Laserfiche WebLink
<br />0022~6 <br /> <br />. <br /> <br />assumptions used in the Floodway hydraulic routing analysis, <br />and the results of the routing of the one-in-one hundred year <br />event on the tr ibutar ies and mainstem of the lower Colorado <br />River. <br /> <br />I. ISSUE <br /> <br />Identify the format and scale most useful for the users <br />of the Floodway boundary maps. <br /> <br />DISCUSSION <br /> <br />. <br /> <br />Several different maps of the lower Colorado River are <br />available. These range from USGS quadrangle map sheets to <br />site specific local contour maps developed by Reclamation for <br />use in channel stabilization activities. Aerial photography <br />also exists for most areas. Some areas along the river <br />consist of vast areas with little development while other <br />areas are heavily developed. The aerial photography is a <br />valuable tool in identifying existing uses of the Floodway: <br />however, in developing areas, the aerial photography can <br />quickly become outdated. <br /> <br />A base map consisting of physical topography overlain <br />with 2-foot contours would provide a good general overview. <br />Where this level of data was not readily 'available, it could <br />be developed using aerial photography techniques with a <br />resolution of +1 foot. Using the standard 7.5 minute <br />quadrangle map sheet scale of l-inch equals 2,000 feet would <br />require 23 map sheets 20 inches by 30 inches to cover the <br />full length of the Floodway, excluding maps for Lake Havasu. <br />This appears to be a useable and manageable package for the <br />official maps. <br /> <br />In areas where maintenance of shoreline facilities or <br />development is planned, a more detailed map will be needed. <br />Reclamation has often used a 1" = 400' scale with 2-foot <br />contours for planning and evaluation of specific sites. The <br />basic aerial photography data and survey data should be <br />collected and maintained so that working maps can be prepared <br />of specific areas as needed. <br /> <br />The Floodway boundary models will produce basic data <br />that can provide the projected water surface elevation at any <br />location along the river. This elevation can be used by <br />governmental entities and private entities to more precisely <br />determine the location of the Floodway boundary at a specific <br />site. <br /> <br />. <br /> <br />VI-2 <br />