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~ , I Ii r ~ I. Introduction This request for a Letter of Map Amendment (LOMA) is being submitted by FLO , Engineering, Inc. on the behalf of Mr. Dean Hill and H-Four Associates, purchasers of the property in question and with the full cooperation of the current owners. The undeveloped parcel of land is located on the Flood Insurance Rate Map (FIRM), Community-Panel Number 4900040 0001 C (panel 1 of 3) for the City of Centerville, Davis County, Utah (revised February 19, 1992); (Fig. 1, Appendix A). This LOMA request for the property is based solely on topographic elevations in relationship to the potential flooding of Barnard Creek. Flooding on the alluvial fan will be the result of overflow from the existing debris basin and the flow initially proceeding down Barnard Drive. These topographic conditions existed when the original NFIP maps were completed in the 1970's and the LOMA request does not involve recent alterations of fan topography. Concurrent with this LOMA request, the 100-year flood elevations for Barnard Creek for both water flooding and mud/debris flows are being restudied for the City of Centerville and Davis County. Official's from the City of Centerville, Davis County, the . State Engineer's Office and the State Hazard Mitigation Office are aware of the LOMA request and are providing input for the restudy. The following information is solely in support of the LOMA request for H-Four Associations. II. Background Many communities along the Wasatch Front Valley in Utah joined the National Flood Insurance Program (NFIP) managed by FEMA in the 1970's. The program, initiated by the Housing and Urban Development Act of 1968, enabled residents of flood-prone areas to purchase flood insurance and required communities to adopt floodplain management plans to reduce potential flood damages. The program was amended in 1968 to include mudflow hazards. Barnard Creek was subjected to mudflows in 1930 and 1983. In 1988, a new Flood Insurance Study (FrS) was completed for Centerville, UT by the Army Corps of Engineers (COE) that analyzed the 100-year mudflow. This superceded the FIS studies completed in the mid 1970's (revised in 1981) that were based on conventional water flood hydraulics. The COE applied a two-dimensional, finite element flood model with a component to simulate mudflows and mud floods to predict the 100-year flood hazard. Flood zones mapped on the Centerville FIRM reflect, in part, the results of ]