Geology topics
Research about Tennessee
Source-linked reports with geographic coverage including Tennessee.
Mapping and measuring land-cover characteristics of New River Basin, Tennessee, using Landsat digital tapes
Land-cover information is needed to select subbasins within the New River basin, Tennessee, for the study of hydrologic processes and also is needed to transfer study results to other sites affected by coal mining. It was believed that data recorded by the first Earth Resources Technology Satellite (Landsat-1) could be processed to yield the needed land-cover information. This study demonstrates that digital computer processing of the spectral information contained in each picture element (pixel) of 1.1 acres (4,500 m2) can produce maps and tables of the areal extent of selected land-cover categories. The distribution of water, rock, agricultural areas, evergreens, bare earth, hardwoods, and uncategorized areas, is portrayed on a map of the entire New River basin (1:62,500 scale) and on 15 quadrangles (1:24,000 scale). Although some categories are a mixture of land-cover types, they portray the predominant component named. Tables quantify the area of each category and indicate that agriculture covers 5 percent of the basin, evergreens cover 7 percent, bare earth covers 6 percent, three categories of hardwoods cover 81 percent, and water, rock, and uncategorized areas each cover less than 1 percent of the basin.
Application of the U.S. Geological Survey rainfall-runoff simulation model to improve flood-frequency estimates on small Tennessee streams
The U.S. Geological Survey rainfall-runoff simulation model was used in conjunction with National Weather Service climatological data to improve flood-frequency estimates for 52 small drainage basins in Tennessee. The basins range in size from 0.17 to 64 square miles (0.44 to 166 square kilometers) and are distributed throughout the State. Model parameters were determined by calibration with observed data from each site. Average error of peak discharge simulation was about 36 percent. Techniques used in screening data for calibration as well as those used to optimize parameter values are discussed. A scheme developed to assess the relative accuracy of the frequency curves based on observed and simulated data indicated that the simulated data are equivalent to nine years of observed data in defining 2-year floods, and fifteen years in defining 100-year floods. Discharges corresponding to the best estimate of flows for selected recurrence intervals are tabulated for each modeled basin. (Woodard-USGS)
Effects of urbanization on flood characteristics in Nashville-Davidson County, Tennessee
Streamflow data from 14 basins in Davidson County were extended in time by use of a digital model of the hydrologic system. The basins ranged in size from 1.58 to 64.0 square miles (4.09 to 165.8 square kilometers) and ranged in extent of man-made impervious cover from 3 to 37 percent. The flood-frequency characteristics were defined by weighting frequency curves based on simulated discharges with those based on observed discharges. The average record length of the three rain-gages used in simulation was 72 years, and the average record length of observed discharges was 11 years. Discharges corresponding to 2-, 5-, l0-, 25-, 50-, and l00-year floods from the modeled basins were compared with discharges from regional equations for estimating peak discharge rates from rural basins. Lag times between rainfall and runoff in the urban basins were compared with those of nearby rural basins. The analyses indicated that in a fully-developed residential area, the flood peaks and the basin lag times will not be significantly different from those expected from an undeveloped area. Data were not sufficient to determine if an increase in flood peaks would occur from extremely small basins with extremely intensive development.
Summary of some current and possible future environmental problems related to geology and hydrology at Memphis, Tennessee
Memphis, Tennessee, like many other cities in the Nation, has some problems related to local geology and hydrology. The city is in the Coastal Plain physiographic province and is underlain at shallow depths by sand, clay, silt, gravel, and lignite. These post-Midway strata (Wilcox and younger) make up geologic units belonging to the uppermost Paleocene, Eocene, and Pliocene (?) Series of the Tertiary System and to the Pleistocene and Holocene Series of the Quaternary System. Environmental problems of immediate or future concern are associated with six general topics: (1) aggregate resources, (2) foundation materials, (3) earthquake hazards, (4) flood hazards, (5) water resources, and (6) solid waste disposal. Consideration of these topics in one report should provide an overall insight into the close interrelation of the problems and the need for coordinated studies of the geology and hydrology at Memphis.
Historic water-level changes and pumpage from the principal aquifers of the Memphis area, Tennessee: 1886-1975
The Memphis Sand ("500-foot" sand) supplies about 95 percent of the water used in the Memphis area for municipal and industrial purposes. In general, pumpage has increased at an irregular rate since the completion of the first well to this aquifer in 1886. These withdrawals are responsible for an almost continuous decline of water levels in wells throughout the Memphis area. Water-level data indicate that over the years a broad, regional cone of depression has developed in the potentiometric surface of the Memphis Sand and is centered near downtown Memphis. Areally smaller, subsidiary cones are superimposed upon this regional cone in areas heavily pumped by municipal and industrial wells. Pumpage from the Memphis Sand in Shelby County, Tenn., was 188 Mgal/d (million gallons per day) or 712 Ml/d (million litres per day) in 1975, although a maximum of 190 Mgal/d (719 Ml/d) was reached in 1974. Pumpage from the Fort Pillow Sand ("1,400-foot" sand) began in 1924 and increased at a yearly rate of about 0.6 Mgal/d (2.3 Ml/d) until 1942. From 1943 to 1962, pumpage averaged about 11.5 Mgal/d (43.5 Ml/d), then was reduced as MLGW (Memphis Light, Gas and Water Division) discontinued wells that became unserviceable. MLGW ceased pumping from the aquifer in 1974, and pumpage from the remaining industrial wells in Shelby County in 1975 was 4.4 Mgal/d (16.6 Ml/d). Water levels in the Fort Pillow Sand generally have risen since 1963. Water l evels in the aquifers in the Memphis area fluctuate inversely with changes in pumping. Analysis of observation-well and pumpage data indicates that local water levels can be altered by changing the pumping rates or by varying the areal distribution of pumping.
Thin-skinned tectonics and potential hydrocarbon traps: Illustrated by a seismic profile in the Valley and Ridge province of Tennessee
Seismic data, although limited to a small part of the western half of the Valley and Ridge province in Tennessee, confirm that the structural style is thin-skinned and that there is a fundamental change from west to east in both the total section preserved and the structural complexities that exist in the subsurface. Cambrian to Upper Ordovician rocks in the Valley and Ridge province have been thrust westward over a 4-mile (6.4-km) projection of Cambrian through Mississippian rocks of the Appalachian Plateau. Structure within the plateau projection is characterized by splay anticlines, whereas structure in the Valley and Ridge is dominated by a series of imbricate thrust sheets containing isolated fault-bound masses of Cambrian sandstone and shale. Both splay anticlines and large fault-bound masses of rocks preserved in the subsurface in east Tennessee may be favorable fracture-porosity traps for the accumulation of hydrocarbons.
Peak stages and discharges on small streams in Tennessee, 1965-1975
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Wolf River at Memphis, Tennessee: floodflow characteristics along proposed Interstate Highway 240, Shelby County
This report has been prepared by the U.S. Geological Survey at the request of Mr. Henry Derthick, Engineer of Structures of the Tennessee Department of Transportation, under the authority of a cooperative agreement between the two agencies. It supplements information contained in a report with the same title dated September 1966. The Department of Transportation proposes to construct a segment of Interstate Highway 240 and several bridges across the Wolf River on the northern side off Memphis, Shelby Count. Mt. Derthick has requested an analysis of the 50-year flood or the maximum flood of record to determine the possible effect of the proposed construction on flood profiles along the Wolf River.