Geology topics

C. Parrett

Publications and source records attributed to C. Parrett.

7 recordsLinked to original sources

USGS2012

Flood hydrology for Dry Creek, Lake County, Northwestern Montana

Dry Creek drains about 22.6 square kilometers of rugged mountainous terrain upstream from Tabor Dam in the Mission Range near St. Ignatius, Montana. Because of uncertainty about plausible peak discharges and concerns regarding the ability of the Tabor Dam spillway to safely convey these discharges, the flood hydrology for Dry Creek was evaluated on the basis of three hydrologic and geologic methods. The first method involved determining an envelope line relating flood discharge to drainage area on the basis of regional historical data and calculating a 500-year flood for Dry Creek using a regression equation. The second method involved paleoflood methods to estimate the maximum plausible discharge for 35 sites in the study area. The third method involved rainfall-runoff modeling for the Dry Creek basin in conjunction with regional precipitation information to determine plausible peak discharges. All of these methods resulted in estimates of plausible peak discharges that are substantially less than those predicted by the more generally applied probable maximum flood technique. Copyright ASCE 2004.

Conference Paper↗

USGS2009

Predicting the probability and volume of postwildfire debris flows in the intermountain western United States

Empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system (GIS) to generate debris-flow hazard maps either before or immediately following wildfires. Models that can be used to calculate the probability of debris-flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the U.S. Intermountain West. The models describe debris-flow probability as a function of readily obtained measures of areal burned extent, soil properties, basin morphology, and rainfall from short-duration and low-recurrence-interval convective rainstorms. A model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires. This model describes debris-flow volume as a function of the basin gradient, aerial burned extent, and storm rainfall. Applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 Hot Creek fire in central Idaho. The predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in August 2003. The mapping approach presented here identifies those basins that are most prone to the largest debris-flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation, warnings, and prefire management efforts throughout the Intermountain West.

Geological Society of America Bulletin↗

USGS2007

Estimation of long-term discharge statistics by regional adjustment

A regional adjustment relationship was developed to estimate long-term (30-year) monthly median discharges from short term (three-year) records. This method differs from traditional approaches in that it is based on site-specific discharge data but does not require correlation of these data with discharges from a single hydrologically similar long-term gage. The method is shown to be statistically robust, and applicable to statistics other than the median.A regional adjustment relationship was developed to estimate long-term (30-year) monthly discharges from short term (three-year) records. This method differs from traditional approaches in that it is based on site-specific discharge data but does not require correlation of these data with discharges from a single hydrologically similar long-term gage. The method is shown to be statistically robust, and applicable to statistics other than the median.

Journal of the American Water Resources Associatio↗

USGS2003

Wildfire-related debris-flow generation through episodic progressive sediment-bulking processes, western USA

Debris-flow initiation processes on hillslopes recently burned by wildfire differ from those generally recognized on unburned, vegetated hillslopes. These differences result from fire-induced changes in the hydrologic response to rainfall events. In this study, detailed field and aerial photographic mapping, observations, and measurements of debris-flow events from three sites in the western U.S. are used to describe and evaluate the process of episodic progressive sediment bulking of storm runoff that leads to the generation of post-wildfire debris flows. Our data demonstrate the effects of material credibility, sediment availability on hillslopes and in channels, the degree of channel confinement, the formation of continuous channel incision, and the upslope contributing area and its gradient on the generation of flows and the magnitude of the response are demonstrated. ?? 2003 Millpress.

Conference Paper↗

USGS1998

Regionalization of precipitation characteristics in Montana using L-moments

Dimensionless precipitation-frequency curves for estimating precipitation depths having small exceedance probabilities were developed for 2-, 6-, and 24-hour storm durations for three homogeneous regions in Montana. L -moment statistics were used to help define the homogeneous regions. The generalized extreme value distribution was used to construct the frequency curves for each duration within each region. The effective record length for each duration in each region was estimated using a graphical method and was found to range from 500 years for 6-hour duration data in Region 2 to 5,100 years for 24-hour duration data in Region 3. The temporal characteristics of storms were analyzed, and methods for estimating synthetic storm hyetographs were developed. Dimensionless depth-duration data were grouped by independent duration (2, 6, and 24 hours) and by region, and the beta distribution was fit to dimensionless depth data for various incremental time intervals. Ordinary least-squares regression was used to develop relations between dimensionless depths for a key, short duration—termed the kernel duration —and dimensionless depths for other durations. The regression relations were used, together with the probabilistic dimensionless depth data for the kernel duration, to calculate dimensionless depth-duration curves for exceedance probabilities from .1 to .9. Dimensionless storm hyetographs for each independent duration in each region were constructed for median value conditions based on an exceedance probability of .5.

Montana↗

USGS1979

Annual peak discharges from small drainage areas in Montana through September 1978

Annual peak stage and discharge data have been collected and tabulated for crest-stage gaging sites in Montana. The crest-stage program was begun in July 1955 to investigate the magnitude and frequency of floods from small drainage areas. The program has expanded from 45 crest-stage gaging stations initially to 173 stations maintained in 1978. Data are tabulated for the period of record. (Woodard-USGS)

Open-File Report↗

USGS1955

Annual peak discharges from small drainage areas in Montana through September 1979

Annual peak stage and discharge data have been collected and tabulated for crest-stage gaging sites in Montana. The crest-stage program was begun in July 1955 to investigate the magnitude and frequency of floods from small drainage areas. The program has expanded from 45 crest-stage gaging stations initially to 173 stations maintained in 1979. Data in the report are tabulated for the period of record. (USGS)

Open-File Report↗