| OCR Text |
Show identification has been accomplished on a case- by- case basis during planning. However, a thorough floodplain assessment may take as long as two years to complete and is often needed to select between competing sites, resulting in inadequate information for many planning projects. The information needed to quantify flood hazards in the ungauged backcountry drainages is lacking. Alternative B: Flood hazard assessment and mitigation ( preferred alternative) Areas of proposed development and heavy visitor use would be assessed for floodplain hazards. Following the assessment, mitigation alternatives would be examined for the visitor use areas, and development sites would be selected only outside of high- hazard zones as required by NPS guidelines. Mitigation options might include identifying flood hazard zones on maps provided to visitors; posting warning signs at trail- and roadheads; restricting use on a seasonal basis; and increasing ranger patrols during periods of heavy flooding. Monitoring of high- hazard zones could be incorporated into the visitor protection program, and cooperative programs may be initiated with surrounding land managers to provide early warning capability. Where hazards are extreme and visitor exposure high, extensive actions such as seasonal area closures, specific flood- proofing of structures such as dikes, raising or relocation of facilities, or radio- controlled remote warning signs or systems could be considered. Alternative C: Comprehensive floodplain assessment Under this alternative all drainages in the NRA would be scheduled for floodplain evaluation and necessary floodplain mapping as funding became available. Maximum use of cooperative investigations with other agencies such as the U. S. Geological Survey would be made. These site- specific evaluations would provide a floodplain delineation of several magnitudes as required by NPS guidelines for consideration under various visitor usage patterns. These evaluations will allow any modification of developed sites as required. Also, the proper development of proposed sites would be based upon these evaluations, which will have been prepared and ready for use. This is an important aspect of the projects in that any one effort may require up to a year for completion. 111. C. 3. Recommended course of action. Floodplain management through Alternative B would identify the areas of principal concern. Alternative C would cover the entire recreation area, but the low additional margin of information gained would probably not justify the expense. Alternative A is not acceptable because of the potential for poor planning coordination, time delays, and incomplete assessment of potential hazards. 28 |
