Matching Items (3)
- Status: Published
The passage of the Grand Canyon Protection Act (1992) and the completion of the Glen Canyon Dam Environmental Impact Statement (1996) ushered in a new era of environmental monitoring and research of the Colorado River corridor in Grand Canyon. Technological advancements in surveying and mapping systems over this period have made it possible to map larger areas with an increasing level of precision and accuracy. All of these mapping efforts rely on an accurate geodetic control network along the rim and inner canyon corridor. Examples of mapping efforts include aerial photographic, topographic, and bathymetric missions. Aerial overflights of the entire canyon corridor have been conducted in 2002, 2009, and 2013 and the high-resolution orthophographs and photogrammetrically-derived topography form the base data set for a number of investigations. From 2009 to 2017, over 160 miles of channel have been mapped using multibeam bathymetry. The bathymetric maps reveal the form of the Channel bed and allow researchers to asses flow operations from Glen Canyon dam on the sediment resources within the Colorado River ecosystem.
Official program of the Mapping Grand Canyon Conference. Document was designed and optimized for digital dissemination and mobile device (smartphone, tablet) viewing and interactive browsing. Document was deliberately not printed in paper format with the intent of minimizing the event's ecological footprint through a reduction of paper and ink waste.
River rafting trips and hikers use sandbars along the Colorado River in Marble and Grand Canyons as campsites. The U.S. Geological Survey evaluated the effects of Glen Canyon Dam operations on campsite areas on sandbars along the Colorado River in Grand Canyon National Park. Campsite area was measured annually from 1998 to 2012 at 37 study sites between Lees Ferry and Diamond Creek, Arizona. The primary purpose of this report is to present the methods and results of the project.
Campsite area surveys were conducted using total station survey methods to outline the perimeter of camping area at each study site. Campsite area is defined as any region of smooth substrate (most commonly sand) with no more than an 8 degree slope and little or no vegetation. We used this definition, but relaxed the slope criteria to include steeper areas near boat mooring locations where campers typically establish their kitchens.
The results show that campsite area decreased over the course of the study period, but at a rate that varied by elevation zone and by survey period. Time-series plots show that from 1998 to 2012, high stage-elevation (greater than the 25,000 ft3/s stage-elevation) campsite area decreased significantly, although there was no significant trend in low stage-elevation (15,000–20,000 ft3/s) campsite area. High stage-elevation campsite area increased after the 2004 and 2008 high flows, but decreased in the intervals between high flows. Although no overall trend was detected for low stage-elevation campsite areas, they did increase after high-volume dam releases equal to or greater than about 20,000 ft3/s. We conclude that dam operations have not met the management objectives of the Glen Canyon Adaptive Management program to increase the size of camping beaches in critical and non-critical reaches of the Colorado River between Glen Canyon Dam and Lake Mead.