Geology topics

B.F. Pope

Publications and source records attributed to B.F. Pope.

7 recordsLinked to original sources

USGS2007

Identification of changes in streamflow characteristics

A set of procedures for identifying changes in selected streamflow characteristics at sites having long-term continuous streamflow records is illustrated by using streamflow data from the Waccamaw River at Freeland, North Carolina for the 55-year period of 1940-1994. Data were evaluated and compared to streamflows in the adjacent Lumber River Basin to determine if changes in streamflow characteristics in the Waccamaw River were localized and possibly the result of some human activity, or consistent with regional variations. Following 1963, droughts in the Waccamaw Basin seem to have been less severe than in the Lumber Basin, and the annual one-, seven-, and 30-day low flows exhibited a slightly increasing trend in the Waccamaw River. Mean daily flows in the Waccamaw River at the 90 percent exceedance level (low flows) during 1985-194, a relatively dry period, were very nearly equal to flows at the same exceedance level for 1970-1979, which represents the 10-year period between 1940 and 1994 with the highest flows. Prior to the 1980s, flows per unit drainage area in the Waccamaw Basin were generally less than those in the Lumber Basin, but after 1980, the opposite was true. The ratio of base flow to runoff in the Waccamaw River may have changed relative to that in the Lumber River in the late 1970s. There was greater variability in Waccamaw River streamflow than in Lumber River flow, and flow variability in the Waccamaw River may have increased slightly during 1985-1994.

North Carolina↗

USGS2001

Low-Flow Characteristics and Discharge Profiles for Selected Streams in the Cape Fear River Basin, North Carolina, Through 1998

An understanding of the magnitude and frequency of low-flow discharges is an important part of evaluating surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized in this report for 67 continuous-record gaging stations and 121 partial-record measuring sites in the Cape Fear River Basin of North Carolina. Records of discharge collected through the 1998 water year were used in the analyses. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, similar to 7Q10 discharge except that only flow during November through March is considered; and (5) 7Q2 low-flow discharge. Low-flow characteristics in the Cape Fear River Basin vary widely in response to changes in geology and soil types. The area of the basin with the lowest potentials for sustained base flows is underlain by the Triassic basin in parts of Durham, Wake, and Chatham Counties. Typically, these soils are derived from basalt and fine-grained sedimentary rocks that allow very little infiltration of water into the shallow aquifers for storage and later release to streams during periods of base flow. The area of the basin with the highest base flows is the Sand Hills region in parts of Moore, Harnett, Hoke, and Cumberland Counties. Streams in the Sand Hills have the highest unit low flows in the study area as well as in much of North Carolina. Well-drained sandy soils in combination with higher topographic relief relative to other areas in the Coastal Plain contribute to the occurrence of high potentials for sustained base flows. A number of sites in the upper part of the Cape Fear River Basin underlain by the Carolina Slate Belt and Triassic basin, as well many sites in lower areas of the Coastal Plain (particularly the Northeast Cape Fear River Basin), have zero or minimal (defined as less than 0.05 cubic foot per second) 7Q10 discharges. In this area, the poorly sustained base flows are reflective of either (1) thin soils that have very little storage of water to sustain streams during base-flow periods (Carolina Slate Belt), or (2) soils having very low infiltration rates (Triassic basin). As a result, there is insufficient water stored in the surficial aquifers for release to streams during extended dry periods. Within the part of the study area underlain by the Carolina Slate Belt, streams draining basins 5 square miles or less may have zero or minimal 7Q10 discharges. The part of the study area underlain by the Triassic basin has a higher drainage-area threshold at 35 square miles, below which streams will likely have zero or minimal 7Q10 discharges. Occurrences of zero or minimal 7Q10 discharges in the Coastal Plain were noted, though on a more widespread basis. In this area, low flows are more likely affected by the presence of poorly drained soils in combination with very low topographic relief relative to other areas in the Coastal Plain, particularly the Sand Hills. In eastern Harnett County and northeastern Cumberland County, basins with less than 3 square miles may be prone to having zero or minimal 7Q10 discharges. Soils in this area have been described as a mixture of sandy and clay soils. In the Northeast Cape Fear River Basin, particularly on the western side of the river, streams draining less than 8 square miles may have zero or minimal 7Q10 discharges. The poorly drained clay soils along with very little topographic relief results in the low potential for sustained base flows in this part of the study area. Drainage area and low-flow discharge profiles are presented for 13 streams in the Cape Fear River Basin; these profiles reflect a wide range in basin size, characteristics, and streamflow conditions. In addition to the Haw River and Cape Fear River main stem, pro

