Geology topics

T. Scott Hedgecock

Publications and source records attributed to T. Scott Hedgecock.

5 recordsLinked to original sources

USGS2003

Simulations of Flooding on Pea River and Whitewater Creek in the Vicinity of the Proposed Elba Bypass at Elba, Alabama

A two-dimensional finite-element surface-water model was used to study the effects of proposed modifications to the State Highway 203 corridor (proposed Elba Bypass/relocated U.S. Highway 84) on water-surface elevations and flow distributions during flooding in the Pea River and Whitewater Creek Basins at Elba, Coffee County, Alabama. Flooding was first simulated for the March 17, 1990, flood, using the 1990 flood-plain conditions to calibrate the model to match measured data collected by the U.S. Geological Survey and the U.S. Army Corps of Engineers after the flood. After model calibration, the effects of flooding were simulated for four scenarios: (1) floods having the 50- and 100-year recurrence intervals for the existing flood-plain, bridge, highway, and levee conditions; (2) floods having the 50- and 100-year recurrence intervals for the existing flood-plain and levee conditions with the State Highway 203 embankment and bridge removed; (3) floods having the 50- and 100-year recurrence intervals for the existing flood-plain, bridge, and highway conditions with proposed modifications (elevating) to the levee; and (4) floods having the 50- and 100-year recurrence intervals for the proposed conditions reflecting the Elba Bypass and modified levee. The simulation of floodflow for the Pea River and Whitewater Creek flood of March 17, 1990, in the study reach compared closely to flood profile data obtained after the flood. The flood of March 17, 1990, had an estimated peak discharge of 58,000 cubic feet per second at the gage (just below the confluence) and was estimated to be between a 50-year and 100-year flood event. The estimated peak discharge for Pea River and Whitewater Creek was 40,000 and 42,000 cubic feet per second, respectively. Simulation of floodflows for the 50-year flood (51,400 cubic feet per second) at the gage for existing flood-plain, bridge, highway, and levee conditions indicated that about 31 percent of the peak flow was conveyed by the State Highway 203 bridge over Whitewater Creek, approximately 12 percent overtopped the State Highway 203 embankment, and about 57 percent was conveyed by the Pea River flood plain east of State Highway 125. For this simulation, flow from Pea River (2,380 cubic feet per second) overtopped State Highway 125 and crossed over into the Whitewater Creek flood plain north of State Highway 203, creating one common flood plain. The water-surface elevation estimated at the downstream side of the State Highway 203 bridge crossing Whitewater Creek was 202.82 feet. The girders for both the State Highway 203 and U.S. Highway 84 bridges were partially submerged, but U.S. Highway 84 was not overtopped. For the 100-year flood (63,500 cubic feet per second) at the gage, the simulation indicated that about 25 percent of the peak flow was conveyed by the State Highway 203 bridge over Whitewater Creek, approximately 24 percent overtopped the State Highway 203 embankment, and about 51 percent was conveyed by the Pea River flood plain east of State Highway 125. The existing levee adjacent to Whitewater Creek was overtopped by a flow of 3,200 cubic feet per second during the 100-year flood. For this simulation, flow from Pea River (6,710 cubic feet per second) overtopped State Highway 125 and crossed over into the Whitewater Creek flood plain north of State Highway 203. The water-surface elevation estimated at the downstream side of the State Highway 203 bridge crossing Whitewater Creek was 205.60 feet. The girders for both the State Highway 203 and U.S. Highway 84 bridges were partially submerged, and the west end of the U.S. Highway 84 bridge was overtopped. Simulation of floodflows for the 50-year flood at the gage for existing flood-plain and levee conditions, but with the State Highway 203 embankment and bridge removed, yielded a lower water-surface elevation (202.90 feet) upstream of this bridge than that computed for the existing conditions. For the 100-year flood, the simulation indi

Water-Resources Investigations Report↗

USGS2002

Surface Water Quality-Assurance Plan for the Alabama District of the U. S. Geological Survey

The U.S. Geological Survey, Water Resources Division, has a policy that requires each District office to prepare a Surface Water Quality-Assurance Plan. The plan for each District describes the policies and procedures that ensure high quality in the collection, processing, analysis, computer storage, and publication of surface-water data. The Alabama District Surface Water Quality-Assurance Plan documents the standards, policies, and procedures used by the District for activities related to the collection, processing, storage, analysis, and publication of surface-water data.

