FLOOD10474 - Laserfiche WebLink

Home Browse Search

2.0 AREA STUDIED 2.1 Scope of Study The streams studied by detailed methods, in part or in whole, within Jefferson County are presented in Table 1, "Streams Studied by Detailed Methods." The streams studied by approximate methods, in part or in whole, are presented in Table 2, "Streams Studied by Approximate Methods." A detailed analysis for a portion of the South Platte River was adopted from the FIS for Douglas County (Reference 20). Technical data for flooding on City Park Channel, Nissen Reservoir Channel, and overflow from Brandywine Creek were taken from a report by the Colorado UDFCD (Reference 21) and the FIS for the City of Broomfield, Colorado (Reference 22). North of the detailed study area in the City of Edgewater, approximate methods of analysis were used to study another sub-basin adjacent to Sloans Lake. The resulting floodplain for this area was not as well defined because of the poorly defined channels in the areas of the street and overland flow upstream of Depew Street ( Reference 24). Ketner Creek (Reference 23), Shaw Heights Tributary and Little Dry Creek (Reference 24), which were studied previously by the UDFCD, were included as approximate study areas within the City of Westminster. Dieital Conversion The mapping for Jefferson County, Colorado and Incorporated Areas has been prepared using digital data. Previously published FIRM and Flood Boundary and Floodway Map (FBFM) data produced manually have been converted to vector digital data by a digitizing process. Jefferson County GIS Department, has provided road and highway name and centerline data. The centerline data were computer plotted with the digitized floodplain data to produce the countywide FIRM. As part of this digital conversion, the panel layout of the FIRM has been revised. The new layout for the FIRM was based on the layout of the USGS quadrangle maps of Jefferson County. Jodi vidual map panel scales were determined so that the flood data represented were at similar scale to that used on the previously effective FIRMs. This countywide update also incorporates the results of mappable Letters of Map Change, including Letters of Map Amendment and LOMRs issued by FEMA for the projects listed in Table 3, "Letters of Map Change." The areas studied by detailed methods were selected with priority given to all known flood hazards and areas of projected development or proposed construction. 5