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The numbers and sizes of sand beaches suitable for recreation along selected whitewater rivers in the western United States depend on sand concentrations, range of discharge and the size, frequency and type of depositional settings. River-width expansions downstream from constrictions are the predominant depositional setting for sand beaches in the upper Grand Canyon and along five Wild and Scenic Rivers in Idaho, but not along other rivers. Beaches located upstream from constrictions are rare, in general, except in the Grand Canyon. Beaches found in expansions without constrictions dominate depositional sites along the Yampa and Green Rivers, are fairly common along the rivers in Idaho, but are relatively rare...
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In this article, we compare chemical (87Sr/86Sr and elemental) analyses of archaeological maize from dated contexts within Pueblo Bonito, Chaco Canyon, New Mexico, to potential agricultural sites on the periphery of the San Juan Basin. The oldest maize analyzed from Pueblo Bonito probably was grown in an area located 80 km to the west at the base of the Chuska Mountains. The youngest maize came from the San Juan or Animas river floodplains 90 km to the north. This article demonstrates that maize, a dietary staple of southwestern Native Americans, was transported over considerable distances in pre-Columbian times, a finding fundamental to understanding the organization of pre-Columbian southwestern societies. In...
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Removal of nonnative riparian trees is accelerating to conserve water and improve habitat for native species. Widespread control of dominant species, however, can lead to unintended erosion. Helicopter herbicide application in 2003 along a 12-km reach of the Rio Puerco, New Mexico, eliminated the target invasive species saltcedar (Tamarix spp.), which dominated the floodplain, as well as the native species sandbar willow (Salix exigua Nuttall), which occurred as a fringe along the channel. Herbicide application initiated a natural experiment testing the importance of riparian vegetation for bank stability along this data-rich river. A flood three years later eroded about 680,000 m(3) of sediment, increasing mean...
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Removal of nonnative riparian trees is accelerating to conserve water and improve habitat for native species. Widespread control of dominant species, however, can lead to unintended erosion. Helicopter herbicide application in 2003 along a 12-km reach of the Rio Puerco, New Mexico, eliminated the target invasive species saltcedar (Tamarix spp.), which dominated the floodplain, as well as the native species sandbar willow (Salix exigua Nuttall), which occurred as a fringe along the channel. Herbicide application initiated a natural experiment testing the importance of riparian vegetation for bank stability along this data-rich river. A flood three years later eroded about 680,000 m(3) of sediment, increasing mean...
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The numbers and sizes of sand beaches suitable for recreation along selected whitewater rivers in the western United States depend on sand concentrations, range of discharge and the size, frequency and type of depositional settings. River-width expansions downstream from constrictions are the predominant depositional setting for sand beaches in the upper Grand Canyon and along five Wild and Scenic Rivers in Idaho, but not along other rivers. Beaches located upstream from constrictions are rare, in general, except in the Grand Canyon. Beaches found in expansions without constrictions dominate depositional sites along the Yampa and Green Rivers, are fairly common along the rivers in Idaho, but are relatively rare...
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