Open-File Report↗

USGS2001

Simulations of flooding on the Tennessee River in the vicinity of U.S. Highway 231 near Huntsville, Alabama

A two-dimensional finite-element surface-water model was used to study the effects of proposed modifications to the U.S. Highway 231 corridor on water-surface elevations and flow distributions during flooding in the Tennessee River Basin south of Huntsville, Madison County, Alabama. Flooding was first simulated for the March 19, 1973, flood for the existing conditions in order to calibrate the model to measured data collected by the U.S. Geological Survey (USGS) and the Tennessee Valley Authority (TVA) during and after the flood. After model calibration, the effects of flooding were simulated for two scenarios---existing and proposed conditions----for the 100-year and 500-year recurrence intervals. The first scenario was to simulate the existing bridge and highway configuration for the U.S. Highway 231 crossing of the Tennessee River flood plain. The second scenario was to simulate the proposed modifications to this bridge and highway configuration. The simulation of floodflow for the Tennessee River flood of March 19, 1973, in the study reach compared closely to discharge measurement and flood profile data obtained during and after the flood. The flood of March 19, 1973, had an estimated peak discharge of 323,000 cubic feet per second and was estimated to be about 50-year flood event. Simulation of the 100-year floodflow for the Tennessee River for the existing conditions at U.S. Highway 231 indicates that of the peak flow, 92.1 percent (316,500 cubic feet per second) was conveyed by the main channel bridge, 4.0 percent (13,800 cubic feet per second) by the northernmost relief bridge, and 3.8 percent (13,200 cubic feet per second) by the southernmost relief bridge. The water-surface elevation predicted in the vicinity of the USGS gaging station was 576.91 feet. No overtopping of U.S. Highway 231 occurrec. For the 500-year flood, the simulation indicates that of the peak flow, 89.2 percent (359,000) cubic feet per second) was conveyed by the main channel bridge, 5.6 percent (22,600 cubic feet per second) by the northernmost relieft bridge, and 5.2 percent (20,900 cubic feet per second) by the southernmost relief bridge. The water-surface elevation predicted in the vicinity of the USGS gaging station was 580.91 feet. No overtopping of U.S. Highway 231 occurred; however, the girders of both relief bridges were partially submerged. Simulation of the 100-year floodflow for the Tennessee River for the proposed conditions indicates that of the peak flow, 93.2 percent (319,800 cubic feet per second) was conveyed by the proposed main channel bridge, 3.3 percent (11,400 cubic feet per second) by the proposed northernmost relief bridge, and 3.4 percent (11,800 cubic feet per second) by the proposed southernmost relief bridge. The water-surface elevation predicted in the vicinity of the USGS gaging station was 576.93 feet. No overtopping of U.S. Highway 231 occurred. For the 500-year flood, the simulation indicates that of the peak flow, 90.9 percent (365,400 cubic feet per second) was conveyed by the proposed main channel bridge, 4.3 percnet (17,300 cubic feet per second) by the proposed northernmost relief bridge, and 4.8 percent (19,400 cubic feet per second) by the proposed southernmost relief bridge. The water-surface elevation predicted in the vidinity of the USGS gaging station was 580.93 feet. No overtopping of U.S. Highway 231 occurred; however, the girders of both relief bridges were partially submerged.

