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Kevin M. Scott

Publications and source records attributed to Kevin M. Scott.

27 records · Page 2Linked to original sources
USGS1981

Erosion and sedimentation in the Kenai River, Alaska

The Kenai River system is the most important freshwater fishery in Alaska. The flow regime is characterized by high summer flow of glacial meltwater and periodic flooding caused by sudden releases of glacier-dammed lakes in the headwaters. Throughout most of its 50-mile course across the Kenai Peninsula Lowlands to Cook Inlet, the river meanders within coarse bed material with a median diameter typically in the range of 40-60 millimeters. Every nontidal section of the stream is a known or potential salmon-spawning site. The stream is underfit, a condition attributed to regional glacial recession and hypothesized drainage changes, and locally is entrenched in response to geologically recent changes in base level. The coarseness of the bed material is explained by these characteristics, combined with the reservoir-like effects of two large moraine impounded lakes, Kenai and Skilak Lakes, that formed as lowland glaciers receded. Throughout the central section of the river the channel is effectively armored, a condition that may have important long-term implications for the ability of this section of channel to support the spawning and rearing of salmon. The 3.8 river miles of channel below Skilak Lake contain submersed, crescentic gravel dunes with lengths in excess of 500 ft and heights of more than 15 ft. Such bed forms are highly unusual in streams with coarse bed material. The dunes were entirely stable from 1950 to at least 1977, so much so that small details of shape were unmodified by a major glacial-outburst flood in 1974. The features are the product of a flood greatly in excess of any recorded discharge. The entrenched section of the channel has been stable since at least 1950-195, only negligible amounts of bank erosion are indicated by sequential aerial photos. Bank erosion is active both upstream and downstream from the entrenched channel, however, and erosion rates in those reaches are locally comparable to rates in streams of similar size. Although erosion rates have been generally constant since 1950-1951, evidence suggests a possible recent decrease in bank stability and an increase in erosion that could be related to changes in river use. The high sustained flow of summer encourages a variety of recreation-related modifications to the bank and flood plain--canals, groins, boat ramps, slips, embankments, as well as commercial developments. As population and recreation use increase, development can pose a hazard to the productivity of the stream through increased suspended-sediment concentration resulting directly from construction and, with greater potential for long-term impact, indirectly from bank erosion. A short-term hazard, to both stream and developments is the cutoff of meander loops, the risk of which is increased by canals and boat slips cut in the surface layer of cohesive, erosion-resistant sediment on the flood plain within nonentrenched meander loops. A significant long-term hazard is an increase in bank erosion rates resulting from the loss of stabilizing vegetation on the high (up to 70 ft) cutbanks of entrenched and partially entrenched sections of channel. Potential root causes of erosion vegetation loss are river-use practices, meander cutoffs, and groin construction.

Alaska↗
USGS1979

Arctic stream processes--an annotated bibliography

This bibliography selectively summarizes investigations to date (1978) dealing with the physical processes of streams in the Arctic. The specialized annotations include aspects of stream processes described in subordinate parts of general papers on the arctic environment and therefore not evident in author-abstract bibliographies. Foreign contributions--Canadian, Scandinavian, and Russian--are summarized, in the case of Russian literature primarily by means of papers in translation journals. Until 1970 the role of streams in development of the arctic landscape was commonly considered subordinate to that of glacial and frost-related processes. This conclusion changed, however, with the findings of the many new studies begun in response to oil and gas discoveries in the late 1960's. The conclusions of these studies, made to provide both the engineering data for resource development and the information to assess the impacts of that development, were in general agreement that stream processes throughout most of the Arctic were significantly more important than previously had been thought.

Water Supply Paper↗
USGS1978

Erosion and sediment yields in the Transverse Ranges, Southern California

Major-storm and long-term erosion rates in mountain watersheds of the western Transverse Ranges of Ventura County, Calif., are estimated to range from low values that would not require the construction of catchments or channel-stabilization structures to values as high as those recorded anywhere for comparable bedrock erodibilities. A major reason for this extreme variability is the high degree of tectonic activity in the area--watersheds are locally being uplifted by at least as much as 25 feet per 1,000 years, yet the maximum extrapolated rate of denudation measured over the longest available period of record is 7.5 feet per 1,000 years adjusted to a drainage area of 0.5 square mile. Evidence of large amounts of uplift continuing into historic time includes structurally overturned strata of Pleistocene age, active thrust faulting, demonstrable stream antecedence, uplifted and deformed terraces, and other results of base-level change seen in stream channels. Such evidence is widespread in the Transverse Ranges, and aspects of the landscape are locally more a function of tectonic activity than of the denudational process. (Woodard-USGS)

Professional Paper↗
USGS1978

Effects of permafrost on stream channel behavior in Arctic Alaska

Sites with drainage areas ranging from 88 to 12,200 sq km were monitored on five streams in northern Alaska during the breakup in 1976 to determine (1) the effects of frozen bed and bank material on channel behavior, and (2) the importance of the annual breakup flood in forming the channels of arctic streams. The thawing and concomitant erosion of channels varied with changes in bed-material size, channel pattern, drainage area, and climate. The response of channels to breakup flooding ranged from total permafrost control of channel processes, including both bed scour and lateral erosion, to only brief restriction of channel behavior early in the rise of the flooding. The watershed characteristic that appears to explain much of this variation is size of drainage area. (Woodard-USGS)

