Modeling Floodplain Changes Below Seven Oaks Dam

A river modeling study was made for the Santa Ana River/Mentone Fan in San Bernardino County, California. The purpose of the study was to characterize the existing and future flooding regimes and sediment transport along an eight-mile length of the river and alluvial fan. A short distance upstream from the study area. Seven Oaks Dam has recently been constructed. In response to such a project, the river channel is expected to undergo changes thereby affecting the habitat and habitat renewal. Seven Oaks Dam will alter the storm flow of the Santa Ana River that is the primary source of flow for the study area. The reservoir will also detain nearly all the bed sediment supply to the study area. In order to quantify the boundaries of the 50- and 100-yr floodplains and the sediment processes under the natural and altered regime, a modeling study was made using the FLUVIAL-12 model. Short term changes were modeling using the 50- and 100-yr floods, respectively. Long-term changes, on the other hand, were modeled using a flood series representative of the long-term flood flow. The reductions in floodplain area for various cases were quantified.