Geology topics

V.R. Schneider

Publications and source records attributed to V.R. Schneider.

6 recordsLinked to original sources

USGS1987

Roughness coefficients for densely vegetated flood plains

Although much research has been done on Manning 's roughness coefficients for stream channels, very little has been done on the selection of roughness values for densely vegetated flood plains. In this report four method for determining roughness coefficients for flood plains are examined and evaluated. Field data were collected at 13 sites on wide, densely vegetated flood plains where verified n values were known. The ' vegetation density ' of representative sample areas was measured at each site for use in determining roughness coefficients. The vegetation density method, proved to be useful in determining n values for wide, densely wooded plains. By measuring the area occupied by tree trunks and vegetation in a representative sample area, the vegetation density can be determined. Using the vegetation density in an equation developed from Manning 's formula, the Manning 's n can be determined for the representative sample area. (USGS)

Water-Resources Investigations Report↗

USGS1984

Performance of ice meter and weight assemblies

The performance of three ice meters and weight assemblies used by the U.S. Geological Survey and Environment Canada were compared in a towing tank. Each meter was rated individually on a rod suspension and then rerated on a cable suspension, with the appropriate weight assembly. Vertical and veer cable angles were measured along with meter yaw angle. The effect of the weight assembly on the rod-suspension rating for each meter was illustrated by computing a correction coefficient which ranged between 0.88 and 1.10 depending on the weight system used and the fluid velocity. A sluch-n-all type weight assembly least affected the meter rating and was the most stable in all flow conditions. (USGS)

Water-Resources Investigations Report↗

USGS1983

Use of flumes in measuring discharge

Flumes for measuring discharge are usually of two general groups-critical-flow flumes and supercritical-flow flumes. In this chapter, the underlying design principles for each group are discussed; the most commonly used flumes are described and their discharge ratings presented. There is also discussion of considerations in choosing and fitting the appropriate flume for a given situation as well as flume construction techniques and operational experiences.

Techniques of Water-Resources Investigations↗

USGS1983

Backwater and discharge at highway crossings with multiple bridges in Louisiana and Mississippi

Data were collected for nine floods in Mississippi and Louisiana at eight stream crossings having two to six separate bridge openings. Discharge through each bridge, water surface profiles, valley cross sections, and bridge geometry were measured. The multiple openings were divided into equivalent single-opening cases by apportioning interior embankments in direct proportion to the area of openings on either side. Using existing procedures for computer discharge, the bias in computed discharge was 2 percent with a root mean square error of 18 percent. Backwater was computed by two current U.S. Geological Survey methods that use the average flow path in the friction loss term for the approach. One method gave a root mean square error of 0.34 ft. with a bias of -0.25 ft., suggesting that the method underestimates backwater. The other method gave a root mean square error of 0.39 ft with a bias of -0.03 ft. The results indicate that the method developed for single-opening highway crossings can be applied to the multiple bridge crossings. (USGS)

Water-Resources Investigations Report↗

USGS1981

Emergency assessment of Mount St. Helens post-eruption flood hazards, Toutle and Cowlitz rivers, Washington

During several periods of volcanic-ash eruption at Mount St. Helens, Wash., (March 30, May 25-26, May 30-June 2, and June 12-13, 1980) strong winds from the north occurred at high altitudes. As a result, the volcanic ash fell some 50 miles to the south in the Bull Run watershed, the principal water-supply source for the metropolitan area of Portland, Oreg. Water samples collected from three stream sites within the watershed were compared with samples collected during the same season in previous years. No detectable changes were noted in chemical characteristics. Precipitation samples collected immediately after the June 12-13 ash fall ranged in specific conductance from 20 to 41 micromhos per centimeter at 25C and in pH from 4.0 to 4.3 pH units. Stream samples collected during the May-June period ranged in specific conductance from 18 to 28 micromhos per centimeter at 25C and in pH from 6.7 to 7.5 pH units. Volcanic-ash samples were collected and analyzed for particle size, chemical composition, and weight. Significant differences in particle size of ash were found in samples from two separate eruptions. (USGS)

Circular↗

USGS1977

Computation of backwater and discharge at width constrictions of heavily vegetated flood plains

The U.S. Geological Survey, cooperated with the Federal Highway Administration and the State Highway Departments of Mississippi, Alabama, and Louisiana, to develop a proposed method for computing backwater and discharge at width constrictions of heavily vegetated flood plains. Data were collected at 20 single opening sites for 31 floods. Flood-plain width varied from 4 to 14 times the bridge opening width. The recurrence intervals of peak discharge ranged from a 2-year flood to greater than a 100-year flood, with a median interval of 6 years. Measured backwater ranged from 0.39 to 3.16 feet. Backwater computed by the present standard Geological Survey method averaged 29 percent less than the measured, and that computed by the currently used Federal Highway Administration method averaged 47 percent less than the measured. Discharge computed by the Survey method averaged 21 percent more then the measured. Analysis of data showed that the flood-plain widths and the Manning 's roughness coefficient are larger than those used to develop the standard methods. A method to more accurately compute backwater and discharge was developed. The difference between the contracted and natural water-surface profiles computed using standard step-backwater procedures is defined as backwater. The energy loss terms in the step-backwater procedure are computed as the product of the geometric mean of the energy slopes and the flow distance in the reach was derived from potential flow theory. The mean error was 1 percent when using the proposed method for computing backwater and 3 percent for computing discharge. (Woodard-USGS)

Mississippi↗