Research about Brandywine Creek

USGS1982

A stormwater management model for the West Branch Brandywine Creek, Chester County, Pennsylvania

Three subbasins in the West Branch Brandywine Creek watershed were modeled by the Dawby, Schaake, and Alley distributed routing rainfall- runoff model. The Honeybrook subbasin could not be calibrated because of nonrepresentative rainfall data. The Coatesville subbasin was calibrated, but not verified; the average standard error of estimate is 34 percent for peak discharge. The Modena subbasin was calibrated and verified. Average error for peak discharge is 38 percent for calibration and 24 percent for verification. Predictive simulations using selected storms were made to determine the effects of projected population and four proposed flood-control structures in the Coatesville and Modena subbasins. Simulation of projected population growth in both subbasins showed that runoff volumes would generally have a greater percentage increase for low-magnitude floods than for high-magnitude floods. Proposed flood-control structure PA-436D had the greatest reduction in peak discharge at West Branch Brandywine Creek at Coatesville when a large quantity of runoff entered the Coatesville subbasin from upstream. WA-2 had the greatest reduction in peak discharge when most of the runoff came from within the Coatesville subbasin. Although WA-2 and PA-430 will control about the same drainage area, WA-2 causes a greater reduction in peak discharge at Coatesville because PA-430 is to be located upstream from Rock Run Reservoir, which provides some flood- water storage. In the Modena subbasin, the simulated effect of proposed flood-control structure PA-428 showed that it would lower the peak discharge of Sucker Run at State Route 82 and either raise or have no effect on peak discharges at West Branch Brandywine Creek at Modena. Most simulations of the effects of proposed flood-control structures in the Coatesville subbasin on peak discharge at Modena showed a reduction in peak discharge.

Pennsylvania↗

USGS1957

The trend of suspended-sediment discharge of the Brandywine Creek at Wilmington, Del., 1947-1955

This report presents an analysis and evaluation of the trend of the sediment yield for the Brandywine Creek at Wilmington, Del., for the period from December 1946 to September 1955. The interest in such an analysis and evaluation stems from the efforts of the Brandywine Valley Association and others to reduce erosion and improve land use in the watershed. The data used for the analysis were taken from the continuous suspended-sediment and water-discharge records of the stream at Wilmington and the precipitation records at 8 standard and 1 recording rain gages. The analysis was made on the basis of 123 storm events for this period of record using only the water and sediment discharge attributed to direct runoff. These data represent 89 percent of the total sediment discharge and 19 percent of the total water discharge. The sediment load for each of the storm runoff events was correlated with storm runoff, rainfall intensity, and season to remove the effect, if ant, of the variation caused by these factors. The evaluation of the relative trend of sediment yield was made by two methods; first, the accumulative graph pr double mass curve as a graphical method, and second, the rank correlation method which results in a numerical coefficient and its significant. The graphical method of this evaluation shows an approximate 38 percent decrease in sediment yield for the period 1952 to 1955 from that for the period 1947 to 1951. The rank correlation coefficient was 0.152 for the same analysis showing a very high level (almost 99 percent) of confidence in the significance of a decreasing trend. A parallel analysis to that above using "peakedness" instead of rainfall intensity as a measure of storm intensity was made because "peakedness" is easier to evaluate than rainfall intensity. The results of this analysis again indicates the probably decreasing trend of sediment yield as shown by the change in slope of the accumulative graph from 0.77 fir the 1947 to 1951 period to 1.05 for the 1952 to 1955 period or 28%, and by the rank correlation coefficient of 0.114 with a 94 percent level of confidence of a decreasing trend. Appendix A of this report shows a similar analysis by usede of monthly sediment discharge and "direct" runoff as determined for an analyses of runoff patterns. The results indicate only a small decreasing trend, if any, in sediment yield. This is probably due to the fact that the correlations with rainfall and season for adjusting these data were rather poor--indicating bias by unknown parameters that cannot be evaluated. Appendix B presents the methodology of using rank correlation to evaluate the trend of variate-values with respect to time with special reference to the trend of sediment yield from a watershed.

Delaware↗