Topic Results: Stream RestorationBack to Currated List of Topics
Beavers are ecosystem engineers that create and maintain riparian wetland ecosystems in a variety of ecologic, climatic, and physical settings. Despite the large-scale implications of ongoing beaver conservation and range expansion, relatively few landscape-scale studies have been conducted, due in part to the significant time required to manually locate beaver dams at scale. To address this need, we developed EEAGER—an image recognition machine learning model that detects beaver complexes in aerial and satellite imagery. We developed the model in the western United States using 13,344 known beaver dam locations and 56,728 nearby locations without beaver dams. Performance assessment was performed in twelve held out evaluation polygons of known beaver occupancy but previously unmapped dam locations. These polygons represented regions similar to the training data as well as more novel landscape settings. Our model performed well overall (accuracy = 98.5%, recall = 63.03%, precision = 25.83%) in these areas, with stronger performance in regions similar to where the model had been trained. We favored recall over precision, which results in a more complete catalog of beaver dams found but also a higher incidence of false positives to be manually removed during quality control. These results have far-reaching implications for monitoring of beaver-based river restoration, as well as potential applications detecting other complex landforms.
Restoring Western Headwater Streams with Low-Tech Process-Based Methods: A Review of the Science and Case Study Results, Challenges and Opportunities
This report reviews published research and unpublished case study information on the effects ofrestoring incised and degraded headwater streams in western states with low-tech processbased restoration methods (LTPBR). LTPBR is a subset of process-based restoration (PBR) that seeks to re-establish natural stream processes by reconnecting incised streams with their floodplains and adjacent wetlands so that more frequent inundation of the floodplain occurs. Projects involve the use of simple, temporary, hand-built wood and rock structures that mimic
natural beaver structures, acting as speed bumps that capture sediments to aggrade the stream. LTPBR approaches are substantially less expensive than form-based stream restoration approaches that employ heavy equipment.i This approach is appealing in part because low project costs enable implementation at a scale that can respond to the extent of floodplain alteration, which is estimated at 45% of headwaters streams in Colorado. ii Negative effects of disconnected floodplains include lower groundwater tables, lower summer base flows,
warmer water temperatures, and substantial loss of riparian habitat.
Within the State of Maryland, the potential water quality benefits of beaver are not recognized as contributing to regulatory-mandated pollution reductions. Therefore, jurisdictions lack a regulatory incentive to either encourage beaver colonization or manage and protect existing beaver habitat. Such an incentive is important, as conflicts between human and beaver habitat regularly arise. While beaver habitat often increases the groundwater table and the wetted extent of a stream system, this is not always welcomed by homeowners and can result in beaver being trapped out, with beaver dams dismantled. If beaver ponds were a recognized BMP to improve water quality, it would assist local jurisdictions with the development of beaver habitat conservation programs via easements and adaptive management. Rather than living on top of nature and replicating nature’s original ecosystem engineers with significant amounts of tax dollars, citizens could live with nature allowing tax dollars to go further, and implement more ecological restoration.
Comparing translocated beavers used as passive restoration tools to resident beavers in degraded desert rivers
Wildlife translocation facilitates conservation efforts, including recovering imperiled species, reducing human–wildlife conflict, and restoring degraded ecosystems. Beaver (American, Castor canadensis; Eurasian, C. fiber) translocation may mitigate human–wildlife conflict and facilitate ecosystem restoration. However, few projects measure outcomes of translocations by monitoring beaver postrelease, and translocation to desert streams is relatively rare. We captured, tagged, and monitored 47 American beavers (hereafter, beavers) which we then translocated to two desert rivers in Utah, USA, to assist in passive river restoration. We compared translocated beaver site fidelity, survival, and dam-building behavior to 24 resident beavers. We observed high apparent survival (i.e., survived and stayed in the study site) for eight weeks postrelease of resident adult beavers (0.88 ± 0.08; standard error) and lower but similar apparent survival rates between resident subadult (0.15 ± 0.15), translocated adult (0.26 ± 0.12), and translocated subadult beavers (0.09 ± 0.08). Neither the pre- nor the post-translocation count of river reaches with beaver dams were predicted well by the Beaver Restoration Assessment Tool, which estimates maximum beaver dam capacity by river reach, suggesting beaver-related restoration is not maximized in these rivers. Translocated beavers exhibited similar characteristics as resident subadult beavers during dispersal; they were more vulnerable to predation and many emigrated from the study sites. High mortality and low site fidelity should be anticipated when translocating beavers, but even so, translocation may have contributed to additional beaver dams in the restoration sites, which is the common goal of beaver-assisted river restoration. Multiple releases at targeted restoration sites may eventually result in establishment and meet conservation objectives for desert rivers.
