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How effective are drainage systems in mitigating flood losses?
Abstract
The impacts of flooding can be devastating. Huge financial burden often follows major storm events to recover from structural damage. Well-designed drainage systems allow for effective discharge of stormwater, reducing property losses and expenditures on recovery. However, a lack of empirical studies on the topic has impeded the determination of which drainage method might be the most effective in preventing or minimizing property losses from flooding. This study assessed the economic impacts of three drainage systems − storage-, conveyance-, and infiltration-based facilities – on reducing flood damage recorded from 2009 to 2012 by Federal Emergency Management Agency in the Buffalo Bayou watershed in Houston, Texas, USA. Ordinary least squares and spatial autoregressive models were developed with a group of variables featuring drainage system, housing structure, geophysical environment, and storm characteristics. The results show that storage-based systems outperform conveyance-based mechanisms. Infiltration-based facilities are found to be less effective in reducing property damage because green spaces disconnected from sewer systems are rapidly inundated after being saturated while excessive overflow is not properly drained. This study confirms that the performance of a drainage system varies by facility type and environmental setting. The results encourage the recovery of wetlands and integration of retention/detention basins into community development in flood-prone areas to prevent potential future economic losses.
... Similar strategies were implemented by communities in Limpopo, South Africa (Munyai et al., 2021). The introduction of drains along the roads was an active flood prevention strategy that reduced flood damage costs by 19% (Sohn et al., 2020). ...
... A culture for flood resilience is another key factor that supports strategy implementation. Drain channels and permeable surfaces require maintenance to continue to remain effective (Sohn et al., 2020;Joseph et al., 2011;Brisibe, 2018). Governments, institutions and communities have contributing roles. ...
... Delayed maintenance and overlooked allocation for maintenance were some of the risks leading to floods. Over time, drainage and permeable surfaces may lose their absorbing properties (Sohn et al., 2020). Debris and soil may fill up these surfaces and clog drain channels leading to compromised performance. ...
Flood is a reoccurring disaster throughout the world. With the increasing effects of climate change, the occurrence of floods is predicted to increase, impeding development and growth. Moving forward towards 2030, the United Nations calls for a strategic recovery, rehabilitation and reconstruction that embodies the “build back better” approach. Existing disaster risk reduction efforts for floods have focused on restorative and preventive measures through an integrated architectural response that encompasses the experiential and inherited knowledge of communities living in flood-prone areas together with technological and disaster risk reduction operations for flood resilience. The study utilised current literature reviews to identify environmental, social and governance (ESG) domains for risk reduction and three key strategies from the ESG domains, extending towards urban design for disaster management opportunities. Results were collated and analysed through a thematic literature review from local and international knowledge. The findings suggested that it is vital to respond to and attend to the ESG-integrated approach to promote and sustain resilient urban design and architecture. The study presented a holistic urban design framework towards flood resilience.
... The main limitations include a restricted typology of study objects and insufficient analysis of cascading effects in urban entity semantic changes. For instance, Alabbad et al. (2021) examined the dynamic impacts of floods on transportation facility functions, while Arrighi et al. (2017) and Sohn et al. (2020) studied flood impacts on water supply systems; however, these studies did not address the interaction mechanisms within these systems. Similarly, Dong et al. (2020) investigated the relationship between critical facilities' physical vulnerability and community tolerance but only focused on differential impacts under various flood scenarios, neglecting facility interdependencies. ...
... Compared to previous research often limited to single domains (e.g. Arrighi et al. 2017;Sohn et al. 2020 on water supply systems, Guimarães et al. 2021 on power facilities) or using simplified relationship models, this method leverages the generalization capabilities of LLMs and the rich structural information of knowledge graphs to dynamically reveal potential, non-intuitive interactions and failure pathways between different infrastructure systems (e.g. power outages affecting communications, which in turn affect emergency responses), advancing the 'System-of-Systems' holistic understanding of flood impacts. ...
Urban flood impact assessment is crucial for effective disaster management. These impacts, driven by changes in entity semantics (function, status), are essential for understanding the true vulnerabilities of urban systems, while current assessment models suffer from low intelligence and poor accuracy in this regard. To address this challenge, this research proposes a novel framework integrating hydrodynamic simulation, knowledge graphs, and semantic reasoning with Large Language Models (LLMs). The framework simulates flood physical processes, combines urban entity knowledge graphs, and utilizes LLMs to automatically reason the dynamic evolution of functional attributes and cross-domain impact chains. Key results demonstrate that this method effectively identifies both known and unknown cascade impact pathways, with LLM reasoning showing high logical consistency (LC = 0.91) in cross-model validation, and automatically inferred impact chains rated as highly reasonable by experts (average score 3.99/5). By introducing dynamic analysis at the semantic level, this research significantly enhances the automation and depth of flood impact assessment, providing a powerful tool for revealing potential functional vulnerabilities in urban systems, which has important implications for improving disaster resilience.
... Z-score < -2.58 or > 2.58 is always followed by p-value < 0.01, while z-score <-1.96 or > 1.96 obtains p-value < 0.05, and z-score < -1.65 or > 1.65 produces p-value < 0.10, assuring statistical confidence level (Hassan et al., 2017;Qiang, 2019;Shariati et al., 2022) 3. Correlation analysis is a methodology employed to investigate the relationship between the categorization of drainage conditions and flood intensity levels within each RT. This approach allows for evaluating the effectiveness of drainage systems in flood mitigation within specific regions (Sohn et al., 2020). The dataset for this examination comprises the scoring derived from the cluster analysis outputs related to flood intensity and drainage conditions, as outlined in Table 1. ...
... Finally, drainage conditions are crucial in flood disaster management for controlling water flow and stormwater to mitigate potential flooding risks (Ndoma et al., 2020;Sohn et al., 2020). Adequate drainage systems have the capacity to effectively manage and direct surface runoff during rainfall. ...
The flood events frequently impacting Samarinda City have not yet been thoroughly examined based on their intensity, particularly in the most flood-prone village in the city, East Sempaja Village. This paper employed a rigorous methodology, including K-means cluster analysis and Getis-Ord G* statistics, to reveal spatial clustering patterns based on flood intensity and residential drainage conditions in East Sempaja. The Spearman correlation was determined to identify the relationship between both factors. The present study demonstrates that using community-derived data can enhance flood disaster mitigation strategies, particularly within regions with insufficient data availability. The analysis shows that most neighborhood areas in East Sempaja have moderate to high flood intensity levels. The areas with high flood intensity are spread across the North. This paper confirms that the condition of drainage channels has a positive, yet weak, significant relationship with the level of flood intensity. Thus, optimizing drainage channels is still relevant in managing flood disasters in East Sempaja, providing practical strategies for a pressing issue.
... In addition, drainage systems provide other benefits such as improving water quality by removing pollutants from stormwater runoff and providing a reliable source of water for irrigation and other uses [15]. Several studies have shown the effectiveness of drainage systems in mitigating the negative effects of heavy rainfall events such as reducing the damage caused by flooding during a heavy rainfall event [16,17]. However, drainage systems also have some limitations and challenges. ...
... Because of the challenges in designing and implementing sustainable drainage system models on rainfall control, there are a few studies in this regard. Therefore, no ample Sustainability 2024, 16, 7349 3 of 30 evidence is found of its effectiveness. The effectiveness of green infrastructure for enhancing livability in different cities was explored through adapting effective measures such as mitigation of stormwater issues and promotion of water quality. ...
Heavy rainfall, a natural phenomenon reinforced by climate change and global warming, can cause severe social, economic, and safety impacts. Due to the impact of climate change and global warming, heavy rainfall events have become more frequent and intense in recent years, underscoring the urgent need to develop robust stormwater management systems that can prevent related social, economic, and safety issues. This is of greater importance in developing countries. The present study identified areas in Urmia City, Iran, that require stormwater management to develop a comprehensive understanding of the hydrological processes within the study area and to prevent the subsequent effects of heavy rainfall. For this purpose, a combination of the watershed modeling system (WMS) and stormwater management model (SWMM) was employed. Also, three possible scenarios that could be implemented to address the issue of water flow in the medium were proposed. Results indicated that the scenario involving the application of a vegetative swale was the most promising solution. Overall, the results of the present study offer a valuable framework for decision-makers in regions facing heavy rainfalls to effectively manage and minimize the adverse impacts of such events.
... Previous research on NbS in urban areas covers heatwaves, water management, or air pollution (Babí Almenar et al., 2021;Kabisch et al., 2017). There are also studies specific to flood hazards; however, the cases are often cities in developed countries, particularly European cities (Green et al., 2016;Davis & Naumann, 2017;Ferreira et al., 2020Ferreira et al., , 2021Maragno et al., 2018;Nedkov & Burkhard, 2012;Sohn et al., 2020;Stürck et al., 2014). NbS are being studied and adopted in Singapore, Berlin, and other European cities (Ferreira et al., 2020). ...
... Policy options include compensation for flood water storage, payment for ecosystem services or the declaration of new natural protected areas to incentivise the provision of flow regulation in communal and ejido lands. Alternatively, charges to disincentivise risk-increasing management could be introduced, such as a "vulnerable natural area tax" of up to 2 % of building construction costs, imposed on developers, as used in France, or a mitigation banking system like that in the United States, where a developer compensates for water storage losses by purchasing credits from a mitigation banker who preserves and restores wetlands at another site (Sohn et al., 2020). The least desirable scenario is the status quo, where targeted instruments are lacking to compensate landholders for peri-urban insurance values. ...
Floods are one of the most frequent natural hazards in almost every country, with climate change exacerbating their frequency and intensity. Nature-based solutions (NbS) can be a cost-effective way to make human settlements more resilient to flooding. However, decision-makers need reliable information on which to base NbS policy and funding.
This research estimates the potential of peri-urban NbS to regulate water flow and the benefits downstream through the development of supply and demand indicators for the context of complex megacities. In our Mexico City case study the supply indicator is the runoff coefficient, which is spatially estimated across peri-urban areas, and the economic value is estimated using replacement cost (grey infrastructure). The demand indicator identifies floodprone areas based on spatially explicit ponding events and avoided costs of insurance flood claims data and estimates with parametric cost functions. The supply indicator provides straightforward information for decisionmakers to spatially target conservation in peri-urban areas where runoff coefficients are high combined with flood-prone areas, while the lowest coefficients reinforce the importance of policies for protected areas. In combination with demand indicator information, we find NbS in peri-urban upstream catchments is cost-effective compared to avoidable flood-related costs and alternative investments in grey infrastructure.
... In terms of the residents' defense in their property, before and after the pumping station was established, they only had a home drainage system. As Sohn et al. (2020) emphasized, these properly planned drainage systems effectively provide efficient stormwater discharge and lower property damage and recovery costs. This effectiveness can mitigate floods and reduce property destruction. ...
Flooding affects several low-lying regions in Metro Manila, such as Valenzuela City, and is usually among the worst hit in every series of flooding. Hence, certain low-lying areas are still exposed and deal with flooding. These flooding situations turned into a significant turning point in the Philippine government's commitment to flood control. The pumping station is one such initiative, aimed at mitigating flooding and managing water waste. Thus, this study aims to evaluate the functionality in reducing the frequency, intensity, and contribution to enhancing urban flood resilience. Moreover, this paper employs a mixed-method approach to gain in-depth understanding, knowledge and strengthen the reliability and validity of the information and data gathered. This approach provides comprehensive data that Local Government Units (LGUs) can use to develop the project further. Based on the study, the researchers found out that the pumping stations are very effective flood control project since they will quickly alleviate flooding in a short period of time and continuously operate even when it is not raining. Additionally, the pumping station has the potential to enhance residence safety, beginning with the local government and continuing up to the national level, as long as it continues to manage solid waste since waste can cause malfunction in the pumping station. Concerning this, it is important to establish a policy and program recommendation designed to strengthen the operations of pumping station projects in Valenzuela City.
... These results indicate that hydrological networks in the same catchments with high connectivity would result in a similar habitat environment, which is more likely to have led to the expansion of one type of BCE (McCauley et al., 2015). At the same time, high FDD could regulate water flow, reducing the impact of floods and stabilizing the environment, which can help BCEs establish and expand (Sohn et al., 2020). ...
... Therefore, surface hardness and water-stable aggregates are selected as specific indicators for MLYF with structural obstacles. Third, waterlogging typically occurs in low-lying areas with poor drainage and is often exacerbated by continuous precipitation or heavy rainstorms [59]. Drainage conditions refer to the ability of farmland to remove surface water and groundwater, which directly influences the soil moisture status. ...
This study aims to systematically examine the concept and characteristics of medium–low yield farmland (MLYF), to identify the key factors influencing the coordination between soil carbon sequestration (SCS) and production capacity (PC) in MLYF, and develop an evaluation indicator system (EIS) to provide innovative approaches for transforming MLYF to enhance food security and emission reduction capabilities. Focusing on the synergistic improvement of SCS and PC in MLYF, this research employs theoretical analysis, systematic inference, and inductive deduction to analyze the relationships between these factors and construct the EIS. The findings reveal that (1) MLYF is characterized by inherent limitations and suboptimal management practices, resulting in low grain PC but significant potential for yield improvement. (2) A positive correlation exists between the soil organic carbon (SOC) content and crop yield, with MLYF demonstrating substantially greater potential for synergistic improvement than high-yield fields. (3) On the basis of soil science principles, the key factors affecting the synergistic enhancement of carbon sequestration and productivity in MLYF include climatic conditions, soil properties, and biological factors. (4) A comprehensive “Demand-Function-Dimension-Element-Indicator” framework was established, incorporating an EIS designed for national, provincial, and city/county levels to address the management requirements of MLYF across various scales, thereby facilitating comprehensive quality improvement. This research contributes to the theoretical understanding of MLYF transformation, offering valuable insights for ensuring national food security and achieving carbon emission reduction goals.
