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<br />"...the channel of a stream and those portions <br />of the adjoining flood plain which are reasonably <br />required to carry and discharge the floodwaters <br />of an intermediate regional flood. In the context <br />of this regulation, it is the designated flood plain <br />less the low hazard zone, if any such low hazard zone <br />has been identified. If no low hazard zone has been <br />identified, then the terms 'designated flood plain' <br />and 'floodway zone' shall be considered as being <br />synonymous." <br /> <br />The flood profile elevations and flood plain limits shown <br />on the Flooded Areas maps can easily be transferred to a field <br />location by simple survey methods using the established <br />monurnentation of the Colorado Water Conservation Board or the <br />USGS by scaling from physical features shown on the map. <br /> <br />Regulation of the Colorado Water Conservation Board, dated <br />February 26, 1975. The floodway zone is defined to be: <br /> <br />To determine the depth of flooding or the flood plain <br />limits at any location in the field, the following procedure <br />should be used: <br /> <br />I <br />! <br />I <br />I <br />I <br /> <br />1. Locate the ground point at which the depth of <br />flooding or the flOOd plain limit is to be <br />established on the 1" 2 200' Flooded Areas map. <br />2. Determine the elevation of the water surface at <br />the selected ground point from the appropriate <br />table or by interpolating between the water <br />surface elevations given for two adjacent <br />cross-sections, as has been done in the flood <br />profile charts. <br />3. Using the closest monument for elevation control <br />and by standard leveling tochniques, locate the <br />point where the ground elevation is the sarne as the <br />water surface elevation along a line perpendicular <br />to the location on the river where the water <br />surface elevation has been determined from the table <br />or flood profile chart. The flood plain limit is <br />established where the water surface elevation intercepts <br />the ground surface. <br /> <br />As established by Larimer County, the low hazard zone is <br />defined as that part of the lOa-year flood plain where flood <br />depths are less than 1.5 feet and average flood velocities <br />are less than 3.0 feet per second. Areas within the 100-year <br />flood plain where depths or velocities are greater than those <br />indicated above, are in the floodway zone. <br /> <br />FLOOD PLAIN MAPS <br /> <br />The Flooded Areas maps and flood profile charts included <br />in Volume II were completed based on the findings of the hydrology <br />and hydraulic studies. The Flooded Areas maps show the location <br />of the floodway and low hazard zone within the lOa-year flood <br />plain. In addition, the maps show the location of most of the <br />cross-sections used in the study as well as the river stationing. <br />The flood prOfile charts graphically show the elevation of the <br />river bed or low wator and the 10-, 50-, 100- and SOO-year flood <br />levels. Figures 2 through 6, Flooded Areas Map Index, show the <br />location of each of the Flooded Areas maps inCluded in Volume II. <br />The flood profiles sheet pertinent to each FlOOded Areas map <br />~s referenced on all FlOOded Areas maps. <br /> <br />An approximate depth of flooding can be established by <br />subtracting the ground elevation estimated from the contour map <br />from the previously determined water surface elevation. <br /> <br />-16- <br /> <br />-17_ <br />