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Sediment yield from small arid basins, particularly in the Mojave Desert, is largely unknown owing to the ephemeral nature of these fluvial systems and long recurrence interval of flow events. We examined 27 reservoirs in the northern and eastern Mojave Desert that trapped sediment from small (< 1 km2) drainage basins on alluvial fans over the past 100 yr, calculated annual sediment yield, and estimated the average recurrence interval (RI) of sediment-depositing flow events. These reservoirs formed where railbeds crossed and blocked channels, causing sediment to be trapped and stored upslope. Deposits are temporally constrained by the date of railway construction (1906–1910), the presence of 137Cs in the reservoir...
Using widely-available software intended for modeling rivers, a new one-dimensional hydraulic model was developed for the Colorado River through Grand Canyon from Lees Ferry to Diamond Creek. Solving one-dimensional equations of energy and continuity, the model predicts stage for a known steady-state discharge at specific locations, or cross sections, along the river corridor. This model uses 2,680 cross sections built with high-resolution digital topography of ground locations away from the river flowing at a discharge of 227 m3/s; synthetic bathymetry was created for topography submerged below the 227 m3/s water surface. The synthetic bathymetry was created by adjusting the water depth at each cross section up...
Categories: Publication; Types: Citation
Holocene debris flows do not occur uniformly on the Colorado Plateau province of North America. Debris flows occur in specific areas of the plateau, resulting in general from the combination of steep topography, intense convective precipitation, abundant poorly sorted material not stabilized by vegetation, and the exposure of certain fine-grained bedrock units in cliffs or in colluvium beneath those cliffs. In Grand and Cataract Canyons, fine-grained bedrock that produces debris flows contains primarily single-layer clays—notably illite and kaolinite—and has low multilayer clay content. This clay-mineral suite also occurs in the colluvium that produces debris flows as well as in debris-flow deposits, although unconsolidated...
The existence of an upper limit to the magnitude of floods in a region is a long-standing and controversial hypothesis in flood hydrology. Regional envelope curves encompassing maximum flood magnitudes stabilize with progressive increases in the areal coverage and period of observation (Wolman and Costa, 1984). However, the short lengths of conventional gaging records limit substantial advances in testing whether this stabilization is evidence of an upper limit. In the Colorado River basin there are 32,120 station years of gage data, but the average period at a gaging station is only 20 years, with most stations having less than 70 years of observation. Paleoflood magnitudes derived from sediments of large prehistoric...
"This title presents new research on the Mojave Desert and the contributors discuss the desert from several perspectives including regional threats such as expanding human populations, climate change, atmospheric nitrogen deposition and invasive plants, the impact of roads in a desert ecosystem, soils and plant communities, shrinking aquifers and the monitoring and sustainability of this fragile ecosystem." --NHBS Environment Bookstore.
Categories: Publication; Types: Citation
Rapids on the Colorado River in Grand Canyon attract over 20,000 white-water enthusiasts a year and are considered one of the premiere collections of rapids in North America. While this collection of rapids is an important recreational resource, relatively little is known of the specific hydraulics of individual rapids. Flow measurements are occasionally made in the low-velocity reaches between rapids, but the turbulent and dangerous nature of rapids makes in-situ data collection challenging. The present study measured hydraulics within a small rapid in Grand Canyon as well as an alluvial reach of the Colorado River in Glen Canyon using a Sontek Argonaut acoustic Doppler velocimeter (ADV)2. The ADV was mounted near...
Categories: Publication; Types: Citation
Strong westerly winds that emanate from San Gorgonio Pass, the lowest point between Palm Springs and Los Angeles, California, dominate aeolian transport in the Coachella Valley of the western Sonoran Desert. These winds deposit sand in coppice dunes that are critical habitat for several species, including the state and federally listed threatened species Uma inornata, a lizard. Although wind directions are generally defined in this valley, the wind field has complex interactions with local topography and becomes more variable with distance from the pass. Local, dominant wind directions are preserved by growth patterns of Larrea tridentata (creosote bush), a shrub characteristic of the hot North American deserts,...
Riverine riparian vegetation has changed throughout the southwestern United States, prompting concern about losses of habitat and biodiversity. Woody riparian vegetation grows in a variety of geomorphic settings ranging from bedrock-lined channels to perennial streams crossing deep alluvium and is dependent on interaction between ground-water and surface-water resources. Historically, few reaches in Arizona, southern Utah, or eastern California below 1530 m elevation had closed gallery forests of cottonwood and willow; instead, many alluvial reaches that now support riparian gallery forests once had marshy grasslands and most bedrock canyons were essentially barren. Repeat photography using more than 3000 historical...
