranspiration. Yet, evapotranspiration is generally assumed to play a minor role in the water balance of stormwater control measures. Since established urban trees can use large quantities of water, their inclusion with stormwater control measures could potentially substantially increase evapotranspiration. We installed infiltration trenches alongside established Lophostemon confertus trees in the grassed verges of a typical suburban street to assess 1) whether redirecting stormwater to trees could increase their transpiration and 2) the contribution of transpiration to the water balance of stormwater control measures. We measured stormwater retention and transpiration for two spring-summer periods and estimated an annual water balance for the infiltration trenches. Although redirecting stormwater to trees did not increase their transpiration, these trees did use large volumes of water (up to 96 L d-1), corresponding to 3.4 mm d-1 per projected canopy area. Annually, stormwater retention was 24% of runoff and tree transpiration was equivalent to 17% of runoff. Our results suggest that streetscapes fitted with tree-based stormwater control measures, could increase the volumetric reduction of stormwater runoff by increasing the proportion of evapotranspiration in the water balance. Since public space is highly contested in cities and increasing canopy cover is a priority for many planners, integrating trees with stormwater control measures could provide dual benefits for a single management intervention, enabling a greater number of distributed stormwater control measures with smaller impervious catchments in the streetscape.
... This lack of understanding hinders GSCA's performance (Chaffin et al., 2016). It results in long term sedimentation (Environmental Protection Agency USA, 2005), deficient vegetation upkeep (Mazer, Booth and Ewing, 2001), inadequate inspection regimes (Blecken et al., 2015), complex budget restrictions (Scharenbroch, Morgenroth and Maule, 2016), public disinterest and neglect (Bowers and Young, 2000), and ineffective pollution removal from flowing waters (Erickson, Weiss and Gulliver, 2013). These in turn, limit the realisation of GSCA's potential, constituting the problem currently faced by GSCA. ...
... As GSCA become a standard procedure, they are expected to become more affordable (Melbourne Water, 2013b). In terms of biodiversity, GSCA can enhance the interconnectivity of green corridors, potentially increasing plant, macrobiotic and microbiotic diversity within the urban environment (Dover, 2015;Scharenbroch, Morgenroth and Maule, 2016;Lowe and Stanley, 2017). In direct relation to carbon emissions, GSCA could be considered urban carbon sinks, under specific conditions at the time of construction (Whittinghill et al., 2014;Kuittinen, Moinel and Adalgeirsdottir, 2016). ...
... Firstly, while the initial two years of operation might have given an indication of the maintenance needs for the different mechanisms observed, a longer observation period might provide deeper insight. This is particularly relevant for vegetated assets, considering both their vulnerability during the plant growth stage, and associated changes they undergo in terms of output and performance (Scharenbroch, Morgenroth and Maule, 2016). Secondly, assertions in terms of dollars provided by the authors might not serve as a general indication of cost and maintenance demands. ...
Thesis
Full-text available
In the context of global warming, with more intense, and more frequent, weather extreme events, like bushfires, heat waves drought and floods, the pressure on governments to guarantee water provision is increasing. Expectations exist at a basic level of service (water supply, access, and security); and further, in developed economies, expectations exist on the protection of public health, social amenity and —in some instances— environmental values. Indeed, these higher needs linked to quality of human life have been identified in literature as the next step in the progression of urban water management. Green Stormwater Control Assets (GSCA) have potential to contribute to these goals. GSCA are assets in the public realm, managed by Local Government; they are connected to urban stormwater drains, and have a vegetated component, that together with filter media, reduce the speed and contaminant load of urban runoff. Despite these assets’ potential contribution to urban water management, they are often found to underperform (in terms of their physical components, and operation, both in the short, and the long terms). Current literature indicates underperformance is due to unsatisfactory management and lacking maintenance. This raised the question driving this thesis: How are Green Stormwater Control Assets being managed at three City Councils within Metropolitan Melbourne? To address this question, six established management frameworks were considered, adapted and applied. Thousands of management frameworks are commonly used across countries and sectors. A management framework refers to a guideline that, when used consistently, can ensure materials, products, processes and services are fit for their purpose. The use of management frameworks can foster higher transparency, environmental awareness and social welfare (Ibanez and Blackman, 2016). Six of such frameworks were selected for review, based on their relevance to GSCA management. The review identified ten key aspects specific to GSCA management. Together they form the “GSCA management framework” developed, which consisted of i) governance, leadership and commitment; ii) roles and responsibilities; iii) resources (financial and human); iv) operational control; v) competence, training, and education; vi) internal and external compliance and accountability; vii) audit, report, analysis and action; viii) documentation and records; ix) engagement (communication and consultation); and x) data and information systems. To investigate these key aspects in practice, a qualitative, exploratory and inductive research approach was employed. Three municipalities within Metropolitan Melbourne informed the research as case studies: The City of Melbourne, the City of Port Phillip, and Hume City Council. In total, thirteen stakeholders were interviewed to investigate the ten elements influencing GSCA management. A Computer Assisted Qualitative Data Analysis System (NVivo) was used to support the analysis that uncovered underlying themes affecting GSCA management at the Municipalities studied. The contribution made to literature and practice enhancing GSCA management is twofold: 1) the GSCA management framework developed, that can prove beneficial for Councils managing GSCA or the like; and 2) the findings, implications, and recommendations specific to the municipalities under study. Notably, it was observed that whilst important efforts have been made by Victorian Local and State governments to develop the Metropolitan Melbourne water management system, attention is still required over the careful definition of an inclusive, coordinated, long‐term management strategy. It should include clear and specific accountabilities for parties involved, at an institutional, as well as government‐official levels. Similarly, to enhance GSCA’s sustained performance, it is necessary to invest on education, both of the general public and incumbent professionals, on key stormwater management matters, and environmental sustainability more broadly. Other findings relate to contractual agreements, and the procurement and use of financial resources.
... To our knowledge, few studies have quantified both runoff retention and tree performance of tree-based SCMs. Scharenbroch, Morgenroth, and Maule, (2016) reported 100% runoff retention from a parking lot fitted with bioswales planted with young trees. Trees in the swales showed at least equivalent stem diameter growth rates and stomatal conductance compared with nearby control trees (Scharenbroch et al., 2016). ...
... Scharenbroch, Morgenroth, and Maule, (2016) reported 100% runoff retention from a parking lot fitted with bioswales planted with young trees. Trees in the swales showed at least equivalent stem diameter growth rates and stomatal conductance compared with nearby control trees (Scharenbroch et al., 2016). Grey, Livesley, Fletcher, and Szota, (2018a) also recently showed significant growth benefits for establishing trees, however, these systems were too small to significantly reduce runoff volumes (Grey, Livesley, Fletcher, & Szota, 2018b). ...
... Preventing clogging of the trench came at the cost of lower retention in certain systems and therefore alternative design philosophies for street tree SCMs should be explored. Bioswales collecting runoff from parking lots have avoided inlet restrictions by removing the kerb, such that runoff is delivered to the length of the system as relatively uniform overland flow, rather than through an inlet (Scharenbroch et al., 2016;Xiao & McPherson, 2011). Kerb cuts have also been used to effectively maintain inflows for bioretention cells and street tree pits (Grey et al., 2018a) and can be cleared relatively easily, easing the maintenance burden and cost (Houle et al., 2013). ...
Article
Full-text available
Directing stormwater runoff to irrigate urban trees has the potential to simultaneously: (i) reduce the volume of runoff generated by impervious surfaces and (ii) reduce tree drought stress and increase growth. Many papers promote this concept, but few have quantified both potential benefits. In this study, we quantified both the runoff retention performance of infiltration trenches retrofitted alongside established street trees and tree drought stress and growth. We compared retention for different soil types, tree phenological types and inlet designs over a period of 18 months. Retention was low on average (18.3%) but was highly variable among infiltration trenches (5.2–43.7%), driven by variation in inlet capacity due to blockages, as well as the flow velocity of runoff leading to the inlet. With appropriately designed inlets, street tree stormwater control measures have significant potential to retain runoff. We observed no clear reduction in tree drought stress or increase in tree growth. This suggests that the established trees in our study already had access to adequate soil water within their rooting volumes, supplemented by nearby irrigated private gardens, or leaky water infrastructure. We suggest that i) mature trees surrounded by greater impervious surface area, ii) newly planted trees, or iii) trees growing in hotter, drier climates, may respond more positively to similar passive irrigation systems. The evolving practice of passive irrigation of street trees with stormwater requires innovative design to maximise runoff capture efficiency under typical sediment and debris loads.
... Few studies have directly quantified ET in biofilters (Denich and Bradford, 2010;Hess et al., 2017;Wadzuk et al., 2015), as it is difficult to measure in situ (Hamel et al., 2014). As such, ET is typically estimated i) by quantifying other measured system losses (Li et al., 2009), ii) the use of standard equations (Brown andHunt 2011a, 2011b) or iii) scaling up from leaf-level measures of stomatal conductance (Scharenbroch et al., 2016). Coupled with the perception that ET represents a minor component of the water balance, the difficulties in quantifying ET from biofilters may explain the relative lack of research focus to increase ET as a means of improving retention performance. ...
... NCDEQ, 2017; Payne et al., 2015) would be highly suitable for deep-rooted tree species and would return to the original design guidelines of Clar and Green (1993), which recommended 1.2 m of substrate for adequate root development of trees and shrubs (Brown and Hunt, 2011b). Storage volume can also be increased by integrating an internal water storage via a raised outflow (Brown and Hunt, 2011a;Glaister et al., 2017;NCDEQ, 2017;Winston et al., 2016), utilising sub-surface structures or engineered soils (Bartens et al., 2009;Page et al., 2015) and/or outlet control structures (Scharenbroch et al., 2016), which will provide a greater opportunity for trees to utilise captured runoff between inflow events (Hess et al., 2017;Scharenbroch et al., 2016;Wadzuk et al., 2015;Xiao and McPherson, 2011). Deeper substrates and more complicated sub-surface structures will likely increase the cost of installation, however, we suggest that integrating trees into biofiltration systems without increasing storage volume may limit the gains achieved by selecting tree species with a high K c . ...
... NCDEQ, 2017; Payne et al., 2015) would be highly suitable for deep-rooted tree species and would return to the original design guidelines of Clar and Green (1993), which recommended 1.2 m of substrate for adequate root development of trees and shrubs (Brown and Hunt, 2011b). Storage volume can also be increased by integrating an internal water storage via a raised outflow (Brown and Hunt, 2011a;Glaister et al., 2017;NCDEQ, 2017;Winston et al., 2016), utilising sub-surface structures or engineered soils (Bartens et al., 2009;Page et al., 2015) and/or outlet control structures (Scharenbroch et al., 2016), which will provide a greater opportunity for trees to utilise captured runoff between inflow events (Hess et al., 2017;Scharenbroch et al., 2016;Wadzuk et al., 2015;Xiao and McPherson, 2011). Deeper substrates and more complicated sub-surface structures will likely increase the cost of installation, however, we suggest that integrating trees into biofiltration systems without increasing storage volume may limit the gains achieved by selecting tree species with a high K c . ...
Article
Biofiltration systems are highly valued in urban landscapes as they remove pollutants from stormwater runoff whilst contributing to a reduction in runoff volumes. Integrating trees in biofilters may improve their runoff retention performance, as trees have greater transpiration than commonly used sedge or herb species. High transpiration rates will rapidly deplete retained water, creating storage capacity prior to the next runoff event. However, a tree with high transpiration rates in a biofilter system will likely be frequently exposed to drought stress. Selecting appropriate tree species therefore requires an understanding of how different trees use water and how they respond to substrate drying. We selected 20 tree species and quantified evapotranspiration (ET) and drought stress (leaf water potential; Ψ) in relation to substrate water content. To compare species, we developed metrics which describe: (i) maximum rates of ET under well-watered conditions, (ii) the sensitivity of ET and (iii) the response of Ψ to declining substrate water content. Using these three metrics, we classified species into three groups: risky, balanced or conservative. Risky and balanced species showed high maximum ET, whereas conservative species always had low ET. As substrates dried, the balanced species down-regulated ET to delay the onset of drought stress; whereas risky species did not. Therefore, balanced species with high ET are more likely to improve the retention performance of biofiltration systems without introducing significant drought risk. This classification of tree water use strategies can be easily integrated into water balance models and improve tree species selection for biofiltration systems.
... Previous studies on the effect of directing stormwater to trees have identified mixed results. Several studies have suggested that directing stormwater to trees can increase tree growth (Denman, May, & Breen, 2006;Mullaney, Lucke, & Trueman, 2015;Scharenbroch, Morgenroth, & Maule, 2015;Xiao & McPherson, 2011). However, the nursery study by Bartens, Day, Harris, Wynn, and Dove (2009) showed that trees receiving stormwater in low exfiltration environments had reduced tree growth. ...
... Alternatively, tree pits without underdrains and with low exfiltration rates into surrounding soils may experience waterlogged conditions (GVSDD, 2012). As such, an improved understanding of the tree pit environment is required to ensure successful establishment and rapid tree growth, and to ensure trees can perform key functions in removing pollutants from stormwater and creating storage capacity for runoff retention via evapotranspiration (Denman, May, & Moore, 2016;Payne et al., 2014;Read, Wevill, Fletcher, & Deletic, 2008;Scharenbroch et al., 2015). There is currently a lack of quantitative data regarding what effect these systems may have on tree growth, and in particular, how to ensure an appropriate water balance during establishment when the tree is arguably most vulnerable (Gilbertson & Bradshaw, 1990;Roman, Battles, & McBride, 2014). ...
