BOARD01085 - Laserfiche WebLink

Home Browse Search

, . ~ . . ;l ATTACHMENT 5 . FPR 00-524 Floodplain Information Report, Roaring Fork River, Town of Basalt, Eagle and Pitkin Counties, Colorado, dated July 2000. KEY ISSUES: . The Flood Insurance Study (FIS) dated June 4, 1987 is not representative of current flooding conditions in the Basalt area, due to changed topographic and hydraulic conditions (man-made and flood-caused), in particular to changed hydraulic conditions at the Upper Basalt Bypass Bridge, and to changed corporate limits. . The new detailed floodplain information contained in this study is based on a current topographic mapping (from aerial surveys and field surveys), a revised hydraulic analysis, and extension of the study area to include the current corporate limits of the Town of Basalt and nearby areas in unincorporated portions of Eagle County and Pitkin County. . The detailed floodplain mapping, which should replace the 1987 FIS, reflects the construction of three new bridges, the construction of the Highway 82 Basalt Bypass, other man-made changes, and physical changes caused by flooding in 1983, 1984, 1985 and 1995. It also refleclsthe engineering assumption that the uncertified berm built by CDOT at the Upper Bypass Bridge will fail, allowing floodwaters to inundate areas south of the Basalt Bypass. . The detailed floodplain mapping shows that 1 DO-year flooding affects a substantial portion ofthe Basalt . area, including numerous buildings. COMMUNITY RESPONSE: The Town of Basalt sent a letter to the CWCB requesting designation and approval of the July 2000 report after a technical review of the June 4, 1987 FIS. In fact, the town initiated the preparation of the July 2000 report. Numerous meetings and telephone calls have been held with the Town to discuss the designation process and answer floodplain-related questions. Several site visits have been performed to review the Roaring Fork River in and around Basalt. The town and Pitkin County are supportive of the Board's proposed designation action. In addition, the town would like to work with the CWCB on a river master plan. SUMMARY: The staff recommends Board approval of the floodplain resolution for the Basalt area designating the Floodplain Information Report dated July 2000, including the new detailed floodplain mapping which replaces the 1987 Flood Insurance Study. The resolution rescinds the FIS, since it is no longer valid. The detailed floodplain information contained in the FIR meets the Board's "Floodplain Designation and Approval Rules", The designation action will assure that the most current floodplain information for the Town of Basalt, Eagle County, and Pitkin County is explicitly approved by the state, thereby complying with state statutory requirements. . 8