... Rights reserved. et al., 2020;Sohn et al., 2020), which emphasizes the vital role that efficient drainage systems play in urban sustainability and flood mitigation. Significant changes are required since the GCC's inadequate drainage infrastructure not only has an impact on day-to-day living but also offers serious health concerns to the population, especially during the monsoon season (Haque et al., 2023a, b). ...
This study investigates the governance practices and their impact on urban sustainability in four city corporations in Bangladesh—Rajshahi, Sylhet, Barisal, and Gazipur—through the lens of Sustainable Development Goal 11 (SDG 11). Employing a mixed-methods approach, primary data was collected from 1200 residents and key informant interviews (KIIs) with local authorities. The study reveals significant infrastructure inadequacies, particularly in drainage and waste management systems, with Gazipur City Corporation (GCC) facing the most severe challenges. Disaster management practices are found to be insufficient, especially in GCC, highlighting the need for more robust community-based disaster risk management. The prevalence of illegal land occupation in GCC poses threats to local development and environmental conservation, contrasting with milder issues in other cities. Urban parks, crucial for environmental health, suffer from poor maintenance and accessibility, particularly in GCC and Sylhet City Corporation (SCC). Exploratory factor analysis identifies four key factors—illegal activities, facilities, management, and environment of entertainment places—impacting urban governance and sustainability. Significant variation in the SDG- 11 index among the city corporations indicates differing levels of progress, with SCC on a better track compared to RCC, BCC, and GCC. The study’s policy implications stress the need for modernizing infrastructure, adopting green technologies, improving disaster management, and strengthening land governance.
... Furthermore, research [32] examined the impact of climate change on port drainage systems and proposed adaptation strategies to enhance resilience to flooding and waterlogging, such as raising infrastructure elevations and using waterresistant materials. Regular maintenance of drainage channels, cleaning of debris and sediment, and monitoring system performance are also crucial to ensuring the effectiveness of the drainage system [33,34]. ...
... Drainage is a system or method used to channel excess water away from an area to prevent flooding and manage surface water [1,2]. Effective drainage systems are crucial for maintaining the quality of roads and other infrastructure [3][4][5][6], as excess water can lead to structural damage, accelerate surface degradation, and increase the risk of flooding [7][8][9][10]. ...
This study aims to determine the rainfall distribution calculations, the consistency of rainfall data, and the drainage channel dimensions on the Pondoktisuk-Kebonkai road section Sta 1+700 – 1+800 in Nagrak District, Sukabumi Regency. The methodology used includes literature review, field observation, collection of primary data such as daily rainfall data over the past 14 years and catchment area data, as well as secondary data including field documentation and location maps. Hydrological analysis was conducted through maximum rainfall calculation, design rainfall calculation, consistency data testing, probability distribution, distribution fitting tests, rainfall intensity analysis, rainwater storage volume calculation, concentration time calculation, flood discharge analysis, and open drainage dimension calculation. The results show that the calculated water flow velocity is 1.323 m/s with a slope of 0.20%. Based on the checking process, the design meets the standard requirements for allowable water flow velocity (1.50 m/s) and slope (1%). A comparison of the planned drainage slope with the existing land slope at the study site indicates that the calculated slope is lower than the existing slope (1%), thus requiring the design of a flow breaker. The rainfall distribution calculation for the Pondoktisuk-Kebonkai road section Sta 1+700 – 1+800 in Nagrak District, Sukabumi Regency, represents all the methods used, with the Gumbel method showing the highest rainfall in all return periods. The rainfall data consistency calculation indicates that Q/n^0.5 and R/n^0.5 are smaller than their critical values, at 0.32 and 0.51 respectively, thus the data is deemed consistent. The drainage channel dimension of 80x80x100 cm with a thickness of 10 cm meets the requirements, with a calculated water flow velocity of 1.323 m/s and a slope of 0.20%, lower than the allowable limits, necessitating the inclusion of a flow breaker.
... Thus, it is required to redesigning the channel's width existing from 2 m and depth 1,5 m to its requirement. Effective stormwater discharge is made possible by well-designed drainage systems, which lowers property losses and recovery costs [6]. Several studies have been carried out to redesign drainage channels. ...
There are up to 50-centimeter-high puddles on the road due to the Jetis Road Drainage Channel in Mojokerto Regency's incapacity to handle the flood discharge from the drainage catchment area. The Jetis Road drainage channel's size and channel bed slope will be affected by the meeting point of the 1000 m long secondary channel and the Jetis Road drainage outlet. The objective of this research is to evaluate the efficiency of drainage channel design considering the implications of the drainage existing condition due to inconsistent dimension and sedimentation. The drainage channel is designed to handle a total discharge of 4.6 m3/sec during 10 years return of period. Under these circumstances, a trapezoidal channel with a width of one meter and a depth of two meters is needed. The Jetis Road drainage channel's enlarged dimensions result in a flood water level of 1.8. The Jetis Road drainage channel has a freeboard of 0.2 meters since the flood water level that occurs in the channel with its new dimensions is 1.8 meters. The flow rate in the intended channel serves as the control in this study to determine channel size. The channel's maximum flow velocity of 1.44 m/sec satisfies the 1.5 m/sec maximum flow velocity allowed in concrete channels.
... Stormwater management is critical during the rainy seasons in the urbanized areas. Floods are frequent in most urban areas due to ill management of increased stormwater runoff (Ramos et al., 2017;Sohn et al., 2020;Stevaux et al., 2009). This would not only bring issues such as floods but also water quality issues (Ahmed et al., 2020). ...
Granular filter media are integral to sustainable drainage systems (SuDS) for their efficiency in removing pollutants from urban runoff. This study focuses on understanding the filtration processes within these media by combining a pilot experimental study with a modeling approach. The experimental study involved characterizing the physical and hydraulic properties of various granular filter media materials, including sand, pea-gravel, gravel, and geotextile membranes. Three laboratory-scale stormwater filtration rigs were tested to evaluate the filter me-dia's pollutant removal capacity and hydraulic performance. This work presents a phenomenological model that predicts the spatial variation in the concentrations of stormwater and urban runoff substances, specifically nitrate ions (NO 3-), phosphate ions (PO 4 3-), chemical oxygen demand (COD), and suspended solids, by studying their concentration profiles. The stormwater quality model was used to predict the concentration profiles for stormwater with an average inflow consisting of 2.9 mg/L nitrates, 3.4 mg/L phosphate ions, 225 mg/L COD, and 3.3 mg/L of suspended solids. The predicted outlet concentrations matched well with measured experimental data. The results showed that adding geotextile membranes to a granular filter significantly improves its ability to adsorb dissolved species for stormwater applications. This research highlights the importance of understanding the physical and hydraulic properties of granular filter media and their impact on stormwater pollutant removal efficiency. The developed model can assist in the design and optimization of stormwater treatment systems by predicting the performance of different filter media materials, allowing for informed decision-making and improved system functionality.
... It offers information on the drainage capacity of the landscape and is a crucial gauge of how rapidly and effectively water is distributed over an area. The risk of flooding may be significantly impacted by high or low drainage densities [45]. The slope is also one of the significant factors in the occurrence of floods due to its direct impact on surface runoff and infiltration potential [37]. ...
Flooding is a global natural disaster that occurs when water rises over normal levels and damages infrastructure, buildings, and land. Lately, a substantial rise has occurred in the frequency and severity of floods in Nigeria due to urbanization, population growth and climate change. This study aims to identify areas in the Osun River Basin (ORB) in southwest Nigeria that are at risk of flooding as a result of increased rainfall patterns that can induce river flooding. 10 flood factors contributing to flood susceptibility were obtained around the study area. These remote sensing data were analyzed using a weighted overlay on ArcGIS. The Analytic Hierarchy Process (AHP) was particularly applied in analysing the flood factors and creating the flood susceptibility maps. Results obtained showed that flood events are probable in areas along the river bank, some areas that are low-lying terrains and areas where there is high rainfall. Ogun State falls within the areas with the lowest digital elevation, therefore the state is very highly susceptible to flooding from the tributaries of the Osun River. Areas such as Ijebu North, Ijebu North East, Ijebu East and Ijebu Ode were identified as highly susceptible to flooding from the maps created. This study will further help stakeholders and policymakers in reducing the impact of flooding in these areas.
... Traditional approaches have mainly focused on expanding existing drainage networks and constructing deep tunnel drainage systems. These methods aim to enhance urban drainage capacity and flood resilience through infrastructure such as barriers and floodgates [12][13][14]. However, large-scale construction and maintenance of these centralized mechanical storage-based facilities are often costly. ...
With accelerated urbanization and escalating severity and frequency of extreme precipitation events, urban flooding has become increasingly prevalent, posing significant threats to human life and economic well-being. Given the scarcity of land resources, the integration of flood mitigation measures into public spaces, particularly in the form of multi-functional storage spaces (MFSs), emerges as an effective strategy for rainwater retention. To assess the efficacy of MFS, a coupled modeling framework, comprising the Storm Water Management Model (SWMM) and the LISFLOOD-FP hydrodynamic model, was employed in the study. Under rainstorms of varying design characterized by diverse return periods and peak rainfall intensity locations, the study simulated and compared the performance of low-impact-development (LID) strategies, MFS, and a combined approach utilizing both LID and MFS (ALL). The findings indicate that the performance of these strategies significantly varies under diverse rainfall intensity and peak coefficients. Specifically, as the return period increases, the reduction rates of the three projects gradually diminish. For lower return periods (P ≤ 10), the order of reduction effectiveness was LID < MFS < ALL; whereas, for higher return periods (P ≥ 20), the order was LID < ALL < MFS. LID exhibited superior performance under low return periods with an early-peak-rainfall position, and under high return periods with a mid-peak position. MFS and the ALL approach achieved the most significant reduction effects under early-peak-rainfall positions. LID may introduce uncertainties into the performance of MFS during rainfall events with higher return periods and peak coefficients. The outcomes of this research offer valuable technical insights that can inform urban planning strategies and enhance the design of flood mitigation measures in urban environments.
... Long-term soil subsidence affects tower foundation thereby causing risk to the operational services. To accommodate changes that may occur at each stage, the design of project needs to be flexible (Sohn et al., 2020). Following this process, tower foundation structure has been designed according to the data from the cone penetration test. ...
Transmission system is one of the national essential objects and should be reliable when functioning. Moreover, disturbances in transmission system can lead to disruption of the service function. A common risk to the reliability of electric distribution is land subsidence on transmission tower. Furthermore, the 150 KV interconnector of South Sumatra-Bangka Belitung (Sumsel-Babel) is located in the coastal area of Banyuasin Dua sub-district, South Sumatra. This area is a river delta with peat and clay soil structures and is prone to land subsidence. Therefore, this research aimed to identify environmental factors that affect land subsidence and cause risk to transmission tower. In the context of this research, Copras (Complex Proportional Assessment) and MCSA (Multi Criteria Spatial Analysis) were used for parameter weighting and risk assessment of tower location, respectively. The results of an expert survey to assess risk of potential land subsidence at tower location showed five parameters, namely, land use, distance to waters or potential flooding, land slope factor, soil type, and conus value. Individual parameters were weighted quantitatively and qualitatively based on the opinions of construction experts. Specifically, the qualitative method was performed by weighting based on criteria and sub-criteria, which were analyzed using Analytic Hierarchy Process (AHP). On the other hand, spatial analysis of locations at risk of land subsidence was conducted using GIS software. Based on the assessment results obtained, land use criteria had the largest weighting influence of 0.340 and the smallest weighting on the cone value was 0.08. Finally, tower location that are most at risk of land subsidence are on peatland, near water, and clay soil.
... This trend indicates a detention and gradual outflow, which can increase the response time downstream, and a real time control system approach could be used to manage downstream flood risk in an efficient manner. Additionally, the extended timeframe provided enables ecosystems to adapt to changes in water quality, fostering a healthier environment (Sohn et al., 2020). On the other hand, the outflow hydrograph in the WO scenario for the 1-20-year return period resulted in high flows over a more extended duration during the experiment. ...
Reduction of runoff flow peaks and volumes is one of the performance objectives of grass swales in the context of Green Stormwater Infrastructure (GSI). Towards this end, a study of the feasibility of using a retrofitted swale outlet control weir (SOCW) to reduce runoff volume and peak flow, by enhancing swale runoff storage and infiltration into swale soils, was conducted in Luleå, Northern Sweden. Experimental field work consisted of 43 irrigation-driven runoff experiments, mimicking rainfall events with return periods between 1-to 50-years, with a constant intensity and duration of 30 min, in a 30-m long grass swale section. Experimental results confirmed that, under the tested conditions, swales with the retrofitted outflow control, reduced runoff volumes and peak flows. Such reductions ranged from 32 percentage points (for 2-year) to 1 and 4 percentage points (for 50-year return period) for runoff volumes and peak flows, respectively. Outcomes of scenarios with outflow controls clearly indicated a decreasing performance with increasing flow rates (and irrigation event return periods). Furthermore, the retrofitted swale controlled the outflow release during less frequent 20 to 50-year events, which would contribute to reducing flood risks in downstream urban areas.
