USGS Science⌕ Search

Geology topics

H. A. Martinson

Publications and source records attributed to H. A. Martinson.

6 recordsLinked to original sources
USGS1998

Evolution of cutoffs across meander necks in Powder River, Montana, USA

Over a period of several decades, gullies have been observed in various stages of forming, growing and completing the cutoff of meander necks in Powder River. During one episode of overbank flow, water flowing over the down-stream bank of the neck forms a headctu. The headcut migrates up-valley, forming a gully in its wake, until it has traversed the entire neck, cutting off the meander. The river then follows the course of the gully, which is subsequently enlarged as the river develops its new channel. The complete process usually requires several episodes of high water: in only one of the five cases described herein was a meander cutoff initiated and completed during a single large flood.

Earth Surface Processes and Landforms↗
USGS1989

Rates and processes of channel development and recovery following the 1980 eruption of Mount St. Helens, Washington

Stream channel development in response to the eruption of Mount St. Helens on 18 May 1980, resulted in some of the largest sediment yields documented anywhere on earth. Development of new channels on the 2.7 km 3 debris-avalanche deposit in the North Fork Toutle River caused net erosion of as much as 1.3 x 10 5 t km −2 annually. Development of these channels followed a four-stage sequence of channel initiation, channel incision with relatively constant width-to-depth ratio, channel widening accompanied by aggradation, and channel widening accompanied by scour-and-fill with little change in average channel elevation. These channels remain unstable both in width and elevation. Lahars affected channel and valley morphology on all flanks of the volcano. Steep, upstream reaches generally incised and widened during the first year following the eruption and aggraded during the following three years. Gently sloping downstream reaches aggraded and widened during the first year and incised during the following three years. The most rapid adjustments occurred during the first two winters following the eruption. The principal effect of the blast on channels throughout the 550 km 2 devastated area was the subsequent rapid delivery of sand- and silt-size sediment eroded from hillslopes. Channels aggraded during early storms of the 1980–1981 winter but incised during later storms the same winter. Subsequent channel enlargement was constrained by logs deposited in channels by the blast and by post-1980 shallow debris slides. Since 1984, instability and sedimentation in laharand blast-affected channels have been within the range of pre-1980 levels.

Hydrological Sciences Journal↗
USGS1986

Channel geometry and hydrologic data for six eruption-affected tributaries of the Lewis River, Mount St. Helens, Washington, water years 1983-84

The May 18, 1980, eruption of Mount St. Helens generated a lateral blast, lahars, and tephra deposits that altered stream channels in the Lewis River drainage basin. In order to assess potential flood hazards, monitor channel adjustments, and construct a sediment budget for disturbed drainages on the east and southeast flanks of the volcano, channel cross sections were monumented and surveyed on Pine Creek, Muddy River, and Smith Creek during September and October of 1980. Additional cross sections were monumented and surveyed on Swift Creek, Bean Creek , and Clearwater Creek during 1981. This network of channel cross sections has been resurveyed annually. Selected cross sections have been surveyed more frequently, following periods of higher flow. Longitudinal stream profiles of the low-water thalweg and (or) water surfaces were surveyed periodically for selected short reaches of channel. Corresponding map views for these reaches were constructed using the survey data and aerial photographs. This report presents plots of channel cross-section profiles, longitudinal stream profiles, and channel maps constructed from survey data collected during water years 1983-84. (USGS)

Open-File Report↗
USGS1984

Changes in channel geomorphology of six eruption-affected tributaries of the Lewis River, 1980-82, Mount St. Helens, Washington

The May 18, 1980, eruption of Mount St. Helens generated a lateral blast, lahars and tephra deposits that altered tributary channels in the Lewis River drainage basin. In order to assess potential flood hazards, study channel adjustments, and construct a sediment budget for the perturbed drainages on the east and southeast flanks of the volcano, channel cross sections were monumented and surveyed on Pine Creek, Muddy River, and Smith Creek during September and October of 1980. Additional cross sections were monumented and surveyed on Swift Creek, Bean Creek, and Clearwater Creek during the summer of 1981. The network of 88 channel cross sections has been resurveyed annually. Selected cross sections have been surveyed more frequently, following periods of higher flow. The repetitive cross-section surveys provide measurements of bank erosion or accretion and of channel erosion or aggradation. The report presents channel cross-section profiles constructed from the survey data collected during water years 1980-82. (USGS)

Washington↗
USGS1984

Channel changes of Powder River between Moorhead and Broadus, Montana, 1939-1978

Bank erosion and changes in channel width, length, and pattern were determined for the Powder River between Moorhead and Broadus, Montana using maps of the bankfull channel made from aerial photographs taken during 1939, 1954, 1967, 1973, and 1978. Contemporaneous daily mean and peak discharge records from Moorhead provide the hydrologic data used to interpret the measurements. Magnitudes and frequency of flows were determined for each interval of time delimited by photographs. Bank erosion is related to the number of days that mean discharge was equal to or greater than bankfull (1.5-year flood). Mean channel width ranged between 264 ft (1973) and 415 ft (1967). The channel was wider after periods of higher annual peak flows. The channel lengthened between 1939 and 1978, although at least 12 meanders cut off between Moorhead and Broadus. Variable rates of lengthening in the reach reflect the degree of bedrock control in the valley and local variations in valley slope. Data from the Powder River verify the concept of thresholds of channel pattern stability that were demonstrated experimentally. (USGS)

Water-Resources Investigations Report↗