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CALIFORNIA BEAVER RESTORATION ASSESSMENT TOOL Building Realistic Expectations for Partnering with Beaver in Conservation and Restoration Recommended Citation
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... The BRAT uses a GIS layer showing infrastructure to determine when beaver dam building (or LTPBR projects) may come into conflict with human activities. Specifically, the BRAT conservation and restoration model assesses risk by identifying the proximity of stream reaches that can support beaver dam building to human infrastructure that can be flooded or clogged and to areas with high-intensity land use (e.g., urban areas, row crop agriculture, and roads) that can be impacted by beaver activity (Macfarlane et al. 2019). ...
... The developers of the BRAT model 3 recently completed BRAT analysis on the majority of California's streams on behalf of The Nature Conservancy (Macfarlane et al. 2019). They analyzed over 78,835 km of perennial streams in 80 hydrologic unit code 8 level watersheds within the Sierra Nevada, Cascades, Coast, and Klamath mountains to identify the most appropriate locations for beaver-assisted restoration projects and BDAs ( Figure 11). ...
... Extent of Beaver Restoration Assessment Tool data available in California(Macfarlane et al. 2019). ...
Summary: This Fish Bulletin discusses low-tech process-based restoration of riverscapes and draws extensively from the work of Wheaton et al. (2019) to describe low-cost restoration techniques that can improve riparian, floodplain, and instream habitat in many California streams.
... Indeed, beavers are often a nuisance in highly anthropized environments, cutting down planted trees, clogging drains, flooding public or private lands, etc. BRAT therefore attempts to assess these negative externalities (W. Macfarlane et al. 2020). The tool takes as input a dataset describing the spatial extent of valley bottoms within the riverscape (typically produced by VBET), the two layers describing roads and railways, the polygon layer of bankfull channels, and a land use layer taken from LANDFIRE in the USA (W. ...
... The tool takes as input a dataset describing the spatial extent of valley bottoms within the riverscape (typically produced by VBET), the two layers describing roads and railways, the polygon layer of bankfull channels, and a land use layer taken from LANDFIRE in the USA (W. Macfarlane et al. 2020). ...
... Infrastructure is classified according to distances typically traveled by beavers, immediately adjacent (less than 30 meters), within a normal forage radius (30-100 meters), within a possible travel radius (100-300 meters), and outside the area of concern (more than 300 meters) (W. Macfarlane et al. 2020). The output data are combined to assign a "risk score" to the reaches (W. ...
The Riverscapes Consortium is an international collaboration of researchers and practitioners dedicated to preserving the healthy functioning of riverscapes. To this end, it is developing "production" grade models for river managers, at Utah State University. The goal of these models is to characterize riverscapes and prioritize restoration and conservation efforts. To do this, they use free, public geospatial data available at a national scale.
However, these models are currently applied almost exclusively in the USA. They are automated in the cloud for American watersheds, and their results are available on a dedicated platform, the " Data Exchange ". The feasibility of applying these models to a context radically different from that of the USA, such as France, was not known before the start of this internship.
This was the context of the internship that produced the present document. The aim was, therefore, to test the feasibility of such an adaptation by creating a database containing all the French geodata layers used and usable by the models, then modifying their Python scripts to allow them to work with French data, modifying some of the models' logic, and creating new French symbologies and "business logics" (XML files allowing standardized presentation of results).
A total of four of the eight "production" grade models were applied and modified to work with French data, namely a model for contextualizing the layers used (Riverscapes Context), a model for estimating the full bankfull width of the riverscape network (Channel Area Tool), a model for topographic analysis (TauDEM), and a model for characterizing the geomorphological units of riverscapes and particularly valley bottoms (VBET).
This project needs to be continued. Further reflection is needed on how to adapt and apply the following models and on the relevance of applying some of them (RCAT). In the future, it will also be necessary to calibrate the models by means of remote sensing and field studies in order to obtain usable results in the French context.
Le Riverscapes Consortium est une collaboration internationale de chercheurs et de praticiens engagés dans la préservation du bon état de fonctionnement des corridors fluviaux. Pour ce faire, elle développe notamment, à l'Université d'Etat de l'Utah, des modèles dits de grade "production" à destination des gestionnaires. Ces modèles ont pour but de permettre la caractérisation des corridors fluviaux, ainsi que la priorisation des actions de restauration et de conservation. Ils utilisent pour ce faire des données géospatiales publiques, gratuites, et disponibles à l'échelle nationale.
