Incentivizing Channel Migration: Channel Migration Zone Easements along the Yellowstone River

Year: 2020
Presenter/s: Wendy Weaver
Symposium Session: 2020 - 08 Pre-Disaster: An ounce of prevention is worth a pound of cure
Topics covered: beavers, climate change, community involvement, floodplain, outside PNW, permits, riparian, risk and resilience, and stream


The expansion of bank armor on the Yellowstone River in Montana has resulted in a reduction in floodplain turnover rates of about 180 acres per year since the 1970s. As a result, the cottonwood forests for which the river corridor is known are aging with dampened rates of forest regeneration associated with channel migration and disturbance. In order to better understand rates and patterns of channel movement on the Yellowstone, Channel Migration Zone (CMZ) maps generated over a decade ago have been extensively used for education, outreach and planning, as the maps are non-regulatory. Recent applications of the maps include the development of a Channel Migration Easement (CME) corridor which prioritizes areas based on rates of channel movement, riparian habitats, cottonwood recruitment potential and flood storage. These footprints have been used to prioritize properties for easements, deed restrictions, and/or acquisition in support of general project development, compensatory mitigation, and in support of a Natural Resource Damage Program settlement following an oil spill on the river. Over the past several years the non-profit organization that operates the in-lieu fee mitigation program for the State of Montana, Montana Aquatic Resources Services (MARS) has implemented channel migration easements and tracked intensive landowner interest for future projects. These easements preclude bank armoring in a defined floodplain area, and may include broader conservation easement footprints that extend beyond the CMZ. This allows ground identified as part of the active river corridor to remain unarmored in perpetuity. Challenges with the CME program include securing easement holders in these non-traditional settings, identifying funding sources and identifying appropriate market values for compensation.