Beavers are ecosystem engineers that can dramatically change the shape of the landscape and how water moves through it. They create and maintain wetland environments across North America and Eurasia in a wide variety of places, including mountains, deserts, coasts, forests, grasslands, shrublands, etc. Despite their large influence on the landscape, there are very few programs that monitor them at the landscape, regional, or continental scale. This is partially due to how much time it takes to find and identify beaver dams in satellite and aerial images. To make it easier for us to find and understand the influence of beavers at larger scales, we built a model that can automatically find beaver dams in satellite and aerial imagery. While our model is trained to find beaver dams, this type of model has promise for finding other landscape features too. The model isn’t perfect, but it is a strong starting point and will continue to improve as more people use it.
A current challenge in ecohydrology is the incorporation of beaver dams into hydrological models. Select works have attempted to solve this problem using routing approaches, Manning coefficient variations, pond dynamics, or fully-distributed hydraulic models; however, all these approaches assume that all beaver dams are homogeneous structures and react in the same way to rainfall events. Recent findings highlight the importance of including the functional heterogeneity of beaver dams, especially the water path past the dam (dam flow state). To overcome the challenge of accounting for different dam flow states interrupting downstream water transmission in different ways, we developed BEAVERPY, a flow state-based Python package that can be coupled with the platform Cold Regions Hydrological Model (CRHM) to represent both streamflow modulation by ponds and dams, while also simulating infiltration and evapotranspiration. We used the broad-crested weir equation for the overflow dams, the Darcy equation for the seep flow dams, and the v-notch weir equation for the gapflow dams, verifying each case with synthetic experiments. To calibrate and validate the model, we instrumented the ponds and streams in a peatland fen in the Canadian Rocky Mountains in Alberta with level sensors and ‘DamCams’ (trail cameras) to capture flow type. Then, we used LIDAR DEM data and high-resolution imagery to delineate the hydrological response units. Each pond is represented as an HRU, which can interact with soil and routing modules. Finally, we conducted a scenario-testing experiment to understand the sensitivity of different beaver dam flow states for several storms. The results indicate the importance of including flow state dynamics for the beaver dam representations, and highlight the importance of integrating animal-ecological aspects into the streamflow modelling. This research has implications for understanding the use of beaver as a nature-based solution for flood mitigation and river restoration.
Hydrologic extremes dominate chemical exports from riparian zones and dictate water quality in major river systems. Yet, changes in land use and ecosystem services alongside growing climate variability are altering hydrologic extremes and their coupled impacts on riverine water quality. In the western U.S., warming temperatures and intensified aridification are increasingly paired with the expanding range of the American beaver—and their dams, which transform hydrologic and biogeochemical cycles in riparian systems. Here, we show that beaver dams overshadow climatic hydrologic extremes in their effects on water residence time and oxygen and nitrogen fluxes in the riparian subsurface. In a mountainous watershed in Colorado, U.S.A., we find that the increase in riparian hydraulic gradients imposed by a beaver dam is 10.7–13.3 times greater than seasonal hydrologic extremes. The massive hydraulic gradient increases hyporheic nitrate removal by 44.2% relative to seasonal extremes alone. A drier, hotter climate in the western U.S. will further expand the range of beavers and magnify their impacts on watershed hydrology and biogeochemistry, illustrating that ecosystem feedbacks to climate change will alter water quality in river systems.
