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R. J. Omang

Publications and source records attributed to R. J. Omang.

31 records · Page 2Linked to original sources
USGS1981

Revised techniques for estimating magnitude and frequency of floods in Montana

Relations for estimating the flood magnitudes for ungaged sites in Montana have been updated. The State was divided into eight regions and separate multiple-regression equations for each region were developed that relate logarithms of annual flood magnitude to logarithms of basin characteristics for exceedance probabilities of 50, 20, 10, 4, 2, and 1 percent. The standard errors of estimate for an exceedance probability of 1 percent ranged from 39 to 58 percent in the western and central parts of the State and from 47 to 83 percent in the eastern part. The standard errors of estimate indicate a substantial improvement over previous studies. Techniques for transferring annual flood-frequency information at gaged sites to ungaged sites on the same stream have been updated. Included are curves relating flood-frequency information to drainage area for eight major streams in the State. Maximum known flood peaks in Montana are compared with estimated 1-percent-chance flood peaks and with national maximum known flood peaks. Values of flood discharges for selected exceedance probabilities and values of significant basin characteristics for all gaging stations used in the analysis are tabulated. Included are data for 339 stations in Montana and 34 nearby stations in Canada and adjoining States. (USGS)

Open-File Report↗
USGS1979

Annual peak discharges from small drainage areas in Montana for stations discontinued before 1978

Annual peak stage and discharge data have been tabulated for crest-stage gage sites in Montana. The crest-stage program was begun in July 1955 to investigate the magnitude and frequency of floods from samll drainage areas. The program has expanded from 45 crest-stage gaging stations initially to 172 stations maintained in 1978. From 1955 to 1978, 156 stations have been discontinued. This report is a tabulation of the stage and discharge data for the discontinued stations. (Woodard-USGS)

Open-File Report↗
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↗
USGS1978

Annual peak discharges from small drainage areas in Montana through September 1977

Annual peak stage and stream-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 191 stations in 1977. Data are tabulated for 336 sites throughout the period of record. (Woodard-USGS)

Open-File Report↗
USGS1977

Annual peak discharges from small drainage areas in Montana through September 1976

Annual peak discharge from small drainage areas is tabulated for 336 sites in Montana. The 1976 additions included data collected at 206 sites. The program which investigates the magnitude and frequency of floods from small drainage areas in Montana, was begun July 1, 1955. Originally 45 crest-stage gaging stations were established. The purpose of the program is to collect sufficient peak-flow data, which through analysis could provide methods for estimating the magnitude and frequency of floods at any point in Montana. The ultimate objective is to provide methods for estimating the 100-year flood with the reliability needed for road design. (Woodard-USGS)

Open-File Report↗
USGS1976

A method for estimating magnitude and frequency of floods in Montana

This report provides methods for estimating flood characteristics at most natural flow sites on rural streams in Montana. It also contains significant flood data and related information for many gaged sites on Montana streams. Frequency curves are provided for 442 gaged sites as defined by log-Pearson Type III analysis. To allow estimates at ungaged sites, mathematical equations relate the 2-, 5-, 10-, 25-, 50-, and 100-year flood magnitudes to basin characteristics. Drainage area, main channel slope, and mean annual precipitation were found to be the most significant estimating variables. Equations presented are limited to use on streams with drainage areas from about 0.1 to 2,600 square miles (0.3 to 6,700 square kilometres), with slope from about 5 to 1,200 feet per mile (1.5 to 366 metres per kilometre), and with precipitation from 10 to 100 inches (250 to 2,500 millimetres). Nomographs provide a simple graphical means of solving the estimating relations, and illustrative examples are presented.

Montana↗
USGS1976

Floods of May-July 1975 Along the Continental Divide in Montana

Extensive flooding occurred along both sides of the Continental Divide in Montana from May through July 1975. Runoff from above average snowpack at low altitudes combined with runoff from rainfall to cause floods in May. Snowmelt from high altitudes and above average rain in June caused flooding and sustained high flows into July. Federal and State agencies estimated flood damage at about $53,000,000. Peak stages, flow rates, and estimated frequencies were determined for 124 sites.

Open-File Report↗
USGS1974

Floods of January 15-17, 1974, in Northwestern Montana

Introduction Rain and snowmelt caused several streams in northwestern Montana to flood during January 15-17, 1974. The flooding was caused by a major rainstorm that extended from Montana through Idaho and Washington. The most damage occurred in the Kootenai River drainage, centering around the town of Libby. Also unusually high flows occurred on some streams in the Clark Fork basin. Throughout the area, ice jams contributed to much of the overbank flooding. Both the towns of Troy and Libby were partly flooded, but damage was greatest in and near Libby. Flood damage was estimated to be $4.9 million. No flood fatalities were listed. Most of the smaller streams equaled or exceeded a 50-year flood. A summary of flood stages and discharges for 24 sites in the Kootenai River drainage and 8 sites in the Clark Fork drainage is tabulated. A map shows the extent of flooding in the Libby area. (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↗
USGS1955

Annual peak discharges from small drainage areas in Montana through September 1980

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 172 stations maintained in 1980. Data in the report are tabulated for the period of record. (USGS)

Open-File Report↗