
SURFACE WATER
RIVERS, LAKES & COASTAL ENVIRONMENTS

San Diego Creek Floodplain Assessment
San Diego, CA
Economic & Floodplain Assessment
San Diego Creek | FEMA
Support | 2D Flood Modeling |
American River Watershed Floodplain Studies
On behalf of the Orange County Watershed and Coastal Resources Division, a study was performed to define the 100-year floodplain from I‑405 to Jamboree Road. Existing hydrologic information was utilized and a HEC-RAS model was developed using new topographic information outside of the main channel banks and an assessment of the Manning’s n-value of the channel and floodplain.
Three scenarios were modeled as part of this study:
Scenario 1-With Levee and 40-foot Vegetation Buffer: This scenario assumes the levees along both channel banks remain in place and do not fail during a 100-year storm event. It also assumes that the existing vegetation along the toe of the east bank is maintained at 40 feet wide from Jamboree Road up to the I-405 Freeway.
Scenario 2-Failed Levee and 40-foot Vegetation Buffer: This scenario assumes the levees along both channel banks are ineffective and fail during a 100-year storm event. It also assumes that the existing vegetation along the toe of the east bank is maintained at 40 feet wide from Jamboree Road up to the I-405 Freeway.
Scenario 3-With Levee and Existing Vegetation Buffer: The levees along both channel banks remain in place and do not fail during a 100-year storm event. The width of the in-channel vegetation buffer is 40 feet wide upstream of Campus Drive. Downstream of Campus Drive the width of the in-channel vegetation buffer was modeled to reflect existing conditions. Calculations were made to determine the volume of flow that left the main channel and stage-storage curves were developed for the floodplain to determine the flooded area.
Mapping
was produced for each scenario to show the floodplain area associated
with the 100-year storm event under the scenario conditions.