Effectiveness Monitoring: Quantifying Geomorphic Change on the Middle Fork John Day River, Oregon

Quantitative process-based restoration monitoring is important to identify and understand the impacts of restoration on physical and ecological processes. On the Middle Fork John Day River (MFJD), a low gradient, meandering river in eastern Oregon, restoration includes the removal of rock spurs and the addition of engineered log structures to increase in-stream complexity and fish habitat diversity. Repeat topographic surveys of river reaches are used to identify spatial patterns of erosion and deposition. Monitoring riverbed channel change through DEMs of differencing (DoD) gives insight to the influence of engineered log structures on reestablishing in-stream variability. This study quantifies bed scour and aggradation associated with in-stream restoration actions (1) after less than 5 year flood events, and (2) after record floods. After less than 5 year flood events between 2008 and 2010 detectable -0.9 to 0.5m elevation changes occurred in and around MFJD log structure sites. With record floods recorded in spring 2011, DoD analysis shows geomorphic changes after significant sediment movement. Quantifying these changes in both major and minor events aids in understanding the physical processes associated with restoration structures.