Professional Paper↗
USGS1974

Erosion and sediment yields in mountain watersheds of the Transverse Ranges Ventura and Los Angeles Counties, California; analysis of rates and processes

Major-storm and long-term erosion rates in mountain watersheds of the western Transverse Ranges of Ventura County are estimated to range from low values that will not require the construction of catchments or channel-stabilization structures to values as high as those recorded anywhere for comparable bedrock erodibilities. A major reason for this extreme variability is the high degree of tectonic activity in the area--watersheds are locally being uplifted by at least as much as 25 feet per 1,000 years, yet the maximum extrapolated rate of denudation measured over the longest available period of record is 7.5 feet per 1,000 years adjusted to a drainage area of 0.5 square mile. Evidence of large amounts of uplift continuing into historic time includes structurally overturned strata of Pleistocene age, active thrust faulting, demonstrable stream antecedence, uplifted and deformed terraces, and other results of base-level change seen in stream channels. Such evidence is widespread in the Transverse Ranges, and aspects of the landscape, such as drainage-net characteristics and hillslope morphology, are locally more a function of tectonic activity than of denudational process. Many of the 72 study watersheds are located on frontal escarpments of mountain blocks cut by recently active thrust faults, along which the upper part of the drainage basin has overthrusted either the lower part of the basin or the adjacent valley area. To define erosion rates in 35 small watersheds in the western Transverse Ranges, a group of 37 similar watersheds with measured sediment yields in debris basins was selected from the eastern Transverse Ranges in Los Angeles County. Sediment yields from this group of watersheds during the record-breaking 1969 storms ranged from relatively low rates to values equivalent to reduction of the entire land surface of a watershed by more than 2 inches. Correlation of erosion rates from the watersheds with measured rates to the group with unknown rates required definition of the chief factors that control the erosion rates. Numerous types and combinations of variables measuring physiography, soil erodibility, slope stability, hydrologic factors, wildfire effects, vegetation, and land use were analyzed by regression. A slope-stability variable retained in regressions at significant levels was the proportion of watershed drainage area underlain by slope failures, a logical measure of increased erodibility caused by uplift. The importance in the area of debris flows, mudflows, and mass movements--forms of sediment transport not involving normal aqueous entrainment--is also a reflection of the active tectonic setting of the Transverse Ranges. Implicit in the detailed study of selected physiographic and slope-failure variables was the logical assumption that correlation with the probability of transport by these exotic but quantitatively important sedimentation processes would be achieved. So prominent and widespread was evidence of debris flows in the small study watersheds after the 1969 storms, that it was possible to formulate a model for the dispersal of sediment in such watersheds: Lateral supply of sediment to stream channels is a relatively continuous process, accomplished in significant part during the dry season by dry-sliding, in addition to wet-season contributions from overland flow and mass movements. During periods without major storms, stream channels undergo more-or-less time-continuous fill. Then, during a storm of high recurrence interval, channel-bed material is mobilized and dispersed in large part by debris flows--coarse granular slurries, some of which are induced by mass movements triggered by the storm. Channels undergo substantial net scour, accomplished by removal of bed material in debris flows and by scour during recession flow. Valley-side slopes are undercut by bank erosion, and a new cycle of channel infilling by hillslope processes is initiated.

California↗
USGS1971

Floods of December 1966 in the Kern-Kaweah area, Kern and Tulare Counties, California; with section on Geomorphic Effects in the Kern River Basin

Past records of peak flow ,and 3-day ,storm-runoff volume in the Kern, Tule, and Kaweah River basins in California were greatly exceeded by the floods of December 1966. Streams rose rapidly following precipitation of as much as 15 inches in a 24-hour period on December 5-6 during a strong inflow of warm moist Pacific air across central California. As heavy rain continued, extremely high peak discharges occurred at most gaging stations between 2300 hours December 5 and 1800 hours December 6. Snowmelt was not a major cause o the floods, although some snow that had accumulated during minor November and early December storms was melted. This snowmelt was offset by snowpack accumulation at high altitudes where little runoff occurred during the storm. This report covers the area of mast intense precipitation and runoff. Areas of central California to the north and west had severe floods, but these, in general, were not nearly as great as ,previous record floods. The terrain of the flood area described in the report ranges from ,the rolling foothills at the east edge of the flat Tulare Lake basin to the steep slopes of the Sierra Nevada where considerable area is above an altitude of 9,000 feet. This report includes discussions of the antecedent hydrology and the meteorology of the stone; a description of the floods, storage regulation, flood damage, comparison to previous floods, sedimentation, channel changes, and flood frequency; a summary of flood stages and discharges; and detailed information on stage, discharge, and reservoir contents for December 1966.

Water Supply Paper↗