Cependant, ces modèles ne sont pour l'heure quasiment qu'exclusivement appliqués sur le territoire étasunien. Ils sont automatisés dans le cloud pour les bassins versants américains et leurs résultats sont disponibles sur une plateforme dédiée, le "Data exchange". La faisabilité de l'application de ces modèles sur un contexte radicalement différent du contexte étasunien, tel que le contexte français, n'était pas connue avant le début de ce stage.
C'est dans ce contexte que s'inscrit le stage ayant donné naissance au présent document. L'objectif a donc été de tester la faisabilité d'une telle adaptation, via la création d'une base de données regroupant l'ensemble des couches de données géospatiales françaises utilisées et utilisables par les modèles, puis la modification de leurs scripts Python pour permettre leur fonctionnement avec les données françaises, la modification de certaines logiques des modèles, et la création de nouvelles symbologies et « Business Logics » (fichiers XML permettant l'affichage standardisé des résultats) françaises.
Au total, quatre des huit modèles de grade "production" ont été appliqués et modifiés pour fonctionner avec les données françaises, à savoir un modèle de contextualisation des couches utilisées (Riverscapes Context), un modèle estimant la largeur à plein bord du réseau hydrographique (Channel Area Tool), un modèle d'analyses topographiques (TauDEM), et un modèle permettant la caractérisation des unités géomorphologiques des corridors fluviaux et notamment du fond de vallée (VBET).
Ce projet appelle à être poursuivi. Des réflexions restent à mener sur la manière de adapter et d'appliquer les modèles suivants, et sur la pertinence même de l'application de certains d'entre eux (RCAT). A l'avenir, une calibration devra également être réalisée via télédétection et études de terrain, afin de permettre aux modèles de fournir des résultats exploitables sur le contexte français.
BRAT was developed to provide more realistic expectation management for beaver assisted restoration and serves as a planning tool intended to help resource managers, restoration practitioners, wildlife biologists and researchers better manage expectations about where beaver might be useful. Specifically, BRAT is a spatially explicit network tool that predicts where along streams and rivers beaver may be useful as a restoration tool and where they may be a nuisance, in which case their impacts can be mitigated or the nuisance beaver can serve as a source population for live-trapping and relocation to areas where they can help achieve restoration and conservation objectives.
Restoration of riparian and wet meadow ecosystems in semi‐arid rangelands of the western U.S. is a high priority given their ecological and hydrological importance in the region. However, traditional restoration approaches are often intensive and costly, limiting the extent over which they can be applied. Practitioners are increasingly trying new restoration techniques that are more cost effective, less intensive, and can more practically scale up to the scope of degradation. Unfortunately, practitioners typically lack resources to undertake outcome‐based evaluations necessary to judge the efficacy of these techniques. In this study, we use freely‐available, satellite remote sensing to explore changes in vegetation productivity (NDVI) of three distinct, low‐tech riparian and wet meadow restoration projects. Case studies are presented that range in geographic location (Colorado, Oregon, and Nevada), restoration practice (Zeedyk structures, beaver dam analogs, and grazing management), and time since implementation. Restoration practices resulted in increased vegetation productivity of up to 25% and increased annual persistence of productive vegetation. Improvements in productivity with time since restoration suggest that elevated resilience may further enhance wildlife habitat and increase forage production. Long‐term, documented outcomes of conservation are rare; we hope our findings empower practitioners to further monitor and explore the use of low‐tech methods for restoration of ecohydrologic processes at meaningful spatial scales.
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Quantifying the natural flow regime is essential for management of water resources and conservation of aquatic ecosystems. Understanding the degree to which anthropogenic activities have altered flows is critical for developing effective conservation strategies. Assessing flow alteration requires estimates of flows expected in the absence of human influence and under current land use and water management.
There are several techniques to predict flows in streams and rivers; however, none have been applied to make predictions of natural flow conditions over large regions and time periods. We utilised machine learning statistical models to predict natural monthly flows (natural streamflows without the influence of water management or anthropogenic land use) in California from 1950 to 2015, using time‐dependent and fixed watershed variables from reference stream gages. These models were then used to make estimates of mean, maximum and minimum monthly flows in all streams in the state.