... On the other hand, changes in climatic patterns leading to variations in precipitation patterns have probably increased the frequency and intensity of river flow (Seidenfaden, Jensen, & Sonnenborg, 2021). The excessive overflow of rivers occurs floods that spread beyond their regular boundaries and become the most severe hydrological catastrophes that generally lead to enormous financial losses, and deaths of humans because of their complexity in prediction, outlined, and mitigation, also flood harm (Mishra et al., 2022;Pathak, Liu, Jato-Espino, & Zevenbergen, 2020;Sohn, Brody, Kim, & Li, 2020). ...
This study aims at developing a physically based semi-distributed rainfall-runoff model in the HEC-HMS platform to predict the historical and future stream flow of the Dhaka River basin. This model adopted and integrated several physio-hydrographic parameters as input data, such as LULC, HSG, DEM, observed stream flow, historical and projected future precipitation of the ACCESS-CM2 ensemble of the Coupled Model Intercomparison Project Phase 6 (CMIP6). The stream flow predictability of the HEC-HMS is observed subject to the model functions and simulation controls. After developing the model architecture, during calibration, a Nash-Sutcliffe efficiency (NSE) of 0.78 and a coefficient of determination (R²) of 0.81 were found, which indicates the simulation efficacy of the model setup. Furthermore, in the validation phase, the model demonstrated its robust performance, with R² = 0.80 and NSE = 0.78. The study showed the predicted yearly peak discharge of about 341685.8 m³/s, 330017.4 m³/s, and 315588.9 m³/s under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, respectively. Here, the Mann-Kendall and Sen's slope tests were conducted to analyze the daily, monthly, and yearly stream flow trends and they substantiate a significant increase in predicted daily streamflow under both the SSP1-2.6 and SSP2-4.5 scenarios and a gradual increase in monthly discharge in May under the SSP5-8.5, as well as in July and August under the SSP1-2.6. Outcome of this study underscores the model’s robustness and contributes vital perceptions for flood control and mitigation strategies.
... Therefore, it is necessary to introduce methods that reduce the uncertainties caused by these large ksat variations and to develop a more comprehensive understanding of the infiltration capacity under actual rainfall events (Venvik & Boogaard, 2020). Additionally, further research is required for the validation of grass swales under extreme rainfall intensities through field experimentation ) and the evaluation of critical conditions for effective flood risk management (Sohn et al., 2020). This becomes especially critical with the anticipated climate change-induced intensification of rainfall. ...
Climate change is expected to lead to more intense and severe rainfall events in the future, significantly increasing the risk of urban flooding. This change, characterized by spatial and temporal shifts in precipitation patterns, presents a challenge to the capacity of existing urban drainage systems, which may lead to higher runoff volumes than the systems were initially designed to handle. Relying solely on enlarging stormwater infrastructure to tackle this issue will be expensive and may transfer the flooding risk downstream, rather than effectively resolving it. Furthermore, climate change may also lead to prolonged dry spells, potentially resulting in soil compaction and diminished soil infiltration rates. Given these considerations, it is essential to ensure that urban drainage systems are both adaptable and space-efficient, with a capacity to manage the changing volume and intensity of rainfall caused by climate change.
As awareness of the hydrological and environmental impacts of urbanization on catchments grows, there has been a paradigm shift towards adopting green infrastructure solutions. These approaches diverge from traditional ‘end-of-pipe’ strategies, emphasizing more holistic and sustainable methods. The overall aim of this thesis is to investigate the implications of climatic conditions and geographic location on the retention and detention capacity of three types of infiltration-based facilities: a biofilter cell, a green roof, and a grass swale. A rainfall-runoff model of a biofilter cell, and a green roof, combined with swale irrigation experiments, were used to evaluate the capacity of these facilities to reduce runoff volumes and attenuate peak flows. Four urban areas were used as geographic locations representing oceanic (Cfc), humid continental (Dfb), and subarctic (Dfc) climatic zones. The assessment also includes the effect of temporal and spatial variation of saturated hydraulic conductivities (ksat). The swale irrigation experiments were conducted to evaluate the effect of outflow control on swale retention and detention capacities, under high soil moisture conditions.
Results for biofilter cells and green roofs showed that retention capacities were influenced by the combined effect of antecedent wetness, the extent of winter periods, and the frequency and intensity of rainfall events. Conversely, green roofs were found to have a higher sensitivity to initial soil conditions and antecedent dry weather periods, which was observed through a wider range of distribution of runoff volume reductions. Grass swales exhibited a large spatial distribution of hydraulic conductivity (ksat) values, with lower values at the swale bottom and higher values in the side slope. Results from a full-scale infiltration test showed that overall, grass swale infiltration capacities are representative of the measured ksat values at the swale bottom. Finally, the presence of outflow controls was observed to enhance the retention and detention capacities of grass swales, even under high levels of soil moisture content. This increase in swale hydrological functionality was positively influenced by swale outflow controls, leading to greater utilization of the grass swale surface area.
... Floods have been recognized as one of the most significant natural disasters globally, with far-reaching socioeconomic and environmental consequences [5]. Floods are a natural outcome of excessive precipitation, inadequate drainage [6], and geographical factors [7]. Precipitation measurement using rain gauges and radar is the traditional approach and has limitations in terms of capturing the broader spatial and temporal variations of rainfall [8], [9]. ...
... The use of green infrastructure stormwater drainage systems could contribute to decreased mosquito habitats. Moreover, structures based on infiltration must be connected to the stormwater drainage networks to avoid the problem identified by [63]. ...
Urban waters (UW) are complex environments, and their definition is related to water systems in urban zones, whether in a natural system or an urban facility. The health of these environments is related to public health and the quality of life because public health is the focal point of environmental and anthropic impacts. Infrastructure is paramount for maintaining public health and social and economic development sanitation. Insufficient infrastructure favors disease vectors. The population and environment suffer from deficient urban water infrastructure in Brazil despite government efforts to manage the existing systems. In this work, machine learning (regression trees) demonstrates the deficiency of sanitation and UW management fragmentation on public health by using the Aedes aegypti infestation index (HI) and water supply, wastewater, stormwater and drainage indicators (SNIS data). The results show that each Brazilian region faces different problems. The more infested regions were Northeastern, Northern and Southeastern. Moreover, municipalities with better SNIS data have lower infestation rates. Minimizing problems related to sanitation through the integrated management of water and urban areas is extremely important in developing countries. UW governance is connected to public health. Water management fragmentation leads to more complex issues, and managers must confront them to improve the quality of life in urban zones.
... Flood disaster is a problem that must be faced by residents who even in certain locations must be faced them routinely. The problem of flooding is inseparable from the poor drainage caused by the development of business and housing areas which often results in the conversion of land functions from safety areas and catchment areas such as river riparian areas, and temporary water storage ponds to turning into residential areas and trading centers [7], [8], [9], [10]. This is what happened in the Ubud District, where there are stagnant water and flooding, especially during the rainy season and for a long time. ...
Ubud District is one of the tourism areas in Bali which is growing very rapidly. Ubud District has problems related to inundation and flooding which often occur during the rainy season. The drainage canals cannot accommodate the peak flood discharge. Because the capacity of the channel is insufficient, besides the influence of sediment and garbage, water overflows through the freeboard of the channel. This study aims to determine the characteristics of inundation and drainage in Ubud District. Primary and secondary data are used in this study which will then be used in data analysis. The analytical method used are field survey, identification of inundation and flood locations, inventory of existing drainage system, hydrology and hydraulics analysis, and drainage network planning. The result is 27 inundation locations were found in Ubud District. The inundation locations included 5 points in Lodtunduh Village, 3 points in Mas Village, 2 points in Peliatan Village, 5 points in Petulu Village, 2 points in Sayan Village, and 10 points in Ubud Village. The duration of the inundation that occurs is a minimum of 15 minutes and a maximum of 360 minutes. The height of the inundation that occurs is 12 – 50 cm with an inundation area of 0.032 – 4.67 ha and an inundation length of 12 – 2.309 m. The frequency of inundation is 3 to 10 times per year. Parameters for determining priority for drainage management based on priority scale are determined based on the characteristic parameters of inundation, economic losses, social disturbances and government facilities, transportation disturbances, and losses in residential areas. The recommendations given include normalizing the existing canal with river stone pairs of the required size that are more adequate to accommodate water discharge, especially during rains; making diversion channel with precast box culvert with the required size; and construction of new channels equipped with inlet drains per segment as entry points for inundation on the roads into the drainage channels.
... Equally important is that flood control measures should reduce the hazard by constraining floodwaters upstream (Jha and Afreen, 2020). A study in arid Texas showed the integration of detention basins or wetlands could contribute to a 92% reduction in flood damage (Sohn et al., 2020), whereas the construction of dry dams for floodwater retention was recommended for alleviating flash floods in Egyptian wadis (Sumi et al., 2013). Also desirable is having effective urban drainage systems in place that can quickly evacuate floodwaters. ...
... To deal with these floods, there is a need to develop adequate projects of urban drainage systems (UDS), given their functionality, incisively influencing the severity of the floods (Wang et al., 2021;Yin et al., 2020). In the context of studies on the importance of drainage systems, Sohn, Brody, Kim, and Li (2020) evaluated the impacts of three systems (based on storage, transport, and infiltration) to check their importance. Zhao et al. (2021) conducted a study to highlight the role of urban drainage systems in preventing surface water pollution. ...
The efficiency of drainage systems in urban centers and especially in their peripheral regions has deserved more and more special attention since their interrelationship with social and environmental aspects is associated with the performance of drainage infrastructures. Integrated urban water management is a major factor in the effectiveness of an urban drainage system. In large cities, negative effects caused by the disorderly urbanization process, especially those related to rainwater runoff, are increasingly present. An evaluation model of urban drainage systems was generated using System Fragility Indicators (IFS) and their ranking via Analytic Hierarchy Process (AHP), in the Jaracati River basin, Maranhão State, Brazil. Indicators were measured through the evaluation of the system and the experience of specialists in drainage systems. The results obtained allowed for the consolidation of a model to support planning and decision-making in the assessment processes of measures to mitigate socio-environmental impacts involved in the urban drainage of a watershed, with performance indicators capable of guaranteeing the support of a model being verified measurement of performance parameters of urban drainage systems.
... Building on a long tradition of focusing on the benefits of community engagement to more traditional hazard planning [67], a stronger focus on the use of L-THIA as a tool for community-informed planning and citizen-science is needed, along with new avenues for research translation of L-THIA generated data to both local governments and community residents [63,68]. This type of engagement is critical in the face of greatly increased risks from urban flooding resulting from urbanization, increases in impervious surfaces and soil compaction, impacts from more frequent and severe hydrological disasters like tropical storms and hurricanes, and climate change [33,69,70]. ...
Low-impact development (LID) is a planning and design strategy that addresses water quality and quantity while providing co-benefits in the urban and suburban landscape. The Long-Term Hydrologic Impact Assessment (L-THIA) model estimates runoff and pollutant loadings using simple inputs of land use, soil type, and climatic data for the watershed-scale analysis of average annual runoff based on curve number analysis. Using Scopus, Web of Science, and Google Scholar, we screened 303 articles that included the search term “L-THIA”, identifying 47 where L-THIA was used as the primary research method. After review, articles were categorized on the basis of the primary purpose of the use of L-THIA, including site screening, future scenarios and long-term impacts, site planning and design, economic impacts, model verification and calibration, and broader applications including policy development or flood mitigation. A growing body of research documents the use of L-THIA models across landscapes in applications such as the simulations of pollutant loadings for land use change scenarios and the evaluation of designs and cost-effectiveness. While the existing literature demonstrates that L-THIA models are a useful tool, future directions should include more innovative applications such as intentional community engagement and a focus on equity, climate change impacts, and the return on investment and performance of LID practices to address gaps in knowledge.
... Floods often happen when rainfall is higher than usual. The Lack of water infiltration zones, insufficient drainage systems, meandering rivers, tidal effects in estuaries, and garbage in waterways can increase the severity of flood events [6] [7]. Besides improving watersheds and drainage systems, engineers have to study changes in future rain patterns and characteristics [8] [9] [10] to be able to evaluate the ability of the drainage system in the effort of flood risk resilience. ...
... Pemerintah daerah Kota Batam sudah beberapa kali melakukan kegiatan pemeliharaan dan normalisasi pada saluran drainase di Jalan Marina. Namun, banjir masih tetap sering terjadi di Jalan Marina sehingga menyebabkan kerugian [8]. Selain itu, dimensi saluran drainase juga belum optimal sehingga tidak dapat menampung air dengan baik saat terjadi pasang surut air laut [9]. ...