Water-Resources Investigations Report↗

USGS1999

Simulations of the effects of U.S. Highway 231 and the proposed Montgomery outer loop on flooding in the Catoma Creek and Little Catoma Creek Basins near Montgomery, Alabama

A two-dimensional finite-element surface-water model was used to study the effects of U.S. Highway 231 and the proposed Montgomery Outer Loop on the water-surface elevations and flow distributions during flooding in the Catoma Creek and Little Catoma Creek Basins southeast of Montgomery, Montgomery County, Alabama. The effects of flooding were simulated for two scenarios--existing and proposed conditions--for the 100- and 500-year recurrence intervals. The first scenario was to model the existing bridge and highway configuration for U.S. Highway 231 and the existing ponds that lie just upstream from this crossing. The second scenario was to model the proposed bridge and highway configuration for the Montgomery Outer Loop and the Montgomery Loop Interchange at U.S. Highway 231 as well as the proposed modifications to the ponds upstream. Simulation of floodflow for Little Catoma Creek for the existing conditions at U.S. Highway 231 indicates that, for the 100-year flood, 54 percent of the flow (8,140 cubic feet per second) was conveyed by the northernmost bridge, 21 percent (3,130 cubic feet per second) by the middle bridge, and 25 percent (3,780 cubic feet per second) by the southernmost bridge. No overtopping of U.S. Highway 231 occurred. However, the levees of the catfish ponds immediately upstream from the crossing were completely overtopped. The average water- surface elevations for the 100-year flood at the upstream limits of the study reach for Catoma Creek and Little Catoma Creek were 216.9 and 218.3 feet, respectively. For the 500-year flood, the simulatin indicates that 51 percent of the flow (11,200 cubic feet per second) was conveyed by the northernmost bridge, 25 percent (5,480 cubic feet per second) by the middle bridge, and 24 percent (5,120 cubic feet per second) by the southernmost bridge. The average water0surface elevations for the 500-year flood at the upstream limits of the study reach for Catoma Creek and Little Catoma Creek were 218.2 and 219.5 feet, respectively. For the 500-year flood, no overtopping of U.S. Highway 231 occurred. Simulation of the 100-year floodflow for Little Catoma Creek for the proposed conditions indicates that, for the existing bridges on U.S. Highway 231, 54 percent of the flow (8,190 cubic feet per second) was conveyed by the northernmost bridge, 22 percent (3,350 cubic feet per second) by the middle bridge, and 24 percent (3,490 cubic feet per second) by the southernmost bridge. The two proposed relief bridges on the Montgomery Outer Loop upstream from the proposed remaining catfish ponds conveyed about 7,750 cubic feet per second (3,400 cubic feet per second for the west relief bridge and 4,350 cubic feet per second for the east relief bridge) with an average depth of flow of about 7 feet. The average water-surface elevation at the upstream limit of the study reach for Little Catoma Creek was 218.8 feet, which is about 0.5 foot higher than the average water-surface elevation for the existing conditions. For the 100-year flood, there was no overtopping of either U.S. Highway 231 or the Montgomery Outer Loop. However, the levees of the proposed remaining catfish ponds were completely overtopped. For the Montgomery Outer Loop crossing of Catoma Creek, simulation of the 100-year floodflow indicates that about 58 percent of the flow (14,100 cubic feet per second) was conveyed by the proposed main channel bridge and 42 percent (10,200 cubic feet per second) by the proposed relief bridge. The average water-surface elevation at the upstream limit of the study reach for Catoma Creek was 216.9 feet, which is the same as the water-surface elevation for the existing conditions. Results of model simulations for the 500-year flood for the proposed conditions indicate that there was no overtopping on either U.S. Highway 231 or the Montgomery Outer Loop. For the existing bridges on U.S. Highway 231, 42 percent of the flow (11,300 cubic feet per second) was conveyed by the northernmost bridge

Water-Resources Investigations Report↗

USGS1996

Scour at selected bridge sites in Alabama, 1991-94

Scour data were collected at 15 sites on streams in Alabama during high flow conditions. The recurrence intervals of the streamflows ranged from less than 2 to 10 years. Scour depths measured near bridge piers ranged from 0.3 to 5.8 feet. The Colorado State University (CSU) local scour equation recommended in the Federal Highway Administration Hydraulic Engineering Circular No. 18 was used to estimate scour depths at the study sites. Estimated scour depths based on the CSU equation ranged from 2.5 to 12.7 feet with residuals (measured scour depth minus estimated scour depth) ranging from -8.1 to -1.4 feet. A comparison of the residuals with the estimated scour depths indicated that the CSU equation overestimated the measured scour depths throughout the range of measured data by an average of 434 percent.

Water-Resources Investigations Report↗