... Irrigating trees with stormwater pushed growth of the Drained treatment into the high growth range expected for trees in an urban setting, whereas the Control trees were in the slow-medium range (Lawrence, Escobedo, Staudhammer, & Zipperer, 2012;Nowak et al., 2008). While the concept of irrigating street trees with stormwater has been widely promoted (Berland et al., 2017), few have provided the quantitative data on potential growth benefits (Scharenbroch et al., 2015) which may assist in justifying their higher installation (Mell, Henneberry, Hehl-Lange, & Keskin, 2013). Here, we provide evidence of substantial tree growth benefits achieved via passive irrigation of street trees and suggest that canopy cover targets set to mitigate urban heat could be met sooner by directing stormwater to establishing trees. ...
Article
Full-text available
Cities around the world are embracing stormwater control measures (SCMs) to reduce the environmental damage caused by impervious runoff. At the same time, there is a push to increase tree canopy cover to green neighborhoods and mitigate urban heat. Establishing SCMs that include trees may achieve these two objectives, but it is important to understand which design characteristics promote or reduce tree health and growth. We therefore undertook an 18-month streetscape experiment comparing four tree pit SCM designs, along with a control (non-SCM) street tree planting, to identify design characteristics influencing the water balance and growth of newly planted trees (Acer campestre (L.)) in an established urban area dominated by clay soils. Trees in pits with an underdrain showed double the growth of conventionally planted street trees receiving no storm-water. However, the low exfiltration rates of some non-drained tree pits resulted in some tree pits experiencing waterlogging and subsequent poor tree growth or even death. In other non-drained tree pits, the heterogeneity of urban soils resulted in sufficiently high exfiltration rates to avoid waterlogging and promote increased tree growth, even in these heavy clay soils. Our results suggest that establishing tree growth can be substantially increased by directing stormwater into tree pits, however, waterlogging conditions should be avoided via an underdrain or limiting installation to soils with a sufficiently high exfiltration rate.
... Infiltration systems like soakage trenches and leaky wells detain stormwater water below ground in leaky pipes, gravel and other porous media, where water can soak into surrounding soils (Government of South Australia, 2009). Most WSUD devices can be designed to deliver stormwater into the soil in root zones as a form of passive irrigation, although the effectiveness of the different devices in managing storm flows and moderating urban microclimates varies widely and is dependent on many factors (Scharenbroch et al., 2016;Brodnik and Brown, 2018;Szota et al., 2018;Lähde et al., 2019;Li et al., 2019;Zhang et al., 2019;Ebrahimian et al., 2021), with some circumstances resulting in decreased performance or unforeseen negative impacts (Scharenbroch et al., 2016;Brodnik and Brown, 2018;Szota et al., 2018Szota et al., , 2019Lähde et al., 2019;Li et al., 2019;Zhang et al., 2019;Tu et al., 2020;Ebrahimian et al., 2021). ...
... Infiltration systems like soakage trenches and leaky wells detain stormwater water below ground in leaky pipes, gravel and other porous media, where water can soak into surrounding soils (Government of South Australia, 2009). Most WSUD devices can be designed to deliver stormwater into the soil in root zones as a form of passive irrigation, although the effectiveness of the different devices in managing storm flows and moderating urban microclimates varies widely and is dependent on many factors (Scharenbroch et al., 2016;Brodnik and Brown, 2018;Szota et al., 2018;Lähde et al., 2019;Li et al., 2019;Zhang et al., 2019;Ebrahimian et al., 2021), with some circumstances resulting in decreased performance or unforeseen negative impacts (Scharenbroch et al., 2016;Brodnik and Brown, 2018;Szota et al., 2018Szota et al., , 2019Lähde et al., 2019;Li et al., 2019;Zhang et al., 2019;Tu et al., 2020;Ebrahimian et al., 2021). ...
Article
Full-text available
Urban water management projects involving stormwater harvesting, detention, and infiltration are being increasingly combined with urban greening to support adaptation and resilience to the changing climate. A novel stormwater harvesting device, the TREENET Inlet, intercepts stormwater runoff from roads and soaks it into the soil through a leaky well to provide passive irrigation directly into street tree root zones. This study investigated the effects of stormwater harvesting through these inlet systems on the growth, water-use, leaf-level gas exchange and productivity of white cedar ( Melia azedarach ) street trees in a semi-arid climate in South Australia. The results indicated that mature trees with TREENET Inlets and leaky wells transpired 17% more water per unit of canopy area per day, on average for about a year, and 21% more during the dry season. White cedar saplings with stormwater harvesting grew 65% more in height and 60% more in diameter at breast height over a 3-year period than saplings without stormwater harvesting. This is consistent with observed 106% greater stomatal conductance and up to 169% greater photosynthesis rate in the dry season for saplings supported by harvested stormwater. This study shows that stormwater harvesting and infiltration by TREENET Inlets provides significant benefit to white cedar trees growing in a suburban street.
... Including trees that can intercept stormwater and transpire at high rates, could not only increase the number of stormwater control measures in public spaces, but also enable greater runoff reduction through evapotranspiration (Deutscher et al., 2019;. At the same time, studies have demonstrated greater growth in trees irrigated with stormwater (Denman et al., 2016;Grey et al., 2018a;Scharenbroch et al., 2016). Hence, passively irrigating trees could contribute to faster expansion of urban forests, while also increasing the potential volume of stormwater that can be transpired from urban environments, thereby reducing the volume of runoff received by downstream waterways. ...
... Passive irrigation systems planted with trees (e.g., raingardens, bioswales, or stormwater tree pits) simultaneously aim to (a) support tree growth and transpiration by increasing soil moisture available to trees and (b) reduce the pollutant load and volume of stormwater runoff, with a spectrum of designs available to address these aims. The impact of passive irrigation systems on tree growth is highly variable (Caplan et al., 2019;Scharenbroch et al., 2016;Szota et al., 2019). To support tree growth and transpiration, passive irrigation systems must ensure trees have adequate soil moisture between rainfall events (Tu et al., 2020), while limiting waterlogging (Grey et al., 2018a). ...
Article
Full-text available
Solutions that use stormwater runoff to rapidly establish tree canopy cover in cities have received significant attention. Passive irrigation systems that direct stormwater to trees have the potential to increase growth and transpiration and may limit drought stress. However, little data from the field demonstrates this, and we lack robust and reliable designs which achieve it. Here, we quantified growth and transpiration for trees: (a) in infiltration pits receiving stormwater, with a raised underdrain and internal water storage (drained), (b) next to infiltration pits receiving stormwater but without an underdrain and internal water storage (adjacent), and (c) planted in standard pits, not receiving stormwater (control). Trees in drained pits grew twice as fast as control trees in the first 2 years, but fast initial growth rates were not sustained in years three and four. Trees outgrowing the small infiltration pits, rather than a lack of water, was most likely responsible for growth rates slowing down. Despite this, rapid initial growth for trees in drained pits meant trees were larger by year three and transpired more than twice as much (5.1 L d⁻¹) as trees adjacent to pits (2.4 L d⁻¹) or control trees (2.3 L d⁻¹). No trees showed drought stress during the study. However, some trees planted adjacent to infiltration pits showed waterlogging stress, suggesting caution installing infiltration pits adjacent to establishing trees in fine‐textured soils. Overall, our results suggest passive irrigation systems can substantially increase initial tree growth, thereby facilitating greater cooling and runoff reduction through increased transpiration.
... Measurements are conducted on both sunlit and shaded leaves throughout the day to account for temporal and spatial differences in transpiration for a plant of interest. Values are then scaled for all leaves according to total leaf area and proportioned for sunlit or shaded leaves (Konarska et al., 2016;Scharenbroch et al., 2016). Using this method, Scharenbroch et al. (2016) was the first study to estimate the contribution of transpiration from tree-based SCMs to the water balance in the field. ...
... Values are then scaled for all leaves according to total leaf area and proportioned for sunlit or shaded leaves (Konarska et al., 2016;Scharenbroch et al., 2016). Using this method, Scharenbroch et al. (2016) was the first study to estimate the contribution of transpiration from tree-based SCMs to the water balance in the field. They suggested transpiration from trees in a 'green parking lot' in Illinois (that included stormwater control measures such as permeable pavements and bioswales) represents a substantial proportion of the water balance (46-72%). ...
... Measurements are conducted on both sunlit and shaded leaves throughout the day to account for temporal and spatial differences in transpiration for a plant of interest. Values are then scaled for all leaves according to total leaf area and proportioned for sunlit or shaded leaves (Konarska et al., 2016;Scharenbroch et al., 2016). Using this method, Scharenbroch et al. (2016) was the first study to estimate the contribution of transpiration from tree-based SCMs to the water balance in the field. ...
... Values are then scaled for all leaves according to total leaf area and proportioned for sunlit or shaded leaves (Konarska et al., 2016;Scharenbroch et al., 2016). Using this method, Scharenbroch et al. (2016) was the first study to estimate the contribution of transpiration from tree-based SCMs to the water balance in the field. They suggested transpiration from trees in a 'green parking lot' in Illinois (that included stormwater control measures such as permeable pavements and bioswales) represents a substantial proportion of the water balance (46-72%). ...
Chapter
This book presents the advancements made in applied metrology in the field of Urban Drainage and Storm water Management over the past two decades in scientific research as well as in practical applications. Given the broadness of this subject (measuring principles, uncertainty in data, data validation, data storage and communication, design, maintenance and management of monitoring networks, technical details of sensor technology), the focus is on water quantity and a sound metrological basis. The book offers common ground for academics and practitioners when setting up monitoring projects in urban drainage and storm water management. This will enable an easier exchange of results so as to allow for a faster scientific progress in the field. A second, but equally important goal, is to allow practitioners access to scientific developments and gained experience when it comes to monitoring urban drainage and storm water systems. In-depth descriptions of international case studies covering all aspects discussed in the book are presented, along with self-training exercises and codes available for readers on a companion website. Numerous detailed examples are given in the book, with corresponding open-source codes and training files available to download here. ISBN: 9781789060102 (Paperback) ISBN: 9781789060119 (eBook)
... Measurements are conducted on both sunlit and shaded leaves throughout the day to account for temporal and spatial differences in transpiration for a plant of interest. Values are then scaled for all leaves according to total leaf area and proportioned for sunlit or shaded leaves (Konarska et al., 2016;Scharenbroch et al., 2016). Using this method, Scharenbroch et al. (2016) was the first study to estimate the contribution of transpiration from tree-based SCMs to the water balance in the field. ...
... Values are then scaled for all leaves according to total leaf area and proportioned for sunlit or shaded leaves (Konarska et al., 2016;Scharenbroch et al., 2016). Using this method, Scharenbroch et al. (2016) was the first study to estimate the contribution of transpiration from tree-based SCMs to the water balance in the field. They suggested transpiration from trees in a 'green parking lot' in Illinois (that included stormwater control measures such as permeable pavements and bioswales) represents a substantial proportion of the water balance (46-72%). ...
Book
This book presents the advancements made in applied metrology in the field of Urban Drainage and Storm water Management over the past two decades in scientific research as well as in practical applications. Given the broadness of this subject (measuring principles, uncertainty in data, data validation, data storage and communication, design, maintenance and management of monitoring networks, technical details of sensor technology), the focus is on water quantity and a sound metrological basis. The book offers common ground for academics and practitioners when setting up monitoring projects in urban drainage and storm water management. This will enable an easier exchange of results so as to allow for a faster scientific progress in the field. A second, but equally important goal, is to allow practitioners access to scientific developments and gained experience when it comes to monitoring urban drainage and storm water systems. In-depth descriptions of international case studies covering all aspects discussed in the book are presented, along with self-training exercises and codes available for readers on a companion website. Numerous detailed examples are given in the book, with corresponding open-source codes and training files available to download here. ISBN: 9781789060102 (Paperback) ISBN: 9781789060119 (eBook)
... During this process, canopy interception and ground infiltration are two main components that reduce rainwater runoff. Evaporation and transpiration of trees return water to the atmosphere, maintain the health of the trees, and restore the interception of the trees before the subsequent rainfall [101]. ...
... interception of the trees before the subsequent rainfall [101]. ...
Article
Full-text available
Urbanization has replaced natural permeable surfaces with roofs, roads, and other sealed surfaces, which convert rainfall into runoff that finally is carried away by the local sewage system. High intensity rainfall can cause flooding when the city sewer system fails to carry the amounts of runoff offsite. Although projects, such as low-impact development and water-sensitive urban design, have been proposed to retain, detain, infiltrate, harvest, evaporate, transpire, or re-use rainwater on-site, urban flooding is still a serious, unresolved problem. This review sequentially discusses runoff reduction facilities installed above the ground, at the ground surface, and underground. Mainstream techniques include green roofs, non-vegetated roofs, permeable pavements, water-retaining pavements, infiltration trenches, trees, rainwater harvest, rain garden, vegetated filter strip, swale, and soakaways. While these techniques function differently, they share a common characteristic; that is, they can effectively reduce runoff for small rainfalls but lead to overflow in the case of heavy rainfalls. In addition, most of these techniques require sizable land areas for construction. The end of this review highlights the necessity of developing novel, discharge-controllable facilities that can attenuate the peak flow of urban runoff by extending the duration of the runoff discharge.
... Many researchers have studied vegetation in the urban fabric from different aspects such as selection, design, planting methods, and its impact on human behaviors. Only a limited number of species are planted as urban trees due to the lack of systematic trials of species and poor access to planting material, even though trials have shown some urban trees to be most hardy, aesthetically pleasing, and easy to propagate [39,40]. Often wild, edible plants with low-care requirements are excellent candidates for ornamental street tree planting. ...
