Case Studies of Channel Migration Zone Mapping in the Clarks Fork Yellowstone Watershed and Ecological Implications

Abstract

Naturally occurring river channel migration is essential for ecosystem health, facilitating nutrient cycling, habitat creation, and groundwater recharge. However, human activities, including agriculture, bank stabilization, and urban development, disrupt these processes, leading to habitat loss and ecological simplification. Therefore, my study aims to examine how human intervention affects river dynamics in the Clarks Fork Yellowstone Watershed through a GIS-based Channel Migration Zone (CMZ) mapping process. To investigate these interactions, I conducted CMZ mapping of three selected case study sites along the watershed, each impacted by varying mechanisms of human development, including agriculture, historical mining, and urbanization. These case studies were selected based on previously known human conflict with channel migration. Using historical aerial imagery and LiDAR data, I delineated migration zones andassessed erosion and avulsion potential using CMZ maps. I also identified areas where channel migration has been restricted. Results reveal that sites heavily influenced by agriculture, mining,and urban structures experience significant alterations to natural migration patterns, restricted lateral river migrations, and ecological consequences. A minimally disturbed case study site, the Anastomosing section on Rock Creek, comparatively shows ecological resilience and support for diverse habitats, although it is experiencing increasing encroachment from exurban expansion.The CMZ maps were further evaluated against damage caused by a 500-year flooding event in 2022. Findings suggest that the CMZ framework successfully identified high-risk areas where significant damage occurred, such as erosion in a mine tailings deposit and various avulsion-prone zones. My analysis underscores the predictive value of CMZ mapping for sustainable land management and conservation. Results from the selected case study sites suggest that a complete CMZ map of the rivers in the Clarks Fork Yellowstone Watershed would help guide development and protect the rivers' ability to migrate laterally across the floodplain. Integrating CMZ insights into planning to maintain these natural river functions can both enhance ecosystem resilience and reduce infrastructure damage.