Lake Mohave Geophysical Survey 2002: GIS Data Release USGS Open-File Report 2002-1247 by VeeAnn A. Cross, David S. Foster, and David C. Twichell INTRODUCTION: Lake Mohave is one of several multi-purpose reservoirs that have been constructed on the Colorado River. The lake was formed upon completion of the Davis Dam in 1953. No mapping of the floor of the lake had been conducted since completion of the Davis Dam. Because of the lack of lake-floor maps, the U.S. Geological Survey in cooperation with researchers from the University of Nevada Las Vegas completed a geophysical survey of this lake in April 2002. The survey included collection of sidescan-sonar imagery of nearly the entire lake floor.In addition to the sidescan-sonar imagery, high-resolution seismic-reflection profiles were collected along widely spaced lines throughout the lake. What follows is a series of images indicating the tracklines along which seismic-reflection data were collected. The detailed mapping of the lake floor was used to determine the amount of sediment that had accumulated in the lake since impoundment, its distribution, and the processes of deposition. DIRECTORY STRUCTURE: Top level directory: index.htm - This file is intended to be the starting point for the CD-ROM access. readme.txt - ASCII text file containing a description of this CD-ROM. mohave.apr - ArcView project file created with ArcView 3.2a on a Windows2000 computer. Directories: Directory data: What follows is a brief description of the data contained in the underlying directories. For a more complete description of the data, refer to the Data/GIS section of this report, or the metadata associated with each data file. This directory contains the following subdirectories: basemap - contains polyline shapefile of the shoreline from Lake Mohave, as well as the polygon shapefile of the states boundaries in the area and a georefenced color-shaded relief TIFF image of the study area. interpretation - ESRI shapefiles of interpreted layers of the reservoir floor. nav - contains navigation data, both as an ASCII text file and as ESRI shapefiles, pertaining to sidescan and seismic data collection in Lake Mohave. seisimages - contains JPEG images of all the seismic-reflection profiles collected as part of this study. sidescan - contains sidescan-sonar mosaics of the reservoir floor. The subdirectories indicate the projection of the imagery, either geographic or UTM (Zone 11, NAD83). These images are available in TIFF and MrSid image formats. Directory htmldocs: contains the HTML pages accessed within this Open-File Report. This directory contains the subdirectory icons which contains all the image files and icons utilized in constructing the Open-File Report HTML pages. Directory metadata: contains the HTML and ASCII text versions of the metadata files for all the data contained in this Open-File Report. This metadata is organized into the following subdirectories: basemap, interpretation, nav, seisimages, and sidescan. DISCLAIMER: This CD-ROM publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. 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