Geology topics

David C. Froehlich

Publications and source records attributed to David C. Froehlich.

9 recordsLinked to original sources

USGS1989

Peak outflow from a breached embankment dam

A relation for rapidly predicting the peak outflow rate from a breached embankment dam has been presented. The prediction equation is based on reliable data from 19 embankment dam failures and requires as input the volume of water in the reservoir at the time a breach begins to form, and the estimated height of the final breach. Peak outflow predicted by the equation can be used with simplified flood routing procedures to determine peak flows at locations downstream of a dam. Use of the prediction equation will improve the accuracy of rapid assessments of damage that would be caused by the flood resulting from an embankment dam failure.

Conference Paper↗

USGS1989

Local scour at bridge abutments

Comparison of local scour depths at bridge abutments computed using different equations yields a large variation in predicted values. To consolidate the fragmented results of previous investigations and assemble the most comprehensive data set possible, reported laboratory measurements of local scour at the end of an obstruction protruding from the side of an open channel of rectangular cross section were compiled from several sources. Regression analysis of these data was used to develop an equation that predicts maximum relative depth of local scour at bridge abutments for both clear-water and live-bed scour conditions.

Conference Paper↗

USGS1989

Hydraulic analysis of the Schoharie Creek bridge

Ten people died on April 5, 1987 as a result of the collapse of two spans of a New York State Thruway bridge into the floodwaters of Schoharie Creek. The cause of the bridge failure was determined to be scour of bed material from under the foundations of piers supporting the bridge. To evaluate the hydraulic conditions that produced the scour, a two-dimensional finite element surface-water flow model was constructed. The model was used to obtain a detailed description of water-surface elevations and depth-averaged velocities within a reach that extends from about 4000 ft downstream of the bridge to about 6000 ft upstream of the bridge.

Conference Paper↗

USGS1988

Basic hydraulic principles of open-channel flow

The three basic principles of open-channel-flow analysis--the conservation of mass, energy, and momentum--are derived, explained, and applied to solve problems of open-channel flow. These principles are introduced at a level that can be comprehended by a person with an understanding of the principles of physics and mechanics equivalent to that presented in the first college level course of the subject. The reader is assumed to have a working knowledge of algebra and plane geometry as well as some knowledge of calculus. Once the principles have been derived, a number of example applications are presented that illustrate the computation of flow through culverts and bridges, and over structures, such as dams and weirs. Because resistance to flow is a major obstacle to the successful application of the energy principle to open-channel flow, procedures are outlined for the rational selection of flow resistance coefficients. The principle of specific energy is shown to be useful in the prediction of water-surface profiles both in the qualitative and quantitative sense. (USGS)

Open-File Report↗

USGS1988

Analysis of alternative modifications for reducing backwater at the Interstate Highway 10 crossing of the Pearl River near Slidell, Louisiana

In April 1979 and April 1980, major flooding along the lower Pearl River caused extensive damage to homes located on the flood plain in the Slidell, Louisiana, area. In response to questions about causes of these floods and means of mitigating future floods, the U.S. Geological Survey, in cooperation with the Louisiana Department of Transportation and Development, Office of Highways, and the U.S. Department of Transportation, Federal Highway Administration, used a two-dimensional finite-element surface-water flow-modeling system to study the effect of four alternative modifications for improving the hydraulic characteristics of the Interstate Highway 10 crossing of the flood plain near Slidell. The analysis used the model's capability to simulate changes in flood-plain topography, flood-plain vegetative cover, and highway-embankment geometry. Compared with the existing highway crossing, the four alternative modifications reduce backwater and average velocities through bridge openings for a flood of the magnitude of the 1980 flood. The four alternatives also eliminate roadway overtopping during such a flood. For the four modifications, maximum backwater on the west side of the flood plain ranges from 0.3 to 1.1 feet and on the east side from 0.3 to 0.7 foot. Results of the alternative-model simulations show that backwater is greater on the west side of the flood plain than on the east side, but upstream from Interstate Highway 10 backwater decreases more rapidly in the upstream direction on the west side of the flood plain than on the east side. Downstream from Interstate Highway 10, modeling of the four alternatives indicates that backwater and drawdown still occur on the east and west sides of the flood plain, respectively, but are less than the values computed for the April 1980 flood with Interstate Highway 10 in place. In addition to other highway-crossing modifications, alternatives 2 and 3 include simulation of a new 2,000-foot bridge opening, and ,alternative 4 includes simulation of a 1,000-foot bridge opening. The new bridge conveys 25, 23, and 21 percent of the total computed discharge in alternatives 2, 3, and 4, respectively. The average velocity through the new bridge is 2.0, 1.9, and 3.4 feet per second for alternatives 2, 3, and 4, respectively.

Water Supply Paper↗

USGS1988

Rainfall intensity-duration equations

A method for rapidly developing a rainfall intensity-duration equation for durations less than one hour and recurrence intervals between 2 and 100 years for any location in the conterminous United States is presented. Optimal parameters of a general rainfall-intensity duration equation are determined using precipitation depths for durations of 5, 10, 15, 30 and 60 minutes obtained from commonly available isopluvial maps. A single set of parameters applies to the entire western U.S. For the central and eastern U.S, a graphical means of determining the parameters is provided.

Conference Paper↗

USGS1988

Analysis of onsite measurements of scour at piers

Existing onsite measurements of local scour at bridge piers were assembled and analyzed to obtain an equation that predicts the expected maximum depth of local scour at a bridge pier. A safety factor is suggested that provides a reasonable margin of error for design purposes.

Conference Paper↗

USGS1987

Review of literature on the finite-element solution of the equations of two-dimensional surface-water flow in the horizontal plane

Published literature on the application of the finite-element method to solving the equations of two-dimensional surface-water flow in the horizontal plane is reviewed in this report. The finite-element method is ideally suited to modeling two-dimensional flow over complex topography with spatially variable resistance. A two-dimensional finite-element surface-water flow model with depth and vertically averaged velocity components as dependent variables allows the user great flexibility in defining geometric features such as the boundaries of a water body, channels, islands, dikes, and embankments. The following topics are reviewed in this report: alternative formulations of the equations of two-dimensional surface-water flow in the horizontal plane; basic concepts of the finite-element method; discretization of the flow domain and representation of the dependent flow variables; treatment of boundary conditions; discretization of the time domain; methods for modeling bottom, surface, and lateral stresses; approaches to solving systems of nonlinear equations; techniques for solving systems of linear equations; finite-element alternatives to Galerkin's method of weighted residuals; techniques of model validation; and preparation of model input data. References are listed in the final chapter.

Circular↗

USGS1987

EMBANKMENT-DAM BREACH PARAMETERS.

The study used data from 43 embankment-dam failures to develop equations that predict breach formation model parameters. These data include the failure mode, embankment characteristics, reservoir conditions at the time of failure, geometry of the final breach, and the time taken to form the breach. Regression equations were developed to predict (1) the average width of a trapezoidal breach, (2) the average side-slope factor of a trapezoidal breach, and (3) the breach formation time.

Conference Paper↗