... These criteria were highlighted as important factors in the selection of tree species [32]. According to S. Pauleit [32], trees in the cities of the United Kingdom are very much undervalued, and only an afterthought in the process of planning, design, and management of streets, and their town's level of expenditure for trees, street tree quality, and site preparation was developed recently [39,42,43]. ...
Article
Full-text available
Urban vegetation is an essential element of the urban city pedestrian walkway. Despite city forest regulations and urban planning best practices, vegetation planning lacks clear comprehension and compatibility with other urban elements surrounding it. Urban planners and academic researchers currently devote vital attention to include most of the urban elements and their impact on the occupants and the environment in the planning stage of urban development. With the advancement in computational design, they have developed various algorithms to generate design alternatives and measure their impact on the environment that meets occupants’ needs and perceptions of their city. In particular, multi-agent-based simulations show great promise in developing rule compliance with urban vegetation design tools. This paper proposed an automatic urban vegetation city rule compliance approach for pedestrian pathway vegetation, leveraging multi-agent system and algorithmic modeling tools. This approach comprises three modules: rule compliance (T-Rule), street vegetation design tool (T-Design), and multi-agent alternative generation (T-Agent). Notably, the scope of the paper is limited to trees, shrubbery, and seating area configurations in the urban pathway context. To validate the developed design tool, a case study was tested, and the vegetation design tool generated the expected results successfully. A questionnaire was conducted to give feedback on the use of the developed tool for enhancing positive experience of the developed tool. It is anticipated that the proposed tool has the potential to aid urban planners in decision-making and develop more practical vegetation planting plans compared with the conventional Two-Dimensional (2D) plans, and give the city occupants the chance to take part in shaping their city by merely selecting from predefined parameters in a user interface to generate their neighborhood pathway vegetation plans. Moreover, this approach can be extended to be embedded in an interactive map where city occupants can shape their neighborhood greenery and give feedback to urban planners for decision-making.
... In these cases, however, particular attention must be given to the prevention of possible pollution of aquifers and subsoil. In fact, the phytodepurant action of the plants is reduced as well as the filtration of the soil and sand layer which, normally, would have helped to retain nutrients, hydrocarbons and heavy metals (Scharenbroch et al., 2016). For this reason, the various national legislations have established specific treatments for the water before the infiltration phase. ...
... In questi casi, tuttavia, particolare attenzione deve essere posta agli aspetti della prevenzione dal possibile inquinamento degli acquiferi e del sottosuolo. Viene, infatti, ridotta l'azione fitodepurante delle piante e, soprattutto, la filtrazione dello strato in terreno vegetale misto a sabbia che, normalmente, avrebbe contribuito a trattenere idrocarburi e metalli pesanti (Scharenbroch et al., 2016). A tal fine le diverse legislazioni nazionali hanno previsto specifici trattamenti cui sottoporre l'acqua prima della fase di infiltrazione. ...
Article
Full-text available
Soil, landscape, water, air, biodiversity, climate: in many areas of the planet the degradation degree of such resources requires a virtuous process of reconversion, regeneration and, in some cases, de-urbanization. Recent research on Mediterranean metropolitan areas has shown, in fact, that de-urbanization constitutes a need that is now an essential requirement of these territories. Where to find necessary financial resources? The North European examples of urban renewing, from the Bo01 of Malmö to the Hammarby Sjöstad of Stockholm, from the London GMV to the Vauban of Friborg, show that the response to housing problems constitutes a privileged catalyst for innovative environmental and social policies on an urban scale. Indeed, they demonstrate that urban planning has the potential to find in itself the financial sources necessary to reverse the processes of ecological degeneration that have affected cities. Some authors believe also that it is too late for an approach limited in preventing new land take and environmental impacts. Furthermore, they think we need widespread building substitutions and the technological adaptation of the infrastructural system. High density would seem to lend itself to become a criterion for the design of such interventions. But high density also needs for an efficient urban water management in order to face both: the increased soil sealing and the increase in rains intensity, that is an effect of climate change. In this contribute, introducing next issue of UPLanD, we focus on upgrading the WSUD approach toward a planning scale one, usually referred as Water Sensitive Urban Planning.
... For example, ET was found to constitute 38% of annual and 81% of summer water balance losses in Vancouver, Canada (Grimmond and Oke, 1986). Scharenbroch et al. (2016) reported a 46 to 72% share for transpiration in total water outputs of parking lot bioswales with trees in Chicago, Illinois. While ET has been heavily studied in agriculture, it is largely unaccounted for in the design of urban GSI. ...
... In-situ ET measurement in vegetated GSI systems (e.g., using chamber systems- Hamel et al., 2014) is difficult ( Szota et al., 2018). Therefore, ET is usually estimated using other methods such as 1) measurements of other water budget components through lysimeter/column/box studies (see Tables 1 and 3), 2) potential ET (PET) estimation equations (see Section 3), and 3) stomatal conductance measurements at the leafscale (e.g., Scharenbroch et al., 2016-beyond the scope of this paper). ...
Article
Full-text available
Evapotranspiration (ET) is a viable runoff reduction mechanism and an important player in the hydrologic cycle of vegetated green stormwater infrastructure (GSI). As a dynamic process, ET is dependent on both meteorological factors (e.g., rainfall characteristics, relative humidity, and air temperature) and GSI properties (e.g., soil media type). This paper investigates the role of ET in runoff volume reduction of green roofs and rain gardens through a comprehensive literature review. Evapotranspiration is mostly unaccounted in the design and crediting of GSI systems because of the complex interaction of soil, plants, and climate that makes its quantification difficult. To improve vegetated GSI design for runoff volume reduction, design methods should consider ET and infiltration processes concurrently. Two methods, complex and simple, are reviewed and discussed herein. The simple method requires minimal input information compared to the more complex continuous simulation method; however continuous simulation yields volume reduction values more similar to field observations. It is demonstrated that modifying the drainage structure and using fine-grained in-situ soils can potentially increase ET in vegetated GSI systems. None of the available ET predictive equations, mostly derived from agricultural sciences, are found to precisely match observed GSI ET data. Until further research is conducted on GSI ET estimation methods, the 1985 Hargreaves method is recommended when performing continuous simulations. The 1985 Hargreaves method is simple, requires limited input data that are readily available, and generates reasonable results. Technical recommendations and directions for future research are provided.
... Previous work on trees in SCMs has focused on permeable paving (Morgenroth and Visser, 2011), structural soils (Bartens et al., 2009;Xiao and McPherson, 2011) and bioswales (Scharenbroch et al., 2015) or as one component of the vegetation within large bioretention systems (Hunt et al., 2006;Li et al., 2009). For tree pits specifically, whilst there has been some work previously on their effectiveness at nutrient reduction (Denman et al., 2016;Denman et al., 2006), it remains to be determined how effective they may be at runoff retention. ...
... This low evapotranspiration component was perhaps unsurprising due to the small tree size even at the conclusion of this study (mean tree height of 3.5 m and mean canopy width of 1.3 m). Previous studies of bioswale and bioretention systems have found the evapotranspiration components of these systems to range from 3% to 72% (Hess et al., 2017;Li et al., 2009;Scharenbroch et al., 2015). This large range suggests that there is potential for the evapotranspiration component of the tree pits to increase as the tree matures and subsequently increases its water usage. ...
Article
Tree pits are attractive stormwater control measures (SCMs) for implementation in dense urban areas because of their small footprint, their potentially low cost and the co-benefits they may bring through improved street tree growth. While they provide street trees with passive irrigation, it remains to be determined if tree pits may achieve meaningful reductions in stormwater runoff. We undertook a streetscape experiment to quantify runoff retention of tree pits in a heavy clay soil with low-rates of exfiltration. We calibrated and validated a water balance model using the field experiment data to identify tree pit characteristics driving runoff retention performance. We then applied the model to different implementation scenarios to ascertain how useful these tree pits may be at reducing runoff to return a more natural flow regime in dense urban areas. The main drivers of runoff retention were identified as exfiltration rates from the tree pits and the connected impervious catchment size. Our results show that it is possible, even in dense urban streetscapes with low conductivity (heavy-clay) soils, to achieve a 90% reduction in annual runoff and to reduce days of runoff to just 15 days per year. However, to achieve this, tree pits need to be sized between 2.5% and 8% of the impervious catchment area, depending on pit exfiltration rates. In practice, achieving these tree pit to catchment area ratios for a dense urban streetscape will require consideration in the planning stages of development works and is expected to be most feasible through implementation of tree pits alongside a suite of other complementary SCMs.
... Moreover, taking into account that these studies were on field studies, i.e., not related to thinner and more permeable bioretention media, further investigations would be needed for better characterizing tree root influences upon infiltration in more related bioretention systems, such as for instance "stormwater tree boxes" that were recently described by Seidl (2019). Besides, despite the fact that bioswale or infiltrating tree trench systems are green infrastructures which may be considered out of the scope of this review dealing on "bioretention" stricto sensu, it should be worth noting that oversizing such systems may result in water deficit altering tree growth (Scharenbroch et al. 2016;Tu et al. 2020). If a tree is intended to be introduced into a rain garden-like system for instance, careful consideration should be also given to its water requirement to avoid any hydric stress and to provide sufficient soil depth for perennial growth (personal communication). ...
Article
Full-text available
Stormwater mitigation efficiency of bioretention systems relies for a large part on their capacity to infiltrate rapidly received runoff. Within this context, the primary aim of this literature review was to clarify the vegetation influences on bioretention media hydraulic conductivity, with the ultimate goal of improving guidance on plant choice for system durability. A thorough synthesis of studies dealing with the comparison of plant species, functional types, or traits on infiltration-related processes in biofilters was achieved. Overall, results converged to a positive impact of plants on water infiltration and percolation, either under greenhouse or field conditions. In most cases, vegetation selection had a determining role in maintaining initial media infiltration rates, with in terms of improvement: turfgrass < prairie grass < shrubs < trees. Wind-induced movements of rigid foliage or stems are believed to avoid complete surface clogging. Species with thick, rhizomatous or fleshy (with maximum root diameter near the centimeter range), and tap or deep root systems could be preferred to maximize infiltration rates in permeable bioretention media. In fine-textured soils, higher specific root length, root length density, or mass density could also enhance infiltration. Root mass densities (0.1–2.2 kg.m³) were positively linked with infiltration rates in unlined systems while roots around 1 mm diameter would favor macropore-related preferential flows and increased hydraulic conductivity. Finally, implementation of high-diversity plant communities would ensure the presence of a more functionally rich vegetation community with species possessing adequate physiological adaptations (including root system architecture) to local environmental conditions for perennial cover and proper bioretention hydrological functioning. Graphical abstract
... As trees mature, increasing in size and stature, their capacity to provide a variety of social and environmental benefits augments substantially (Barro, Gobster, Schroeder, & Bartram, 1997;Berland et al., 2017;Lohr, Peterson-Mims et al., 2004;Scharenbroch, Morgenroth, & Maule, 2016). According to a meta-analysis of street tree survival rates conducted by Roman and Scatena (2011), the population half-life for trees installed in a city street tree pit was found to only be 13-20 years. ...
Article
Full-text available
Urban forestry NGOs commenced gaining prominence in the socio-political landscape of the 20th century. Despite a dramatic increase in the number of urban forestry NGOs (50%) in recent decades, they are rarely described in the scientific literature, and they have not been investigated in any formal, systematic manner. Little is known about the origins of many of these organisations or how many formal urban forestry NGOs are presently active across the United States. Knowledge gaps persist pertaining to organisational structure, programming, and funding. To address these gaps in knowledge, this article presents findings from a survey of 81 urban forestry NGOs in the temperate forest region of the United States. We report on typical traits of urban forestry NGOs across five themes that include “origin”, “organisational structure”, “funding”, “partnerships”, and “programming”. Nearly 80% of respondents indicated that their urban forestry NGO has helped develop, shape, or implement policy in their community (e.g. tree policies & ordinances, urban forest master plans). An overwhelming majority of NGOs (90% and 83%, respectively) indicated that both private citizens and local departments were important collaborators. A vast majority of respondents (86%) indicated that their NGO routinely engages in planting trees and over 70% of urban forestry NGOs routinely participate in public events including Arbor Day celebrations and local tree giveaways. There is widespread variation regarding the size, composition, and even function of urban forestry NGOs.
... Durch einige Studien konnte bestätigt werden, dass eine zielgerichtete Zuleitung von Niederschlagswasser in verschiedene Baumstandorte, die in "stormwater control measures" integriert waren, das Baumwachstum und die -vitalität erhöht [43][44][45][46]. In einer Feldstudie ermittelten Grey et al. [46] über 18 Monate, dass neu gepflanzte Stadtbäume (Acer Campestre) in sogenannten "tree pits" mit unterliegender Drainage nach der Versuchszeit eine doppelt so hohe Wuchsleistung aufwiesen wie die Vergleichsbäume ohne Zufuhr von Niederschlagswasser. Die Autoren sowie andere Studien weisen ausdrücklich auf die Bedeutung einer ausreichenden Infiltrationsrate bzw. ...
