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C. H. Robbins

Publications and source records attributed to C. H. Robbins.

7 recordsLinked to original sources
USGS1987

Man-induced gradient adjustment of the South Fork Forked Deer River, west Tennessee

Channel modifications from 1968 to 1969 on the South Fork Forked Deer River in western Tennessee have caused upstream degradation, downstream aggradation, and bank failures along the altered channels, adjacent reaches, and tributaries. The result of these adjustments is a general decrease in gradient as the channel attempts to absorb the imposed increase in energy conditions created by channelization. Headward degradation at a rate of approximately 2.57 km/yr on the South Fork Forked Deer River caused from 1.52 m to about 3.14 m of incision over a 13.5 km reach from 1969 to 1981. As a consequence of substantially increased sediment supply, approximately 2.13 m of aggradation was induced downstream of this reach during the same period. This accumulation represents a 60% recovery of bed level at the downstream site since the completion of channel work in 1969. Gradient adjustment with time is described by exponential decay functions. The length of time required for adjustment to some new quasi-equilibrium condition is computed by these decay functions and is about 20 years from the completion of channel work. Adjusted slopes are less than predisturbed values, probably because straightened channels dissipate less energy by friction, allowing more energy for sediment transport. An equivalent sediment load, therefore, can be transported at a considerably gentler slope. The predisturbed slope exceeds the adjusted slope by an order of magnitude on the downstream reach of the South Fork Forked Deer River. ?? 1987 Springer-Verlag New York Inc.

Environmental Geology and Water Sciences↗
USGS1986

Techniques for simulating flood hydrographs and estimating flood volumes for ungaged basins in central Tennessee

A dimensionless hydrograph developed for a variety of basin conditions in Georgia was tested for its applicability to central Tennessee streams by comparing it to a similar dimensionless hydrograph developed for central Tennessee streams. Statistical analyses were performed by comparing simulated (or computed) hydrographs, derived by application of the Georgia-study dimensionless hydrograph and the central Tennessee dimensionless hydrograph, with 163 observed hydrographs from 38 stations having a wide range of drainage area sizes and basin conditions, at 50 and 75 percent of their peak flow widths. Test results indicate the two dimensionless hydrographs are essentially the same. Using the Georgia-study dimensionless hydrograph, the standard error of estimate was + 21.2 percent at the 50 percent of peak flow width and + 24.8 percent at the 75 percent 07 peak flow width. Study results indicate the Georgia dimensionless hydrograph is applicable to central Tennessee streams. Equations for rural and urban basin lagtime were derived from multiple-regression analyses that relate lagtime to physical basin characteristics. At the 95-percent confidence level, channel length was significant for the rural basin equation and channel length and percentage of impervious area were significant for the urban basin equation. A regression equation that related flood volumes to drainage area size, peak discharge, and basin lagtime also was developed. The flood-hydrograph and flood-volume techniques are useful for estimating a typical (average) flood hydrograph and volume for any specified recurrence interval peak discharge at any ungaged stream site draining areas less than 500 square miles in central

Tennessee↗
USGS1985

Hydrology of the Reelfoot Lake basin, Obion and Lake counties, northwestern Tennessee

Hydrologic data and analyses and ground-water modeling results are provided to aid in the evaluation of proposed lake management strategies for Reelfoot Lake in northwestern Tennessee. Surface-water and ground-water data collected from May 1 to December 31, 1984, were used to evaluate the Reelfoot Lake hydrologic system. Long-term streamflow, rainfall, evaporation, and lake-level data were used to describe the normal hydrologic conditions at Reelfoot Lake. Estimated monthly water budgets, assuming normal climatic and hydrologic conditions, were derived for Reelfoot Lake in order to determine the time required to refill the lake beginning on November 1, following a proposed mid-summer drawdown of 5.8 feet below normal pool. Additionally, estimates of the time required to fill the lake to 1.0 foot above normal pool were made. Results of these determinations indicate that a normal pool elevation of 282.20 feet above sea level would probably be achieved by mid-January, and a pool elevation of 283.24 feet above sea level by the end of January. A calibrated two-dimensional ground-water flow model was used to simulate groundrater levels following the proposed lake drawdown and refill. Simulation results are presented as ground-water level difference maps which indicate the potential difference in ground-water elevations for the two proposed lake-level extremes. Low lake-level simulation results indicate ground-water levels may decline approximately 5.7 feet below normal in the areas immediately adjacent to the lake. The high lake-level simulation results indicate ground-water-levels may increase approximately 1.0 foot above normal in the areas immediately adjacent to the lake.