Drainage is a basic facility that must be provided to meet community needs, so it’s very important in urban spatial planning. The benefit of building drainage is to prevent stagnant water so that it does not interfere with community activities. The condition of the drainage channels on Jalan Marina isn’t maintained because the dimensions of the channels are small and sedimentation occurs, causing silting of the channels. This causes floods that always occur every year. Re-dimension of the drainage channel was carried out because the initial dimensions could not accommodate the planned flood discharge. Some of data the basic for determining the re-dimensional drainage channels are rainfall data, sea tide data, and initial drainage channel dimension data. From the calculation results, the value of planned flood discharge is 172.634 mᶟ/s. So, the dimensions of the drainage channel are re-planned because the channel discharge value is smaller than the planned flood discharge value. The results of this study are that the planned flood discharge is greater than the drainage channel water discharge so that the initial channel dimensions cannot accommodate water. The results of re-planning the dimensions of the drainage channel based on the planned flood discharge value are h of 8.5 meters, b of 9.8 meters, and W of 2 meters. Re-dimensional planning of the drainage channel is fulfilled because Qs<Qp (172.634 mᶟ/s <227.103 mᶟ/s). This research is expected to provide dimensions of drainage channels that are in accordance with field conditions so that no more flooding occurs.
... Many urban areas in the Philippines experience extreme flooding problems when heavy rainfall occurs. Flooding is caused by different factors such as insufficient drainage systems, improper waste disposal, and deforestation [1]. Flooding is severe in areas near rivers due to the rising of river levels that may cause danger to the community [2]. ...
Flooding is one of the problems experienced by many countries no matter what their economic status is. Even rich and developed countries experience it too. Flooding is mainly caused by natural events such as typhoons and monsoon rains even anthropogenic causes that sometimes could not be stopped even if there are flood control structures in place. The Philippines is located in the Pacific Ring of Fire and is visited by an average of 20 typhoons each year. People are used to experiencing flooding and it is about time that we somehow do something about it. There have been many technologies available right now that could aid us to improve our capability to adapt to such phenomena. Heavy precipitation is usually experienced during the monsoon season that leads to severe flooding in a specific area. The application of HEC-RAS (Hydrologic Engineering Centre’s River Analysis System) Modelling Software was used in the study in Manghinao River for comprehensive hazard mapping and risk assessment in the downstream area of the Bauan River for 100-year return period flood. 2D flood hazard simulation was done and the river water level that would trigger flooding downstream was identified. At 0.5 m of flood height, people are considered immobilized to move from one place to another so the best time to evacuate people is before the flood reaches that level. Results showed that LGU has 4 hours to evacuate people starting when the river water at the gaging station reads 0.5 m, this gives them enough time to give warning and ask people to move to evacuations sites to prevent them being stranded in their houses. This study can support future planning and for the development of flood control plans and flood mitigation measures to minimize the losses due to flood disasters in Batangas Province, Philippines particularly in the Bauan area.
... Flood risk can be reduced not only by physical flood defences (Willner et al., 2018), but also through improved flood resistance for exposed buildings by measures such as wet and dry-proofing (de Moel et al., 2013) and other means of private precaution , emergency response (Molinari et al., 2013) and behaviour (J. C. J. H. Aerts et al., 2018), higher (local) retention (Förster et al., 2005), more efficient drainage (Sohn et al., 2020) or relocation (Dottori et al., 2021b). Risk may also be efficiently redistributed through insurance (Tariq et al., 2014;Solín et al., 2018). ...
Hochwasser stellt ein großes Risiko für Wohngebäude in Europa dar, und es wird erwartet, dass das Risiko in der Zukunft aufgrund klimatischer und sozioökonomischer Veränderungen zunehmen wird. Aktuelle Hochwasserrisikomodelle basieren meist auf einfachen Wasserstands-Schadenskurven. Diese Ansätze vereinfachen die Hochwasserschadensprozesse stark, können ungenau sein und bergen große Unsicherheiten, die oft nicht quantifiziert. Die Doktorarbeit stellt die Integration neuer Daten in probabilistische, multivariable Schadensmodelle zur Verbesserung ihrer Übertragbarkeit vor. Diese neuen Datenquellen und Modellierungsansätze werden verwendet, um zukünftige Veränderung des Hochwasserrisikos für Wohngebäude in Europa abzuschätzen und Risikokomponenten zu analysieren. Die Arbeit zeigt, OpenStreetMap (OSM) Daten liefern nützliche Informationen für die Modellierung von Hochwasserschäden und ermöglichen Modelltransfers. Die Integration von aus OSM abgeleiteten Gebäudeeigenschaften und Hochwassererfahrung aus Ereignisdatenbanken in das Bayes’sche Netzwerk basierte Hochwasserschadensmodelle für den privaten Sektor (BN-FLEMOps) ermöglichte die Implementierung auf der Mesoskala. Durch Vergleiche von Schadensschätzungen mit beobachteten Schäden in mehreren Fallstudien in Europa wurde das Modell validiert und detailliert mit einem Ensemble aus 20 Schadensmodellen verglichen. In einer abschließenden Studie werden die zukünftigen Veränderungen des Risikos für Wohngebäude in Europa modelliert. Die erwarteten jährlichen Schäden bis zum Ende des 21. Jahrhunderts werden um das 10-fache ansteigen. Die Britischen Inseln und der größte Teil von Zentral-Europa müssen mit einer starken Risikozunahme rechnen. Teile Skandinaviens und des Mittelmeerraums werden dagegen ein stagnierendes oder abnehmendes Hochwasserrisiko verzeichnen. Eine Verbesserung der privaten Vorsorgemaßnahmen könnte das Hochwasserrisiko im Mittel um 15 % und in einigen europäischen Regionen um bis zu 20 % verringern.
... Although with the developments of the "green" measures or GI practices (Green infrastructure), drainage systems remain the most important and reliable engineering approach for alleviating the problem of pluvial floods in urbanized environments, and their effects are critical in modeling urban floods for scientific research or forecasting practice. The performance of urban drainage networks to convey runoff should also be analyzed and their effects are vital for being considered on the urban flood propagation (Jang et al., 2018;Palla et al., 2018;Sohn et al., 2020). ...
Drainage loss effects are crucial for flash flood modelling induced by torrential rains in urbanized environment. This paper proposes a novel approach for incorporating drainage loss effects into two-dimensional hydrodynamic overland flow simulations with the open source databases offered by geographical information providers. Street inlet locations within the road network are determined using street view images based on feature points extracted throughout automatic navigation along the roads in the panoramas, where the runoff of the surface flood flow is determined by the drainage network's capacity. By implementing the proposed data acquisition and drainage loss calculation method into the 2D overflow model HiPIMS as an alternative to the often-unrealizable physically based method or to the overly simplistic rainfall reduction method, the flood modelling results are validated against field observations during severe flood events in an intensely urbanized area to demonstrate the feasibility and effectiveness of the newly proposed method. In comparison to other simulation scenarios without drainage loss effects or with those considered by the rainfall reduction method, the drainage loss effects induced by the newly proposed method are analyzed for both the spatially lumped and distributed urban flood patterns. While the drainage effects are more essential after the rainfall peak hours for the flood extent as spatially lumped results, the low-lying area with dense building complexes are found to benefit more from the drainage effects in a spatially distributed way. Variations of the speed and direction of flood flows caused by the drainage effects at inlets are observed to depend on the surrounding environment. Competitions between the drainage effects and the gravity effects induced by topographical features are revealed with street-level evaluations of the flood modeling results using high-resolution hydrodynamic modeling in conjunction with the proposed drainage calculation approach.
... But input-output methods generally required much basic data and calculation, demand greater accuracy from the data, and have lower calculation value . After flood, recovery from structural damage and return to normal functioning generally accompanied by considerable economic losses and burdens (Sohn et al., 2020). Flood losses estimation could provide necessary basis for optimizing flood-risk management and making decisions about flood control and disaster reduction (Schröter et al., 2018). ...
Increasing urban flood posed serious threat to urban safety and sustainable development, and resulted in great loss and damage. It was significant and indispensable to master the potential change of urban flood for flood risk mitigation and adaption. Floods not merely caused the physical losses, but also led to potential damage and harm during flood risk propagation. Studies have mainly focused on the physical features of flood risk and post-disaster reconstruction, while few have discussed the potential risk consequence considering flood risk propagation. Therefore, this study analyzed flood risk propagation based on modified Susceptible Infected Recovered (SIR) model. We performed flood simulation and modelling, mapped urban flood risk in consideration of flood risk propagation, and estimated flood losses in Nanjing with flood return periods of 5, 10, 20, 50, and 100 years. Results indicated that inundated area occupied 517.19, 654.11, 657.92, 834.49 and 1045.80 km² with return periods from 5 to 100 years respectively. Jianye District showed high flood risk and it was suggested to protect people’s lives and assets to reduce susceptibility and vulnerability, and enhance urban drainage capacity for recovery improvement. Moreover, total economic losses reached 27.85, 30.89, 32.91, 35.50 and $38.55 billion and led to the 14.38%, 15.94%, 15.94%, 18.32% and 19.90% GDP loss rate respectively. This study could support the effective flood risk mitigation practice for adaptive urban development.
The United Nations (UN) framework defines indicator 13.1.1 as the number of deaths, missing persons, and directly affected individuals due to disasters per 100,000 population. This indicator is associated with target 13.1, which calls for urgent actions against climate-related hazards and natural disasters in all countries. However, there is a lack of official data providers and well-established methodologies for assessing the resilience of populated areas to natural disasters. Earth observation (EO), geospatial technologies, and local data may support the estimation of this indicator and, as such, enhance the resilience of specific communities against hazards. Thus, the present study aims to enhance the capacity to monitor Sustainable Development Goals (SDGs) using the abovementioned technologies. In this context, a methodology that integrates ecoregion-specific model training and flood potential related geospatial datasets has been developed to estimate the number of houses affected by floods. This methodology relies on disaster-related databases, such as the UN’s DesInventar, and flood- and exposure-related data, including precipitation and soil moisture products combined with hydro-modelling based on digital elevation models, infrastructure datasets, and population products. By integrating these data sources, different machine learning regression models were trained and stratified by ecoregions to predict the number of affected houses and, as such, provide a more comprehensive understanding of community resilience to floods in the Sahel region. This effort is particularly crucial as the frequency and intensity of floods significantly increase in many areas due to climate change.
Flooding is an environmental problem with global consequences, affecting millions of people and causing extensive damage to infrastructure and ecosystems. Nigeria is one of the countries that experiences frequent flooding due to heavy rainfall and poor drainage systems. The government has been working on implementing better flood management strategies to mitigate the impact on communities and improve disaster response efforts. This review presents an overview of the strategies used in Nigeria for flood monitoring and evaluation. The review also indicates a global shift in modeling from physical to an advanced data-driven approach in the effort to improve the accuracy and timeliness of flood forecasting. Whereas in Nigeria, traditional methods such as river gauges and satellite imagery are still commonly used, although there is a growing recognition of the importance of incorporating technology and data analytics for more effective flood management in studies around the southern part of Nigeria. Incorporating technology and data analytics can enhance the efficiency of flood management by providing real-time data and more accurate predictions. By embracing these advanced approaches, Nigeria can better prepare for and respond to future flood events, ultimately reducing the impact on communities and infrastructure.
As the intensity of flood disasters in old communities continues to escalate, the resilience of flood disaster response networks (FDRNs) is under growing threat. Addressing this pressing challenge, this study develops an enhanced framework integrating Dynamic Network Analysis (DNA) and Interpretive Structural Model (ISM) to systematically elucidate the factors and mechanisms that influence FDRN resilience. This framework first employed DNA to conceptualize the complex flood disaster response as the ‘A-T-R-I’ dynamic network, delineating interrelationships among stakeholders, tasks, resources, and information. Subsequently, ISM was utilized to analyze the
mechanisms that affect FDRN resilience. Validation of this framework through a case study of the Y community in Xuzhou City of China led to the development of a five-level ISM model, clarifying the interconnections between 10 critical FDRN nodes and 12 determinants of the FDRN resilience. Moreover, strategies for enhancing FDRNs resilience were provided, and the advantages of the enhanced DNA-ISM framework were highlighted. Overall, this study not only enriches the knowledge system of community resilience but also offers actionable guidance for decisionmakers to develop resilient flood response networks, highlighting a globally applicable framework to enhance community resilience against flood disasters.
Telaga Tujuh Village, located in West Langsa Sub-district, Langsa City, on the eastern tip of Aceh, has a very high population density. In addition, 373 housing units in the village do not meet the technical criteria set out in the Minister of Public Works and Housing Regulation No.02/PRT/M/2016, and the city has limited access to critical infrastructure. Based on seven criteria, including building regularity, neighborhood road network, neighborhood drainage, drinking water needs, wastewater management system, waste management facilities and infrastructure, and fire protection facilities, Telaga Tujuh Village is classified as a severe slum, with an average slum rate of 100%. Discovering the structural needs of the slum environment in Telaga Tujuh Village and creating a structural design is the objective of this study. Five indicators - on-site upgrading, on-site relocation, on-site redevelopment, land sharing, and relocation - were used in the communal housing methodology in this study. On-site redevelopment was chosen as the minimum solution after the five indicators were selected using the Analytical Hierarchy Process (AHP) method. After on-site redevelopment, the settlement pattern in this area is in the form of an iron grid, with main centers-the construction of places of worship, village halls, auxiliary health centers (pustu), and village offices that function as government and community service centers-and supporting centers-education and neighborhoods-by providing public open spaces.
