Developing Mitigation Plans for Matilija Dam Removal

Matilija Dam in Ventura County, California is being considered for removal. Approximately 6 million cubic yards of sediment has accumulated behind Matilija Dam near Ventura, California since its construction in 1947, and only 7% of the original reservoir capacity remains. It is also a barrier to the migration of Steelhead Trout in the Ventura River Basin. The relatively flat, low-lying areas adjacent to the lower 14 miles of the Ventura River are, for the most part, extensively developed, and prone to inundation despite appreciable flood control measures. In addition, an important water supply diversion is located approximately 2 miles downstream of the dam. Two requirements of the project are to maintain the current water diversions and to maintain or reduce the current flood risk. This paper describes the analysis performed and procedures followed to develop plans to meet these requirements.