Sixty Years of River Corridor Change Induced by the Construction, Operation, and Maintenance of Flood Control Infrastructure on Lower Deer Creek, California

Deer Creek drains 540 km2, joining the Sacramento River near Vina, about 160 km north of the city of Sacramento. The U.S. Army Corps of Engineers constructed a levee and partly straightened the lower five miles of Deer Creek in 1949. Repeated levee failures and the presence of the federally threatened spring-run Chinook salmon (Oncorhynchus tshawytscha) in Deer Creek have prompted investigations on habitat restoration coordinated with more effective flood protection. The Deer Creek Watershed Conservancy (1998) identified a significant reduction in channel complexity between 1938 (pre-levee) and 1997, but did not attempt to quantify this reduction. In this study, we examined high quality aerial photographs from 1938, 1952, 1966, 1979, 1985, and 1998, and systematically quantified (in ArcGIS) changes in river corridor complexity by digitizing a range of features in each set of photos. Total active channel length in the levee reach decreased from 14.4 km to 12.6 km between 1938 and 1998. In addition, we documented a significant increase in average active channel width and a decrease in shaded riverine aquatic habitat between 1938 and 1998. Most of these changes occurred during the levee project in 1949, and the simplified channel form persisted through 1998. We also identified a significant decrease in aquatic and riparian habitat resilience (i.e. resistance to habitat damage and destruction by large floods) between 1937 and 1998. These results provide a basis for prioritizing, locating, and developing designs for alternative flood management approaches that would contribute to the enhancement and restoration of aquatic and riparian habitat along lower Deer Creek.