This ambitious book will enthrall armchair naturalists and river runners alike, offering a stunning tour through the natural, environmental, and human history of Cataract Canyon, a seventeen-mile run of free-flowing river above Lake Powell in the canyonlands of southern Utah. Setting the stage with preliminary chapters on geology and hydrology, prehistory and geography, biology, and river-running history the authors take the reader on a "downriver journey," narrating an exploration of the river that is breathtaking in scope. From the plants and animals that live along its banks to the humans who seek out its rapids, from the wind and water that continue to shape the landscape to the government agencies that seek...
Categories: Publication; Types: Citation
The failure of a lava dam 165,000 yr ago produced the largest known flood on the Colorado River in Grand Canyon. The Hyaloclastite Dam was up to 366 m high, and geochemical evidence linked this structure to outburst-flood deposits that occurred for 32 km downstream. Using the Hyaloclastite outburst-flood deposits as paleostage indicators, we used dam-failure and unsteady flow modeling to estimate a peak discharge and flow hydrograph. Failure of the Hyaloclastite Dam released a maximum 11 × 109 m3 of water in 31 h. Peak discharges, estimated from uncertainty in channel geometry, dam height, and hydraulic characteristics, ranged from 2.3 to 5.3 × 105 m3 s−1 for the Hyaloclastite outburst flood. This discharge is an...
From July 31 to August 1, 2006, an unusual set of atmospheric conditions aligned to produce record floods and an unprecedented number of slope failures and debris flows in southeastern Arizona. During the week leading up to the event, an upper-level low-pressure system centered over New Mexico generated widespread and locally heavy rainfall in southeastern Arizona, culminating in a series of strong, mesoscale convective systems that affected the region in the early morning hours of July 31 and August 1. Rainfall from July 27 through 30 provided sufficient antecedent moisture that the storms of July 31 through August 1 resulted in record streamflow flooding in northeastern Pima County and eastern Pinal County. The...
Categories: Publication; Types: Citation
Perennial vegetation data from 68 permanent plots on the Nevada Test Site, Nye County, Nevada, are given for the period of 1963 through 2002. Dr. Janice C. Beatley established the plots in 1962 and then remeasured them periodically from 1963 through 1975. We remeasured 67 of these plots between 2000 and 2003; the remaining plot was destroyed at some time between 1975 and 1993. The plots ranged from 935 to 2,274 m in elevation and are representative of common plant associations of the Mojave Desert, the transition to Great Basin Desert, and pinyon-juniper woodlands. The purpose of this report is to describe the complete set of ecological data that Beatley collected from the Nevada Test Site from 1963 through 1975...
Categories: Publication; Types: Citation
This ambitious book will enthrall armchair naturalists and river runners alike, offering a stunning tour through the natural, environmental, and human history of Cataract Canyon, a seventeen-mile run of free-flowing river above Lake Powell in the canyonlands of southern Utah. Setting the stage with preliminary chapters on geology and hydrology, prehistory and geography, biology, and river-running history the authors take the reader on a "downriver journey," narrating an exploration of the river that is breathtaking in scope. From the plants and animals that live along its banks to the humans who seek out its rapids, from the wind and water that continue to shape the landscape to the government agencies that seek...
Ample geologic evidence indicates early Holocene and Pleistocene debris flows from the south side of the Santa Catalina Mountains north of Tucson, Arizona, but few records document historical events. On July 31, 2006, an unusual set of atmospheric conditions aligned to produce record floods and an unprecedented number of debris flows in the Santa Catalinas. During the week prior to the event, an upper-level area of low pressure centered near Albuquerque, New Mexico generated widespread heavy rainfall in southern Arizona. After midnight on July 31, a strong complex of thunderstorms developed over central Arizona in a deformation zone that formed on the back side of the upper-level low. High atmospheric moisture (2.00‘...
Categories: Publication; Types: Citation
Habitat modeling is an important tool used to simulate the potential distribution of a species for a variety of basic and applied questions. The desert tortoise (Gopherus agassizii) is a federally listed threatened species in the Mojave Desert and parts of the Sonoran Desert of California, Nevada, Utah, and Arizona. Land managers in this region require reliable information about the potential distribution of desert tortoise habitat to plan conservation efforts, guide monitoring activities, monitor changes in the amount and quality of habitat available, minimize and mitigate disturbances, and ultimately to assess the status of the tortoise and its habitat toward recovery of the species. By applying information from...
Categories: Publication; Types: Citation