Rivers and streams, when fully connected to their floodplains, are naturally resilient systems that are increasingly part of the conversation on nature-based climate solutions. Reconnecting waterways to their floodplains improves water quality and quantity, supports biodiversity and sensitive species conservation, increases flood, drought and fire resiliency, and bolsters carbon sequestration. But, while the importance of river restoration is clear, beaver-based restoration—for example, strategic coexistence, relocation, and mimicry—remains an underutilized strategy despite ample data demonstrating its efficacy. Climate-driven disturbances are actively pushing streams into increasingly degraded states, and the window of opportunity for restoration will not stay open forever. Therefore, now is the perfect time to apply the science of beaver-based low-tech process-based stream restoration to support building climate resilience across the landscape. Not every stream will be a good candidate for beaver-based restoration, but we have the tools to know which ones are. Let us use them.
A Review of Two Novel Water-Tight Beaver Dam Analogs (WTBDA) to Restore Eroded Seasonal Creeks in Drain Tile Zones to Permanent Beaver Wetlands
Reducing nutrient runoff in streams is an important task to reduce algae blooms and associated environmental damage in large waterbodies. Beaver Dam Analogs (WTBDA) are an means to address this problem. These Water Tight Beaver Dam Analogs (WTBDA) present a novel approach to this technique that also aim to restore eroded seasonal creeks to perennial wetlands.
Published in Chesapeake Bay Magazine in March 2021, the article highlights various industry professionals who attended BeaverCON 2020. Professionals in stream restoration, water control devices, and environmental journalism were interviewed for this article, discussing successes related to coexisting with beavers. Several important beaver-related studies are mentioned.
The Impact of Beaver Dams on the Morphology of a River in the Eastern United States with Implications for River Restoration
A case study of the impacts of beaver dams on a low gradient, fine-grained alluvial channel on the Atlantic Coastal Plain, illustrating the role that exists for beavers in stream restoration.
A decision support and planning tool for beaver management, to analyze all perennial rivers and streams in Utah. This model assess the upper limits of riverscapes to support beaver dam-building activities.
A short presentation from the Society of Wetland Scientists webinar in April 2021, given by Mark Beardsley of Eco Metrics, LLC in Colorado. Beardsley amplifies many voices of the beaver community in a presentation about how a lack of understanding of stream ecosystems has prevented human and beaver from reaching a complete state of collaboration. He describes in detail how active beaver wetlands create ecosystem services more abundant than wetlands without beaver.
Although the beaver-related restoration has broad appeal, especially in water-limited systems, its effectiveness is not yet well documented. This article presents a process-expectation framework that links beaver-related restoration tactics to commonly expected outcomes by identifying the set of process pathways that must occur to achieve those expected outcomes. Due to changes in expectations, a more useful paradigm for evaluating process-based restoration would be to identify relevant processes and to rigorously document how projects do or do not proceed along expected process pathways using both quantitative and qualitative data.
Idaho Beaver Restoration Assessment Tool Building Realistic Expectations for Partnering with Beaver in Conservation and Restoration
Traditional restoration efforts are barely scratching the surface of what could be restored. Moreover, a disproportionate amount of funds are spent on too few miles of streams and rivers leaving millions of miles of degraded streams neglected. To fill this gap, restoration practitioners are increasingly trying restoration techniques that are more cost?effective, less intensive, and can more practically scale up to the enormous scope of degradation.
A synthesis of scientific literature and our current level of: 1) understanding of the relationship between habitat quantity and quality and salmon production, 2) quantify the improvements in salmon production and survival that can be expected with different restoration actions, and 3) use models to help identify habitat factors limiting production and quantify population-level responses to restoration.
We have developed and implemented a simple approach that emulates the ecosystem engineering effects of beaver. This approach is less expensive and disruptive than typical large-scale engineering efforts and has the potential to restore both fish habitat and floodplain vegetation more rapidly than simply revegetating and waiting for the riparian zone to mature. (Pg 246 – 255)
Beaver (Castor Canadensis) of the Salinas River: A Human Dimensions-Inclusive Overview for Assessing Landscape-Scale Beaver-Assisted Restoration Opportunities
Study to gather and produce human dimensions-inclusive, basin-centralized beaver knowledge through an explorative, benefits-maximizing approach to landscape-scale BAR opportunities assessment in the Salinas River.