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- .5 - <br />Average annual acres flooded are to be 21 acres of <br />and i -pasture ($739 damage) under presenit: cun,02'.tions a 1 150 acres <br />(13423 damage) under future conditions t-fitll L Str irt- _tailed <br />,and .-,orking, The relatively low reduction LA acros T`ooclad oil all <br />average annual basis (64 acres or 301,) is due to `Lhe oli-la. of the <br />floodplain wherein part of the floodplain Iv too fill-ch Channel capacity <br />and a. few parts lhas relatively no chan -_I .So the fdat <br />that the maxim,ira per cent o-f the floodpiziin are& zeservoircd is 64 <br />per cent at Larkspur and drops to A2 per ceTtz a Castle Rock, <br />L <br />In addition to the above crop and pas 't. (Jamages, <br />there is an ar, of cropland beloT. strulctux�- sit.a on <br />Carpenter Creel: which suffers an estimatc-d 'I ?9 :average ann�_Ial flood- <br />water damage, <br />The party geologist estirnares thrt on Lhe - -Uains1 - .Prri of East Plum <br />Creek there will be 23 acres of land lost _' sl! erosion <br />and 17 acres of cropland lost from sediment deposition during. the <br />50-yeai evaluation period, In addition, 67 acres of hayland will <br />suffer, reduced yields through repeated sediric-rit deposition,. The <br />average annual land damages from sediment deposition and streambank, <br />erosion is estimated at , (See Tables 7 and 8).1 <br />Road and bridge damage in the floodplain area was estimated by <br />inspection, interviews and by comparing the area with dasitiages found <br />in. similar watershed areas, Average annual road and bridge ecama(,je <br />was calculated to be 433,750 to the bridges, approaches, and road <br />grades in the floodplain area below structure sites EP-1 and EP-2 <br />Floodwater damages to railroads along F-ast Plum Creek imre <br />calculated to be $2,960 on an average annual basis, with most of the <br />damage occurring frm a 10-year frequency or larger storm runoff, <br />since all culverts and bridges have been enlarged during the past <br />yearss. Some channel relocations have been done by the railroad, <br />Total average annual damages in the evaluation area below the <br />structure sites EP-1 an ' EP-2 is calculated to be $10,245 and the <br />average annual monetary benefits to structural ateasures is estimated <br />to be 1 4 1'4,190 or, a damage reduction of 41 par cent. Thus, the ratio <br />of average annual benefits ($4,190) to average annual costs <br />($13,327) is 31 to 1,00.. <br />