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Unformatted text preview: 2003 by CRC Press LLC 33 Quality of Urban Runoff 33.1 Urban Runoff Point Sources Nonpoint Sources 33.2 Quality of Urban Runoff Point Source Pollution Nonpoint Source Pollution National Urban Runoff Program Comparison of Pollution Sources 33.3 Water Quality Regulations and Policies Receiving Water Guidance Water Quality Criteria 33.4 Modeling Modeling Categories Data Point Source Models Nonpoint Source Models Modeling Considerations 33.5 Best Management Practices Point Source Programs Total Maximum Daily Loads Nonpoint Source Programs Structural Measures 33.1 Urban Runoff Urban runoff is a major environmental concern. The old paradigm of only controlling flow to mitigate flood damage must be extended to incorporate preventing deterioration of water quality. For the purposes of this chapter, urban runoff is water flowing because of urbanization and may occur from the following sources: stormwater runoff, combined sewer overflows, sanitary sewer overflows, publicly owned treat- ment works and industrial outfalls, and/or miscellaneous runoff. There are other sources of runoff that contribute to the deterioration of water quality, including agricultural runoff, but those are not considered urban sources. The major volume of urban runoff is composed of water that flows from landscaped areas, driveways, streets, parking lots, roofs, and from other impervious surfaces. This chapter provides an overview of the sources of urban runoff in terms of quantity and quality, discusses water quality regulations and criteria, and shares best management practices, which often require detailed modeling of the urban system. Relevant investigations carried out by various agencies are included, such as NURP (National Urban Runoff Program, EPA, 1983). The TMDL (Total Maximum Daily Load) program is discussed and should be viewed as a management practice to control the quality of urban runoff (EPA, 2000c). Before considering the impacts of pollution on urban water quality, the effect of urbanization on the hydrologic cycle must be investigated. As watersheds become urbanized, hydrological characteristics drastically change. Urbanization can result in the following changes of a catchments hydrologic cycle (WEF/ASCE, 1998): reducing the degree of infiltration and increased runoff volumes resulting from surface changes (altered grading, form, or cover); changing the available depression storage because of re-grading; Amrou Atassi CDM Stephen D. Ernst Christopher B. Burke Engineering, Ltd. Ronald F. Wukash* Purdue University * Due to the untimely death of Dr. Wukasch, this chapter was completed by his co-authors and was reviewed by Reggie Baker of the Indiana Department of Environmental Management. changing evapotranspiration as vegetative cover is removed; and reducing the residence time of water in a catchment as a result of increased impervious areas or the construction of efficient sewer systems....
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