This study evaluated the economic benefits of early Warning services for floods in Rubavu district, in Rwanda, focusing on gender distribution, awareness, satisfaction, and perceived economic advantages. Survey data from 180 respondents indicated high awareness among both genders, with generally satisfactory perceptions of existing systems. Economic benefits included job creation and business protection, with positive technological perceptions correlating with higher perceived benefits. Recommendations included funding allocation, collaboration, research, and community engagement to enhance system effectiveness. The research aimed to assess the economic advantages of investing in flood early warning systems in Rubavu District, proposing strategies for funding alongside climate change adaptation. It marked the first empirical investigation into the correlation between investment, flood-related losses, and socio-economic development across various economies. Methodological instruments such as questionnaires, interviews, GIS, remote sensing, and statistical analysis were employed. The study found a positive relationship between investment and flood- related losses, supported by a statistically significant p- value of 0.0379. This indicates ample evidence for correlation between the variables. Thus, the study emphasized the importance of early notice systems in vindicating flood economic impressions and advocated for concerted efforts to maximize socio-economic benefits in Rubavu district.
Climate change, an emerging issue, significantly impacts international health, particularly malaria, a critical issue that affects tropical and subtropical areas. Researchers have identified climate variability as a major determinant of malaria transmission and distribution. This review aims to disentangle the interplay between climate variability and malaria transmission, with a focus on temperature, rainfall, humidity, and extreme weather events and their influence on the Anopheles mosquito and Plasmodium parasites' life cycles. Writing this review article involved consulting several scientific databases and compiling information from them. Thus, incorporating data from epidemiology, ecology, climatology, and public health, this paper aimed at integrating knowledge on how climatic factors influence malaria incidence, distribution, and transmission density. This study emphasizes the importance of cross-disciplinary approaches in addressing these issues and highlights the need for synergy in implementing climate change mitigation, improved health care systems, advanced surveillance, and community mobilization to mitigate and manage malaria in the changing climate. Awareness of the factors determining climate variability and their relationship with malaria transmission patterns is important in formulating adequate strategies to cushion the impact of climate change on malaria incidence and secure world health.
In the context of climate change, transportation resilience to flood threats has received significant attention. However, measures to improve practical resilience have not been addressed and elucidated. Various studies from the domains of disaster and transport have been devoted to commuting vulnerability analysis and transport network robustness assessment, whereas a systematic perspective is rarely used to analyze the damage mechanism of floods to the commuting system. To fill this research gap, we constructed an index system from the dimensions of hazard, transport network condition, and commuting pattern as driving factors of commuting risk during floods. The contribution to commuting loss was first assessed to guide intervention prioritization based on flood modeling and commute simulation. We adopted gradient boosting decision trees to examine the relationship between driving factors from three dimensions and commuting. The results of this study conducted in Wuhan indicate that the contribution rate of commuting pattern is the highest, followed by hazard, and finally road network conditions. The effective thresholds of the driving factors were also identified to guide urban governance. This study is a novel exploration of disaster impact mechanism that can provide new insights for the improvement of commuting resilience practices under climate change.
Shotcrete is a sprayed concrete placed on steep slopes that have been widely used because it can prevent surface weathering and erosion, and in some cases, small-scale control rock falls. However, shotcrete is usually thin, and it is directly affected by the surrounding environment, resulting in cracks. In this study, sugarcane residues (bagasse fiber and ash) were applied in shotcrete, and mechanical properties were investigated. The results showed that shotcrete with addition of sugarcane residues, obtained similar or better mechanical strength than the control mixture.
Integrated Water Resources Management (IWRM) merupakan suatu pengelolaan sistem sumber daya air terpadu yang berkelanjutan seperti siklus yang membutuhkan komponen lima pilar sumber daya air agar terwujud. Lima pilar sumber daya air yang dimaksud adalah (1) konservasi sumber daya air, (2) pendayagunaan sumber daya air, (3) pengendalian daya rusak air, (4) sistem informasi sumber daya air (SISDA), dan (5) peranan masyarakat dan swasta dalam pengelolaan SDA. Buku referensi ini hadir membawa nafas integrasi penelitian aplikatif yang dapat digunakan sebagai sumber referensi pembelajaran maupun penelitian kepada sivitas akademika yang bergerak di pendidikan tinggi vokasi maupun akademik di Indonesia.
Ruang lingkup pembahasan pada setiap bab diantaranya: (1) membahas masalah manajemen kualitas air menggunakan model RMA, lahan basah buatan, dan model WASP; (2) analisis kelayakan perencanaan pembangkit listrik tenaga mikro hidro dalam pemenuhan kebutuhan air bersih dan air irigasi; (3) investigasi bencana keairan seperti banjir dan longsor menggunakan alternatif mitigasi struktural dan non-struktural, didukung dengan pemodelan dan perencanaan desain sesuai pedoman SNI; (4) mengelaborasi peran teknologi dalam pengelolaan sumber daya air seperti mengetahui kondisi hidrometeorologi dan hidrogeologi; dan (5) teknologi terapan terkait manajemen sumber daya air dengan melibatkan pemberdayaan masyarakat.
Buku referensi ini tentu diharapkan dapat bermanfaat lebih luas tidak hanya pada institusi pendidikan tinggi, tetapi juga praktisi, industri, masyarakat/pegiat komunitas konservasi sumber daya air, dan pemerintahan (Penta Helix) dalam mengelola sumber daya air yang lebih komprehensif dan aplikatif, sesuai dengan amanat yang tersimpan pada Undang-undang Dasar (UUD) Tahun 1945 Pasal 33 Ayat 3 dengan salah satu tujuannya adalah mendayagunakan air sebesar-sebesarnya untuk kemakmuran rakyat.
Tropical and subtropical regions can be particularly severely affected by flooding. Climate change is expected to lead to more intense precipitation in many regions of the world, increasing the frequency and magnitude of flood events. This paper presents a review of studies assessing the impacts of climate change on riverine flooding in the world's tropical and subtropical regions. A systematic quantitative approach was used to evaluate the literature. The majority of studies reported increases in flooding under climate change, with the most consistent increases predicted for South Asia, South East Asia, and the western Amazon. Results were more varied for the Latin America and Africa where there was a notable paucity of studies. Our review points to the need for further studies in these regions as well as in Australia, in small to mid-sized catchments, and in rapidly urbanising catchments in the developing world. Adoption of non-stationary flood analysis techniques and improved site-specific socio-economic and environmental model scenarios were identified as important future directions for research. Data accessibility and mitigation of model uncertainty were recognised as the principal issues faced by researchers investigating the impacts of climate change on tropical and subtropical rivers.
Water management system is an effort of planning, management, control, and supervision of runoff water that is structured and integrated in an area according with the policies. In Governor Regulation of Jakarta Capital City Administration No. 43 of 2013 on the Peil of Building Floor Licence, it is explained that the implementation of the zero Delta Q principle is to keep the runoff remain in the area up to 100% or to drain the water out of the region up to zero percent or zero runoff. In this regard, this research is expected to develop a concept of a regional water system implementation which compares the hydrological analysis method with related regulatory methods, to obtain a technical policy that can be applied in order to meet the regional regulations based on the zero delta Q or zero runoff concept for all to be developed areas in Jakarta by taking case study of South Jakarta area as a pilot project. The method used is to compare the Governor Regulation of Jakarta as the reference in zero run off calculation with the Indonesian National Standard Regulation (SNI) No. 03 2453 2002 on the Procedure of Planning Technique of Rainwater Recharge wells for Grounds using hydrological and hydraulics analysis. The conclusion is the calculation by hydrological analysis in accordance with the Indonesian National Standard Regulation (SNI) No. 03 2453 2002 on the Procedure of Planning Technique of Rainwater Recharge wells for Grounds becomes the chosen method, because it has a more detailed result and zero runoff concept can be met, so the runoff at the study site did not increase the load of Grogol River.
Eleven storm water treatment strategies were evaluated for water quality performance and storm volume reduction during rainfall–runoff events between September 2004 and August 2005. Evaluated treatment strategies included structural best management practices (BMPs) (swales, retention ponds), low-impact development (LID) designs (treatment wetland, filtration and infiltration designs), and manufactured BMPs (filtration, infiltration, and hydrodynamic separators). Contaminant event mean concentration, performance efficiency, and mass-based first flush were evaluated for storms with varying rainfall–runoff characteristics. Previous research demonstrated that treatment performance of storm water control measures varies widely in response to site-specific contaminant loading functions. For that reason, the devices were tested in parallel, with a single influent source providing uniform loading to all devices. Treatment strategies were uniformly sized to target a rainfall–runoff depth equivalent to 90% of the annual volume of rainfall. Under the parallel and uniformly sized configuration, a normalized performance evaluation is possible because treatment strategies of the same scale receive runoff from events of the same duration, intensity, peak flow, volume, antecedent dry period, and watershed loading. Runoff constituent analyses included total suspended solids (TSS), total petroleum hydrocarbons-diesel, dissolved inorganic nitrogen, and total zinc. Several water quality parameters (temperature, dissolved oxygen, pH, conductivity) were monitored as real-time data. Performance evaluations indicate that several LID designs have removal efficiencies of 80% to 100%. In contrast, conventional structural BMPs perform poorly for most measures except for the pond with TSS. The manufactured systems tended to vary widely and were dependent on the design and contaminant of interest.
Urbanization increases directly connected impervious area (DCIA), the impervious area that is hydraulically connected to downstream drainage by closed pipelines. Although the benefits of low-impact development (LID) have been examined in other studies, its effect on alleviating DCIA levels has seldom been assessed. This study measured the DCIA of urban watersheds in Houston, TX, USA. Five land-use types were categorized and the contribution of LID facilities to reducing DCIA in each type was estimated by using Sutherland's equations. The results showed (1) DCIA in commercial areas was greater than that in residential areas, especially for big-box retailers; (2) the percentage of DCIA reduction by LID varied by land-use type; and (3) optimal combinations of LID application could maximize the effectiveness of DCIA reduction. The results contribute to prioritizing land-use type for implementing LID practices and providing local governments with a useful measure to estimate runoff volume.
Determination of imperviousness, which is defined by total impervious area (TIA) and effective impervious area (EIA), is mandatory for hydrological modeling of water quantity and quality in urban areas. The determination of TIA is relatively easy and preferred to determination of EIA, even though the latter is considered to be more appropriate for hydrological studies. Accurate and representative determination of EIA requires knowledge of drainage network connectivity with the impervious surface, which cannot be ascertained from remote sensing data alone. A more realistic semiautomated direct method is suggested in this study to determine EIA by integrating the remote sensing data, the digital format of the drainage network, and a digital elevation model (DEM) of the study area. Based on the results obtained from the proposed method, a power relationship [EIA=0.0035×(TIA)2.17] relating easily measurable TIA and hydraulically relevant EIA was determined for an ungauged urban catchment in northeast India. There are no such relationships available in the literature for an urban Indian catchment. EIA was also determined using two indirect methods reported in the literature, and the results were compared. The present study indicates that there is a distinct difference between the EIA values obtained by the direct method and those obtained by the indirect methods. Among indirect methods, Sutherland’s equation was observed to predict EIA values close to the directly determined EIA. The maximum overestimation of EIA by the Sutherland equation was 4 times, that by the Alley and Veenhuis equation was 20 times and, TIA was observed to be 56 times more than the directly estimated EIA. If EIA determined by indirect methods or easily measureable TIA were used as input for hydrological studies like flood modeling, it would result in considerable overestimation of peak discharge. The design of hydraulic structures or flood management strategies based on the overestimated peak discharge would have far-reaching undesirable impacts on efficient planning and management, causing overexpenditure.
Major coastal flooding events over the last decade have led decision makers in the United States to favor structural engineering solutions as a means to protect vulnerable coastal communities from the adverse impacts of future storms. While a resistance-based approach to flood mitigation involving large-scale construction works may be a central component of a regional flood risk reduction strategy, it is equally important to consider the role of land use and land cover (LULC) patterns in protecting communities from floods. To date, little observational research has been conducted to quantify the effects of various LULC configurations on the amount of property damage occurring across coastal regions over time. In response, we statistically examine the impacts of LULC on observed flood damage across 2,692 watersheds bordering the Gulf of Mexico. Specifically, we analyze statistical linear regression models to isolate the influence of multiple LULC categories on over 372,000 insured flood losses claimed under the National Flood Insurance Program per year from 2001 to 2008. Results indicate that percent increase in palustrine wetlands is the equivalent to, on average, a $13,975 reduction in insured flood losses per year, per watershed. These and other results provide important insights to policy makers on how protecting specific types of LULC can help reduce adverse impacts to local communities.
This study explored the hydrological impacts of urbanization, rainfall pattern and magnitude in a developing catchment. The Stormwater Management Model (SWMM) was parameterized, calibrated and validated in three development phases which had a same catchment area (12.3 ha) but different land use intensities. The model calibration and validation by using sub-hourly hydro-meteorological data demonstrated a good performance of the model in predicting stormwater runoff in the different development phases. Based on the results a threshold between minor and major rainfall events was identified and conservatively determined to be about 17.5 mm in depth. Direct runoff for minor storm events has a linear relationship with rainfall; however, events with a rainfall depth greater than the threshold yields a rainfall-runoff regression line with a clearly steeper slope. The difference in urban runoff generation between minor and major rainfall events diminishes with the increase of imperviousness. Urbanization leads to an increase in the production of stormwater runoff, but during infrequent major storms the runoff contribution from pervious surfaces reduces the runoff changes due to urbanization. Rainfall pattern exerts an important effect on urban runoff, which is reflected in pervious runoff. With a same magnitude, prolonged rainfall events with unvarying low intensity yield the smallest peak flow and the smallest total runoff, yet rainfall events with high peak intensity produce the largest runoff volume. These results demonstrate the different roles of impervious and pervious surfaces in runoff generation and how runoff responds to rainstorms in urban catchments depends on hyetograph and event magnitude. Furthermore, the study provides a scientific basis of the design guideline sustainable urban drainage systems, which are still arbitrary in many countries. This article is protected by copyright. All rights reserved.