Article
Full-text available
Water-sensitive urban development is becoming an essential field of action for municipal urban planners amidst growing droughts and, at the same time, more intense heavy rainfall events. The model of decentralised water retention is becoming increasingly crucial for municipal water management and green space management. Synergy effects can be especially high if rainwater retention is coupled with planting sites for roadside trees. In recent years, various structural variations combining the two have been developed and implemented in Germany in keeping with the concept of swales. This first part of this article presents a few of these combinations and construction methods as examples and details their impact on water management. Measures already implemented in German-speaking countries are showcased using international case studies. These projects are the basis and starting point for scientific research to date on vitality, water balance, pollution mitigation and cooling of heat islands. The second part of the article casts the spotlight on the insights and research results gained to date on construction methods, evaporation and pollutant retention as part of the BMBF joint research project BlueGreenStreets. Drawing on many pilot projects, the authors examine the effectiveness of planning tools and regulations on green urban infrastructure, urban water management, the redevelopment of roads along with traffic and open space planning. It also carries out a vari- ety of measurements and models on the ways that roadside measures can affect the climate, evaporation and pollutant re- tention. Key Words: drainage systems, heavy rainfall, water retention,seepage, swale, urban planning, climate change, evaporation, cooling KA : Korrespondenz Abwasser, Abfall 5/2022
... As trees mature, increasing in size and stature, their capacity to provide a variety of social and environmental benefits augments substantially (Barro, Gobster, Schroeder, & Bartram, 1997;Berland et al., 2017;Lohr, Peterson-Mims et al., 2004;Scharenbroch, Morgenroth, & Maule, 2016). According to a meta-analysis of street tree survival rates conducted by Roman and Scatena (2011), the population half-life for trees installed in a city street tree pit was found to only be 13-20 years. ...
Article
Full-text available
This article presents the results of a literature review related to volunteerism in urban forestry in the United States. Themes explored were inductively emergent from the research reviewed and included ‘volunteer demographics’, ‘motivations of volunteers’, ‘benefits of volunteering’, ‘volunteer engagement and barriers’, ‘value of volunteering’, and ‘volunteer recruitment and retention’. Urban forestry volunteers are often motivated by personal, social, and environmental considerations. Volunteers in urban forestry may not be representative of a cross-section of the communities that they are serving, rather they are often middle-aged, well-educated white women. Further research is required both to ascertain barriers to volunteerism and to enhance future volunteer recruitment and retainment efforts. Volunteers in the United States account for 5% of municipal tree care in urban forests – accounting for an estimated $35 million USD in value. Volunteers perform critical urban forestry-related tasks that aim to increase urban tree canopy cover through tree selection and planting efforts. Volunteers encourage urban tree survival by advocating for, as well as performing, important maintenance-related duties including the administration of supplemental watering and urban tree pruning. With proper training and support, volunteers may accurately perform important data collection efforts that may inform management decisions and urban tree care maintenance programmes.
... These sub-used sites are negative externalities that demean the use of the public space in the city, and adding Parking Trees, in sum, can generate a beneficial impact. As mentioned, a Parking Tree that integrates a bioswale is a component of a sustainable urban drainage system based on ditches covered with a layer of vegetation located between streets and sidewalks or parking lots to capture, temporarily retain, and filter rainwater runoff [14]. The depth of the bioswales ranges from 15 to 30 cm from the vehicular road level. ...
Article
Full-text available
Nature-based solutions (NbS) include all the landscape’s ecological components that have a function in the natural or urban ecosystem. Memorial Parking Trees (MPTs) are a new variant of a nature-based solution composed of a bioswale and a street tree allocated in the road, occupying a space that is sub-utilised by parked cars. This infill green practice can maximise the use of street trees in secondary streets and have multiple benefits in our communities. Using GIS mapping and methodology can support implementation in vulnerable neighbourhoods. In this research, we based vulnerability assessments for London, Rio de Janeiro, and Los Angeles on the following three indicators: extreme temperature, air quality, and flood-prone areas. Evidence is emerging that disadvantaged populations may live at higher risks of exposure to environmental hazards [1]. The income and healthcare accessibility of neighbourhoods are the two indicators that will help us target these communities for a better and faster decision-making process. The contrast between the results and the 15-min city concept supports our detecting and prioritising neighbourhoods for MPTS implementation, among other NbS solutions integrated into a more inclusive and sustainable urban design.
... Taking into account all the trees within the study location, the total annual plot rainfall (excluding any extreme rainfall events) was approximately equal to total transpiration, what was shown for boreal urban trees of other municipalities [61,63]. Such information obtained in real-time could considerably contribute to cities' stormwater management [97][98][99]. On the other hand, it is widely discussed that rain interception by leaf buffering during heavy rains also contributes to run-off mitigation [66,100,101], which is based on leaf area index, as discussed further in the text. ...
Article
Full-text available
Urban green infrastructure plays an increasingly significant role in sustainable urban development planning as it provides important regulating and cultural ecosystem services. Monitoring of such dynamic and complex systems requires technological solutions which provide easy data collection, processing, and utilization at affordable costs. To meet these challenges a pilot study was conducted using a network of wireless, low cost, and multiparameter monitoring devices, which operate using Internet of Things (IoT) technology, to provide real-time monitoring of regulatory ecosystem services in the form of meaningful indicators for both human health and environmental policies. The pilot study was set in a green area situated in the center of Moscow, which is exposed to the heat island effect as well as high levels of anthropogenic pressure. Sixteen IoT devices were installed on individual trees to monitor their ecophysiological parameters from 1 July to 31 November 2019 with a time resolution of 1.5 h. These parameters were used as input variables to quantify indicators of ecosystem services related to climate, air quality, and water regulation. Our results showed that the average tree in the study area during the investigated period reduced extreme heat by 2 °C via shading, cooled the surrounding area by transferring 2167 ± 181 KWh of incoming solar energy into latent heat, transpired 137 ± 49 mm of water, sequestered 8.61 ± 1.25 kg of atmospheric carbon, and removed 5.3 ± 0.8 kg of particulate matter (PM10). The values of the monitored processes varied spatially and temporally when considering different tree species (up to five to ten times), local environmental conditions, and seasonal weather. Thus, it is important to use real-time monitoring data to deepen understandings of the processes of urban forests. There is a new opportunity of applying IoT technology not only to measure trees functionality through fluxes of water and carbon, but also to establish a smart urban green infrastructure operational system for management.
... Policy changes have led to green belts being conceived more broadly in some cities to include the concept of GI providing corridors for ecological restoration and recreation aimed to mitigate the future impacts of climate change [36]. Because of their aboveground and below-ground biomass, trees are known to reduce runoff very efficiently [37]. Therefore, some municipal policies promote GI through major tree planting programs [28 ,29], or ordinances that promote urban tree canopy (from street trees to urban forests) [38,39]. ...
Article
Multifunctional and connected green infrastructure (GI) systems have been linked to urban resilience. Although there have been significant scholarly efforts to assess resilience and to evaluate the benefits of GI, it remains unclear the degree in which GI efforts enhance resilience. Following theoretical frameworks that study coupled infrastructure systems, this paper explores the state of the art on the contribution of GI to urban resilience from multiple dimensions: (1) policy - that promotes the adoption of GI, (2) performance - assessment of GI impacts on water infrastructure systems resilience, (3) connectivity - evaluation of human and wildlife movement through GI, and (4) social - community cohesion as a result of GI efforts. We argue that beyond their individual contributions to supporting urban resilience, the interactions across the various dimensions are key to enhancing resilience. Ultimately, participatory processes are needed to assess resilience originating from GI systems and avoid injustice.
... A bioswale is a depressed or channeled drainage area that receives rainwater runoff (often from an impervious surface like a parking lot) that is vegetated. One study found that trees installed in engineered bioswales can absorb 46 to 72% of total water within the system (Scharenbroch, Morgenroth, & Maule, 2016). ...
Technical Report
Full-text available
This report, a renewed inquiry into urban public spaces, synthesizes research to guide decision making and shape future investments in, and maintenance of, our urban public spaces. https://williampennfoundation.org/what-we-are-learning/benefits-and-costs-urban-public-spaces
... Our study focused on the herbaceous understory plants of the bioswales, but other life forms such as trees and shrubs are often planted in these types of green infrastructure installations, and would be beneficial to examine in future studies to get integrated estimates of plant water movement from soils. One study of bioswale trees near Chicago found similar results to ours in that tree species varied widely in their transpiration and growth rates, and had dramatic differences on estimated bioswale water budgets (Scharenbroch et al., 2016). Bioswale plant choice can also influence the quantity of pollutants filtered from diverted stormwater (Read et al., 2008), although plant-associated microbes likely mediate those effects. ...
Article
Full-text available
Bioswales and other forms of green infrastructure can be effective means to reduce environmental stresses in urban ecosystems; however, few studies have evaluated the ecology of these systems, or the role that plant selection and microbial assembly play in their function. For the current study, we examined the relationship between plant transpiration rates for five commonly planted herbaceous species in three bioswales in New York City, as well as bioswale soil microbial composition and soil chemistry. Soils were sampled near individual plants, with distinction made between upper (bioswale inlet) and lower slopes (bioswale outlet). We found high variation in transpiration rates across species, and that Nepeta × faassenii was the highest conductor (13.65 mmol H2O m–2s–1), while Panicum virgatum was the lowest conductor (2.67 mmol H2O m–2s–1) (p < 0.001). There was significant variation in percent N of leaves and soil, which did not relate to the higher water conductance in bioswales. Significantly higher C, N, and water content on the high end of bioswale slopes suggest storm water run-off is mostly absorbed on the inlet side. Bacterial and fungal communities were significantly clustered by bioswale and by plant species within each bioswale implying there are micro-environmental controls on the soil microbial composition, and that plant composition matters for microbial assemblages within bioswales. Plants with higher transpiration rates were associated with greater fungal and bacterial diversity at the level of the bioswale and at scale of the individual plant, suggesting a possible link between plant physiological traits and soil microbial communities. These data suggest that the specific plant palette selected for planting bioswales can have deterministic effects on the surrounding microbial communities which may further influence functions such as transpiration and nutrient cycling. These results may have implications for bioswale management to improve urban water quality and reduce stress on sewage systems after storm events by revising plant species palette selection based on the functional consequences of plant-microbial associations in engineered green infrastructure.
... This is good news for water-limited cities, since urban trees can require a significant amount of irrigation for transpiration and related growth and productivity [10,11]. While research of green infrastructure performance provides mixed results [12,13], passive irrigation has shown to support increased growth rates for trees [14,15]. Still, research is needed to understand how passive green infrastructure can best support the urban forest [16]. ...
Article
Full-text available
The infiltration of stormwater runoff for use by urban trees is a major co-benefit of green infrastructure for desert cities with limited water resources. However, the effects of this passive irrigation versus regular, controlled moisture inputs, or active irrigation, is largely unquantified. We monitored the ecohydrology of urban mesquite trees (Prosopis spp.) under these contrasting irrigation regimes in semiarid Tucson, AZ. Measurements included soil moisture, sap velocity, canopy greenness, and leaf-area index. We expected both irrigation types to provide additional deep (>20 cm) soil moisture compared to natural conditions, and that trees would depend on this deep moisture for transpiration and phenological activity. Results show that active irrigation supported higher soil moisture throughout the study than passive irrigation. Passive irrigation only provided additional deep moisture when green infrastructure features received impervious runoff from a city street. Sap velocity and greenness were similar under both irrigation types, outside of isolated periods of time. These differences occurred during the extremely wet summer 2017 when passively irrigated trees exhibited a greenness peak, and the dry conditions of spring when actively irrigated trees had higher sap flow and relative greenness. Finally, it was not determined that deep soil moisture had a stronger relationship with mesquite productivity than shallow moisture, but both relationships were stronger in the spring, before summer rains. This study aims to contribute empirical observations of green infrastructure performance for urban watershed management.
... Water runoff is a serious issue in the city environment, as runoff can increase the exposure to pollution and cause property damage (Braden & Johnston, 2004). Trees can help reduce and intercept stormwater and improve the quality of runoff water (Berland et al., 2017;Bolund & Hunhammar, 1999;Brack, 2002;Livesley, McPherson, & Calfapietra, 2016;Scharenbroch, Morgenroth, & Maule, 2016). With less contact on impervious surfaces, stormwater is cooler and has fewer pollutants when it enters local waterways and water-related ecosystems (Schwab, 2009). ...
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We live in an era influenced by humans to the point that the Earth's systems are now altered. In addition, a majority of the world's population live in cities. To meet the needs of people in a changing world, The United Nations General Assembly created the United Nations Sustainable Development Goals (UN SDG) to improve the quality of life for people. These broad goals outline the greatest challenges of our time. An effective strategy to assist in meeting these goals is to plant and protect trees, especially in cities where the majority of people live. This paper serves as a critical review of the benefits of trees. Trees promote health and social well‐being by removing air pollution, reducing stress, encouraging physical activity, and promoting social ties and community. Children with views of trees are more likely to succeed in school. Trees promote a strong economy and can provide numerous resources to the people that need them. While cities are getting hotter, trees can reduce urban temperatures. They provide habitat and food for animals. Finally, trees are valuable green infrastructure to manage stormwater. Money spent on urban forestry has a high return on investment. As we navigate this human‐dominated era, we need skilled people who understand the nuances of the built environment and trees as we strategically plan the cities of the future. The overwhelming evidence from the scientific literature suggests that investing in trees is an investment in meeting the UN SDG, and ultimately an investment for a better world.
... Similarly, Hess et al. (2017) used weighing lysimeters in rain gardens planted with switch grass, perennials, and deciduous shrubs in three media types with varied drainage configurations to conclude that ET accounted for between 43% and 70% of water losses. Scharenbroch et al. (2016) found that tree transpiration levels varied between species and accounted for 46-72% of the water balance from a parking lot in Illinois outfitted with green infrastructure practices, and recommended that species with large mature size and greater total leaf area will likely contribute more toward system hydrologic function. ...
