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.

Engineers engaged in watersupply or power projects are often faced with the problem of dealing the adequency of the supply, as well as that of the extremes of flow on which the safety of hydraulic structures depends. / Master of Science