: 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 streamflow 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.

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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 floodinsurance 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 rainfall 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 characteristics also were included in the database. Estimation equations were developed by relating flood-frequency characteristics 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 floodfrequency 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.

Water Resources, initiated an investigation in 1994 of the Streamflow characteristics of the Waccamaw River. The objectives of the investigation were to (1) characterize streamflow in the Waccamaw River at Freeland for the period 1940-94, and (2) compare Waccamaw River flow characteristics to flow characteristics of nearby streams.

In 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 percent of the time before and 18 percent of the time after open-marsh water management. Water levels in canals adjacent to the Hobucken study marsh are primarily controlled by wind-driven tides. Daily maximum tides at this marsh exceeded the upper marsh surface 34 percent of the time before and 24 percent of the time after openmarsh water management. Natural variation in tidal conditions resulted in varying numbers and duration of floods at the study marshes. Duration analyses indicated that 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 ground water were not indicated by the data collected during this study.