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USGS1996

Estimation of flood-frequency characteristics of small urban streams in North Carolina

A statewide study was conducted to develop methods for estimating the magnitude and frequency of floods of small urban streams in North Carolina. This type of information is critical in the design of bridges, culverts and water-control structures, establishment of flood-insurance rates and flood-plain regulation, and for other uses by urban planners and engineers. Concurrent records of rainfall and runoff data collected in small urban basins were used to calibrate rainfall-runoff models. Historic rain- fall records were used with the calibrated models to synthesize a long- term record of annual peak discharges. The synthesized record of annual peak discharges were used in a statistical analysis to determine flood- frequency distributions. These frequency distributions were used with distributions from previous investigations to develop a database for 32 small urban basins in the Blue Ridge-Piedmont, Sand Hills, and Coastal Plain hydrologic areas. The study basins ranged in size from 0.04 to 41.0 square miles. Data describing the size and shape of the basin, level of urban development, and climate and rural flood charac- teristics also were included in the database. Estimation equations were developed by relating flood-frequency char- acteristics to basin characteristics in a generalized least-squares regression analysis. The most significant basin characteristics are drainage area, impervious area, and rural flood discharge. The model error and prediction errors for the estimating equations were less than those for the national flood-frequency equations previously reported. Resulting equations, which have prediction errors generally less than 40 percent, can be used to estimate flood-peak discharges for 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals for small urban basins across the State assuming negligible, sustainable, in- channel detention or basin storage.

North Carolina↗

USGS1996

Streamflow characteristics of the Waccamaw River at Freeland, North Carolina, 1940-94

Streamflow characteristics of the Waccamaw River at Freeland, North Carolina, for the period 1940-94 were described and compared to stream- flows in the adjacent Lumber River Basin. Precipitation in the two basins was about equal for the study period. During 1940-63, stream- flows in the Waccamaw and Lumber Rivers were essentially identical relative to average conditions. The flow regime from the late 1950's to the early 1980's was distinctly wetter than the flow regimes which immediately preceded and followed this period. Following 1963, droughts in the Waccamaw Basin seem to have been less severe than in the Lumber Basin, and the annual 1-, 7-, and 30-day low flows exhibited a slightly increasing trend in the Waccamaw River. Mean daily flow in the Wacca- maw River at the 90-percent exceedance level (low flows) during 1985- 94, a relatively dry period, was very nearly equal to flows at the same exceedance level for 1970-79, the wettest 10-year period between 1940 and 1994. Prior to the 1980's, flows per unit drainage area in the Waccamaw Basin were generally less than those in the Lumber Basin, but after 1980, the opposite was true. There is an increasing trend in the difference between Waccamaw River and Lumber River high flows, primarily as a result of increases in Waccamaw River high flows. On average, streamflow in the Waccamaw River consisted of 53.3 percent base flow, but base flow accounted for 70.6 percent of the total flow in the Lumber River, which is more typical of Coastal Plain streams. The ratio of base flow to runoff in the Waccamaw River may have changed relative to that in the Lumber River in the late 1970's. There was greater variability in Waccamaw River streamflow than in Lumber River flow, and flow variability in the Waccamaw River may have increased slightly during 1985-94.

