The project included surface runoff and groundwater drainage measurements in addition to determinations of physical and chemical characteristics from three watersheds located within the same drainage basin in Montgomery County, Virginia. Watershed number 1 included 80 acres of heavily forested land; number 2 consisted of 50 acres of pasture land and approximately 0.1 acre of barren land; and number 3 included 20 acres of brush land and steep embankments adjoining a paved highway. The research period covered from March 15 to July 1, 1974. Dry weather groundwater drainage was sampled on four separate occasions. Surface runoff was sampled during five storms. A single composite sample was made from individual samples taken periodically from each watershed. The amount of rainfall which was present as runoff from watershed number 3 averaged over 85 percent and was much greater than that from the other two watersheds. Significant concentrations of TKN and N0₃-N were found in both groundwater drainage and surface runoff from all three watersheds. Steep embankments contributed the largest amount of TKN, N0₃-N, and COD, averaging 0.290, 0.203, and 19.2 lb/acre respectively in surface runoff. Pasture and barren land contributed the most total phosphorus and suspended matter, with values averaging 0.084 lb/acre P0₄-P and 167 lb/acre SS. / Master of Science

The erosion process was characterized on two small agricultural watersheds in Piedmont Virginia. Rainfall and runoff were measured for all storms at both watersheds over a two year monitoring period. Although the data base was relatively short, the data covered a wide range of rainfall and runoff conditions. Runoff samples were collected, analyzed, and used to compute loading rates of sediment, nitrate N, ammonium N, TKN, orthophosphate P, and total P on an event basis. Yields from missed storms were estimated from log-log linear least squares regression rating curves. Seasonal and annual totals of loading rates were computed by summing the yields for all storms. Existing estimation techniques were used to calculate rainfall energy, rainfall energy contributing to rainfall, the runoff/rainfall ratio, gross erosion and delivery ratios. USLE C-factors for each field were evaluated for changes in crop and cover conditions. Enrichment ratios for available P, nitrate N, and TKN were estimated on an annual basis. Clay enrichment and particle size distributions of the surface soil and the sediment in runoff from each watershed were also determined. These erosion characteristics were contrasted between the two watersheds whose land management practices differed. A comparison between years was also made on the conservation watershed, where part of the conservation plan was abandoned the second year. The use of conservation practices resulted in smaller estimates of gross erosion, smaller sediment and sediment-bound nutrient yields, and less runoff. / M.S.

An investigation was made of the flash flood of July 9, 1943, on the Blacksburg watershed with a view toward an approximation of the actual amount of water passing as run-off during the storm, as well as the peak rate of flow. All the available data have been reviewed with the above purpose in mind. The unit graph method has been applied to this investigation as the most logical method of solution. With the data already available plus that gathered by the writer, the unit graph method was readily applied. In this connection, the writer has kept continuous rainfall records at the Mineral Industries Building and continuous water level records at the Virginia Polytechnic Institute dam. After arriving at a solution as to the actual run-off conditions at the Virginia Polytechnic Institute dam following the above storm, further investigation was made of that point of the drainage area above the Blacksburg depot of the Norfolk and Western Railroad. The capacities of both the culvert on Eakia Street and the channel above Eakia Street were determined by calculations, and an opinion based on the review of observed data was offered as to why the culvert did not properly take care of the run-off from the drainage area above it. Using the calculated maximum rate of run-off, a cross section of Strouble’s Creek at the site of the proposed Virginia Polytechnic Institute sewage disposal plant has been analyzed. A solution has been offered as to low high the maximum flood crest of Strouble’s Creek at that point will reach. This information is necessary because the sewage plant must be build above the flood waters. / M.S.

The relationships between contaminant removal from impervious pavements and raindrop impact energy, cumulative kinetic energy of rainfall events, and rainwater fit were evaluated. A commercial urban area was chosen to perform simulated rainfall experiments. The runoff from these experiments was collected and analyzed for total suspended solids, volatile suspended solids, total Kjeldahl nitrogen, soluble Kjeldahl nitrogen, oxidized nitrogen, ammonia, ortho-phosphate, total phosphorus, soluble phosphorus, total lead and total zinc. Raindrop impact energy, rainfall intensity, rainfall duration, and rainwater pH were factors which were varied to examine their effect on contaminant wash-off phenomena. The present exponential decay theory of contaminant removal was verified and modified to incorporate the cumulative kinetic energy of rainfall events. An empirical model for contaminant removal was also developed. Data showed that both raindrop impact energy and cumulative storm energy had significant effects on contaminant removal. Contaminant wash-off was found to be independent of rainwater pH except for solids removal at low rain intensities. Additional results indicated that there is a "threshold impact energy" necessary before significant removal of contaminants associated with insoluble material can occur. The kinetic energy attributed to surface runoff overflow was found to be very important in the mechanisms responsible for contaminant removal at high rainfall intensities. / M.S.