Inadvertent soil compaction at the urban lot scale is a process that reduces infiltration rates, which can lead to increased stormwater runoff. This is particularly important in low impact development strategies where stormwater is intended to infiltrate rather than flow through a traditional stormwater network to a detention basin. The effect of compaction on infiltration rates on sandy soils in North Central Florida was measured with a double ring infiltrometer on urban construction sites and across various levels of compaction. Average non-compacted infiltration rates ranged from 377 to 634 mm hr1 (14.8 to 25.0 in hr-1) for natural forest, from 637 to 652 mm hr-1 (25.1 to 25.7 in hr-1) for planted forest, and 225 mm hr-1 (8.9 in hr1) for pasture sites. Average infiltration rates on compacted soils ranged 8-175 mm hr1 (0.3-6.9 in hr1), 160 to 188 mm hr1 (6.3 to 7.4 in hr1), and 23 mm hr1 (0.9 in hr1) for the same respective sites. Although there was wide variability in infiltration rates across both compacted and non-compacted sites, construction activity or compaction treatments reduced infiltration rates 70 to 99 percent. Maximum compaction as measured with a cone penetrometer occurred in the 20 to 30 cm (7.9 to 11.8 in) depth range. When studying the effect of different levels of compaction due to light and heavy construction equipment, it was not as important how heavy the equipment was but whether compaction occurred at all. Infiltration rates on compacted soils were generally much lower than the design storm infiltration rate of 254 mm hr 1 (10.0 inches hr1) for the ioo-yr, 24-hr storm used in the region. This implies that construction activity in this region increases the potential for runoff and the need for large stormwater conveyance networks not only due to the increase in impervious area associated with development but also because the compacted pervious area effectively approaches the infiltration behavior of an impervious surface.
For all 26 basins, plots of rainfall and runoff depths were used to estimate the effective impervious area and the impervious area initial loss. The data plotted close to a single straight line on all basins, indicating that the effective impervious area remained constant for all storm sizes. The effective impervious fraction was related to total impervious area and the directly connected impervious fraction estimated from maps. For the basins with pervious runoff, the depth of rain in the storm was the most important factor in determining pervious runoff for rainfall less than 50 mm, while for larger storms other factors including rainfall intensity and antecedent wetness were also found to be significant. -from Authors
The perception of the maintenance demands of low impact development (LID) systems represents a significant barrier to the acceptance of LID technologies. Despite the increasing use of LID over the past two decades, stormwater managers still have minimal documentation in regard to the frequency, intensity, and costs associated with LID operations and maintenance. Due to increasing requirements for more effective treatment of runoff and the proliferation of total maximum daily load (TMDL) requirements, there is a greater need for more documented maintenance information for planning and implementation of stormwater control measures (SCMs). This study examined seven different types of SCMs for the first 2-4years of operations and studied maintenance demands in the context of personnel hours, costs, and system pollutant removal. The systems were located at a field facility designed to distribute stormwater in parallel in order to normalize watershed characteristics including pollutant loading, sizing, and rainfall. System maintenance demand was tracked for each system and included materials, labor, activities, maintenance type, and complexity. Annualized maintenance costs ranged from for a vegetated swale to for a wet pond. In terms of mass pollutant load reductions, marginal maintenance costs ranged from TSS removed for porous asphalt, a vegetated swale, bioretention, and a subsurface gravel wetland, to TSS removed for a wet pond, a dry pond, and a sand filter system. When nutrients such as nitrogen and phosphorus were considered, maintenance costs per gper year removed ranged from reasonable to cost-prohibitive, especially for systems with minimal to no nutrient removal. As such, SCMs designed for targeting these pollutants should be selected carefully. The results of this study indicate that generally, LID systems, as compared to conventional systems, have lower marginal maintenance burdens (as measured by cost and personnel hours) and higher water quality treatment capabilities as a function of pollutant removal performance. Cumulative amortized system maintenance expenditures equal the SCM capital construction costs (in constant dollars) in 5.2years for wet ponds and in 24.6years for the porous asphalt system. In general, SCMs with higher percentages of periodic and predictive or proactive maintenance activities have lower maintenance burdens than SCMs with incidences of reactive maintenance. (C) 2013 American Society of Civil Engineers.
Low impact development (LID), an ecologically sensitive development strategy and stormwater management (SWM) method, is beginning to be implemented in more suburban and metropolitan projects. However, construction firms that work in Florida have been relatively slow to adopt LID. One significant reason being that many professionals in the development community believe LID practices raise the cost of construction compared to conventional, “pipe and pond” methods. Our objective for this study was to determine how specific capital costs differed between LID and conventional SWM methods. We surveyed a group of LID-experienced design professionals to collect cost data from projects that were designed using both a LID and conventional scheme. Data on four such projects was received and reported on. We focused on site grading and stormwater piping costs because combined they typically represent a large percentage of conventional SWM costs. Our analysis of the data showed that using LID methods consistently reduced excavation and stormwater piping needs compared to conventional practices. LID cost savings, when site grading and stormwater piping costs were totaled, ranged from 2,925,000. Results suggest that development practitioners should give adequate consideration to LID because it could possibly reduce overall SWM costs compared to conventional practices.
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.
This study investigates the impacts of suburban development on the direct runoff response to a range of storm events using hydrological data from a developing catchment under construction and two residential control catchments in the capital area in Finland. Construction works caused the largest relative changes in the runoff response to frequently occurring small storms. An event precipitation of 17-–20 mm was identified as a threshold indicating a change in the runoff contributing area from the impervious area onto pervious surfaces. The results provided locally derived, updated data that are needed for runoff estimation. Average runoff coefficients from the previous studies, e.g., in the US, as well as those currently used in Finnish stormwater manuals over-estimated the observed volumetric runoff coefficients (CVOL). The new results about the precipitation threshold and the impact of imperviousness and storm event magnitude on runoff contributing area and CVOL provide a hydrological basis for redefining stormwater management principles towards more sustainable urban drainage systems in Finland and in similar climates.
The risk of urban flooding is increasing as a result of rapid urbanization. Green infrastructure (GI) is an emerging planning and design concept to mitigate urban flooding. A community scale simulation model was developed to quantify the effectiveness of GI on reducing the volume and peak flow of urban flooding. Five scenarios, namely expanding green space, converting to concave green space, constructing a runoff retention structure, converting to porous brick pavement, and combining previous four measures were considered for an urban community in Beijing. The outcomes showed that the model performed responsively to simulate the storm runoffs at varying recurrence intervals under these scenarios. Simulation results showed that, the impervious surfaces have the most contribution to the storm runoffs of the community. The reduction capacity for single GI facility was limited, especially in bigger storm events. The integrated GI configuration has effective reduction percentage, such as the total runoff reduction was ranged from 100% to 85.0% and the peak flow reduced 100–92.8%. This work can guide local planners and decision makers in their actions on green infrastructures in community scale.
Flood exposure is increasing in coastal cities owing to growing
populations and assets, the changing climate, and subsidence. Here we
provide a quantification of present and future flood losses in the 136
largest coastal cities. Using a new database of urban protection and
different assumptions on adaptation, we account for existing and future
flood defences. Average global flood losses in 2005 are estimated to be
approximately US52billion by 2050
with projected socio-economic change alone. With climate change and
subsidence, present protection will need to be upgraded to avoid
unacceptable losses of US60-63billion per
year in 2050. To maintain present flood risk, adaptation will need to
reduce flood probabilities below present values. In this case, the
magnitude of losses when floods do occur would increase, often by more
than 50%, making it critical to also prepare for larger disasters than
we experience today. The analysis identifies the cities that seem most
vulnerable to these trends, that is, where the largest increase in
losses can be expected.
The risk of flood disasters is increasing for many coastal societies owing to global and regional changes in climate conditions, sea-level rise, land subsidence and sediment supply. At the same time, in many locations, conventional coastal engineering solutions such as sea walls are increasingly challenged by these changes and their maintenance may become unsustainable. We argue that flood protection by ecosystem creation and restoration can provide a more sustainable, cost-effective and ecologically sound alternative to conventional coastal engineering and that, in suitable locations, it should be implemented globally and on a large scale.
Low impact development (LID) is a land development strategy for managing stormwater at the source with decentralized micro-scale control measures. Since the emergence of LID practices, they have been successfully used to manage stormwater runoff, improve water quality, and protect the environment. However, discussions still surround the effectiveness of many of these practices, resulting in a reluctance to widely adopt them. This paper highlights evidence in the literature regarding the beneficial uses of LID practices. A discussion of how LID practices are represented in hydrologic/water quality models is also provided using illustrative examples of three computational models developed with algorithms and modules to support widespread adoption of LID practices. Finally, the paper suggests directions for future research opportunities.
Wetlands cover at least 6 % of the Earth’s surface. They play a key role in hydrological and biogeochemical cycles, harbour a large part of the world’s biodiversity, and provide multiple services to humankind. However, pressure in the form of land reclamation, intense resource exploitation, changes in hydrology, and pollution threaten wetlands on all continents. Depending on the region, 30–90 % of the world’s wetlands have already been destroyed or strongly modified in many countries with no sign of abatement. Climate change scenarios predict additional stresses on wetlands, mainly because of changes in hydrology, temperature increases, and a rise in sea level. Yet, intact wetlands play a key role as buffers in the hydrological cycle and as sinks for organic carbon, counteracting the effects of the increase in atmospheric CO2. Eight chapters comprising this volume of Aquatic Sciences analyze the current ecological situation and the use of the wetlands in major regions of the world in the context of global climate change. This final chapter provides a synthesis of the findings and recommendations for the sustainable use and protection of these important ecosystems.
The impervious cover model (ICM) has attracted considerable attention in recent years, with nearly 250 research studies testing its basic hypothesis that the behavior of urban stream indicators can be predicted on the basis of the percent impervious cover in their contributing subwatershed. The writers conducted a meta-analysis of 65 new research studies that bear on the ICM to determine the degree to which they met the assumptions of the ICM and supported or did not support its primary predictions. Results show that the majority of research published since 2003 has confirmed or reinforced the basic premise of the ICM, but has also revealed important caveats and limitations to its application. A reformulated conceptual impervious cover model is presented in this paper that is strengthened to reflect the most recent science and simplify it for watershed managers and policy makers. A future challenge is to test the hypothesis that widespread application of multiple management practices at the catchment level can improve the urban stream degradation gradient that has been repeatedly observed by researchers across the country.
Increased impervious surface area is a consequence of urbanization, with correspondent and significant effects on the hydrologic cycle. It is intuitive that an increased proportion of impervious surface brings with it shorter lag times between onset of precipitation and subsequently higher runoff peaks and total volume of runoff in receiving waters. Yet, documentation on quantitative relationships between the extent and type of impervious area and these hydrologic factors remains dispersed across several disciplines. We present a literature review on this subject to better understand and synthesize distinctions among different types of impermeable surface and their relative impacts, and describe the manner in which these surfaces are assessed for their putative impacts on landscape hydrology.
In the decade since the Corps of Engineers (Corps) and Environmental Protection Agency (EPA) officially blessed wetland mitigation banking for purposes of satisfying mitigation requirements under Section 404 of the Clean Water Act (CWA), the practice has fueled an ongoing debate about its pros and cons. For the most part, however, the debate has focused on the relative advantages and disadvantages of banking programs in terms of administrative efficiency and ecological impact, with little attention being paid to the effects of wetland mitigation banking on people. This article presents the first comprehensive empirical study of the demographics of wetland mitigation banking, revealing what has long been suspected - that banking facilitates the redistribution of wetland resources from urban to rural areas, taking with them the important ecosystem service values wetlands provide to human communities.After an overview of the economic service values wetlands provide, the structural biases inherent in the wetland mitigation banking program, and the lack of information about the effects of wetland banking in general, we present the results of an empirical study of 24 wetland mitigation banks in Florida accounting for over 95 percent of all bank activity. By comparing the demographic attributes of the area around each bank to the areas around the development projects that purchase mitigation bank credits to satisfy their mitigation requirements, we show that the loss of wetland resources is concentrated in urban areas, whereas the compensatory mitigation provided by wetland banks is concentrated in rural areas, and that the composition of the project area and bank area populations is significantly different. We examine the policy implications of this effect and suggest several steps that can be taken to better understand and respond to its impact on the distribution of ecosystem services associated with wetland resources.
1. The world's population is increasingly urban, and streams and rivers, as the low lying points of the landscape, are especially sensitive to and profoundly impacted by the changes associated with urbanization and suburbanization of catchments.
2. River restoration is an increasingly popular management strategy for improving the physical and ecological conditions of degraded urban streams. In urban catchments, management activities as diverse as stormwater management, bank stabilisation, channel reconfiguration and riparian replanting may be described as river restoration projects.
3. Restoration in urban streams is both more expensive and more difficult than restoration in less densely populated catchments. High property values and finely subdivided land and dense human infrastructure (e.g. roads, sewer lines) limit the spatial extent of urban river restoration options, while stormwaters and the associated sediment and pollutant loads may limit the potential for restoration projects to reverse degradation.
