Beaver Dam Analogs for Riparian Restoration on Left Hand Creek, Colorado
Vincent L. Sortman
Biohabitats Inc.
Denver, CO
During the September 2013 flood, Left Hand Creek suffered extreme erosion, deposition, and habitat degradation. The Left Hand Watershed Center has been obtaining and managing grants to implement flood recovery restoration projects on Left Hand Creek. One of those projects included a reach of Left Hand Creek located on an alluvial depositional area. The reach is at the downstream end of Left Hand Canyon and provides the first significant floodplain (about 400’ wide) where flood flows can spread out and deposit a large portion of its sediment load. During the 2013 flood, several flow channels were formed in the new floodplain deposits. A large area of the new floodplain deposits are high enough that even after several years, little vegetation has been able to establish on the floodplain.
One of the objectives of the restoration for this reach is to establish diverse, native vegetation in the riparian areas. In some areas we removed flood deposits to lower the riparian areas so that plants could reach groundwater. But in the wide, alluvial deposition area, we decided to raise the groundwater by installing beaver dam analogs on one of the secondary channels that runs through the middle of the floodplain. This secondary channel is directly connected to the main flow channel and activates first when flows are elevated.
We installed three different styles of beaver dam analogs: a simple post and weave dam, a log jam dam, and an “engineered” rootwad/log dam. Each dam was successful at ponding water and we noticed that water started appearing in the dry channels and other low areas in the floodplain - an indication that we were successful at raising the groundwater. We will monitor how well planted vegetation and volunteer vegetation respond to the higher groundwater, but initial results indicate that the beaver dam analogs will meet the objective of vegetating the floodplain.
About Vincent L. Sortman
Vince Sortman has been up to his waders in stream and river systems for more than 30 years. A senior fluvial geomorphologist at the renowned ecological consulting firm, Biohabitats, Vince has applied the science of ecology to help communities across the U.S. to protect, restore, and regenerate streams, rivers and wetlands. He has designed and managed the construction of hundreds of restoration projects in locations ranging from the Coastal Plains of Maryland to the Grand Prairies of Texas and the Colorado Piedmont. In doing so, he has helped countless clients to achieve goals related to water quality, habitat, climate change resilience, flood protection, and constituent quality of life. Vince has been engaged in ecological restoration since its emergence as a field, so he brings deep knowledge--not only of geomorphology, but also of the application of evolving restoration design and construction techniques. He has taught principals of stream restoration at workshops sponsored by the U.S. EPA, Natural Resource Conservation Service, and state and local agencies across the country. Vince's passion for stream restoration is matched only by his love of singing in a barbershop quartet, so he is one of few practitioners who has not only been "Down by the Old Mill Stream" but knows how it's constructed in four-part harmony.