Geology topics
Gregg J. Wiche
Publications and source records attributed to Gregg J. Wiche.
Precipitation in the upper Mississippi River basin, January 1 through July 31, 1993
Excessive precipitation produced severe flooding in a nine-State area in the upper Mississippi River Basin during spring and summer 1993. Following a spring that was wetter than average, weather patterns that persisted from early June through July caused the upper Midwest to be deluged with an unusually large amount of rainfall. Monthly precipitation data were examined at 10 weather-station locations in the flood-affected region to illustrate precipitation patterns and amounts in the flood-affected area. In 1993, all 10 of the selected locations received greater than the normal rainfall for January through June 1961-90, 8 of the 10 locations received more than 200 percent of the normal rainfall for July 1961-90, and 3 received more than 400 percent of the normal rainfall for July. (The average rainfall for any given 30-year period is termed the 'normal' rainfall for the given period.) May through July 1993 was the wettest or nearly the wettest such period on record at many locations in the flooded area. Of the 10 locations, 6 received more rainfall in the first 7 months of 1993 than generally is received in a year.
Application of digital elevation models to delineate drainage areas and compute hydrologic characteristics for sites in the James River basin, North Dakota
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Streamflow at selected gaging stations on the James River in North Dakota and South Dakota, 1953-82, with a section on climatology
Historic stream flow data were compiled and record extension techniques were used, when necessary, to develop a monthly stream flow record for 1953-82 at streamflow-gaging stations on the James River in North Dakota and South Dakota. The record extension techniques included both Maintenance of Variance Extension Type 1 and Ordinary Least Squares. In addition to the historic stream flow record, synthesized unregulated streamflow was computed for gaging stations on the James River for 1953-82 by eliminating the effects of Jamestown Reservoir, Pipestem Reservoir, Sand Lake National Wildlife Refuge, and the consumptive surface-water withdrawals. Maintenance of Variance Extension Type 1, Ordinary Least Squares regression, water-balance procedures, and drainage-area ratio methods were used to compute the unregulated streamflows. Mean annual historic stream flow of the James River at Jamestown is about 7,000 acre-feet less than the mean annual unregulated streamflow. Mean monthly unregulated streamflow is greater than mean monthly historic streamflow during March, April, and May; during all other months, unregulated stream flow is less than historic streamflow. The climate during 1953-82 was compared to the climate records, which range in length from 53 to 102 years, in the James River basin to determine if the climate during 1953-82 was similar to the climate that has occurred during the last 90 years. On the basis of the climate analysis, the data-development period (1953-82) does not represent an abnormally wet or dry period. Thus, the streamflow during the data-development period represents a range of streamflows that might be expected to occur during the last 90 years.
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.