CS1C - Concurrent Session 01C: Terror in the San Francisquito Canyon

Abstract Description: St. Francis dam built in San Francisquito Canyon was part of the water supply system of Los Angeles, California. The construction of the dam began in April 1924 and was completed on May 4th, 1926. The constructed structure was a 205-foot tall concrete-gravity arch dam. The dam began filling upon completion of construction and reached a full capacity of 38,000 ac-ft at elevation 1834.75-feet on March 5th, 1928. The dam collapsed on the night of March 12th, 1928, one week after reaching full storage capacity, and the resultant floodwaters killed a total of 450 people. According to the 1983 Bureau of Reclamation report, the entire dam emptied in about 70 minutes following the dam collapse and resulted in a peak discharge greater than 500,000-cubic feet/second. This case study aims to discuss the structural integrity of the dam and to recreate the St. Francis Dam Failure using a HEC-RAS 2D model to assess the likely damages to Los Angeles, assuming it were to fail today.