This study was conducted in order to obtain information that would permit comparisons of six nutrient parameters, both organic and inorganic, in runoff from five different land types. Sampling and laboratory determinations were conducted on runoff samples collected during the summer of 1973, in and around the town of Blacksburg, Virginia. The five different types of runoff that were studied were construction, residential, commercial, agricultural, and forest. The six parameters investigated during the study were five-day biochemical oxygen demand (BOD₅), chemical oxygen demand, orthophosphorous, total phosphorous, nitrate, and total organic carbon. The major interest was in BOD₅ concentrations because of the importance of land runoff in stream assimilation modeling. Analyses were also performed during low flow periods to permit a comparison with runoff collected during storm events. Concentrations of BOD₅ in runoff from all six land types were higher than the 2 mg/l normally assumed as a value for runoff in stream assimilation models. Also, nitrogen and phosphorous concentrations in all runoff samples were high enough to constitute a significant contribution of fertilizer elements to streams. Of the types of runoff tested, commercial and construction runoff were greater sources of pollution than residential, agricultural, or forest runoff. / Master of Science

Residential infill development and the associated increases in impervious cover and stormwater runoff have the potential to overwhelm aging infrastructure causing erosion, flooding, and ecological degradation of waterways. The lack of greenfield sites available for new development around urban centers coupled with a desire for maintaining a traditional neighborhood aesthetic drives residential infill and replacement of existing smaller homes by significantly larger structures, minimizing open space available for stormwater mitigation. An analysis of residential infill development trends in Fairfax County was performed to characterize the effects of intensified development. Development patterns were identified and assessed using digitized impervious cover data extracted from aerial imagery of the study area for six selected years from 2002 to 2015. The average annual increase in percent impervious area was computed to be 0.3%. Redevelopment was found to be mainly occurring in areas zoned as lower-density residential. The spatial distribution of redevelopment showed trends of clustered increases as opposed to isolated events. The hydrologic analysis performed revealed that from 2002 to 2015, there was an 8,930 m3 (7.2 acre-ft) increase in stormwater runoff volume, 38% of which is contributed to by runoff generated from development that is considered exempted from regulation in Fairfax County. Additionally, there was a 28 kg/year (62 lb/year) increase in total phosphorus loads attributable to the change in impervious cover due to residential development throughout the study area. The results of this study provide a quantitative basis for municipalities to amend policies regulating residential development and its associated stormwater management. / Master of Science / Residential infill and redevelopment is contributing to significant increases in impervious cover in suburban areas, resulting in increased stormwater runoff. This has the potential to overwhelm aging infrastructure causing erosion, flooding, and ecological degradation of waterways. The lack of greenfield sites available for new development around urban centers coupled with a desire for maintaining a traditional neighborhood aesthetic drives residential infill and replacement of existing smaller homes by significantly larger structures, minimizing open space available for stormwater mitigation. An analysis of residential infill development trends in a watershed within Fairfax County was performed to characterize the effects of intensified development. Development patterns were identified and assessed using digitized impervious cover data extracted from aerial imagery of the study area for six selected years from 2002 to 2015. The average annual increase in impervious area was evaluated against metrics such as lot size and location to determine historical trends and predict future rates of infill development. A hydrologic analysis was conducted to quantify the increase in stormwater runoff and associated quality of runoff impacts attributable to the change in impervious cover due to residential development throughout the study area. The results of this study provide a quantitative basis for municipalities to amend policies regulating residential development and its associated stormwater management.

Project Completion Report, OWRT Project No. A-049-ARIZ / Agreement No. 14-31-0001-4003 / Project Dates: July 1, 1973 - June 30, 1974. / Acknowledgement: The work upon which this report is based was supported by funds provided by the United States Department of the Interior, Office of Water Research and Technology, as authorized under the Water Resources Research Act of 1964. / A non-linear reservoir model is used to represent the rainfall-runoff relationships for thunderstorms on the urban watersheds of Tucson, Arizona. Two types of computer programs are developed: a calibration program to obtain a best -fit calculated hydrograph; and a verification program to generate storm hydrographs given the watershed characteristics and a hyetograph. Calibration reveals the relationship of the model parameters, namely, (f) the inflow coefficient, (a) the constant coefficient, and (TL) the time lag, to the total rainfall, drainage area, channel length, and infiltration capacity of the watershed. The average discrepancy between the predicted hydrograph and the actual hydrograph for Tucson urban watersheds is 20 -25 percent.