Tennessee↗
USGS1984

Effects of urbanization on the magnitude and frequency of floods on small streams in Tennessee; basic data report No. 3

Rainfall and discharge data collected at 21 urban hydrology sites in Tennessee from July 1977 to September 1983 are summarized. These rainfall-runoff data will be used to calibrate a U.S. Geological Survey Rainfall-Runoff Model. The results of the model calibrations will then be used to develop reliable methods for determining the magnitude and frequency of floods on small streams in Tennessee where urbanization is a factor. (USGS)

Tennessee↗
USGS1984

Synthesized flood frequency for small urban streams in Tennessee

Bridge, culvert, and highway design often require knowledge of the magnitude and frequency of flood discharge from small streams where the drainage basin is urbanized. The results of a 6-year study by the U.S. Geological Survey provide methods for estimating flood magnitudes for selected frequencies on small streams draining urban areas in Tennessee. A total of 22 rainfall-runoff sites located in basins with drainage areas of 0.21 to 24.3 square miles in size and in municipalities with populations between 5,000 and 100,000 were used to derive regionalized flood-frequency equations. Impervious area, measured from recent aerial photographs, ranged between 4.7 percent and 74.0 percent of the basin. The equations were derived by multiple regression analyses of snythetic flood-frequency estimates, derived from a rainfall-runoff modeling procedure, versus physical basin characteristics and a precipitation factor. These equations can be used to estimate the magnitude of future floods with recurrence intervals of 2 to 100 years on ungaged urbanized streams in Tennessee. One equation for each recurrence interval applies statewide. Flood-frequency estimates for stations used in the analyses and example computations demonstrating applications of the regression equations to urban streams in Tennessee are given in the report. (USGS)

Water-Resources Investigations Report↗
USGS1983

Man-induced channel adjustment in Tennessee streams

Channel modifications in Tennessee, particularly in the western part, have led to large-scale instabilities in the channelized rivers and may have contributed to several bridge failures. These modifications, together with land-use practices, led to downcutting, headward erosion, downstream aggradation, accelerated scour, and bank instabilities. Changes in gradient by channel straightening caused more severe channel response than did dredging or clearing. Large-scale changes continue to occur in all the channelized rivers: the Obion River, its forks, and the South Fork Forked Deer River. However, the non-channelized Hatchie River in west Tennessee not only withstood the natural stresses imposed by the wet years of 1973 to 1975 but continues to exhibit characteristics of stability. Water-surface slope, the primary dependent variable, proved to be a sensitive and descriptive parameter useful in determining channel adjustment. Adjustments to man-induced increases in channel-slope are described by inverse exponential functions of the basic form S=ae(-b(t)); where ' S ' is some function describing channel-slope, ' t ' is the number of years since completion of channel work, and ' a ' and ' b ' are coefficients. Response times for the attainment of ' equilibrium ' channel slopes are a function of the magnitude and extent of the imposed modifications. The adjusted profile gradients attained by the streams following channelization are similar to the predisturbed profile gradients, where no alteration to channel length was made. Where the channels were straightened by constructing cut-offs, thus shortening channel length, then slope adjustments (reduction) proceed past the predisturbed profile gradients, to new profiles with lower gradients. (USGS)

Water-Resources Investigations Report↗