Civil & Environmental Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2753
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Item The Spatial Distribution of Imperviousness in Watershed Hydrology(2009) Mejia, Alfonso Ignacio; Moglen, Glenn E.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urbanization affects the hydrology of watersheds often leading to increases in runoff volumes and peak flows. These impacts are mainly attributed to the presence of imperviousness on the landscape which inhibits the soil infiltration process. Normally, these impacts are studied at the hillslope scale and under lumped watershed conditions. The impacts at the watershed scale under more spatially distributed conditions have been studied less. Advancements in spatial observations and techniques, distributed hydrologic modeling, and greater understanding of the importance of scale in hydrology have increased the feasibility and need for including spatial data sets and methods into hydrologic investigations. This dissertation focuses on understanding the role and importance of the spatial distribution of imperviousness in watershed hydrology. The spatial distribution of imperviousness is investigated by incorporating various spatial datasets, techniques, and modeling approaches that are used routinely for the hydrology of natural watersheds but less frequently for urbanized conditions. The distribution of imperviousness is investigated based on three approaches. The first approach uses optimization concepts to study where imperviousness can be placed in the watershed to reduce negative impacts on flooding. The second approach develops, implements, and tests a hydrologic event-based model to study the influence of the spatial distribution of imperviousness on the hydrologic response. The last approach relates analytically the space-time variability of rainfall, runoff, and the routing process to the imperviousness pattern, and synthesizes the complex space-time variations into a simpler framework. From the first approach distinct patterns of imperviousness were obtained that embodied water resources objectives. For example, the clustering of imperviousness along the main channel was found to globally reduce peak flows along the stream network. The second approach indicated that the overall imperviousness pattern can have a considerable impact on the hydrologic response. The last approach showed that the spatial patterns of rainfall and imperviousness can interact to increase or decrease the average amount of rainfall excess. The main contribution from this research is a larger understanding of the role of the spatial distribution of imperviousness in watershed hydrology. It also demonstrates the usefulness of applying hydrologic knowledge of natural watersheds to anthropogenically-altered watersheds.Item Development and Application of a Stream Flashiness Index based on Imperviousness and Climate using GIS(2007-07-26) Ravirajan, Karthik; Moglen, Glenn E; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This work examines the relationship between imperviousness, climate, and the Richards-Baker (R-B) index, a measure of ow variability. Regression equations to predict the R-B index are developed for annual, cool, and warm seasons. The re- gression equations developed, are calibrated using stream ow data from 1970-2000 for 29 USGS streamgages throughout Maryland. Regression equations for the R-B ashiness index are developed as a function of imperviousness, precipitation char- acteristics, and drainage area. The relationship is used to estimate stream quality conditions throughout Maryland for present and future land use and climate. The regression equations are used to calculate the future stream ow variability by pro- jecting the R-B index predictors to re ect the following conditions: (1) Increasing imperviousness only, (2) Climate change only, and (3) Jointly changing impervious- ness and climate. Finally, the relationship between R-B index and stream quality is studied.