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<br />0018u4 <br /> <br />POTENTIAL FLOOD DAMAGES <br /> <br />An economic analysis was made of the potential flood losses in the <br />area, resulting from the flood inundation of the community. The <br />purpose of this analysis was to determine an estimate of the cost of <br />the average annual flood risk. <br /> <br />The analysis was done according to applicable portions of the Design <br />of Encroachments on Flood Plains Using Risk Analysis, Hydraulic <br />Engineering Circular No. 17, published by the Federal Highway <br />Administration, April 19, 1981, (Ref. 3). Also, flood depths reported <br />in the Flood Insurance Study (Ref. 1) reports for the City and County <br />were used for this economic flood risk estimate. <br /> <br />The useful 1 ife of improvements was cons i dered to be 50 years wi th a <br />discount rate of 8.25% used in generating the Capital Recovery Factor <br />(CRF). The discount rate has been suggested by the CWCB and is <br />consistent with that published by the U.S. Water Resource Council. <br /> <br />For purposes of this analysis, the bridges over the Rio Grande within <br />the study area were assumed to not fail duri ng the 50-year desi gn <br />life. <br /> <br />Costs for repai ri ng flood-damaged roadways, ut il it i es and rail roads, <br />were estimated at 24% of the total val ue of structural damage to <br />residential, commercial and mobile home buildings (not including <br />contents). This value was felt to be a reasonable "rule-of-thumb" for <br />reconnaissance level damage estimates, by Fritz Blake of the COE. <br /> <br />Traffic data for state highways in the area was obtained from <br />Accidents and Rates on State Hi hwa s, 1983, CDOH Staff Traffic and <br />a ety Branc es ef. . For purposes of the economic analysis, it <br />was assumed that, during flood conditions, U.S. Highway 160 and State <br />Avenue would be closed through Alamosa. Local traffic crossing the <br />bridges in town would be virtually halted in a flood condition, but <br />through traffic to and from points east and west would require a <br />detour around the City. Traffic volumes estimated through town were <br />derived from Accidents and Rates on State Highways at points outside <br />the corporate limits on U.S. 160 and U.S. 285. The detour route has <br />been assumed to be U.S. 285 north from Monte Vista to S.H. 374; then <br />easterly along S.H. 374 to S.H. 150; then southerly on S.H. 150 to <br />U.S. 160. The additional travel distance is approximately 19 miles. <br />The average through volume was estimated at 4,225 vehicles per day. <br /> <br />Vehicle occupancy rate was estimated at 2-persons per vehicle. From <br />information provided by the Alamosa County planner, detour time losses <br />can be estimated using a value of $6.00 per hour per vehicle occupant. <br />Mileage costs for the longer route were estimated at $.25 per mile to <br />cover gas, oil, tires, parts and repairs. <br /> <br />-12- <br />