North Carolina↗

USGS1996

Simulated peak flows and water-surface profiles for Scott Creek near Sylva, North Carolina

Peak flows were simulated for Scott Creek, just upstream from Sylva, in Jackson County, North Carolina, in order to provide Jackson County officials with information that can be used to improve preparation for and response to flash floods along the reach of Scott Creek that flows through Sylva. A U.S. Geological Survey rainfall-runoff model was calibrated using observed rainfall and streamflow data collected from March 1994 through September 1995. Standard errors for calibration were 34 percent for runoff volumes and 21 percent for peak flows. The calibrated model was used to simulate peak flows resulting from syn- thetic rainfall amounts of 1.0, 2.5, 5.0, and 7.5 inches in 24-hour periods. For each rainfall amount, peak flows were simulated under low-, moderate-, and high-antecedent soil-moisture conditions, represented by selected 3-month periods of daily rainfall and evaporation record from nearby climatic-data measuring stations. Simulated peak flows ranged from 89 to 10,100 cubic feet per second. Profiles of water-surface elevations for selected observed and simu- lated peak flows were computed for the reach of Scott Creek that flows through Sylva, North Carolina. The profiles were computed using the U.S. Army Corps of Engineers HEC-2 Water Surface Profiles computer program and channel cross-section data collected by the Tennessee Valley Authority. The stage-discharge relation for Scott Creek at the simulation site has changed since the collection of the cross-section data. These changes, however, are such that the water-surface profiles presented in this report likely overestimate the true water-surface elevations at the simulation site for a given peak flow

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USGS1993

Hydrology of two tidal marshes in North Carolina where open-marsh water management modifications have been implemented

In 1988 and 1989, open-marsh water management modifications were implemented at tidal marshes near West Onslow Beach and Hobucken, North Carolina, as part of a pilot program to evaluate the effectiveness of ditching techniques as a mosquito-control method in open marshes. In 1984, before implementation of the modifications, a study was initiated to allow definition of the effects of those modifications on the hydrology of the marshes. Water levels in canals near the West Onslow Beach study marsh are controlled by periodic, gravitational tides. Daily maximum tides exceeded the elevation of the upper marsh surface 30% of the time before and 18% of the time after open-marsh water management. Daily maximum tides at this marsh exceeded the upper marsh surface 34% of the time before and 24% of the time after open-marsh water management. Variation in tidal conditions resulted in varying numbers and duration of floods at the study marshes. Duration analyses indicated relations between tide levels and marsh surface-water levels were unchanged after modifications. Groundwater movement through the marshes varies seasonally and is primarily vertical. Withdrawals are by evapotranspiration and recharge is by infiltration. During nongrowing months saturated conditions prevail. Groundwater flow to the marsh interior from the surrounding tidal canals was not detected during these declines. Changes in the natural variation in withdrawals from and recharge to groundwater were not indicated by the data collected during this study. Water levels in canals adjacent to the Hobucken study marsh are primarily controlled by wind-driven tides.

North Carolina↗

USGS1992

Ground-water level data for North Carolina, 1988-90

Continuous and periodic water-level measurements were made in 59 key wells throughout North Carolina. Additional measurements were made in 112 supplementary wells completed in Coastal Plain aquifers of the State. Changes in groundwater storage are shown in 3-year and 10-year hydrographs of selected wells in the State. The water table in the shallow aquifers was higher throughout most of 1989 and early 1990 than in 1988, indicating that these aquifers were sufficiently recharged by precipitation to replenish the late 1987-88 deficit in groundwater storage. Water levels in the heavily pumped Coastal Plain aquifers declined as a result of water being withdrawn from aquifer storage. Record low water levels were measured in 8 to 13 wells completed in the Castle Hayne aquifer and in 6 of 8 wells in the Peedee aquifer; the maximum annual declines during 1988-90 averaged 3.3 and 1.6 ft/yr, respectively, for these two aquifers. All wells in the Black Creek, upper Cape Fear, and lower Cape Fear aquifers had record low water levels during 1988-90, with maximum annual declines averaging 9.0, 2.2, and 2.6 ft/yr, respectively. Water levels in two of three wells in the Yorktown aquifer did not show a general downward trend during 1988-90, although water levels declined in the third well, reaching a record low in 1990. The effects of water withdrawals from major pumping centers in the North Carolina Coastal Plain are shown in potentiometric-surface maps of the Black Creek and lower Cape Fear aquifers.

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