4. To be effective, urban stream restoration efforts must be integrated within broader catchment management strategies. A key scientific and management challenge is to establish criteria for determining when the design options for urban river restoration are so constrained that a return towards reference or pre-urbanization conditions is not realistic or feasible and when river restoration presents a viable and effective strategy for improving the ecological condition of these degraded ecosystems.
In the United States, mitigating the adverse impacts of flooding has increasingly become the responsibility of local decision
makers. Despite the importance of understanding why flood mitigation techniques are implemented at the local level, few empirical
studies have been conducted over the last decade. Our study addresses this lack of research by examining the factors influencing
local communities to adopt both structural and non-structural flood mitigation strategies. We use statistical models to predict
multiple flood mitigation techniques implemented by cities and counties based on a survey of floodplain administrators and
planning officials across Texas and Florida. Particular attention is paid to the role of organizational capacity to address
floods in addition to various local geophysical and socioeconomic characteristics. Results indicate that organizational capacity
is a significant factor contributing to the implementation of both structural and non-structural flood mitigation techniques,
even when controlling for contextual characteristics.
Current and future energy use from burning of fossil fuels and clearing of forests for cultivation can have profound effects on the global environment, agriculture, and the availability of low-cost, high-quality food for humans. Individual farmers and consumers are expected to be affected by changes in global and regional climate. The agricultural sector in both developing and developed areas needs to understand what is at stake and to prepare for the potential for change wisely. Despite tremendous improvements in technology and crop yield potential, food production remains highly dependent on climate, because solar radiation, temperature, and precipitation are the main drivers of crop growth. Plant diseases and pest infestations, as well as the supply of and demand for irrigation water are influenced by climate. For example, in recent decades, the persistent drought in the Sahelian region of Africa has caused continuing deterioration of food production; the 1988 Midwest drought led to a 30% reduction in U.S. corn production and cost taxpayers $3 billion in direct relief payments to farmers and, weather anomalies associated with the 1997-98 El Niño affected agriculture adversely in Nordeste, Brazil and Indonesia. Earlier in the century, the 1930s U.S. Southern Great Plains drought caused some 200,000 farm bankruptcies in the Dust Bowl; yields of wheat and corn were reduced by as much as 50%.
This paper presents a simple model for assessing the cost-effectiveness of investments in low impact development (LID) for reducing combined sewer overflows (CSOs) in urban watersheds. LID systems, including green roofs, porous pavement, and stormwater treatment wetlands, are site-specific controls for stormwater runoff. If applied throughout a watershed, LID systems like these can reduce the amount of runoff entering the sewer system and reduce CSOs. To be conservative, we focus solely on the function of LID systems as stormwater management techniques, neglecting the other environmental benefits commonly associated with these technologies. A model is presented that can be used to simulate the cost-effectiveness of reducing CSOs through incremental installation of LID technologies across urban watersheds, when they are introduced alone, or in combination with conventional CSO abatement technologies. The potential reduction in CSOs resulting from various levels of LID adoption is simulated using a modified Rational Method. A life-cycle cost analysis is used to compare LID with other alternatives. Given that LID implementation on private property leads to reduced CSOs, a cost sharing scheme is presented that divides the total LID cost into a private cost fraction (born by the property owner) and a public cost fraction (provided by a public agency). The implications of such a policy are discussed with reference to a CSO-shed that drains to the Gowanus Canal (Brooklyn, NY). The results indicate that individual LID systems have differing levels of cost-effectiveness in terms of CSO reduction, but that under a variety of performance and cost scenarios a public subsidy to encourage LID installation represents a cost-effective alternative for public agencies to consider in their efforts to reduce CSOs. Future areas of research in this field are outlined.
The environmental benefits of having retention/detention ponds as major stormwater management facilities in a neighborhood have been well documented since the adoption of green infrastructure strategies in early 1990s. However, the capitalization effect of stormwater treatment ponds in real estate values still remains unclear. This study developed classic hedonic pricing and spatial econometric models to examine the capitalization effects of neighborhood-level detention and retention ponds using both cross-sectional and longitudinal housing prices. The housing market value from 2007 to 2016 was assessed in four subdivisions in Houston, Texas. A subdivision, located in the upper neighborhood, had retention ponds which were converted from detention ponds in 2011, while three subdivisions in the lower neighborhood had detention ponds over the same study period. The study results show that living near retention ponds has positive capitalization impacts on single-family housing prices, not only cross-sectionally but also longitudinally. In contrast, maintaining detention ponds depreciates housing values, and living nearby lowers the price increase over a decade. The findings in this study imply the importance of converting stormwater facilities into a park-like amenity to enhance aesthetic value and generate long-term economic benefits to a neighborhood.
Floods have been the costliest and most disruptive of all natural hazards worldwide. In particular, urban flooding continues to be a concern for both developed and developing countries. Increasing physical risk associated with environmental changes combined with rapid land use change and development make many urban areas more vulnerable to floods. Floods are not solely based on hydro-meteorological conditions, but also result from human activities such as unplanned land use or haphazard development.
While there is a growing body of research focused on understanding the impacts of land use on flood impacts in the United States, little empirical research has been conducted outside of the country although many other nations experience flooding. In particular, many countries in south and east Asia have undergone rapid urbanization concurrent with industrialization and population growth, resulting in worsening flood problems over time.
To address this knowledge gap, this study examines the factors contributing to flood loss in Seoul, Korea, with a particular focus on land use status and change. Panel regression models are analyzed using actual flood loss data for Seoul from 2003 to 2012.
Results indicate that urban built-up land with higher impervious surfaces and agricultural land may cause more flood damage than other land uses analyzed in the study. However, a high density development of compact design can decrease flood loss. These results indicate the importance of resilient land use planning in urban areas. Overall, this study provides insights to planners and decision makers about how they can effectively reduce flood risk and associated adverse impacts.
The Houston Metropolitan Statistical Area has experienced rapid population growth in the past decades. The impact of this growth on the streamflows and 100-year floodplain extent in the Sims Bayou over the 1980 - 2000 period has been studied and is reported. The growth of development and imperviousness over time was determined using parcel data provided by the Harris County Appraisal District and Fort Bend Central Appraisal District, and aerial photographs. The change in the annual streamflow volume over time was studied, and found to have a statistically significant increasing trend. A similar analysis of the annual instantaneous peak flows showed that, although an increasing trend in their values is not apparent, there is a statistically discernible increase in their variability. Strong relationships between the annual streamflow volume and annual instantaneous peak flow, and the imperviousness were found. The imperviousness increased from 15% in 1980 to 18% in 2000. For the 100-year 24-hr storm event, hydrologic analysis with HEC-HMS resulted in peak flows of 41,000 cfs under the 1980 development conditions, and 43,000 cfs under the 2000 conditions. A HEC-RAS hydraulic analysis of the flood inundation extents, resulting from these peak flows, estimated 6,500 acres flooded in 1980, and 7,500 acres in 2000. Assuming that residential parcels have an area between 0.12 and 0.30 acres, it was concluded that, because of development in the 1980s, around an additional 2,100 households were subject to flooding in a 100-year event; while, because of development in the 1990s, a further additional 1,400 households. Although development is needed to accommodate population and employment growth, the negative consequences to people and the built environment can be devastating. Local government implementation of low-impact development policies is needed to reduce the effect of urbanization on the watershed’s hydrology and hydraulics, and also to limit adverse flooding impacts.
Climate change, urbanization, and ecological concerns are all driving the need for new stormwater management strategies. The effects of urbanization are exaggerated by climate change and thus the development of innovative stormwater management techniques are necessary to mitigate these impacts. One emerging stormwater management philosophy is low impact development (LID). LID utilizes distributed stormwater controls (often green infrastructure) as well as green spaces and natural hydrologic features in order to bring the hydrology of urban catchments closer to pre-development conditions. The review provides a summary of the knowledge of LID as a stormwater management technique and climate change mitigation measure as well as the current state of research and implementation of this topic. In order to provide a better understanding of the extensive scope that should be considered for design of low impact developments, methods of optimization, modelling, monitoring and the performance of LID alternatives is covered. LID has been widely adopted and proven successful in many cases; however, there remains uncertainty of its benefits. This review brings together knowledge from many sources in order to provide an overview of LID and examine its performance and implementation.
To mitigate the impacts of impervious surfaces in urban areas, structures such as bioretention systems and permeable pavements have been installed to enhance infiltration in many countries. However, relatively little knowledge is available regarding the performance of such infiltration-based structures in humid tropical and highly urbanized areas. This study investigates the feasibility of enhancing the infiltration of stormwater in tropical urbanized areas using Singapore as a case study. It first shows that the rainfall depth and intensity are both high, but the time interval between consecutive rainfall event is long in Singapore. It then numerically simulates single-event local infiltration and finds that the fraction of infiltrated rainfall is actually high. It finally performs catchment-scale simulations and finds that bioretention systems can enhance infiltration and groundwater recharge particularly during wet periods. However, local mounding of groundwater can be significant and can hinder the performance of those structures. Furthermore, with 5% of catchment area being converted to such structures, the infiltration of the entire catchment is enhanced but still not yet up to the natural level. To increase the overall effectiveness, future studies can look into bioretention systems with underdrain systems.
Resilience discourse is shifting the very meaning of “resilience” from “bouncing back” to “bouncing forward” in the twenty-first century. International policies have provoked cities to play a proactive role in applying land-use and environmental planning strategies for disaster resilience. Strategies of urban flood resilience include prevention, accommodation, fortification, protection, retreat, and green infrastructure. In general, four models of resilience against flooding are primarily adopted: the structure model, the non-structure model, the land-use and environmental planning model, and the retreat planning model. Results indicate that planning more space for the river, wetland planning, polder and retention areas, and permeable surface design do matter in reducing flood risks. Additionally, urban growth management, directing developments and populations away from floodplains, could reduce flood risks and damages. Finally, in retreat model, urban resilience stresses retreat and evacuation to reduce flood damages. Retreat strategies and alternatives, such as property buyouts, relocations, new towns for accommodations, and land swaps for less risky areas, could be applied in helping to achieve urban flood resilience.
Increasing recognition is being given to the adoption of green roofs in urban areas to enhance the local ecosystem. Green roofs may bring several benefits to urban areas including flood mitigation. However, empirical evidence from full-scale roofs, especially those that have been operational for more than several years is limited. This study investigates the hydrologic performance of a full-scale extensive green roof in Leeds, UK. Monitoring of the green roof took place over a 20 month period (between 30th June 2012 and 9th February 2014). The results indicate that the green roof can effectively retain and detain rainfall from the precipitation events included in the analysis. Retention was found to correspond significantly with rainfall depth, duration, intensity and prior dry weather period. Significant differences in retention values between the summer and winter seasons were also noted. Regression analysis failed to provide an accurate model to predict green roof retention as demonstrated by a validation exercise. Further monitoring of the green roof may reveal stronger relationships between rainfall characteristics and green roof retention.
European coasts are coming under increasing threat as a result of climate change from erosion and flooding. While coastal defences such as sea walls have been constructed since Roman times to protect human settlements from the sea, it is now increasingly recognised that these defences are unsustainable. The security provided by ‘hard’ engineered defences has encouraged development on the coast, and the defences themselves have led to the loss of intertidal habitat and the natural protection it provides.
An alternative to maintaining ‘hard’ defences (hold-the-line) to protect land from increasing sea levels is managed realignment, where the engineered defences are deliberately breached. By allowing the coastline to recede to a new line of defence further inland, intertidal habitat is created providing natural protection from flooding and erosion.
The study evaluates the economic efficiency—using cost–benefit analysis—of various managed realignment scenarios compared to a strategy of holding-the-line within the Humber estuary in North-east England. The results of this analysis show that managed realignment can be more economically efficient than holding-the-line over a sufficiently long time period—generally greater than 25 years. Sensitivity analysis demonstrates that results are more sensitive to the amount and value of intertidal habitat generated than they are to the amount and value of carbon stored by this habitat. Cost–benefit analysis is viewed as one component of a wider policy appraisal process within integrated coastal management.
Urbanization impacts the stormwater regime through increased runoff volumes and velocities. Detention ponds and low impact development (LID) strategies may be implemented to control stormwater runoff. Typically, mitigation strategies are designed to maintain postdevelopment peak flows at predevelopment levels for a set of design storms. Peak flow does not capture the extent of changes to the hydrologic flow regime, and the hydrologic footprint residence (HFR) was developed to calculate the area and duration of inundated land during a storm. This study couples a cellular automata land cover change model with a hydrologic and hydraulic framework to generate spatial projections of future development on the fringe of a rapidly urbanizing metropolitan area. The hydrologic flow regime is characterized for existing and projected land cover patterns under detention pond and LID-based control, using the HFR and peak flow values. Results demonstrate that for less intense and frequent rainfall events, LID solutions are better with respect to HFR; for larger storms, detention pond strategies perform better with respect to HFR and peak flow.
This article addresses this understudied aspect of development patterns and community resiliency by examining a five-year record of insured flood loss claims across 144 counties and parishes fringing the Gulf of Mexico. Linear regression models are employed to isolate the effects of five different development patterns on observed flood losses from 2001 to 2005 while controlling for multiple contextual variables. A novel approach is taken to measuring development form by using a series of landscape metrics usually reserved for ecological analysis. These measures enable the assessment of the form of the regional built environment with more specificity than has been possible in previous studies. Results indicate that more connected and concentrated development patterns lead to a reduction in the amount of observed flood losses. These findings illustrate the importance of regional planning and design for fostering flood-resilient communities.
