An experimental water release from the Glen Canyon Dam into the Colorado River above Grand Canyon was conducted in September 2000 by the U.S. Bureau of Reclamation. To determine the sediment characteristics of the Colorado River bed before and after the release, the U.S. Geological Survey (USGS) conducted sidescan sonar surveys between Glen Canyon Dam (mile -15) and Phantom Ranch (mile 87.7), Arizona. The first survey (R3-00-GC, 28 Aug to 5 Sep 2000) was conducted before the release when the river was experiencing its Low Summer Steady Flow (LSSF) of 8,000 cfs. The second survey (R4-00-GC, 10 to 18 Sep 2000) was conducted immediately after the September 2000 experimental release during which average daily flow was as high as 30,800 cfs below Glen Canyon Dam. Riverbed sediment properties interpreted from the sidescan sonar images include sediment type, sandwave fields, and calculated changes in these properties between the two surveys.
These data are intended for science researchers, students, policy makers, and the general public. The data can be used with geographic information systems (GIS) software to display geologic information.
Additional information about the field activities from which this data set was derived are available online at <URL:http://walrus.wr.usgs.gov/infobank/r/r300gc/html/r-3-00-gc.meta.html> <URL:http://walrus.wr.usgs.gov/infobank/r/r400gc/html/r-4-00-gc.meta.html>
Sidescan sonar data were collected at approximately 15 to 20 stretches of the Colorado River and targeting pools between rapids in these sections of the river:
tail waters section (mile -15 to mile 0) Paria Riffle (Mile 1) to Cathedral Riffle (Mile 3) small area above Badger Creek Rapid (Mile 7) Silver Grotto Riffle (Mile 29.3) to South Canyon or just above Vasey's Paradise (Mile 31.4) President Harding Rapid (Mile 44) to between Eminence Break to Saddle Canyon (Mile 47) 60 Mile Rapid to the Little Colorado River (Mile 65) below the Little Colorado River to Crash Canyon (Mile 62-63) to Carbon Creek (Mile 64) to Lava Chuar (Mile 65) Cremation Camp to Grand Canyon Gauge (Mile 87-89)These pools are part of the Grand Canyon Monitoring and Research Center (GCMRC <http://www.gcmrc.gov/>) physical sciences study.
Maps interpreted from the sidescan sonar images show the distribution of sediment types (bedrock, boulders, pebbles or cobbles, sand) and the extent of fields of sandwaves for each of the pre- and post-flow surveys. In addition, a derived set of data describes the changes that were observed between the two surveys (fining, coarsening, erosion, deposition, change in bedforms).
This data set includes sidescan sonar images and interpreted map files for each of the pre- and post-flow surveys and the changes between for the following sections of river (<URL:http://geopubs.wr.usgs.gov/open-file/of03-265/metadata/indexmap.gif>)
mile id description ---- -- ----------- -15 to 0 tw Glen Canyon Dam to Lees Ferry 0 to 3 bp below Paria Riffle, Lees Ferry to Cathedral Wash 4 to 8 bch below Cathedral Wash 27 to 29 ts Tiger Wash to Shinumo Wash 30 to 32 ssc Shinumo Wash to South Canyon 36 to 39 tp Thirty-Six Mile to President Harding Rapid 44 to 47 phs President Harding Rapid to Saddle Canyon 47 to 52 sn Saddle Canyon to Nankoweap Rapid 60 to 61 slc Sixty Mile Rapid to Little Colorado River 62 to 69 blcr below Little Colorado River 85 to 87 zc Zoroaster Rapid to CremationFile naming convention where xxxx is one of the river segment abbreviations (id above) plus a number:
r300xxxx.tif R3-00-GC sidescan sonar image, 0.2 m resolution r300xxxx.tfw world file for registration of sidescan sonar image r300xxxx.prj projection file for sidescan sonar image r400xxxx.tif R4-00-GC sidescan sonar image, 0.2 m resolution r400xxxx.tfw world file for registration of sidescan sonar image r400xxxx.prj projection file for sidescan sonar image r300xxxx/ interpreted sediment types, R3-00-GC r300xxxxsw/ sandwave fields, R3-00-GC r400xxxx/ interpreted sediment types, R4-00-GC r400xxxxsw/ sandwave fields, R4-00-GC chgxxxxsw/ bedform changes between R3-00-GC and R4-00-GC chgxxxx/ deposition or erosion between R3-00-GC and R4-00-GCAny use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.
The coverages were checked and manually registered if the navigation data were insufficient. The image and vector files in UTM 11 coordinates were converted to Arizona State Plane coordinates for conformance to GCMRC requirements. Processor: Florence Wong (fwong@usgs.gov).
r300xxx.tif, r400xxx.tif - 0.2-meter resolution sidescan
sonar images with pixel values 0 to 255. 0 represents
nodata areas. Image color is black (0) to white (255).
r300xxxx, r400xxxx - polygon coverage of interpreted
sediment types
Attribute: sedtype
Values: bedrock, boulders, pebbles_cobbles, sand, shoreline
r300xxxsw, r400xxxsw - polygon coverage of sandwave fields
Attribute: sedtype
Values: starved_sand
chgxxxsw - polygon coverage of areas of bedform change
between R3-00-GC and R4-00-GC
Attribute: sedchange
Values: new sandwaves, sandwaves lost
chg_r4xxx - polygon coverage of areas of fining, coarsening, erosion or
deposition between R3-00-GC and R4-00-GC
Attribute: sedchange
Values: fining, coarsening, deposition, erosion
Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data.
The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.