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Cities across the world are increasingly utilizing green infrastructure practices as part of their stormwater management programs. Bioretention areas have become a popular green infrastructure practice due to their widespread success in improving water quality and reducing runoff generated from impervious surfaces. Several studies have demonstrated that pollutant removal performance can be improved when plants are included in bioretention design; however, while numerous benefits of trees in urban areas have been identified, little knowledge of their contributions to stormwater management in green infrastructure currently exists. To address this need, a controlled mesocosm experiment was conducted to characterize the degree of stormwater treatment provided by bioretention columns planted with one of three native tree species commonly found across the eastern United States (Acer rubrum – red maple, Pinus taeda – loblolly pine, and Quercus palustris – pin oak). Tree pollutant removal performance was compared to nonvegetated mesocosms using a semi-synthetic stormwater mixture applied to the mesocosms over a period of 17 weeks. The hydrologic benefits of each species were characterized using data-logging scales placed below the mesocosms to compare evapotranspiration (ET) rates and drainage in each configuration. Differences in pollutant removal between tree species were largely not significant, indicating the dominant role of the bioretention media in mitigating dissolved and particle-bound constituents. Mesocosms planted with red maple (Acer rubrum) had significantly greater average ET rates (3.2 mm d⁻¹) than all other configurations, attributable to plant development and increased growth and canopy size. All mesocosms planted with trees had significantly higher ET rates than the nonvegetated mesocosms, illustrating the role of transpiration in bioretention hydrology which, depending on species, accounted for 8.2–37.5% of average daily water losses from the mesocosms during testing. These results suggest that trees contribute to bioretention hydrology through evapotranspiration, and that significant differences between species exist and are likely related to growth rate.
... Urban tree canopies influence stormwater runoff through rainfall interception, whereas their root systems improve infiltration, limit soil erosion, and regulate soil nutrient cycles involved in stormwater pollutant removal (Xiao and McPherson 2011;Bartens et al. 2008;Day et al. 2010;Kuehler et al. 2017). As with other types of vegetation, little research has been conducted to identify the potential contributions urban trees may bring to stormwater management in bioretention systems, or how the unique environmental conditions found in bioretention systems influence tree health and function (Denman et al. 2016;McPherson et al. 2011;Scharenbroch et al. 2016). Thus, the 1 extent to which current bioretention designs, species selection, and planting/maintenance practices contribute to tree health and promote various environmental benefits associated with healthy trees is unknown. ...
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... Urban forests are valuable and integral components of the urban environment. In previous studies, urban forests have been shown to provide numerous ecological and environmental benefits such as enhancing water quality, improving air quality, conserving energy, carbon storage, reducing storm water runoff, and enhancing biodiversity (e.g., [1][2][3][4][5][6][7][8]). At the same time, it has been well documented that urban forests and parks increase property values and housing prices in major urban dwellers (e.g., [33][34][35]), and the preferred attributes of urban forests can be estimated in monetary terms [33,36,37]. ...
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It is important to integrate user preferences and demands into the design, planning, and management of urban forests. This is particularly important in highly urbanized areas where land is extremely limited. Based on a survey with 600 participants selected by quota sampling in Seoul, Korea, we developed a conjoint choice model for determining the preferences of urban dwellers on urban forest attributes, the levels of attributes, and the preferences for particular attributes. Then, the preferences were transformed into monetary values. The results indicated that urban dwellers preferred broadleaved forests over coniferous forests, soil-type pavement materials over porous elastic pavement materials on trails, and relatively flat trails over trails with steep slopes. The model indicated that participants were willing to pay an additional 11.42 USD to change coniferous forest to broadleaved forest, 15.09 USD to alter porous elastic pavement materials on trails to soil-type pavement materials on trails, and 23.8 USD to modify steeply sloping trails to relatively flat trails. As previously reported, considerable distance decay effects have been observed in the user preferences for urban forests. We also found a significant difference in the amount of the mean marginal willingness to pay among sociodemographic subgroups. In particular, there were significant positive responses from the male group to changes in urban forest attributes and their levels in terms of their willingness to pay additional funds. By contrast, the elderly group had the opposite response. In this study, we were not able to integrate locality and spatial variation in user preferences for urban forests derived from locational characteristics. In future studies, the role of limiting factors in user preferences for urban forests and their attributes should be considered.
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Aşırı kentleşme ve beraberinde getirdiği altyapı sorunları yağmur suyundan kaynaklı bir takım çevresel problemlere yol açmaktadır. Büyüyen ve gelişen kentlerimizde zamanla meydana gelen yoğun yapılaşma, beton, asfalt vb. gibi geçirimsiz yüzey miktarlarının artmasına ve yeşil alan gibi geçirimli yüzeylerin azalmasına sebep olmaktadır. Bunun sonucunda ise yeryüzüne inen yağmur suları geçirimsiz yüzeyler tarafından emilemeyip yüzeysel akışa neden olmakta ve sonucunda sel, taşkın vb. gibi çevresel problemlere yol açmaktadır. Bu problemlere çözüm oluşturması sebebiyle dünya genelinde alternatif yaklaşımlara doğru bir eğilim olmaktadır. Bu yaklaşımlardan biride yeşil altyapı/düşük etkili gelişim bileşenleridir. Bu çalışmada yağmur suyunun meydana getirdiği sorunlara yeşil altyapı/düşük etkili gelişim bileşenleri gibi alternatif yaklaşımlarla çözüm üretilmeye çalışılmıştır. Bu bağlamda yapılaşmanın yaşandığı Malatya kent merkezinde, yağmur suyunun meydana getirdiği yüzeysel akışların belirlenmesi ve düşük etkili gelişim bileşenlerinin etkinliğinin değerlendirilmesi amacıyla süreç tabanlı bir yağmur suyu yönetim modeli SWMM (Storm Water Management Model) uygulanarak çeşitli simülasyon çalışmaları gerçekleştirilmiştir. Dört farklı düşük etkili gelişim bileşeninin; yeşil çatı (1), yağmur varilleri (2), geçirimli kaplamalar (3), ve yağmur bahçeleri (4), planlanan alanın uygun kısımlarına belirli oranlarda entegre edilmesiyle gerçekleştirilen simülasyon çalışmalarında toplam yüzeysel akışlarda; yeşil çatı sistemlerinin kullanılmasıyla %2.15, yağmur varilleri kullanılmasıyla %8.10 ve eşit oranda geçirimli kaplama sistemleri ve yağmur bahçeleri kullanılmasıyla ise her iki bileşen için %6.60 oranında bir düşüş meydana gelmiştir. Bütün bileşenler birbiriyle entegreli olarak kullanıldığında ise yağmur suyunun meydana getirdiği yüzeysel akışlar %22.20 oranında azalarak bu sistemlerin kentsel alanlarda geleneksel altyapı sistemlerine alternatif olarak kullanılabileceği tespit edilmiştir.
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Increasingly, public land managers face decisions about using fruit-bearing perennial plants (including fruiting trees, shrubs, and vines) on public lands. While public trees provide many positive ecological, economic, and community health benefits, fruit-bearing perennials provide similar benefits and more. Expanded benefits include enhanced pollinator habitat, increased food access, unique educational opportunities, and ways for residents to interact more deeply with public vegetation. Despite the benefits of fruit-bearing perennials, their use and incorporation into public spaces vary among cities, resulting in an uneven and often inequitable distribution of public services. This study aims to better understand public land managers’ decision-making processes by exploring what factors are considered when deciding to plant, or not plant, fruit-bearing perennial vegetation. Specifically, interviewees (n = 12) described what they perceive as the most significant benefits and barriers to establishing fruit-bearing perennials in public spaces. Respondents reported using fruit-bearing perennials to augment species diversity, community engagement, wildlife habitat, and public education. Barriers cited included limited time and financial resources for management, lack of specialized training, fears associated with liability, limited public awareness, and competing urban forestry goals. This study contributes to the literature on public land manager decision-making which has not previously focused specifically on fruit-bearing perennials. The findings inform vegetation decision-making and urban natural resource planning by outlining key risks and rewards of adopting fruit-bearing perennials.
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Urbanization is a major driver of environmental change, which calls for multifunctional and comprehensive actions such as Nature-based Solutions (NbS). They are “inspired and supported by nature… and must benefit biodiversity and support the delivery of a range of ecosystem services”. But what nature should one aim for? We tested the hypothesis that local vegetation may not always be the best source of inspiration, as environmental changes impact both extant conditions and species suitability for restored ecosystems. We analyzed the megacity of São Paulo, where laws promote the use of species from the local Atlantic Forest biome. We trained a Linear Discriminant Analysis to classify the Brazilian biomes and predicted the biomes' correspondence considering city's vegetation cover and climate. With 80% accuracy, the model predicted correspondence with the Atlantic Forest in 57% of the city, while 43% is better represented by the Cerrado, a dense Tropical Savanna biome. Cerrado species are naturally adapted to higher insolation, temperature and more seasonal precipitation, and they can parallel the ecosystem services of the Atlantic Forest. To help guide NbS implementation, we consider four “urban biomes”: Atlantic Forest, Seasonally Flooded Atlantic Forest, Cerrado, and the Seasonally Flooded Cerrado, whose dynamics seem to depend mainly on changes in the proportion of dense vegetation cover. We then discuss possible examples of NbS in the city. Results According to the PCA (Tables S3-S6), the main difference between the classification of the green spaces classified is the higher proportion of forest cover in those classified as Mata Atlantica, with almost any influence from other vegetation cover types (Fig. 5E). This pattern is still consistent when vegetation cover is evaluated outside the largest green spaces where the presence of even small forest patches across the urban fabric results in the Mata Atlântica category Discussion The urban ecosystem restoration could benefit from such natural and dynamic processes in which the Cerrado could act as a transient urban biome in the way of restoring the urban forests through soil horizon development and species succession followed by the densification of the vegetation whenever this planting scheme is possible. Conclusions These transitions among urban biomes may occur as local conditions change with the implementation of NbS, and the results point to the effectiveness of increasing the vegetation density wherever possible.
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Bioretention systems have known benefits for managing urban stormwater, but there remain knowledge gaps about evapotranspiration (ET) and its role in these systems. This paper investigated how design parameters including growing media and vegetation, as well as climatic variables, can influence ET in bioretention systems. To this end, twenty-four bioretention mesocosms constructed using three media types (i.e., two sandy media types and clay loam mixed with wood chips) and planted with three vegetation types (i.e., herbaceous mixture, woody mixture, and turfgrass as control) in Okotoks, Alberta, Canada were monitored during the growing seasons (from May to October) between 2018 and 2020. The media moisture in the mesocosms was monitored at the depths of 20 and 40 cm to study how the design parameters and their interactions could influence ET. The results confirmed the roles of design and climatic variables on ET, while their effects were more prominent at the surface layer. The sandy media with the low organic matter (SD1) and the woody vegetation appeared to outperform the other media and vegetation types in promoting ET. The findings demonstrated the non-stationary nature of the ET function in the mesocosms. The effects of the design variables, in particular the vegetation, became more prominent over time. In addition, the impact of media-vegetation interactions on ET was identified. The results suggest the need for optimizing bioretention systems with consideration to the design variables, whose roles on ET are time- and depth-variant, to promote ET and, in turn, bioretention performance.
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Chapter
Urban blue-green infrastructure (UBGI) has been recognized as vital component of urban environment management, disaster risk reduction, and climate change adaptations. There has been growing consensus and advancement in the conceptualization, research, implementation, and mainstreaming of UBGI in urban policy planning to enhance urban resilience to increasing disaster risks and climate change. Despite the growing interest in UBGI, most of the global research on UBGI has been carried out in the Global North, while uncertainty linked with the performance of UBGI in the Global South has resulted in lack of confidence, and public acceptance has limited its adoption and implementation in many developing Asian countries. This edited book volume investigates the issues, gaps, opportunities, and advances related to UBGI from the diverse perspectives of researchers and experiences of professionals from various science and policy disciplines to enhance and enrich the existing knowledge on effective mainstreaming of UBGI across Asia. Case studies highlighting UBGI successes, gaps, opportunities, and threats from different Asian countries are presented in this volume. However, all the cases discussed in the book stress on identifying and managing biophysical and sociopolitical threats for enhancing and ensuring the mainstreaming of UBGI as practical and scientifically sound sustainable solutions that involve multi-stakeholder groups. The volume especially highlights the potential of UBGI in providing ecosystem services for addressing emerging urban environmental risks, enhancing climate change adaptation, and urban disaster risk reduction. The thematic and cross-cutting chapters bring in scientific evidence-based innovations to enhance the prospects of UBGI (environmental, economic, and social benefits).KeywordsUrban ecosystemsDisasterClimate changeUrban blue-green infrastructureResilienceSustainability
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Rainfall in cities can generate large volumes of stormwater runoff which degrades receiving waterways. Irrigating trees with runoff (passive irrigation) has the potential to increase transpiration and contribute to stormwater management by reducing runoff received by downstream waterways, but the stochastic nature of rainfall may expose trees with high transpiration to drought stress. We hypothesized that for success in passive irrigation systems, tree species should exhibit i) high maximum transpiration rates under well-watered conditions, ii) drought avoidance between rainfall events, and iii) high recovery of transpiration with rainfall following a drought. We assessed 13 commonly planted urban species in Melbourne, Australia against three metrics representing these behaviours (crop factor, hydroscape area, and transpiration recovery, respectively) in a glasshouse experiment. To aid species selection, we also investigated the relationships between these three metrics and commonly measured plant traits, including leaf turgor loss point, wood density, and sapwood to leaf area ratio (Huber value). Only one species (Tristaniopsis laurina) exhibited a combination of high crop factor (>1.1 mm mm⁻¹ d⁻¹) indicating high transpiration, small hydroscape area (<3 MPa²) indicating drought avoidance, and high transpiration recovery (>85%) following water deficit. Hence, of the species measured, it had the greatest potential to reduce runoff from passive irrigation systems while avoiding drought stress. Nevertheless, several other species showed moderate transpiration, hydroscape areas and transpiration recovery, indicating a balanced strategy likely suitable for passive irrigation systems. Huber values were negatively related to crop factor and transpiration recovery and may therefore be a useful tool to aid species selection. We propose that selecting tree species with high transpiration rates that can avoid drought and recover well could greatly reduce stormwater runoff, while supporting broader environmental benefits such as urban cooling in cities.