Stormwater treatment is commonly performed with a combination of approaches including the utilization of natural systems and engineered devices. Before using a proprietary treatment instrument it is required to verify its performance and efficiency in reducing different pollution components including the TSS. Different states have developed strategies and regulations for accepting new instruments. In this thesis the stormwater management plan of the City of Portland, Oregon(2008), is analyzed in order to improve the current regulations. These rules apply to new technologies which are proposed by vendors to be used in Portland's stormwater treatment plans. Each requirement which should be met by the applying vendors is thoroughly analyzed followed by a comparison with the Stormwater management plan(2008)regulations of the state of Washington the so called Technology Assessment Plan-Ecology TAPE (Howie, 2011). Because of the similarities in the climate and land use between these two testing frameworks in order to evaluate the potential applicability of data submitted by vendors who had devices approved by Washington, to be utilized by Portland. The treatment of total suspended solids (TSS) is the focus of this thesis since it is central to the testing process and since most of the other pollutions are attached to TSS and will get treated if TSS is treated. The overall analysis shows that Portland adopts more restrictive requirements on the characterization of stormwater event samples to be treated by a technological instrument while Washington's restriction are more stringent on the efficiency of total suspended solid removal, in which it demands higher standards on the treatment of TSS compared to Portland's efficiency requirements. In order to study practical context in which regulations are administrated by Portland, rainfall data from 66 gauges covering the period of 1980-2011 was studied and the impacts of seasonality, land use, land form, periods of no rain before and after an event and Portland's Modified Performance line on the number of accepted rain events were analyzed. The results which were accepted by state of Washington were also compared with the results accepted by the city of Portland on Portland's Standard Performance line. Our seasonality study suggests that Portland's requirements are unnecessarily restrictive which results in the disqualification of many otherwise useful stormwater events, sometimes allowing no natural events to be available for testing in dry years. The analysis of land use showed that land use has no statistically significant impact on the concentration levels of TSS, thereby indicating that land use restrictions in the testing rules could be usefully relaxed. Decreasing the interevent no-rain period significantly increases the total number of events providing sufficient data to assess the performance of treatment facilities. We also showed that many more events become suitable for performance testing if events separated by one hours or less are considered a single, longer event. Finally we identified a statistical relationship between number of forecasted accepted stormwater events and the total average daily precipitation in a given year.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Additional advisors: Robert Angus, Paul D. Blanchard, Sarah Culver, Alan Shih. Description based on contents viewed June 3, 2009; title from PDF t.p. Includes bibliographical references (p. 48-51).

Published Article / To assess and predict runoff and soil loss on different tillage methods coupled with alternative cropping systems in the central highland vertisols of Ethiopia, a study was carried out at Ginchi, Agricultural Research Sub-Center during 1996. The experiment was conducted on runoff plots of 4 meter wide by 22 meter long, on surface slopes that range between 0.1% and 2.3%. The data collected was analyzed using regression models and an empirical formula developed by the Soil Conservation Service of America (SCS, 1964; 1972), known as curve number (CN). Both the regression model and the SCS simulated the mean daily runoff reasonably well with R2 93% and 83%, respectively. The overall results obtained explain that the improved tillage practice, BBF could drain the excess surface water safely.

Flash floods caused by localized thunderstorms are a natural hazard of the semi -arid Southwest, and many communities have responded by installing ALERT flood forecasting systems. This study explored a rainfall- runoff modeling approach thought to be appropriate for forecasting in such watersheds. The kinematic model KINEROS was evaluated because it is a distributed model developed specifically for desert regions, and can be applied to basins without historic data. This study examined the accuracy of KINEROS under data constraints that are typical of semi -arid ALERT watersheds. The model was validated at the 150 km2, semi -arid Walnut Gulch experimental watershed. Under the conditions examined, KINEROS provided poor simulations of runoff volume and peak flow, but good simulations of time to peak. For peak flows, the standard error of estimate was nearly 100% of the observed mean. Surprisingly, when model parameters were based only on measurable watershed properties, simulated peak flows were as accurate as when parameters were calibrated on some historic data. The accuracy of KINEROS was compared to that of the SCS model. When calibrated, a distributed SCS model with a simple channel loss component was as accurate as KINEROS. Reasons for poor simulations were investigated by examining a) rainfall sampling errors, b) model sensitivity and dynamics, and c) trends in simulation accuracy. The cause of poor simulations was divided between rainfall sampling errors and other problems. It was found that when raingage densities are on the order of 1/20 km2, rainfall sampling errors preclude the consistent and reliable simulation of runoff from localized thunderstorms. Even when rainfall errors were minimized, accuracy of simulations were still poor. Good results, however, have been obtained with KINEROS on small watersheds; the problem is not KINEROS itself but its application at larger scales. The study also examined the hydrology of thunderstorm -generated floods at Walnut Gulch. The space -time dynamics of rainfall and runoff were characterized and found to be of fundamental importance. Hillslope infiltration was found to exert a dominant control on runoff, although flow hydraulics, channel losses, and initial soil moisture are also important. Watershed response was found to be nonlinear.

No description available.

The first purpose of this thesis is to provide a framework for the inclusion of data from a secondary source in Bayesian decision analysis as an aid in decision making under uncertainty. A second purpose is to show that the Bayesian procedures can be implemented on a computer to obtain accurate results at little expense in computing time. The state variables of a bridge design example problem are the unknown parameters of the probability distribution of the primary data. The primary source is the annual peak flow data for the stream being spanned. Information pertinent to the choice of bridge design is contained in rainfall data from gauges on the watershed but the distribution of this secondary data cannot be directly expressed in terms of the state variables. This study shows that a linear regression equation relating the primary and secondary data provides a means of using secondary data for finding the Bayes risk and expected opportunity loss associated with any particular bridge design and single new rainfall observation. The numerical results for the example problem indicate that the information gained from the rainfall data reduces the Bayes risk and expected opportunity loss and allows for a more economical structural design. Furthermore, the careful choice of the numerical methods employed reduces the computation time for these quantities to a level acceptable to any budget.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy