Snake River Watershed Geomorphology Report

Healthy watersheds are biologically diverse and connected ecosystems. Healthy watersheds also produce other ecosystem services and products that contribute to the state's economic and social vitality (e.g., habitat, fish, wildlife, timber, and recreation). The Department of Natural Resources (DNR) uses a five component framework to describe watersheds as systems: biology, hydrology, fluvial geomorphology, connectivity, and water quality. Understanding the interplay between these components will make it easier to identify the root cause of an issue that is impairing one aspect of a healthy watershed. For example, if land use changes increase the flashiness of river flows, this may lead to an unstable stream condition. To adjust to these changes, the river may down cut and the banks erode as it attempts to find a new equilibrium with the changes to hydrology. As a result of this instability, variables like in-stream and overhead cover, substrate composition, pool quality, temperature, oxygen, spawning habitat, habitat diversity, and Index of Biological Integrity (IBI) scores would all be expected to degrade. In contrast, an evolution or restoration from the unstable form to a stable river form would result in a reversal of these negative consequences. This report is primarily focused on fluvial geomorphology, but it also provides some general watershed characteristics and information on hydrology.