GIS-Based Stochastic Event Flood Model
The objective of this project is to improve the Stochastic Event Flood Model (SEFM) and expand its capabilities. Modifications to the model will allow users to model runoff on a distributed basis using geographic information systemn generated by the model is needed to improve flood control operations on Reclamation projects. This will increase public safety in the floodplain downstream from our projects by allowing dam operations personnel to better operate the dam and outlet works during a flood.
Need and Benefit
The Stochastic Event Flood Model (SEFM) model provides a means for estimating large floods which can be used for improving flood control operations and increasing project water supplies. SEFM is the only stochastic rainfall/runoff model available which is capable of modeling extreme floods and placing them in proper probabilistic context. The information generated by the model is needed to improve flood control operations on Reclamation projects. This will increase public safety in the floodplain downstream from our projects by allowing dam operations personnel to better operate the dam and outlet works during a flood. Model results may be used to formulate more reliable and efficient reservoir flood control operating plans. Work has already begun on applying the model to Folsom Dam and Reservoir.
Another benefit to Reclamation and the Nation includes the ability to increase project water supplies by reallocating reservoir surcharge space to active conservation storage. The recent drought has highlighted the need for additional water in the West. Several Reclamation facilities are being examined as possible candidates for enlargement including Pathfinder, Folsom, Shasta, Fresno, Gerber, Pueblo, and Thief Valley Dams. Reevaluating the flood potential at these facilitites will greatly reduce and possibly eliminate the structural modification costs for enlargement. Floods are seasonal in nature, and floods vary greatly in magnitude, volume, and frequency of occurrence. Recognizing these variations and using risk assessments to standardize our design criteria will help engineers identify dams with excess surcharge flood storage. The excess surcharge storage space can be used to store additional water for environmental, municipal, or agricultural uses while still maintaining a safe dam. This may eliminate or minimize the need for enlarging many dams in the future. Pathfinder Dam will be examined next fiscal year as a possible candidate for study. This analysis is expected to result in an additional 40,000 acre-feet of storage that can be used to store project water supplies.