Economic & Floodplain Assessment
  San Diego Creek | FEMA Support | 2D Flood Modeling | American River Watershed Floodplain Studies

Tetra Tech provides technical review support to Michael Baker Jr., Inc. for their FEMA review contract. Under this contract, FEMA-funded studies, as well as studies not contracted by FEMA (LOMR/CLOMR requests) are reviewed for Regions 7, 8 and 9. The work has primarily included studies and revision requests from communities in California and Arizona. The extent of review included hydrologic analyses including gage analysis, regression equations and rainfall-runoff modeling. The hydraulic analysis review consists of backwater calculations (using HEC-RAS), split flow calculations (using normal depth calculations or the XRATE program). The floodplain delineations were verified to ensure consistency with the hydraulic results. Floodways were reviewed to ensure that they meet the FEMA guidelines regarding surcharges. Coordination was required between the study cntractors, revision requestors, MCC and FEMA staff. Draft Flood Insurance Studies or LOMR/ LOMR letters were prepared along with other mapping to be used by the MCC to finalize the revised maps.

In addition, Tetra Tech staff has made many LOMR and CLOMR submittals to FEMA on behalf of private developers and local municipalities. These submittals have encompassed all aspects of related work, including hydrologic and hydraulic analysis, floodway determinations, floodplain mapping, and flood insurance study reports. Requests have been submitted to update the floodplain limits based on new topographic information, channel improvements and culvert construction. Submittals have been made based on existing FEMA discharges as well as revised discharges based on new analyses. Hydraulic analyses have been performed to delineate approximate flood areas, detailed Special Flood Hazard areas and revised floodways. Flooding scenarios include riverine and alluvial fan areas and subcritical as well as supercritical flow regimes. Submittals completed in Orange County and Riverside County, California; Las Vegas and Clark County, Nevada; and Scottsdale, Arizona.