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Stormwater control measures (SCMs) in the form of highly permeable tree pits can be useful in two ways. On one hand, they can help reduce surface runoff and on the other hand, the presence of trees in these pits can potentially help mitigate the urban heat island effect. Therefore, it is important to understand the pit designs that underpin tree health and growth performances. Here in this study, four pit designs namely, a control which did not receive runoff water, another that receive runoff into a sandy clay loam soil, yet another that was filled with structural soil, and a third that received runoff into structural soil with an underdrain system, used to test and identify which designs were best able to maintain hydrological balance and growth of Calophyllum inophyllum in an urban area dominated by sandy clay loam soil. Trees in pits which had structural soil and drainage installed had 6-fold more growth than the controls (that received no stormwater runoff), and 3-fold more growth when compared against street trees grown in pits that had sandy clay loam soil (that had run off channelled towards these pits). Treatments with structural soils also experienced more efficient exfiltration rates which helped avoid waterlogging which in turn, benefitted growth. The lower exfiltration rates of the poorly drained sandy clay loam soils resulted in periods of saturation and subsequent slower tree growth. Treatments with structural soil together with drainage and those that had sandy clay loam soils were found to have saturated water levels at a depth greater than 400 mm and between 100−200 mm (from the surface), respectively. The outcomes from this study indicated that tree growth can be improved by channelling stormwater into tree pits with structural soil and especially those that also have drainage installed. Noteworthy however, is that while waterlogging may be avoided through the application of structural soil and a drainage system, the high exfiltration rates may result in water stress when rainfall is scarce though this did not happen here. The need for hydrological balance will be the key to successful urban street tree planting.
Chapter
Cycle lanes and green infrastructures may be expensive at first, but they involve long-term profits enhancing the quality of human life. This paper focuses on an easily replicable methodology for a cost-benefit analysis to estimate the economic value of benefits provided by cycling mobility and urban forestation in the city of Pisa. Open-source tools easily adaptable to local contexts and supported by a lot of experimentations and user guides were selected: HEAT (Health Economic Assessment Tool), a web tool designed by World Health Organization to quantify the monetary value of reduced mortality due to regular cycling, and i-Tree Eco, a software developed by the USDA Forest Service to assess the economic benefits provided by ES (Ecosystem Services) of urban trees. These tools provide an economic appraisal to verify and validate the suitability of political and economic choices and/or estimate the number of resources required in the long term.
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Sustainable urban water management initiatives are increasingly required to combat rapid urbanisation and climate pressures. Initiatives include the role of tree planting for which there is need for strong evidence of benefits and drawbacks to support effective future planning. We report robustness of evidence from an assimilated database of urban hydrological impact studies which often had differing primary purposes. Consistent impacts were found at local level, with trees reducing runoff and infiltration. Despite the consistency of evidence, much is undermined by being somewhat lacking in robustness and scientific rigour. Many studies lack adequate controls, and models are often not strongly tested against observations. Moreover, evidence of impact at larger scales is lacking. Effects of tree characteristics were also investigated; such as maturity and species for which evidence is consistent and detailed, and arrangement for which there is less evidence. Realising the full potential of trees in urban water management decision-making would benefit from more-rigorous evidence.
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Background The benefits of trees in urban areas include the following: an increase in ecosystem health, an increase in human health, the mitigation of the effects of heat and drought at microclimate level, the storage and sequestration of carbon, and a reduction in air pollution and noise. These ecosystem services can be provided only by trees that are in good health. The main cause of salt stress in urban environments is the use of de-icing salts on the streets in winter. Salt stress is a complex process that includes changes in plants on the physiological, histological, cellular and molecular levels, leading to limitations in nutrient uptake, disrupting the ionic balance of trees and resulting in the death of roadside trees. In response to salinity, trees have developed a variety of defence mechanisms that allow them to minimize the effects of stress and maintain homeostasis. Methodology The reactions of two species Acer species: A. platanoides and A. campestre , which have different sensitivities to the unfavourable conditions of the urban environments (mainly salt stress), were investigated. The research included two experiments: a field experiment with city trees and a controlled pot experiment with young trees treated with increasing doses of salt. In both experiments, the following were performed: an assessment of the health condition of the trees and the content of macroelements as well as the Cl and Na in leaves and a qualitative and quantitative analysis of polyprenols. Results A. campestre had a more specific strategy than A. platanoides for dealing with Na and Cl, which resulted in undamaged leaves. Under the same conditions, A. platanoides leaves contained more Cl and Na and were severely damaged. The disruption of the ion balance due to salt stress was lower in A. campestre than in A. platanoides . Compared with A. platanoides , A. campestre synthesized more polyprenols in the field experiment. This ability was acquired during the process of acclimation, because it occurred only in the mature trees in the field experiment and not in the young trees in the pot experiment. Conclusions The use of two experimental methods (i.e., the field and pot experiments) allowed for a more complete assessment of tree strategies to mitigate salt stress. A. campestre displayed a more specific strategy than A. platanoides . This strategy was based on several elements . A . campestre limited Cl and Na transport to the leaves, which resulted in a lack of damage to those organs. Under the same conditions, A. platanoides individuals contained more Cl and Na in their leaves and were seriously damaged. A. campestre synthesized larger amounts of polyprenols, which probably have the ability to mitigate salt stress. This ability was acquired during the process of acclimation, because it occurred only in the mature trees in the field experiment and was not observed in the young trees in the pot experiment.
Chapter
Owerri city, south east of Nigeria is a city bedeviled with perennial flood disasters. These disasters usually come with attendant loss of lives and properties of inestimable values. A critical study of Owerri city was conducted with respect to its flood plain, diverse range of drainages (drainage system), canals, rivers together with rain gauge values for the past 2 decades and other extenuating factors. All the varying factors were extrapolated to highlight possible cause or causes of constant flood disasters. These highlighted causes were made spring boards of solutions to mitigate future occurrence and establish smart city status for new Owerri with respect to flood control.
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Developing biosolids-based composts or soil blends suitable for use in urban areas is increasingly common. End uses for compost vary and can include use as a soil conditioner for existing turf, to establish new turf, for tree planting, in urban agriculture, and for use along highway right-of-ways. The carbon benefits/costs of biosolids compost were modeled for King County, Washington. Soil carbon sequestration was highest for use on disturbed soils such as new housing developments, neglected urban soils, or highway right-of-ways (–1.1 Mg CO2eq per Mg compost) and lowest for use in well-tended yards or other highly maintained landscapes (–0.036 Mg CO2eq per Mg compost). Compost use for tree growth, calculated over a 30-year period, added above-ground sequestration benefits ranging from –1.53 Mg CO2eq per Mg compost for a mature tree grown on a healthy soil to –4.58 Mg CO2eq per Mg compost for a newly planted tree grown on a disturbed site. Assuming a 20 km haul distance, transport costs ranged from 0.005 Mg CO2eq per Mg compost for delivery in a 5 Mg truck to 0.09 Mg CO2eq per Mg compost for pick up in a personal vehicle. Ecosystem services associated with different end uses for compost in urban areas also vary. This model suggests that while uses for biosolids compost will likely be varied, for a program as a whole, significant carbon benefits can be expected.
Book
It is a goal for every urban area to be resilient from any form of catastrophe. One strategy to make this possible is by developing our cities in a healthy environment with the existence of the diverse forest. Most of the towns in the first world countries are renowned for gardens, historical parks, and boulevards. Putting up the City like this contributes to its character and enhance the social and cultural life of the area. Urban forest brings life to cities around the world, and it is an essential character that attracts more active endeavors. Urban Forest Ecosystem Management needs an integrated approach to understanding the concept of the whole forest and managing its resources. Most of our current cities have developed 100 years ago and platform different landscapes, unpredictable climatic conditions, and diverse social environment. There are large numbers of trees cut from several views, and existing landscapes are battling to adapt to the variations in the current climate conditions and changes. Today is now the right opportunity to develop our cities and plant the forest for a greener future. It is necessary for most cities to counter climate change and expansion in urban areas and strengthens the well-being, health, and livability of cities and its populations. The destination of this scheme is a huge transition on how to make most cities as a resilient landscape, varied and healthy that suffice the requirement of the present society and making it sustainable for the forthcoming generations. Our goal is to make our cities greener by creating a town within a forest. Most of our cities are facing three big challenges: • Population growth; • Urban heating; and • Climate change. These problems put so much burden on the facilities and individuals dwelling in the City. Maintaining a strong green city environment and sustaining it to be livable is a critical responsibility. Climate change will continuously challenge every City in every state and country for the next 20 years. The temperature will become warmer, drier, and liable for most extreme heats that will be a source of several diseases. The most significant function of the urban forest is to give a cooling effect and shade. The increasing canopy all over the City will help lessen the city temperature and improved the warm air condition of the towns. The presence of healthy vegetation would also increase water-holding capacity in urban areas and supports soil moisture that will enhance City’s green state (Kendal & Jess, 2016). Climate change is introducing lots of threats not just in the field of environment, but mostly in the urban forestry research. The climate variations have the potential to cause pest infestation or disease emergence in urban forest areas due to extreme heat conditions. Due to these problems, it needs an innovative tactic on how to manage the city forest ecosystem, to minimize the vulnerability of the cities and maximized the potential benefits. We expect to have a rapid growth of population in most of our City areas. Introduction of green infrastructure in dense areas like cities and promoting ecosystem services will help address the pressures brought by different issues. The existence of urban forests in the towns with the provision of ecosystem services will attract more people to visit, work and live in the City (Brandt et al., 2016). Most of our urban forest is facing drought problems and water constraints due to irreversible weakening of many species of trees. Most of these trees are age-related decline. It was reported that in the next ten years, most of the tree population would end their useful life. We wanted to address these problems as early as possible and plan our urban forest in a sustainable way for the future. There are a series of tools and programs formulated to help address these issues. When we build an urban forest, we must think of its greatest benefits and the living conditions. It can support the people. It is necessary to select the correct species of trees to plant, that can hold enough water and can make keep soil moisture, reduce storm-water flows in inundated areas, improve the water quality of the cities and that give canopy cover and shade without conflicts to infrastructures (Fazio, 2010). Urban forestry is now developing a newer approach of how important it is making a City livable and sustainable. It is important that cities can adapt to unpredictable climate variations. Putting up an urban forest within a town others an enormous number of benefits to the communities, the environment and economy's well-being and health. It is necessary that we recognize and shape upon those welfares now to secure the future of our cities. A fully developed urban forest will be loved and enjoy with our children and families. The perfect time and opportunity to make our cities resilient, healthy, diverse in our future. Our primary vision is to develop a varied, and resilient forest in our cities that influence on the welfare of our communities, and to make our City livable by creating a better urban setting for every individual. The following are the strategies to adopt in the managing of the city's forest ecosystem and will transform the current City into a more priceless community in the future. • reducing the heat in our cities; • mitigate and adapt to climate change variations; • transform into a water sensitive city; • design a livable and healthy community; • preserve the cultural integrity; and • create and improve ecosystems. All these targets will give more benefits as we can think. Today, there is a unique opportunity to work as one group and develop an urban forest City that will serve as a leader for other urban forest cities worldwide. All these principles and theories will be used two strategies, modern cities across first world countries and strengthen a greener urban forest (Livesley, 2016).
Article
Soil sealing and a decrease in vegetation cover in urban areas increase the likelihood and frequency of localised flooding. Populating the remaining green areas with vegetation, which can efficiently capture excess rainfall, is therefore important. We argue that urban hedges can be a useful tool in mitigating rainfall, so the understanding of optimal plant choice, and underlying traits which enable most rain attenuation, is needed. We tested the hypothesis that higher plant evapo-transpiration rates and larger canopy size can be linked with reduced rainfall runoff in urban hedge species. We first characterised seven hedge species grown in individual containers. These were both deciduous and evergreen species, with a range of inherent canopy sizes and water requirements. We assessed their plant water use, leaf stomatal conductance, canopy rainfall retention, and runoff delay and reduction capacity. The species showing highest and lowest potential for runoff reduction were then investigated for their outdoor performance, when planted in a hedge-like form. Our findings suggest that—after 3 days between rainfall events—species such as Cotoneaster and Crataegus with larger and wide canopies, and with high evapo-transpiration/water use rates, delayed the start of runoff (by as much to 10–15 min compared to bare substrate) as well reduced the volume of rainfall runoff. For example, < 5% of the applied rainfall had runoff with Cotoneaster and Crataegus, compared with > 40% in bare substrate. Substrate moisture content at the time of rainfall (which is linked to plants’ ET rate) was the key explanatory variable.