We compared observed flows measured at 540 stream gages across the state with expected natural flows at the same locations, to quantify the type, frequency and magnitude of flow alteration over the past 20 years (1996–2015). A gage was considered altered if an observed flow metric (monthly mean, annual maximum, annual minimum) fell outside the 80% prediction interval of the modelled flow estimate.
We found that 95% of the 540 stream gages in California had at least 1 month of altered flows over the past 20 years, and 11% of gages were frequently altered (over two‐thirds of the months recorded had evidence of altered flows). The type of alteration varied across the state with flows being either depleted, inflated or a mix of both at different times of the year. Most altered gages (68%) exhibited both depletion and inflation in monthly flows over the time period. Inflation of monthly mean flows was most prevalent during the summer months, while depletion of monthly flows was evident throughout the year.
Type, frequency and magnitude of flow alteration varied by region. Flow depletion was present at >80% of gages in the North Coast and Central Coast, flow inflation was measured at >80% of gages in the South Coast and San Francisco Bay and both depletion and inflation were evident at >80% of gages in the Sacramento River and San Joaquin and Tulare regions. Annual maximum flows were consistently depleted and annual minimum flows were commonly inflated in the Sierra Nevada and Central Valley (Sacramento River and San Joaquin and Tulare regions). This is the first study to comprehensively assess flow alteration at stream gages across California. Understanding the patterns and degree of alteration can aid in prioritising streams for environmental flow assessment and developing conservation strategies for native freshwater biota.
In highly impaired watersheds, it is critical to identify both areas with desirable habitat as conservation zones and impaired areas with the highest likelihood of improvement as restoration zones. We present how detailed riparian vegetation mapping can be used to prioritize conservation and restoration sites within a riparian and instream habitat restoration program targeting 3 native fish species on the San Rafael River, a desert river in southeastern Utah, United States. We classified vegetation using a combination of object-based image analysis (OBIA) on high-resolution (0.5 m), multispectral, satellite imagery with oblique aerial photography and field-based data collection. The OBIA approach is objective, repeatable, and applicable to large areas. The overall accuracy of the classification was 80% (Cohen's κ = 0.77). We used this high-resolution vegetation classification alongside existing data on habitat condition and aquatic species' distributions to identify reaches' conservation value and restoration potential to guide management actions. Specifically, cottonwood (Populus fremontii) and tamarisk (Tamarix ramosissima) density layers helped to establish broad restoration and conservation reach classes. The high-resolution vegetation mapping precisely identified individual cottonwood trees and tamarisk thickets, which were used to determine specific locations for restoration activities such as beaver dam analogue structures in cottonwood restoration areas, or strategic tamarisk removal in high-density tamarisk sites. The site prioritization method presented here is effective for planning large-scale river restoration and is transferable to other desert river systems elsewhere in the world.
Beaver have been referred to as ecosystem engineers because of the large impacts their dam building activities have on the landscape; however, the benefits they may provide to fluvial fish species has been debated. We conducted a watershed-scale experiment to test how increasing beaver dam and colony persistence in a highly degraded incised stream affects the freshwater production of steelhead (Oncorhynchus mykiss). Following the installation of beaver dam analogs (BDAs), we observed significant increases in the density, survival, and production of juvenile steelhead without impacting upstream and downstream migrations. The steelhead response occurred as the quantity and complexity of their habitat increased. This study is the first large-scale experiment to quantify the benefits of beavers and BDAs to a fish population and its habitat. Beaver mediated restoration may be a viable and efficient strategy to recover ecosystem function of previously incised streams and to increase the production of imperiled fish populations.
Restoration projects in the United States typically have among the stated goals those of increasing channel stability and sediment storage within the reach. Increased interest in ecologically based restoration techniques has led to the consideration of introducing beavers to degraded channels with the hope that the construction of beaver dams will aggrade the channel. Most research on beaver dam modification to channels has focused on the long‐term effects of beavers on the landscape with data primarily from rivers in the western United States. This study illustrated that a role exists for beavers in the restoration of fine‐grained, low gradient channels.