The respective runoff from a 200-m2 permeable pavement test site and an adjacent 850-m2 conventional asphalt road catchment in Auckland, New Zealand, was monitored concurrently between 2006 and 2008. Despite installation over relatively impermeable subgrade soils, and on an atypically high slope (6.0-7.4%) and active roadway, the overall hydrologic performance of the permeable pavement was exceptional. Measured discharge from the permeable pavement underdrain demonstrated peak flow (81 storms) comparable to or below modeled predevelopment conditions for most storms, regardless of antecedent conditions, including a 10-year, 24-h annual recurrence interval event. For large events (5% exceedance), underdrain discharge volume was comparable to predevelopment conditions, but it was substantially less than asphalt runoff for all events up to approximately 70% exceedance. The distributions of peak flow and volume were statistically different between the asphalt catchment runoff and the permeable pavement underdrain discharge (0.05 level of significance). Runoff coefficients ranged from 0.29-0.67 for underdrain discharge (10th-90th percentile events), and from 0.41-0.74 when permeable pavement comprises about one-half of an otherwise impervious catchment. Underdrain lag time and hydrograph duration were reminiscent of a vegetated area. Spearman correlation indicated influences of rainfall depth, intensity, and duration on runoff parameters from both catchments, while antecedent moisture condition was correlated to underdrain discharge lag time. Surface infiltration measurement at four permeable pavement sites revealed that surrounding land uses likely have more influence on pavement clogging than does traffic load. Permeable pavements should be given strong consideration as an low impact development source control, and can also mitigate conventional large design storm flows, but care must be taken during installation to ensure proper function.
Overland flow on a hillslope is significantly influenced by its microtopography, slope length and gradient, and vegetative cover. A 1D kinematic wave model in conjunction with a revised form of the Green-Ampt infiltration equation was employed to evaluate the effect of these surface conditions. The effect of these conditions was treated through the resistance parameter in the kinematic wave model. The resistance in this paper was considered to be made up of grain resistance, form resistance, and wave resistance. It was found that irregular slopes with microtopography eroded more easily than did regular slopes. The effect of the slope gradient on flow velocity and flow shear stress could be negative or positive. With increasing slope gradient, the flow velocity and shear stress first increased to a peak value, then decreased again, suggesting that there exists a critical slope gradient for flow velocity and shear stress. The vegetative cover was found to protect soil from erosion primarily by enhancing erosion-resisting capacity rather than by decreasing the eroding capability of overland flow.
The unprecedented losses from Hurricane Katrina can be explained by two paradoxes. The safe development paradox is that in trying to make hazardous areas safer, the federal government in fact substantially increased the potential for catastrophic property damages and economic loss. The local government paradox is that while their citizens bear the brunt of human suffering and financial loss in disasters, local officials pay insufficient attention to policies to limit vulnerability. The author demonstrates in this article that in spite of the two paradoxes, disaster losses can be blunted if local governments prepare comprehensive plans that pay attention to hazard mitigation. The federal government can take steps to increase local government commitment to planning and hazard mitigation by making relatively small adjustments to the Disaster Mitigation Act of 2000 and the Flood Insurance Act. To be more certain of reducing disaster losses, however, the author suggests that we need a major reorientation of the National Flood Insurance Program from insuring individuals to insuring communities.
The urbanization process and the hydraulic insufficiency of drainage systems are two of the most common causes of urban flooding. In some technical regulations, distributed stormwater management practices (DSMPs) are regarded as a solution for urban flooding problems. They can prevent the formation of runoff, dispose of it locally, or dampen its peak before it reaches the drainage system. Due to their diffuse localization and the wide number of available solutions, the evaluation of their efficiency in terms of flood reduction is very difficult.
The methodology proposed in the present paper relies on the concept that the mitigation effects of DSMPs can be expressed as a function of the changes of the hydrological parameters of a catchment. Once the relation between a DSMP and the equivalent hydrological parameter is established, the efficiency of DSMPs can be evaluated using mathematical models simulating the runoff formation and propagation in urban areas and applying methodologies similar to parameter sensitivity analysis and model uncertainty propagation. Studying the effect of parameter variation on model output, it is possible to analyse quickly several different stormwater management solutions and to identify the best distribution of measures in order to achieve a defined mitigation task.
The simplified procedure has been compared with a more detailed approach obtained by fully integrate DSMPs in the drainage system hydrodynamic model. The procedure has been applied to the real case study of Mondello catchment in Palermo (Italy), and the analysis of the results allows the identification of some guidelines for the mitigation plan preparation.
Channel instability and aquatic ecosystem degradation have been linked to watershed imperviousness in humid regions of the U.S. In an effort to provide a more process-based linkage between observed thresholds of aquatic ecosystem degradation and urbanization, standard single event approaches (U.S. Geological Survey Flood Regression Equations and rational) and continuous hydrologic models (HSPF and CASC2D) were used to examine potential changes in flow regime associated with varying levels of watershed imperviousness. The predicted changes in flow parameters were then interpreted in concert with risk-based models of channel form and instability. Although low levels of imperviousness (10 to 20 percent) clearly have the potential to destabilize streams, changes in discharge, and thus stream power, associated with increased impervious area are highly variable and dependent upon watershed-specific conditions. In addition to the storage characteristics of the pre-development watershed, the magnitude of change is sensitive to the connectivity and conveyance of impervious areas as well as the specific characteristics of the receiving channels. Different stream types are likely to exhibit varying degrees and types of instability, depending on entrenchment, relative erodibility of bed and banks, riparian condition, mode of sediment transport (bedload versus suspended load), and proximity to geomorphic thresholds. Nonetheless, simple risk-based analyses of the potential impacts of land use change on aquatic ecosystems have the potential to redirect and improve the effectiveness of watershed management strategies by facilitating the identification of channels that may be most sensitive to changes in stream power.
This study compared lag time characteristics of low impact residential development with traditional residential development. Also compared were runoff volume, peak discharge, hydrograph kurtosis, runoff coefficient, and runoff threshold. Low impact development (LID) had a significantly greater centroid lag-to-peak, centroid lag, lag-to-peak, and peak lag-to-peak times than traditional development. Traditional development had a significantly greater depth of discharge and runoff coefficient than LID. The peak discharge in runoff from the traditional development was 1,100% greater than from the LID. The runoff threshold of the LID (6.0 mm) was 100% greater than the traditional development (3.0 mm). The hydrograph shape for the LID watershed had a negative value of kurtosis indicating a leptokurtic distribution, while traditional development had a positive value of kurtosis indicating a platykurtic distribution. The lag times of the LID were significantly greater than the traditional watershed for small (<25.4 mm) but not large (≥25.4 mm) storms; short duration (<4 h) but not long duration (≥4 h) storms; and low antecedent moisture condition (AMC; <25.4 mm) storms but not high AMC (≥25.4 mm) storms. This study indicates that LID resulted in lowered peak discharge depth, runoff coefficient, and discharge volume and increased lag times and runoff threshold compared with traditional residential development.
The capacity of a watershed to urbanize without changing its hydrologic response and the relationship between that response and the spatial configuration of the developed areas was studied. The study was conducted in the Whiteoak Bayou watershed (223 km2), located northwest of Houston, Texas, over an analysis period from 1949 to 2000. Annual development data were derived from parcel data collected by the Harris County Appraisal District. Using these data, measures of the spatial configuration of the watershed urban areas were calculated for each year. Based on regression models, it was determined that the annual runoff depths and annual peak flows depended on the annual precipitation depth, the developed area and the maximum 12-h precipitation depth on the day and day before the peak flow took place. It was found that, since the early 1970s, when the watershed reached a 10% impervious area, annual runoff depths and peak flows have increased by 146% and 159%, respectively. However, urbanization is responsible for only 77% and 32% of the increase, respectively, while precipitation changes are responsible for the remaining 39% and 96%, respectively. Likewise, an analysis of the development data showed that, starting in the early 1970s, urbanization in the watershed consisted more of connecting already developed areas than of creating new ones, which increases the watershed’s conveyance capacity and explains the change in its response. Before generalizing conclusions, though, further research on other urban watersheds with different urbanization models appears to be necessary.
This article presents an overview of GeoDa™, a free software program intended to serve as a user-friendly and graphical introduction to spatial analysis for non-geographic information systems (GIS) specialists. It includes functionality ranging from simple mapping to exploratory data analysis, the visualization of global and local spatial autocorrelation, and spatial regression. A key feature of GeoDa is an interactive environment that combines maps with statistical graphics, using the technology of dynamically linked windows. A brief review of the software design is given, as well as some illustrative examples that highlight distinctive features of the program in applications dealing with public health, economic development, real estate analysis, and criminology.
Increases in concentrations of greenhouse gases projected for the 21st century are expected to lead to increased mean global
air and ocean temperatures. The National Assessment of Potential Consequences of Climate Variability and Change (NAST 2001)
was based on a series of regional and sector assessments. This paper is a summary of the coastal and marine resources sector
review of potential impacts on shorelines, estuaries, coastal wetlands, coral reefs, and ocean margin ecosystems. The assessment
considered the impacts of several key drivers of climate change: sea level change; alterations in precipitation patterns and
subsequent delivery of freshwater, nutrients, and sediment; increased ocean temperature; alterations in circulation patterns;
changes in frequency and intensity of coastal storms; and increased levels of atmospheric CO2. Increasing rates of sea-level rise and intensity and frequency of coastal storms and hurricanes over the next decades will
increase threats to shorelines, wetlands, and coastal development. Estuarine productivity will change in response to alteration
in the timing and amount of freshwater, nutrients, and sediment delivery. Higher water temperatures and changes in freshwater
delivery will alter estuarine stratification, residence time, and eutrophication. Increased ocean temperatures are expected
to increase coral bleaching and higher CO2 levels may reduce coral calcification, making it more difficult for corals to recover from other disturbances, and inhibiting
poleward shifts. Ocean warming is expected to cause poleward shifts in the ranges of many other organisms, including commercial
species, and these shifts may have secondary effects on their predators and prey. Although these potential impacts of climate
change and variability will vary from system to system, it is important to recognize that they will be superimposed upon,
and in many cases intensify, other ecosystem stresses (pollution, harvesting, habitat destruction, invasive species, land
and resource use, extreme natural events), which may lead to more significant consequences.
The Scheldt is a tidal river that originates in France and flows through Belgium and the Netherlands. The tides create significant
flood risks in both the Flemish region in Belgium and the Netherlands. Due to sea level rise and economic development, flood
risks will increase during this century. This is the main reason for the Flemish government to update its flood risk management
plan. For this purpose, the Flemish government requested a cost-benefit analysis of flood protection measures, considering
long-term developments. Measures evaluated include a storm surge barrier, dyke heightening and additional floodplains with
or without the development of wetlands. Some of these measures affect the flood risk in both countries. As policies concerning
the limitation of flood risk differ significantly between the Netherlands and Flanders, distinctive methodologies were used
to estimate the impacts of measures on flood risk. A risk-based approach was applied for Flanders by calculating the impacts
of flood damage at different levels of recurrence, for the base year (2000) and in case of a sea level rise of 60cm by 2100.
Policy within the Netherlands stipulates a required minimal protection level along the Scheldt against storms with a recurrence
period of 1 in 4,000years. It was estimated how flood protection measures would delay further dyke heightening, which is
foreseen as protection levels are presently decreasing due to rising sea levels. Impacts of measures (safety benefits) consist
of delays in further dyke heightening. The results illustrate the importance of sea level rise. Flood risks increased fivefolds
when a sea level rise of 60cm was applied. Although more drastic measures such as a storm surge barrier near Antwerp offer
more protection for very extreme storms, a combination of dykes and floodplains can offer higher benefits at lower costs.
KeywordsFlood risk management–Cost-benefit analysis–Sea level rise–Floodplain restoration–Ecosystem services
When information about soil quality is complete, wetland creation with a take-it-or-leave-it contract, which specifies wetland size and transfer, yields higher social benefits than if a uniform contract, which offers a payment proportional to the wetland size, had been used. This result points to a paradox because uniform contracts have been used a lot in practice.This article concentrates on the presence of asymmetric information about soil quality as a possible explanation for this paradox. It shows that the choice of instrument for wetland creation has welfare implications. Different contracts typically yield quite different social welfare surpluses and distribution between interest groups. It is not obvious, which of four contracts studied dominates when a farm characteristic affecting costs is unknown to the social planner. The probability distribution of the characteristic, the size of the excess burden, the elasticity of costs and benefits to wetland size and the cost of acquiring missing information influence the outcome.
This paper considers the implications of a range of global-mean sea-level rise and socio-economic scenarios on: (1) changes in flooding by storm surges; and (2) potential losses of coastal wetlands through the 21st century. These scenarios are derived from the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES). Four different storylines are analysed: the A1FI, A2, B1 and B2 ‘worlds’. The climate scenarios are derived from the HadCM3 climate model driven by the SRES emission scenarios. The SRES scenarios for global-mean sea-level rise range from 22 cm (B1 world) to 34 cm (A1FI world) by the 2080s, relative to 1990. All other climate factors, including storm characteristics, are assumed to remain constant in the long term. Population and GDP scenarios are downscaled from the SRES regional analyses supplemented with other relevant scenarios for each impact analysis.