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Channe 1 and overban~ r'Oughness factors (~Ianning' s "n") ",'ere determined frOTllfield inspection of the study area. A factor of O.04\'iilsuse<Jfortnechannelbottor.. The factors used for the overbank flow areas ranged from 0.05 to 0.07, depending on the typ<: of existing and proposedvegetatiol1. Flow i 11 the ri ver ~Ias ,,"S5 Uliied to be subcriti ca 1. Tr.e l-fec~2 program COf;,pl.ltestilel'iatersurfaceprofileofsubcritica1flowsta'fting at the downstream end of the reach an<:l proceeds upstream. The out- put noted that tile CO;;lputer assumed critical flow at two nonsuccesshe sections duringtr.e 50, 100 and 500 year flood events. This indicates that the fl ow ~:ay be supercri ti ca 1 at those sections. HOl>.'ever, be~ cause the flo'~ was found to be subcritical at the sections upstream and downstream and at the 10 year flow, it is believed that it is not necessary to run the profile assuming supercritical flo~I, Because critiCal depth is higherthansupercritiCdl depth, using the assumed critical depthisconserviltive. Tables 1 and 2, consecutively. FJA Tdille 1 for flooaw~y Odil and FIATable 2 for flood insurdncezone data are includ"d in Addend.i!" 2 and are sho'~n in this report as Tables 3 and a, consecutively. The 100 year flood plain is sh()'v.'n in Figure 2. The floodway and tr.e flood,idyfringe portions of tI:e floodplain are indicated. He boun~aries betwe~n cross sections were determined usi~g topographical I~iipping of the area. The natural 100 year flood water surface elevation at each of the cross sections are shown in Figurc 3. The boundaries between the floodway and the flood'~dY fringes are also shown. The ~Iilter surface profi1 es for each of the 10, 50, 100 and 500 year flood events are Shown in Figure 4. Results of Analysis Two runs of the l-fec-2 prograrn were mil<Je. output are incl uded as Addend~f;1s 1 ar;d 2. t.~e output for the foll owi ng pl.ofil es; Copies of the COIITputer The add~ndums contain Application of Results The infonrlation regarding the flooding characteristics of the Eagle River determined 1n this analysis will be used to control construction in the Eagle River Estates Subdivision to assure that no residence be inundated by a flood of il magnitude no greater than the 100 year flood event. The 100 year flood plain area ar.delevations defined in this report wi 11 te used to deterr.:ine construction restrictio ns. No improven:ents shall be al10wed within the 100 year floodway to maintain the necessary conveyance capacity. Construction in the f]oodliay frin~e will be allowed, but th~ first floor of all resi- dences s;lall be at least one foot higher than tile comp~ted 100 year ,... flooc, water surface elevation. i'.ddencium Profile 1'10. Flood trcq\Jer.cy Encroachment Option ----.- 1 1 100 [,0 1 1 10'J y" 1 1 10 No 2 2 50 ~:o 2 3 1()(1 No 1 , 5CO No Tne encroac.~r;",ent opti on used in AddenuUIl1 1 clefi nes the floodway and !l:e flOO~'...ay fringe portiOIlS of the 100 year flood plair.. Tlla~ opti()n (;0111pute:; tn" .ollcrO<ld:lllerlt st<1LiOfLS so that convey;u:ce \'<ithin tile encroaChed cross section, at some I-,igherelevation, is equal to the conveyance of tlw nat~r~l cross section at the natural water level. ThishiyhereleVdtior:isnor,-,or",thanonefootabovethe natural 100 year profile. The cOl.lputed encroachll:ent stations are tile boulluary bet\;e~r: th~ f1oud~lay and the floodway fringe, the f1ood'~ay beir.g tlldt portien of the floodplain that can maintain the neCe5Sdry conveyance if not E:ncroached upon. Tile prin~O'Jt in :\dJ~i~dJI:1 1 inc1wies all inp~t elata, Sun:r:ary print- out Table no for enCl'oachment dilta ,1nd FIA Table 1 for floodway data Jre incll:deJ ir. ,r',cdembr: 1 and dre SilOW1' in this report as