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<br />Tne flooded ~re~s Shown on plates 2 t~rough 5 indicate <br />the wieth or extent of flooding corresaondin~ to the flood elevations <br />shown on the prollles. The IIOOded areas are rot precise bOCiluseol <br />the limitation 01 tho topograPhic maoping, but do indicate the <br />general nature of a llood. For ~ more precise determination of <br />f loodi ng, the elevation of a II are~s 01 cOnCern shou I a be determined <br />anocCV!1pareatotheflooaelovationsshownontlleprofiles. <br />Except in a vory generdl way, the flooded areas have not <br />beonshown lor that portion of left-Hanl! Creek betweenU. S. Highwa v <br />287andtheSt.VrainCrook. The flood plain widens in the shapool <br />a dolta as it merges with tho St. Yrain. The overbank flows are <br />CQrrieo by little drai~ge courses that diverge from the creek sep- <br />arating the water into shallow inaepenl!ent streams, each with its <br />own profile. The flooa profiles are not valid inthis reach and apply <br />only toare<ls adJacent to the stream. Another location of indeter- <br />minate II00ding Is shown by the crOss hatched area below State Highway <br />119. lloththe highway and railway bridges, at this location, have <br />adequate capacities lor tho Intermediate Regional Flood, but the lelt <br />upstream ovorbank is low and flows are di~erted northeast along fhe <br />highway. Tho toos of both tho rOilO and railroaaembankments slope <br />in a northeasterly direction and ultimately the water overtops thorn. <br />Once lIcross Ha, "",banl<Inents, the water follows v""lous shallow path5 <br />oack to thd strAHm. <br /> <br />they will be much hIgher. These velocities are erosive but the e~tent <br />oferosloolsllmlteabyanumberoffllctors. Consiaerable laterlll <br />erosion has been observed in slmllllr streams oven during mInor flooding. <br />Buildings located close to the streom, although above the flood stages, <br />have been damaged from unoercuttlng as the Channel blinkS were erodea. <br />Basldes erosIon, the force crelltod by the swift-flowIng water against <br />buildings can result In structurlll damage especially If floating debrIs <br />15 presont. A similar hazardouS condition exists at 16 of the IS <br />bridgeS, Which can be fianked or overtopped. People often attempt to <br />cro$s sutlmerged roadwayS. In some cases, cars havll been swept off <br />the roads, but the usual case Is for the cars to become stalled and <br />the occupants swept into the flood after they emerge from their cars. <br /> <br />Tcn cross sections portraying various Channel and valley <br />characteristics are provldod on plates Sdn<! 9. They show the aepths <br />of overbank flooding, and when used with the flooded area maps ana <br />the profiles help complete the pldure of the left-Hana Creek's flood <br />potential. <br />In addition to damages from inundation, other darnages <br />could bacaused by filst-flowlngwater. Juringlln Intermediate Regienal <br />r I cod , the velocit ios I n the channel ~'i II be in th" range 01 si~ to <br />ten feet por second but at the bridges and ether IOCdllzed areas, <br /> <br />>9 <br /> <br />20 <br />