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Green infrastructure (GI) has been identified as a promising approach to help cities adapt to climate change through the provision of multiple ecosystem services. However, GI contributions to urban resilience will not be realized until it is more fully mainstreamed in the built environment and design professions. Here, we interrogate five key challenges for the effective implementation of GI: (1) design standards; (2) regulatory pathways; (3) socio-economic considerations; (4) financeability; and (5) innovation. Methods include a literature review, case studies, and interviews with resilience managers. We propose a people-centred and context-dependent approach to advance effective implementation of GI in urban planning. We highlight two underlying currents that run across all of the challenges – (1) the role of political will as a pre-condition for tackling all challenges holistically; and (2) the role of stakeholder engagement in achieving public support, harnessing funding, and maintaining and monitoring GI in the long term. Highlights: • The effective implementation of GI is context-specific and should adhere to the basic principles of appropriate technology. • Continuous community engagement is needed to ensure the inclusivity and multi-functionality of GI. • Challenges to successful GI are intersectional and therefore cannot be addressed singly in isolation.
Article
Impervious surfaces, such as roads, parking areas, and buildings, found in cities throughout the world have significant impacts on urban hydrology due to increased volumes and peak flow rates of runoff delivered to receiving waterbodies. Bioretention practices are a common stormwater control measure (SCM) used to mitigate the impacts of urban runoff. When coupled with suspended pavement systems, which provide tree roots with an uncompacted soil matrix that enhances root access to oxygen and water, engineers can design subsurface alternatives to manage urban stormwater. Two suspended pavement systems designed to function as subsurface bioretention practices were installed on the campus of the University of Tennessee, Knoxville, Tennessee, USA. Sap flow sensors using the heat ratio method were installed in two bald cypress (Taxodium distichum) trees to characterize the role of transpiration in the suspended pavement systems. Mean transpiration rates were greater when water availability was higher in the bioretention media. Regression models indicated that atmospheric vapor pressure deficit (kPa) was the most influential environmental parameter on tree transpiration, and that stomatal regulation of water losses was evident when water was limiting. Findings from this study illustrate how tree transpiration rates can vary, even between individual trees of the same species, based on conditions within the practice and provide insight to practitioners on how design parameters influence fine‐scale tree‐water relations in bioretention systems to maximize the contributions of transpiration on system hydrology.
Article
With increases in storm frequency and intensity, municipalities are finding new ways of managing stormwater. Solutions require collaboration across planning disciplines and input from an informed public. This study compares a system of bioswales to existing curb and gutter infrastructure in a post-industrial streetscape of Hamilton, Ontario. Using the geodesign process, a section of Ottawa St. North was modelled to show how green infrastructure can ease the burden on aging, combined sewer systems. Qualitative data was gathered from residents of the neighbourhood through field notes, and quantitative geospatial data through GIS. Parametric modelling was used to generate a design, and scenarios created to show resulting impacts on stormwater run-off. The model was posted online as an interactive presentation, accessible to all stakeholders for review and comment. The results of the study demonstrate powerful new tools that can assist landscape architects in designing, collaborating and communicating stormwater strategies.
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The world's population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.
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The management of urban stormwater has become increasingly complex over recent decades. Consequently, terminology describing the principles and practices of urban drainage has become increasingly diverse, increasing the potential for confusion and miscommunication. This paper documents the history, scope, application and underlying principles of terms used in urban drainage and provides recommendations for clear communication of these principles. Terminology evolves locally and thus has an important role in establishing awareness and credibility of new approaches and contains nuanced understandings of the principles that are applied locally to address specific problems. Despite the understandable desire to have a ‘uniform set of terminology’, such a concept is flawed, ignoring the fact that terms reflect locally shared understanding. The local development of terminology thus has an important role in advancing the profession, but authors should facilitate communication between disciplines and between regions of the world, by being explicit and accurate in their application.
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This paper analyzes the processes and characteristics of urbanization in Shanghai, focusing on the population and land use and land cover (LULC) change, and its correlation with the evolution of climatic and ecological indicators based on the historical land use data, meteorological station data, social statistical data, normalized difference vegetation index (NDVI) and land surface temperature (LST) data. The possible association between urban heat island (UHI) and urbanization indicators are also discussed. Examination of the population variation indicates a continuously increase of registered population and a rapid increase of floating population that mainly comes from neighboring provinces in recent years. With rapid urban sprawl, a large amount of cultivated lands has been replaced with building lands around urban areas and towns of Shanghai. Urbanization is correlated with the increase of air temperature, hot days and the decrease of relative humidity, wind speed and vegetation NDVI in Shanghai. The growth of UHI in Shanghai has been driven by the continuous increase of buildings, paved roads, buses, population and GDP, as well as the decrease of cultivated land. Boosting the area of green land in urban areas has to a certain extent mitigated the UHI in Shanghai in recent years.
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A one-dimensional mass and energy balance model was developed to simulate rainfall interception in Sacramento County, California. The model describes tree interception processes: gross precipitation, leaf drip, stem flow, and evaporation. Kriging was used to extend existing meteorological point data over the region. Regional land use/land cover and tree canopy cover were parameterized with data obtained by remote sensing and ground sampling. Annual interception was 1.1% for the entire county and 11.1% of precipitation falling on the urban forest canopy. Summer interception at the urban forest canopy level was 36% for an urban forest stand dominated by large, broadleaf evergreens and conifers (leaf area index = 6.1) and 18% for a stand dominated by medium-sized conifers and broadleaf deciduous trees (leaf area index = 3.7). For 5 precipitation events with return frequencies ranging from 2 to 200 years, interception was greatest for small storms and least for large storms. Because small storms are responsible for most pollutant washout, urban forests are likely to produce greater benefits through water quality protection than through flood control.
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Logarithmic regression equations were developed to predict leaf area and leaf biomass for open-grown deciduous urban trees based on stem diameter and crown parameters. Equations based on crown parameters produced more reliable estimates. The equations can be used to help quantify forest structure and functions, particularly in urbanizing and urban/suburban areas. For. Sci. 42(4):504-507.
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The aim of this study was to test the possibility of using geoelectrical measurements to detect and differentiate different root samples of trees rooted in dikes. A laboratory experiment was performed to describe the electrical signal of buried freshly cut root samples according to tree species, root sample orientation and number and nature of earthfill materials. The geoelectrical measurements were performed at the soil surface in containers. First, the electrical properties of three soil materials (gravel, sand and silt) were characterized in containers without buried roots. In subsequent steps, the root samples were buried at a depth of 0.05m with different orientations: horizontally and parallel or perpendicular to the electrode array, and vertically. The complex conductivity spectra were observed in the frequency range 22.9mHz–750Hz. The measurements without buried roots were repeated after completing all the measurements with the roots. In most cases, the conductivity of buried root samples increased the integral conductivity of the ground. This trend was observed mainly in gravel and sand. The parallel orientation resulted in the most significant increase of the real part of conductivity. Channelling of the current flow in the root seems to be a reliable explanation. This laboratory experiment now opens the way for in-situ measurement. KeywordsRoot detection–Electrical measurements–Induced polarisation–Wood electrical properties–Earth dike materials
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The world’s population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.
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The Middle Chattahoochee River Watershed in western Georgia is undergoing rapid urban development. Consequently, Georgia’s water quality is threatened by extensive development as well as other land uses such as grazing. Maintenance of stream water quality, as land development occurs, is critical for the protection of drinking water, biotic integrity, and stream morphology. A two-phase, watershed-scale study was established to develop relationships among land use and water quality within western Georgia. During phase 1 (year one), physio-chemical, biological and morphological measurements were taken within 16 sub-watersheds, ranging in size from 500–2500 ha. Nutrient and fecal coliform concentrations within watersheds with impervious surface > 5% often exceeded those in other watersheds during both baseflow and storm flow. Also, fecal coliform bacteria in more urbanized areas often exceeded the US EPA’s standard for recreational waters. During the second phase of the study, models will be tested and calibrated based on newly chosen watersheds.
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Limitations to vegetation establishment and abundance in biofiltration swales (also called biofilters or bioswales), vegetated storm-water facilities intended to improve runoff water quality, was studied through field monitoring and greenhouse experimentation. The various environmental factors influencing vegetation and organic litter abundance was investigated in eight bioswales in western Washington state, including three that were retrofitted. A nested 4×4 factorial greenhouse experiment tested the response of four turfgrass species commonly seeded in bioswales to three inundation regimes plus a control. In the greenhouse experiment and in the field, persistent inundation significantly suppressed germination and growth. Field monitoring further revealed that heavy shade overwhelms all other environmental factors. Where light is adequate, vegetation and organic litter biomass is strongly and inversely related to the proportion of time bioswales are inundated above 2.5-cm depth during the driest time of year (summer). For most bioswales, flow velocity and hydraulic loading during storm events appear too large to permit sedimentation of silt and clay particles, even with dense vegetation and abundant organic litter. Thus, herbaceous vegetation abundance may not provide a good indication of bioswale treatment performance, and actual storm-water treatment may be much poorer than is generally anticipated from previous studies.
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Europe is a highly urbanised continent. The consequent loss and degradation of urban and peri-urban green space could adversely affect ecosystems as well as human health and well-being. The aim of this paper is to formulate a conceptual framework of associations between urban green space, and ecosystem and human health. Through an interdisciplinary literature review the concepts of Green Infrastructure, ecosystem health, and human health and well-being are discussed. The possible contributions of urban and peri-urban green space systems, or Green Infrastructure, on both ecosystem and human health are critically reviewed. Finally, based on a synthesis of the literature a conceptual framework is presented. The proposed conceptual framework highlights many dynamic factors, and their complex interactions, affecting ecosystem health and human health in urban areas. This framework forms the context into which extant and new research can be placed. In this way it forms the basis for a new interdisciplinary research agenda.
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The rain garden is an urban storm water best management practice that is used to infiltrate runoff close to its source, thereby disconnecting impervious area while providing an avenue for groundwater recharge. Groundwater recharge may provide additional benefits to aquatic ecosystems via enhancement of stream base flow. Yet, soil conditions can impact on certain aspects of rain garden performance and its provision of ecosystem services. In the context of a watershed-level study to determine the effectiveness of decentralized storm water management, we performed an order 1 soil survey of the Shepherd Creek watershed (Cincinnati, Ohio) to delineate soils and identify and describe representative soil pedons, and then we assessed subsoil saturated hydraulic conductivity (Ksat) in each of the three dominant subsoils with qualitative estimation methods and directly with constant-head permeametry. We next simulated the effect of subsoil hydrology of a hypothetical implementation of a par- cel-level rain garden on groundwater recharge in this watershed. Measured subsoil Ksat were overall very low with a mean of 0.01 cm hr-1 (4 × 10-3 in hr-1) for Eden soil and a mean of 0.2 cm hr-1 (0.08 in hr-1) for both the fine-silty family and Switzerland soils. Compared with the measured values, qualitative measures overestimated Ksat and depth of recharge for Eden and fine-silty, and underestimated the same for Switzerland. Based on median parcel features and 2004 warm-season storm records, rain gardens in the fine-silty family and Switzerland subsoils would be expected to contribute about 6 cm (2.4 in) of recharge as compared to the 2 cm (0.8 in) expected in Eden soils. Our results also suggest the highest potential for abate- ment of storm water quantity abatement in Eden soils, with some partitioning of this water to recharge as an added benefit. Our approach and results form the basis for a comprehensive understanding of how storm water management decentralized at the watershed level may positively impact ecosystem services.
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The impact of urbanization on stream ecosystems is linked by land cover changes to the alteration of the natural hydrology and subsequent physical disruption of stream biota and habitat. Seasonal floods are part of the natural disturbance regime of many streams, but urbanization increases their frequency and magnitude. This study evaluated the impact of hydrologic disturbance on fish and aquatic macroinvertebrates in 81 (56 urban/25 reference) Ohio streams. Hydrologic variables included annual and monthly 24-h rainfall maxima and computed annual peak discharge, with computation supported by GIS-based drainage area delineation and land cover characterization. Ohio biological criteria for fish and macroinvertebrates measured during the late spring and summer were negatively impacted by annual peak discharge in urban streams as compared to reference streams. Results support the application of stormwater best management practices as part of stream restoration efforts to mitigate urbanization impacts to fish and macroinvertebrates.
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Global land use patterns and increasing pressures on water resources demand creative urban stormwater management. Strategies encouraging infiltration can enhance groundwater recharge and water quality. Urban subsoils are often relatively impermeable, and the construction of many stormwater detention best management practices (D-BMPs) exacerbates this condition. Root paths can act as conduits for water, but this function has not been demonstrated for stormwater BMPs where standing water and dense subsoils create a unique environment. We examined whether tree roots can penetrate compacted subsoils and increase infiltration rates in the context of a novel infiltration BMP (I-BMP). Black oak (Quercus velutina Lam.) and red maple (Acer rubrum L.) trees, and an unplanted control, were installed in cylindrical planting sleeves surrounded by clay loam soil at two compaction levels (bulk density = 1.3 or 1.6 g cm(-3)) in irrigated containers. Roots of both species penetrated the more compacted soil, increasing infiltration rates by an average of 153%. Similarly, green ash (Fraxinus pennsylvanica Marsh.) trees were grown in CUSoil (Amereq Corp., New York) separated from compacted clay loam subsoil (1.6 g cm(-3)) by a geotextile. A drain hole at mid depth in the CUSoil layer mimicked the overflow drain in a stormwater I-BMP thus allowing water to pool above the subsoil. Roots penetrated the geotextile and subsoil and increased average infiltration rate 27-fold compared to unplanted controls. Although high water tables may limit tree rooting depth, some species may be effective tools for increasing water infiltration and enhancing groundwater recharge in this and other I-BMPs (e.g., raingardens and bioswales).
