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Articles 211 - 218 of 218

Full-Text Articles in Geography

Channel Instability In A Braided Sand Bed River, William L. Graf Jan 1981

Channel Instability In A Braided Sand Bed River, William L. Graf

Faculty Publications

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 …


The Effect Of Dam Closure On Downstream Rapids, William L. Graf Jan 1980

The Effect Of Dam Closure On Downstream Rapids, William L. Graf

Faculty Publications

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 …


The Distribution Of Glaciers In The American Rocky Mountains, William L. Graf Jan 1977

The Distribution Of Glaciers In The American Rocky Mountains, William L. Graf

Faculty Publications

No abstract provided.


Network Characteristics In Suburbanizing Streams, William L. Graf Jan 1977

Network Characteristics In Suburbanizing Streams, William L. Graf

Faculty Publications

Analysis of hydrologic, geomorphic, and suburbanization data from a small instrumented drainage basin near Iowa City, Iowa, indicates that channel networks are radically altered when suburban development overtakes a drainage basin. Changes in channel networks are such that the network becomes much more efficient in collecting water quickly, so that lag time and kurtosis of storm hydrographs are altered to produce the familiar flash floods of urban areas. The data show that network changes are closely associated with lag time and kurtosis of storm hydrographs and suggest that corrective measures should be concentrated on the internal links of the network. …


Cirques As Glacier Locations, William L. Graf Jan 1976

Cirques As Glacier Locations, William L. Graf

Faculty Publications

A comparison between the 319 cirques that contain glaciers and a sample of 240 empty cirques in the Rocky Mountains shows that in the present climatic situation, landforms are strong factors in determining the locations of glaciers. An optimum glacier location is a large cirque facing northeast, with a planimetric shape of width greater than length, high steep walls, a pass located to the windward, and a peak to the southwest. Glaciers survive in the present climatic conditions because of a geomorphic feedback system, whereby glaciers are protected by cirque forms that owe their morphology to glacial processes.


The Impact Of Suburbanization On Fluvial Geomorphology, William L. Graf Jan 1975

The Impact Of Suburbanization On Fluvial Geomorphology, William L. Graf

Faculty Publications

Analysis of aerial photography for the period 1950–1971 and field data collected from 1970 to 1974 indicate that in the Denver area suburban development has caused significant changes in fluvial systems. By first introducing large quantities of sediment and later by increasing surface runoff, suburban development leads to an expansion of floodplains followed by downcutting of streams. As areas of suburban development increase, greater percentages of stream lengths are dominated by transportation, and lesser percentages are dominated by erosion and deposition.


Quantitative Analysis Of Pinedale Landforms, Beartooth Mountains, Montana And Wyoming, William L. Graf Jan 1971

Quantitative Analysis Of Pinedale Landforms, Beartooth Mountains, Montana And Wyoming, William L. Graf

Faculty Publications

The spatial distribution of terminal moraines in alpine valleys can be quantitatively described using distance/regression models. Surface parameters indicative of age may also be numerically analyzed. Evaluation of postglacial modification of valley sides between terminal moraines provides an additional indicator of relative age of valley segments. Analysis of the geomorphology of alpine features in the upper Rock Creek drainage in the southeastern Beartooth Mountains, Montana, shows that glaciers in this area deposited evidence of two Bull Lake, four Pinedale, and two Neo glacial advances.


The Geomorphology Of The Glacial Valley Cross Section, William L. Graf Jan 1970

The Geomorphology Of The Glacial Valley Cross Section, William L. Graf

Faculty Publications

Several alpine valley systems in the southeastern Beartooth Mountains, Montana and Wyoming, have been examined using techniques similar to methods of stream system analysis. The general equation y = a x**b is the most adequate mathematical model for the cross valley profile; b values range between 1.5 and 2.0, indicating a parabolic form. As intensity of erosion increases in the glacial valley system, the b value also increases, indicating relatively deeper and narrower valley cross sections. The law of stream numbers, the law of stream lengths, and the bifurcation ratio, derived from fluvial geomorphology, are also applicable in glacial geomorphology.