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S. A. Schumm

Publications and source records attributed to S. A. Schumm.

11 recordsLinked to original sources
USGS2014

Yield of sediment in relation to mean annual precipitation

Effective mean annual precipitation is related to sediment yield from drainage basins throughout the climatic regions of the United States. Sediment yield is a maximum at about 10 to 14 inches of precipitation, decreasing sharply on both sides of this maximum in one case owing to a deficiency of runoff and in the other to increased density of vegetation. Data are presented illustrating the increase in bulk density of vegetation with increased annual precipitation and the relation of relative erosion to vegetative density. It is suggested that the effect of a climatic change on sediment yield depends not only upon direction of climate change, but also on the climate before the change. Sediment concentration in runoff is shown to increase with decreased annual precipitation, suggesting further that a decrease in precipitation will cause stream channel aggradation

Eos, Transactions, American Geophysical Union↗
USGS1993

Geological applications of multi-response permutation procedures

The multi-purpose permutation procedures (MRPP) test statistic is designed to analyze multivariate data at the ordinal or higher levels. It is based on the weighted averages of symmetric distance functions over all paired objects within a priori disjoint groups of objects from a finite population of objects where each object's response is a point in an r-dimensional space. Thus, the arguments of each r-dimensional point correspond to the r measured responses of each object in the finite population of objects. The null hypothesis underlying MRPP is that the observed sample of objects within groups of a specified size structure is randomly obtained from the pooled collection of objects comprising the finite population. The procedure is used to test the presumed geomorphic differences among three reaches of the Lower Mississippi River. A combination of the proposed reaches is favored and several variable-based reach configurations are proposed. ?? 1993 International Association for Mathernatical Geology.

Mathematical Geology↗
USGS1991

Channel evolution and hydrologic variations in the Colorado River basin: Factors influencing sediment and salt loads

Suspended-sediment and dissolved-solid (salt) loads decreased after the early 1940s in the Colorado Plateau portion of the Colorado River basin, although discharge of major rivers - the Colorado, Green and San Juan - did not change significantly. This decline followed a period of high sediment yield caused by arroyo cutting. Reduced sediment loads have previously been explained by a change in sediment sampling procedures or changes in climate, land-use and conservation practices. More recent work has revealed that both decreased sediment production and sediment storage in channels of tributary basins produced the decline of sediment and salt loads. Sediment production and sediment storage are important components of incised-channel evolution, which involves sequential channel deepening, widening and finally floodplain formation. Accordingly, the widespread arroyo incision of the late nineteenth century resulted initially in high sediment loads. Since then, loads have decreased as incised channels (arroyos) have stabilized and begun to aggrade. However, during the 1940s, a period of low peak discharges permitted vegetational colonization of the valley floors, which further reduced sediment loads and promoted channel stabilization. This explanation is supported by experimental studies and field observations. Both geomorphic and hydrologic factors contributed to sediment storage and decreased sediment and salt loads in the upper Colorado River basin.

Arizona, California, Colorado, Nevada, New Mexico,↗
USGS1967

Rates of surficial rock creep on hillslopes in western Colorado

The average rate of downslope movement of rock fragments on shale hillslopes is directly proportional to the sine of the slope angle or that component of the gravitational force which acts parallel to the hillslope. The rates of surficial rock creep range from a few millimeters per year on a 3degree slope to almost 70 millimeters per year on a 40-degree slope, but these rates vary with natural variations in soil characteristics and microclimate, as well as with accidental disturbances.

Colorado↗
USGS1963

Sinuosity of alluvial rivers on the great plains

Data on the morphologic and sediment characteristics of stable alluvial rivers of the Great Plains were collected at 50 cross sections. The channel patterns of these rivers were classified into five types: tortuous, irregular, regular, transitional, and straight. Because no clear demarcation existed between each of the types, the pattern of the rivers was described by sinuosity , a ratio of channel length to valley length. The sinuosity ((P)) of these rivers is related to the shape of the channels expressed as a width-depth ratio (F) and to the percentage of silt and clay in the perimeter of the channel (M) as follows: Sinuous streams are characterized by a low width-depth ratio (F), a high percentage of silt-clay in the perimeter of the channel (M), a high percentage of silt-clay in the banks (although the banks of straight channels may also contain large amounts of silt-clay), and a lower gradient than straight channels having the same mean discharge. Discharge itself does not appear to affect the sinuosity of streams. Another possible distinction between straight and sinuous streams is in the proportions of the components of total sediment load. In a wide, shallow channel much of the sediment transported is bed-material load. In a narrow, deep channel most of the sediment transported is wash load. On the Great Plains both straight and sinuous streams may flow on the surface of alluvial valley fills at about the same valley slope. The departure of a stream from a straight course down the alluvial valley results from changes in both the caliber of the sediment load and in the relative proportions of bed-material load and wash load during the post-Pleistocene alluviation of these valleys. When during this alluviation the proportion of wash load increased, most probably by a decrease in bed-material load, the stream adjusted itself by decreasing its gradient through the development of a sinuous course. Recent changes in stream sinuosity in response to changes in the proportions of bed load and suspended load support this hypothesis.

Geological Society of America Bulletin↗
USGS1962

Erosion on miniature pediments in badlands national monument, South Dakota

Measurements of erosion on miniature pediments in Badlands National Monument , South Dakota , show that during almost eight years, the pediments were lowered by sheetwash. The adjacent hillslopes have retreated leaving a belt of newly formed pediment from 6 to 12 cm wide at their bases. The hillslopes are rough and relatively permeable; the miniature pediments are smooth and less permeable. Calculations based on the Manning equation suggest that the velocity of overland flow on the pediments may be of the same magnitude as that on the hillslopes. The decrease in roughness from hillslope to pediment compensates for the decrease in slope angle. The pediments are swept free of debris and are regraded by a more effective utilization of runoff energy.

South Dakota↗
USGS1961

Hydrology of the upper Cheyenne River basin: Part A. Hydrology of stock-water reservoirs in upper Cheyenne River basin; Part B. Sediment sources and drainage-basin characteristics in upper Cheyenne River basin

The objective of this investigation was to determine the effect on runoff of the many stock reservoirs in the Cheyenne River basin above Angostura Dam. As a first step it was necessary to determine, within reasonable limits of accuracy, the number of reservoirs in the basin, the storage capacity, the drainage area, and the water loss from each. A sampling method was adopted because the size of the basin, 9,100 square miles, prohibited examination of all reservoirs within the drainage area. Forty-nine sample areas of 9 square miles each were selected as a 5-percent sample of the 955 complete quarter townships within the basin above Angostura Dam. All reservoirs located within the sample quarter townships were surveyed.

South Dakota, Wyoming↗