An incised stream occurs when a stream cuts its channel into the bed of a valley through degradation (erosion). As a stream cuts its channel the water table drops and the surrounding vegetation changes from wetlands and meadows to dry shrublands. Incised streams are thought to be a result of the removal of beaver from arid landscapes in the western United States.
The beaver is a keystone species, as their presence on the landscape allows other organisms to exist that would not otherwise. This is because of beaver impoundments and dams, change the spatial distribution of water as well as water flow rate. Through the creation of ponds and wetlands, beavers can increase plant and animal biodiversity. With the restoration of streams with beaver or simulated beaver dams, short-term streams can thus become perennial or long-term flowing streams.
If you are interested in efforts to restore beavers as a way to restore an incised stream view recently updated Beaver Restoration Guidebook: Working with Beaver Restoration Guidebook: Working with Beaver to Restore Streams, Wetlands, and Floodplains, Version 2. Here we provide a few case studies of incised stream restoration throughout the Western U.S.:
Silvies Valley Ranch, OR: using artificial beaver dams to restore incised streams
Silvies Valley Ranch before and after incised stream restoration efforts