Derby Dike

Derby Dike is an Earthworks levee embankment built along the San Diego River in San Diego County, California, by Lieutenant George Derby in 1853. The Derby Dike is a California Historical Landmark No. 244 listed on June 10, 1936. The Derby Dike ran from Old Town San Diego to Point Loma, about 5 miles (8km). A California historical marker is at Taylor Street and Presidio Drive.

Before the Derby Dike was built the San Diego River would often overflow its banks and flood parts of Old Town, San Diego and San Diego, California. The other problem was the river would flood San Diego harbor with debris. Lieutenant George Horatio Derby with the United States Army Corps of Topographical Engineers had the Derby Dike built so the river would flow into False Bay, now called Mission Bay, rather than into the at San Diego Bay's harbor. This was one of the first major US Government projects in California. While the Derby Dike helped with the flooding and debris flow into the Harbor, there were still major floods that overwhelm the Derby Dike. A major flood in 1853 destroyed parts of the Derby Dike, and the San Diego River flowed back into the harbor. By 1875, the Derby Dike was repaired and the river was flowing back into False Bay. A major flood in 1884 again destroyed parts of the Derby Dike, and was repaired again. The Sweetwater Dam was built in 1888 to help stop the flooding problem. Six other dams were built on San Diego River, the last in 1898. The San Diego River was not fullly contained til the 1950s. The largest dam on the river is the El Capitan Dam completed in 1934 that is 27 miles up river from Old Town, San Diego.

Derby-Pendleton House was constructed in 1851 by Lieutenant George Horatio Derby.