A channel on the Atlantic Coastal Plain was analyzed before, during, and after beaver dams were constructed to evaluate the lasting impact of the beaver on channel morphology. The channel was actively evolving in a former reservoir area upstream of a dam break. Colonization by the beaver focused the flow into the channel, allowed for deposition along the channel banks, and reduced the channel width such that when the beaver dams were destroyed in a flood, there was no channel migration and net sediment storage in the reach had increased. However, the majority of the deposition occurred at the channel banks, narrowing the channel width, while the channel incised between sequential beaver dams. The study indicated that where channels are unstable laterally and bank erosion is a concern, the introduction of beavers can be a useful restoration tool. However, because of the likelihood of increased channel bed erosion in a reach with multiple beaver dams, they may not be the best solution where aggradation of an incised channel bed is the desired result. Copyright © 2014 John Wiley & Sons, Ltd.
Abstract The construction of beaver dams facilitates a suite of hydrologic, hydraulic, geomorphic, and ecological feedbacks that increase stream complexity and channel–floodplain connectivity that benefit aquatic and terrestrial biota. Depending on where beaver build dams within a drainage network, they impact lateral and longitudinal connectivity by introducing roughness elements that fundamentally change the timing, delivery, and storage of water, sediment, nutrients, and organic matter. While the local effects of beaver dams on streams are well understood, broader coverage network models that predict where beaver dams can be built and highlight their impacts on connectivity across diverse drainage networks are lacking. Here we present a capacity model to assess the limits of riverscapes to support dam-building activities by beaver across physiographically diverse landscapes. We estimated dam capacity with freely and nationally-available inputs to evaluate seven lines of evidence: (1) reliable water source, (2) riparian vegetation conducive to foraging and dam building, (3) vegetation within 100 m of edge of stream to support expansion of dam complexes and maintain large colonies, (4) likelihood that channel-spanning dams could be built during low flows, (5) the likelihood that a beaver dam is likely to withstand typical floods, (6) a suitable stream gradient that is neither too low to limit dam density nor too high to preclude the building or persistence of dams, and (7) a suitable river that is not too large to restrict dam building or persistence. Fuzzy inference systems were used to combine these controlling factors in a framework that explicitly also accounts for model uncertainty. The model was run for 40,561 km of streams in Utah, USA, and portions of surrounding states, predicting an overall network capacity of 356,294 dams at an average capacity of 8.8 dams/km. We validated model performance using 2852 observed dams across 1947 km of streams. The model showed excellent agreement with observed dam densities where beaver dams were present. Model performance was spatially coherent and logical, with electivity indices that effectively segregated capacity categories. That is, beaver dams were not found where the model predicted no dams could be supported, beaver avoided segments that were predicted to support rare or occasional densities, and beaver preferentially occupied and built dams in areas predicted to have pervasive dam densities. The resulting spatially explicit reach-scale (250 m long reaches) data identifies where dam-building activity is sustainable, and at what densities dams can occur across a landscape. As such, model outputs can be used to determine where channel–floodplain and wetland connectivity are likely to persist or expand by promoting increases in beaver dam densities.
The US Castor canadensis population has caused severe damage to valuable timberland through dam-building and flooding of bottomland forest. Since beaver populations are mobile, beaver extermination in controlled parcels results in beaver immigration from neighbouring less controlled parcels. This study develops a bioeconomic model that incorporates dispersive population dynamics of beavers into the design of a cost-minimizing trapping strategy. The optimality system for this problem is solved numerically. The validity of the theoretical model is examined using the bioeconomic data collected for the Wildlife Management Regions of the New York State Department of Environmental Conservation. The optimal trapping program causes the initially uneven population to eventually smooth out across the habitat. -from Authors
Through dam building and feeding activities, beaver act as a keystone species to alter hydrology, channel geomorphology, biogeochemical pathways and community productivity. In Quebec, density of dams on the small streams (= or <4th order) studied averages 10.6 dams/km; the streams retain up to 6500 m3 of sediment per dam, and the wetted surface area of the channel is increased up to several hundredfold. Beaver are also active in larger order streams (= or >5th order), but their effects are most noticeable along riverbanks and in floodplains. Comparative carbon budgets per unit area for a riffle on 2nd order Beaver Creek and a beaver pond downstream show the pond receives only 42% of the carbon acquired by the riffle annually, but because the pond has a surface area 7 times greater than the riffle, it receives nearly twice as much carbon as the riffle per unit of channel length. Carbon in the pond has an estimated turnover time of 161 yr compared to 24 yr for the riffle. Beaver ponds are important sites for organic matter processing. -from Authors