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The southeastern United States is experiencing rapid urban development. Consequently, Georgia's streams are experiencing hydrologic alterations from extensive development and from other land use activities such as livestock grazing and silviculture. A study was performed to assess stream hydrology within 18 watersheds ranging from 500 to 2500 ha. Study streams were first, second, or third order and hydrology was continuously monitored from 29 July 2003 to 23 September 2004 using InSitu pressure transducers. Rating curves between stream stage (i.e., water depth) and discharge were developed for each stream by correlating biweekly discharge measurements and stage data. Dependent variables were calculated from discharge data and placed into 4 categories: flow frequency (i.e., the number of times a predetermined discharge threshold is exceeded), flow magnitude (i.e., maximum and minimum flows), flow duration (i.e., the amount of time discharge was above or below a predetermined threshold), and flow predictability and flashiness. Fine resolution data (i.e., 15-min interval) were also compared to daily discharge data to determine if resolution affected how streams were classified hydrologically. Urban watersheds experienced flashy discharges during storm events, whereas pastoral and forested watersheds showed less flashy hydrographs. Also, in comparison to all other flow variables, flow frequency measures were most strongly correlated to land cover. Furthermore, the stream hydrology was explained similarly with both the 15-min and daily data resolutions.
Article
Eutrophication in coastal ecosystems is often attributed to elevated nitrogen levels. Reducing the amount of nitrogen entering Port Phillip Bay is therefore an important objective for Melbournians. This article details the performance of a pilot scale street tree bioretention system in reducing nitrogen loads in urban stormwater. Three tree species (Eucalyptus polyanthemos, Lophostemon confertus and Platanus orientalis) and three sandy soils of different hydraulic conductivity (4, 95 and 170 mm/hr) were tested in a randomised block design. Over the course of the experiment, all species displayed seasonal height growth patterns with maximum growth rates occurring in late Spring and Summer. Applications of stormwater increased height growth and root length density compared with tapwater applications. Tree growth was similar in the three soils studied. During the warmer months, leachate volumes from the planted systems were significantly less than the unplanted systems due to transpirational drying. Leached nitrogen loads were significantly reduced in systems with a tree. Whilst there were some statistically significant differences in ammonium, oxidised nitrogen and organic nitrogen removal between species, these were not large in practical terms. In December, total nitrogen load removal from stormwater was 82 to 95% in planted systems (L. confertus), compared to 36 to -7% in the unplanted systems
Article
Understanding how trees influence water movement in an urban landscape is important because in an ‘engineered xeriscape’ small changes in rainfall frequency or magnitude have significant implications to plant water availability and mortality at one extreme, and stormwater runoff and flooding at the other. This study relates direct measures of tree canopy interception and discusses their implication for catchment hydrology in different urban landscape contexts. We measured canopy throughfall and stemflow under two eucalypt tree species in an urban street setting over a continuous five month period. Eucalyptus nicholii has a dense canopy and rough bark, whereas Eucalyptus saligna has a less-dense canopy and smooth bark. E. nicholii, with the greater plant area index, intercepted more of the smaller rainfall events, such that 44% of annual rainfall was intercepted as compared to 29% for the less dense E. saligna canopy (2010). Stemflow was less in amount and frequency for the rough barked E. nicholii as compared to the smooth barked E. saligna. However, annual estimates of stemflow to the ground surface for even the smooth barked E. saligna would only offset approximately 10 mm of the 200 mm intercepted by its canopy (2010). Tree canopy and bark characteristics should be considered when planting in pervious green space, or impervious streetscapes, because of their profound impact upon tree and surrounding water availability, soil water recharge or runoff. This study provides an evidence base for tree canopy impacts upon urban catchment hydrology, and suggests that rainfall and runoff reductions of up to 20% are quite possible in impervious streetscapes. Street tree canopies can function as a cost-effective compliment to water sensitive urban design for stormwater reduction benefits.
Article
We used a two-layer canopy model to study transpiration of tree species as affected by energy-balance properties of a vegetated and paved surface. During several dawn-to-dusk studies, tree transpiration, stomatal conductance, leaf temperature (Tl), and several microclimate variables, were measured over turf and an asphalt surface. Cumulative transpiration was estimated from a leaf energy-balance equation applied to a tree crown apportioned between sunlit and shaded layers. Afternoon asphalt surface temperatures (Ts) were 20–25°C higher than turf Ts in all studies. Air-temperature differences between sites were minimal due to the size and proximity of the two surfaces that resulted in mixing of air. Trees over asphalt had consistently higher T, than those over turf, apparently due to interception of the greater upwards long-wave radiation flux from higher Tl. In one study flowering pear over asphalt in a humid environment bad higher Tl resulting in one-third more total water loss compared to trees over turf. In other studies, however, water loss of green ash and Norway maple over asphalt in an arid environment was either equal to or less than that over turf. Less water loss was due to higher Tl over asphalt causing prolonged stomatal closure. Model manipulation indicated that tree water loss over asphalt will depend on the degree of stomatal closure resulting from how interception of increased energy-fluxes and ambient humidity affect leaf-to-air vapor pressure differences.
Article
Urban street-tree-planter soils provide inadequate growing space for root systems of trees and are subject to increased concentrations of pollutants not typically found in native soils. An examination of planting media in selected Geneva, Illinois street tree planters revealed physical and chemical soil properties that Only the most stress-tolerant species could endure. The planter soils generally consisted of brick rubble, gravel, sand, and cinders. Drainage in the planters was impeded due to textural discontinuities. Soil pH and sodium values were high enough to classify these soils as sodic. Sodic soils naturally occur in arid and semi-arid regions where evapotranspiration exceeds precipitation. Planter soils need testing for physical and chemical characteristics before being used for trees. They can then be modified, if necessary, to provide the plant with the best possibilities to survive the urban environment.
Article
The impacts of land use intensity, here defined as the degree of imperviousness, on stormwater volumes, runoff rates and their temporal occurrence were studied at three urban catchments in a cold region in southern Finland. The catchments with ‘High’ and ‘Intermediate’ land use intensity, located around the city centre, were characterized by 89% and 62% impervious surfaces, respectively. The ‘Low’ catchment was situated in a residential area of 19% imperviousness. During a 2-year study period with divergent weather conditions, the generation of stormwater correlated positively with catchment imperviousness: The largest annual stormwater volumes and the highest runoff coefficients and number of stormwater runoff events occurred in the High catchment. Land use intensity also altered the seasonality of stormwater runoff: Most stormwater in the High catchment was generated during the warm period of the year, whereas the largest contribution to annual stormwater generation in the Low catchment took place during the cold period. In the two most urbanized catchments, spring snow melt occurred a few weeks earlier than in the Low catchment. The rate of stormwater runoff in the High and Intermediate catchments was higher in summer than during spring snow melt, and summer runoff rates in these more urbanized catchments were several times higher than in the Low catchment. Our study suggests that the effects of land use intensity on stormwater runoff are season dependent in cold climates and that cold seasons diminish the differences between land use intensities. Copyright © 2013 John Wiley & Sons, Ltd
Article
A bioswale integrating an engineered soil and trees was installed in a parking lot to evaluate its ability to reduce storm runoff, pollutant loading, and support tree growth. The adjacent control and treatment sites each received runoff from eight parking spaces and were identical except that there was no bioswale for the control site. A tree was planted at both sites. Storm runoff, pollutant loading, and tree growth were measured. There were 50 storm events with a total precipitation of 563.8 mm during February 2007 and October 2008. The bioswale reduced runoff by 88.8% and total pollutant loading by 95.4%. The engineered soil provided a better aeration and drainage for tree growth than did the control's compacted urban soil. The superior performance of the bioswale demonstrated its potential use for large-scale application in parking lots and roadsides to reduce runoff and support tree growth.
Article
Biofiltration systems are a recommended and increasingly popular technology for stormwater management; however there is a general lack of performance data for these systems, particularly at the field scale. The objective of this study was to investigate the hydrologic and pollutant removal performance of three field-scale biofiltration systems in two different climates. Biofilters were shown to effectively attenuate peak runoff flow rates by at least 80%. Performance assessment of a lined biofilter demonstrated that retention of inflow volumes by the filter media, for subsequent loss via evapotranspiration, reduced runoff volumes by 33% on average. Retention of water was found to be most influenced by inflow volumes, although only small to medium storms could be assessed. Vegetation was shown to be important for maintaining hydraulic capacity, because root growth and senescence countered compaction and clogging. Suspended solids and heavy metals were effectively removed, irrespective of the design configuration, with load reductions generally in excess of 90%. In contrast, nutrient retention was variable, and ranged from consistent leaching to effective and reliable removal, depending on the design. To ensure effective removal of phosphorus, a filter medium with a low phosphorus content should be selected. Nitrogen is more difficult to remove because it is highly soluble and strongly influenced by the variable wetting and drying regime that is inherent in biofilter operation. The results of this research suggest that reconfiguration of biofilter design to manage the deleterious effects of drying on biological activity is necessary to ensure long term nitrogen removal.
Article
A large-scale column study was conducted in Melbourne, Australia, to test the performance of stormwater biofilters for the removal of sediment, nitrogen and phosphorus. The aim of the study was to provide guidance on the optimal design for reliable treatment performance. A variety of factors were tested, using 125 large columns: plant species, filter media, filter depth, filter area and pollutant inflow concentration. The results demonstrate that vegetation selection is critical to performance for nitrogen removal (e.g. Carex appressa and Melaleuca ericifolia performed significantly better than other tested species). Whilst phosphorus removal was consistently very high (typically around 85%), biofilter soil media with added organic matter reduced the phosphorus treatment effectiveness. Biofilters built according to observed 'optimal specifications' can reliably remove both nutrients (up to 70% for nitrogen and 85% for phosphorus) and suspended solids (consistently over 95%). The optimally designed biofilter is at least 2% of its catchment area and possesses a sandy loam filter media, planted with C. appressa or M. ericifolia. Further trials will be required to test a wider range of vegetation, and to examine performance over the longer term. Future work will also examine biofilter effectiveness for treatment of heavy metals and pathogens.
Article
Stormwater runoff is an important source of toxic substances to the marine environment, but the effects of antecedent dry period, rainfall intensity, and duration on the toxicity of runoff are not well understood. In this study, simulated rainfall was applied to parking lots to examine the toxicity of runoff while controlling for antecedent period, intensity, and duration of rainfall. Parking areas were divided into high and low use and maintained and unmaintained treatments. The parking stalls were cleaned by pressure washing at time zero. Simulated rainfall was then applied to subplots of the parking lots so that antecedent periods of 1, 2, and 3 months were achieved, and all of the runoff was collected for analysis. On a separate parking lot, rainfall was applied at a variety of intensities and durations after a 3-month antecedent period. Runoff samples were tested for toxicity using the purple sea urchin fertilization test. Every runoff sample tested was found to be toxic. Mean toxicity for the sea urchin fertilization test ranged from 2.0 to 12.1 acute toxic units. The toxicity increased rapidly during the first month but then decreased approximately to precleaning levels and remained there. No difference in toxicity was found between the different levels of use or maintenance treatments. The intensity and duration of rainfall were inversely related to degree of toxicity. For all intensities tested, toxicity was always greatest in the first sampling time interval. Dissolved zinc was most likely the primary cause of toxicity based on toxicant characterization of selected runoff samples.
Article
Biofiltration systems use vegetation to improve efficiency of pollutant removal from stormwater, but little is known of how plants vary in their capacity to improve biofilter effectiveness. We used a pot trial of 20 Australian species to investigate how species vary in the removal of pollutants from semisynthetic storm water passing through a soil filter medium. Effluent levels of total suspended solids (TSS), Al, Cr, Cu, Pb and Zn were similarly low for vegetated and non-vegetated soils, with reduction to <1-12% of levels in the stormwater input. N and P effluent concentrations were generally lower from vegetated than non-vegetated soils, but total N increased on average in effluent of both vegetated and non-vegetated soils relative to stormwater input. Effluent concentrations varied 2-4-fold among species for TSS, total N and P, total dissolved N (TDN), organic nitrogen and Cu, to more than 20-fold for NOx, NH4+, Mn, Pb and Fe. Species also varied markedly in pollutant removal per root mass (a means of standardising for plant size), with 18-50-fold variation among species in effluent concentrations of total P and N, TDN and organic N, to >150-fold variation in NOx and NH4+. Hence, choice of plant species may have marked effects on biofilter effectiveness.
Urban tree health: A practical and precise estimation method
  • J Bond
Bond, J. 2012. Urban tree health: A practical and precise estimation method. Urban Forest Analytic, Geneva, NY.
Street trees as stormwater treatment measures
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Breen, P., L. Denman, P. May, and S. Leinster. 2004. Street trees as stormwater treatment measures. In: WSUD 2004: Cities as catchments. International Conference on Water Sensitive Urban Design, Proceedings of. Engineers Australia, Barton, Australia. p. 701.
Methods of soil analysis. Part 3. Chemical methods
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Nelson, D.W., and L.E. Sommers. 1996. Total carbon, organic carbon, and organic matter. In: A.L. Page, et al., editors, Methods of soil analysis. Part 3. Chemical methods. SSSA Book Ser. 3. SSSA, Madison, WI. p. 961-1010.
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Urban soil primer. USDA-NRCS National Soil Survey Center
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Scheyer, J.M., and K.W. Hipple. 2005. Urban soil primer. USDA-NRCS National Soil Survey Center, Lincoln, NE.
Methods of soil analysis. Part 3. Chemical methods
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Thomas, G.W. 1996. Soil pH and Soil Acidity. In: D.L. Sparks, editor, Methods of soil analysis. Part 3. Chemical methods. SSSA Book Ser. 3. SSSA, Madison, WI. p. 475-490.
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