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Locational Probability For A Dammed, Urban Stream: Salt River, Arizona, William Graf
Locational Probability For A Dammed, Urban Stream: Salt River, Arizona, William Graf
William L. Graf
Data from historical aerial photographs analyzed with a GIS show that river channel change on the Salt River in the Phoenix metropolitan area of central Arizona has been driven by large-scale regional flood events and local human activities. Mapping of functional surfaces such as low-flow channels, high-flow channels, islands, bars attached to channel banks, and engineered surfaces shows that during the period from 1935 to 1997, the relative areal coverage of these surfaces has changed. Flood events have caused general changes in sinuosity of the low-flow channel, but islands have remained remarkably consistent in location and size, while channel-side bars …
The Rate Law In Fluvial Geomorphology, William Graf
The Rate Law In Fluvial Geomorphology, William Graf
William L. Graf
No abstract provided.
Variability Of Sediment Removal In A Semi-Arid Watershed, William L. Graf
Variability Of Sediment Removal In A Semi-Arid Watershed, William L. Graf
William L. Graf
Field and documentary data from Walnut Gulch Watershed, an instrumented semiarid drainage basin of approximately 150 km2 (57 mi2) in southeastern Arizona, show that 83% of the alluvium removed from the basin during a 15‐year erosion episode beginning about 1930 was excavated from the highest‐order stream. The amount of alluvium removed in the erosion episode would have been equal to a covering of about 4 cm (1.6 in) over the entire basin. The rate of sediment removal during the erosion episode was 18 times greater than the rate of present channel sediment transport. Production of sediment from slopes and channel …
A Probabilistic Approach To The Spatial Assessment Of River Channel Instability, William L. Graf
A Probabilistic Approach To The Spatial Assessment Of River Channel Instability, William L. Graf
William L. Graf
The deterministic approach to the analysis of river channel instability has not proved to be a completely useful basis for geographic predictions of channel behavior. Economic estimates for benefits of structural channel control projects commonly account for flood inundation, but in arid and semiarid regions these estimates are incomplete because they fail to take into account destructive channel migration and erosion. As a solution, a method whereby historical records of channel locations are reduced to spatially defined probabilistic functions allows calculation of the probability that given parcels of near-channel terrain will be destroyed by erosion. The probability of erosion for …
Tamarisk And River-Channel Management, William Graf
Tamarisk And River-Channel Management, William Graf
William L. Graf
Tamarisk (Tamarix chinensis, Lour.) an artificially introduced tree, has become a most common species in many riparian vegetation communities along the rivers of the western United States. On the Salt and Gila rivers of central Arizona, the plant first appeared in the early 1890s, and by 1940 it grew in dense thickets that posed serious flood-control problems by substantially reducing the capacities of major channels. Since 1940 its distribution and density in central Arizona have fluctuated in response to combined natural processes and human management. Groundwater levels, channel waters, floods, irrigation return waters, sewage effluent, and sedimentation behind retention and …
The Distribution Of Glaciers In The American Rocky Mountains, William Graf
The Distribution Of Glaciers In The American Rocky Mountains, William Graf
William L. Graf
No abstract provided.
Channel Instability In A Braided Sand Bed River, William Graf
Channel Instability In A Braided Sand Bed River, William Graf
William L. Graf
The Gila River of central Arizona is representative of braided, sand bed rivers in alluvial valleys that have inherent unstable behavior and destructive channel migration. The 112-year record of channel conditions along a portion of the Gila River provides data for the construction of locational probability maps for main flow channels. Zones of stability and hazardous instability alternate with each other at 3.2 km (2 mi) intervals. During the past century the overall sinuosity of the main flow channel has remained close to 1.18, despite numerous changes in actual location. Spatial and temporal variation of sinuosity have occurred in subreaches …
Development Of Montane Arroyos And Gullies, William Graf
Development Of Montane Arroyos And Gullies, William Graf
William L. Graf
Field investigations in the Front Range of Colorado, U.S.A., confirm that the spatial distribution of vegetation in watersheds exerts strong control on the entrenchment of streams in the montane zone. When tractive force in channels exceeds threshold values of resistance on the valley floors, cutting of arroyos begins, producing forms that change allometrically. An algorithm based on the Cooke Method for discharge, the Manning Equation for depth of flow, and the DuBoys Equation for tractive force can be used to evaluate force for observed and experimental conditions. In small (<5 km2) basins in the Front Range of Colorado, forces …
Distance Decay And Arroyo Development In The Henry Mountains Region, Utah, William Graf
Distance Decay And Arroyo Development In The Henry Mountains Region, Utah, William Graf
William L. Graf
No abstract provided.
Dam Nation: A Geographic Census Of American Dams And Their Large-Scale Hydrologic Impacts, William Graf
Dam Nation: A Geographic Census Of American Dams And Their Large-Scale Hydrologic Impacts, William Graf
William L. Graf
Newly available data indicate that darns fragment the fluvial system of the continental United States and that their impact on river discharge is several times greater than impacts deemed likely as a result of global climate change. The 75,000 dams in the continental United States are capable of storing a volume of water almost equaling one year's mean runoff, but there is considerable geographic variation in potential surface water impacts. In some western mountain and plains regions, darns can store more than 3 year's runoff, while in the Northeast and Northwest, storage is as little as 25% of the annual …
The Effect Of Dam Closure On Downstream Rapids, William Graf
The Effect Of Dam Closure On Downstream Rapids, William Graf
William L. Graf
The force of flowing water and the resistance of the largest boulder provide a means of evaluation of the stability of rapids in canyon rivers. Field measurements and calculations show that the closure of Flaming Gorge Dam, Utah, has had a significant effect on the stability of rapids in the canyons of the Green River in Dinosaur National Monument 68 km (42 mi) downstream from the dam. The reduction in peak flows by the dam has limited the competence of the river to move boulders deposited in the main channel by tributary processes, landslides, and prehistoric floods. Before the dam …