Geology topics

Lawrence D. Becker

Publications and source records attributed to Lawrence D. Becker.

3 recordsLinked to original sources

USGS1994

Investigation of bridge scour at selected sites on Missouri streams

Scour around bridge piers is a major concern in the design of a new bridge or the evaluation of the structural stability of an existing bridge. An adequate estimation of potential scour at bridge piers is essential to effective design, construction, and maintenance of hydraulic structures. Reasonably accurate estimates of scour depth are needed for safe, cost-effective bridge design. Although many equations have been developed on the basis of laboratory work that can be used to estimate local scour at piers, site-specific data have not previously been collected to verify the accuracy of these equations or applicability to Missouri streams. Scour data were collected during floods at 10 sites on streams in Missouri. The recurrence intervals of the floods ranged from less than 2 to more than 50 years. Local-scour holes near bridge piers ranged from 0.5 to 7.1 feet deep. Seven local-pier-scour equations were evaluated as to their usefulness in estimating the measured scour at the sites studied. Scour depths estimated using the Froehlich equatin without a safety factor had an interquartile range nearest in magnitude to the interquartile range of the measured scour depths. None of the medians of scour depths estimated using the seven equations were statistically equal to the median of the measured scour depths at a 0.05 level of significance. However, the Froehlich equation without a safety factor provided the "best fit" estimates of the equations considered. Contraction scour exceeded local scour by several times in some cases. Total scour of approximately 19 feet, largely becasue of contraction scour, was measured at the Chariton River near Prairie Hill during the flood of July 8, 1993. This large scour was, in part, the result of an accumulation of woody debris de- creasing the bridge-opening area. A bridge on State Highway 32 near Lebanon over North Cobb Creek (drainage area 52.5 square miles) was destroyed during the flood of May 26, 1990. Bridge scour attributable to contraction of the flood flow caused this loss.

Missouri↗

USGS1982

Magnitude and frequency of floods from selected drainage basins in South Dakota

The 2-, 5-, 10-, 25-, 50-, and 100-year floods are determined for gaged sites on 120 selected, small drainage basins in South Dakota. These estimates are from the frequency curves defined from the streamflow records. Short-term records for 66 sites were extended on the basis of long-term climatic records and a rainfall-runoff model. These frequency curves may provide the best estimates of floods at these gaged sites. Analyses of flood-frequency information from these gaged sites have been the basis for techniques (published previously) used in estimating flood magnitude and frequency at ungaged sites in South Dakota. This report supplements flood-frequency information published earlier. It presents: Annual peak discharges colected during a 25-year period at 124 crest-stage partial-record stations; maximum observed and unit discharges determined for 124 crest-stage and 120 continuous-record gaging stations; updated flood-frequency curves for 120 crest-stage gages; a documentation of analytical procedures used; and a summary of the small-streams flood-peak data collection program in the State from 1955 to 1981. Maximum flood peaks determined at 244 partial- and continuous-record gaging stations and at 52 miscellaneous sites are compared with regional flood relationships.

South Dakota↗

USGS1974

A method for estimating magnitude and frequency of floods in South Dakota

A general flood-frequency analysis has provided a method for estimating flood magnitudes and frequencies on South Dakota streams. Related flood data useful in planning and design also are included in the report. Two distinct hydrologic regions are delineated within the State. The divisional boundary for these regions is, in general, the western divide of the James River basin. For each region, the 2-, 5-, 10-, 25-, 50-, and 100-year floods are related to basin and climatic characteristics by regression equations. Indices based on contributing drainage area size, elevation, and mean annual precipitation were found to be the most useful variables in estimation of South Dakota floods. Regional relationships based on these variables can be used to estimate floods of selected frequency at most ungaged sites where peak flows are not significantly affected by regulation or other manmade works. Equations and graphs presented are applicable to drainage basins with areas approximately from 0.1 to 4,000 square miles (0.3 to 10,400 square kilometres) in the Eastern Region and from 0.1 to 9,000 square miles (0.3 to 23,300 square kilometres) in the Western Region. Limitations on use of these equations are given and the accuracy of resulting estimates is discussed. Flood characteristics are tabulated for 130 gaging stations having 10 or more years of record. These frequency data may provide the best estimates of floods at these gaged sites. Also, maximum flood peaks determined at 188 gaging stations and 52 miscellaneous sites are compared with regional flood relationships. Individual relationships are presented for the main-stem portions of selected streams where significant regulation is a factor or where drainage areas exceed the limits of applicability of the regional relationships.

South Dakota↗