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Floodplains are presumed to be important rearing habitat for the endangered razorback sucker (Xyrauchen texanus). To help recover this endemic Colorado River Basin species, the Upper Colorado River Endangered Fish Recovery Program implemented a floodplain acquisition and enhancement program. Levee removal was initiated in 1996 as one component of this floodplain restoration program. The goal of the Levee Removal Study was to evaluate the system responses to levee removal and make specific recommendations concerning the value of floodplain/river reconnecting for endangered species (specifically razorback sucker) recovery.
Imagine a stream of water thousands of kilometers long and as wide as the distance between New York City and Washington, D. C., flowing toward you at 30 miles per hour. No, this is not some hypothetical physics problem—it is a real river, carrying more water than 7–15 Mississippi Rivers combined. But it is not on land. It's a river of water vapor in the atmosphere. Atmospheric rivers (ARs) are narrow corridors of water vapor transport in the lower atmosphere that traverse long swaths of the Earth's surface as they bind together the atmospheric water cycle (Figure 1). The characteristic (indeed defining) dimensions of these ARs are (1) integrated water vapor (IWV) concentrations such that if all the vapor in the...
We present herein clear field evidence for the persistence of a coarse surface layer in a gravel-bed river during flows capable of transporting all grain sizes present on the channel bed. Detailed field measurements of channel topography and bed surface grain size were made in a gravel-bed reach of the Colorado River prior to a flood in 2003. Runoff produced during the 2003 snowmelt was far above average, resulting in a sustained period of high flow with a peak discharge of 27 m3/s (170% of normal peak flow); all available grain sizes within the study reach were mobilized in this period of time. During the 2003 peak flow, the river avulsed immediately upstream of the study reach, thereby abandoning approximately...
This study explores how the relationship between flow and riparian vegetation varies along a montane river. We mapped occurrence of woody riparian plant communities along 58 km of the San Miguel River in southwest- ern Colorado. We determined the recurrence interval of inundation for each plant community by combining step-back- water hydraulic modeling at 4 representative reaches with Log-Pearson analysis of 4 stream gaging stations. Finally, we mapped bottomland surficial geology and used a Geographic Information System to overlay the coverages of geology and vegetation. Plant communities were distinctly arrayed along the hydrologic gradient. The Salix exigua Nuttall (sand- bar willow) community occurred mostly...
The geomorphic effectiveness of extreme floods increases with aridity and decreasing watershed size. Therefore, in small dry watersheds extreme floods should control the age structure and spatial distribution of populations of disturbance-dependent riparian trees. We examined the influence of extreme floods on the bottomland morphology and forest of ephemeral streams in a semiarid region. Along six stream reaches on the Colorado Piedmont we examined channel changes by analyzing a rectified sequence of aerial photographs spanning 56 yr, and we investigated the spatial distribution of different-aged patches of forest by aging 189 randomly sampled cottonwood trees. Channel change in these ephemeral sand-bed streams...
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Canyon riparian zone vegetation is vulnerable to effects of upstream river regulation. We studied box elder (Acer negundo) dominated canyon riparian forests intensively on the Green and Yampa rivers in Dinosaur National Monument, Colorado, and extensively in four other major rivers of the upper Colorado River Basin to determine the effects of river regulation on riparian tree establishment patterns. We: 1) aged individuals to determine if establishment was correlated with high annual peak flows, 2) mapped cohorts to determine if the areal extent of post-regulation cohorts was reduced on regulated compared to unregulated river reaches, and 3) measured the floodplain position of cohorts in regulated and unregulated...
Although ?70 dams have been decommissioned in Wisconsin over the past 30 y, little is known about the physical and ecological effects of dam removal on riverine ecosystems. The purpose of our study was to document changes in channel form and macroinvertebrate assemblages following the removal of a low-head, run-of-river dam from the Baraboo River,Wisconsin, in January 2000. We surveyed cross sections and collected benthic macroinvertebrate samples in 6 reaches (an upstream reference reach, reaches immediately above and below the dam that was to be removed, and sequential unimpounded and impounded reaches further downstream) in a multiple-dam sys- tem. Surveys were conducted in December 1999, before dam removal,...
A mass of snow and ice 400-m-wide and 105-m-thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8 × 106 m3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9...
This study explores how the relationship between flow and riparian vegetation varies along a montane river. We mapped occurrence of woody riparian plant communities along 58 km of the San Miguel River in southwest- ern Colorado. We determined the recurrence interval of inundation for each plant community by combining step-back- water hydraulic modeling at 4 representative reaches with Log-Pearson analysis of 4 stream gaging stations. Finally, we mapped bottomland surficial geology and used a Geographic Information System to overlay the coverages of geology and vegetation. Plant communities were distinctly arrayed along the hydrologic gradient. The Salix exigua Nuttall (sand- bar willow) community occurred mostly...
Experimental observations collected during meteorological field studies conducted by the National Oceanic and Atmospheric Administration near the Russian River of coastal northern California are combined with SSM/I satellite observations offshore to examine the role of landfalling atmospheric rivers in the creation of flooding. While recent studies have documented the characteristics and importance of narrow regions of strong meridional water vapor transport over the eastern Pacific Ocean (recently referred to as atmospheric rivers), this study describes their impact when they strike the U.S. West Coast. A detailed case study is presented, along with an assessment of all 7 floods on the Russian River since the experimental...
    map background search result map search result map Effects of river regulation on riparian box elder (Acer Negundo) forests in Canyons of the upper Colorado River Basin, USA Effects of river regulation on riparian box elder (Acer Negundo) forests in Canyons of the upper Colorado River Basin, USA