River Design Group was retained by the U.S. Fish and Wildlife Service to assess wetland restoration potential at Swan River National Wildlife Refuge at Swan Lake, Montana. Objectives were to identify opportunities for wetland hydrology restoration, and to determine the likely impact of restoration actions on existing plant communities and wetland habitat. Currently, a large network of drainage ditches intercept and collect ground- and surface water and move it downslope to Swan Lake. These changes to wetland hydrology, combined with the spread of the invasive reed canarygrass (Phalaris arundinacea), have resulted in a striking departure from the natural vegetation communities and habitat that likely existed prior to the turn of the 19th century.
The assessment resulted in identification of approximately 15 miles of drainage ditches, including 4 miles classified as Priority 1 ditches that significantly affect wetland hydrology. Ditch fill volume analysis coupled with identification of on-site excavation material from ditch spoil berms and artificial levees allowed for various restoration options to be presented to the client. With project implementation, approximately 490 acres of Refuge area is estimated to convert from reed canarygrass to desirable wetland vegetation due to a groundwater level increase.