Urban Stormwater Management in the United States (2009) / Chapter Skim
Currently Skimming:
1 Introduction
1 Introduction
Pages 13-46
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 13... ...
Urban land, however, does continue to change over time; by one estimate, 42 percent of land currently considered "urban" in the United States will be redeveloped by 2030 (Brookings Institute, 2004)
|
From page 14... ...
Most broadly, stormwater runoff is the water associated with a rain or snow storm that can be measured in a downstream river, stream, ditch, gutter, or pipe shortly after the precipitation has reached the ground. What constitutes "shortly" depends on the size of the watershed and the efficiency of the drainage system, and a number of techniques exist to precisely separate stormwater runoff from its more languid counterpart, "baseflow." For small and highly urban watersheds, the interval between rainfall and measured stormwater discharges may be only a few minutes.
|
From page 15... ...
"Land cover," however, and particularly the percentage of impervious cover, is the metric most commonly used in studying the effects of urban development on stormwater, because it clearly expresses the hydrologic influence and watershed scale of urbanization. Box 1-2 describes the ways in which the percent of impervious cover in a watershed is measured.
|
From page 16... ...
The reason for such an approach lies in the difficulty in identifying such areas and estimating their contribution, and because of the credible belief that the degree to which pervious areas shed water as overland flow should be related, albeit imperfectly, with the amount of impervious area: where construction and development are more intense and cover progressively greater fractions of the of the literature demonstrates that many different factors can be important, such as changes to flow regime, physical and chemical constituents in the water column, or the physical form of the stream channel itself (Paul and Meyer, 2001)
|
From page 17... ...
This parameter, at least conceptually, captures the hydrologic significance of imperviousness. EIA is the parameter normally used to characterize urban development in hydrologic models.
|
From page 18... ...
have a wide range of potential values for a given position along the urban gradient but are not observed above a maximum possible limit of the biological index. The bottom graph illustrates actual biological responses, using a biotic index developed to show responses to urban impacts plotted against a standardized urban gradient comprising urban land use, road density, and population.
|
From page 19... ...
INTRODUCTION 19 FIGURE 1-3 Example relationships between road density (a surrogate measure of urban development) and common water quality constituents.
|
From page 20... ...
The association between watercourse degradation and landscape alteration in general, and urban development in particular, seems inexorable. The scientific and regulatory challenge of the last three decades has been to decouple this relationship, in some cases to reverse its trend and in others to manage where these impacts are to occur.
|
From page 21... ...
These constituents have direct impacts on aquatic ecosystems and public health, which form the basis of the water quality standards set for these compounds. Sediments can harm fish and macroinvertebrate communities by introducing sorbed contaminants, decreasing available light in streams, and smothering fish eggs.
|
From page 22... ...
However, Table 1-1 can be misleading if it implies that degraded water quality is the primary metric of impairment. In fact, many of the nation's streams, lakes, and estuaries also suffer from fundamental changes in their flow regime and energy inputs, alteration of aquatic habitats, and resulting disruption of biotic interactions that are not easily measured via pollutant concentrations.
|
From page 23... ...
Center for Watershed Protection FIGURE 1-5B A destabilized stream in Vermont. SOURCE: Courtesy of Pete LaFlamme, Vermont Department of Environmental Conservation.
|
From page 24... ...
Recognition of urban stormwater's role in the degradation of the nation's waters is but the latest stage in the history of this byproduct of the human envi
|
From page 25... ...
. These numbers must be considered an underestimate, since the urban runoff category does not include stormwater discharges from municipal separate storm sewer systems (MS4s)
|
From page 26... ...
, property damage from all types of flooding, from flash floods to large river floods, averages $2 billion a year. The chemical effects of stormwater runoff are pervasive and severe throughout the nation's urban waterways, and they can extend far downstream of the urban source.
|
From page 27... ...
WHY IS IT SO HARD TO REDUCE THE IMPACTS OF STORMWATER? "Urban stormwater" is the runoff from a landscape that has been affected in some fashion by human activities, during and immediately after rain.
|
From page 28... ...
of a vegetated landscape to one with roads, houses, and other structures. Although the role of urban stormwater in degrading the nation's waters has been recognized for decades (e.g., Klein, 1979)
|
From page 29... ...
runoff reservoir of tremendous volume is removed from the stormwater runoff system; water that may have lingered in this reservoir for a few days or many weeks, or been returned directly to the atmosphere by evaporation or transpiration by plants, now flows rapidly across the land surface and arrives at the stream channel in short, concentrated bursts of high discharge. This transformation of the hydrologic regime from one where subsurface flow once dominated to one where overland flow now dominates is not simply a readjustment of runoff flow paths, and it does not just result in a modest increase in flow volumes.
|
From page 30... ...
Urban stormwater has resulted in such widespread impacts, both physical and biological, in aquatic systems across the world that this phenomenon has been termed the "Urban Stream Syndrome" (see Figure 1-5; Walsh et al., 2005b)
|
From page 31... ...
Sources and Volumes The "source" of stormwater runoff is dispersed, making collection and cen tralized treatment challenging. To the extent that collection is successful, how ever, the flip side of this condition -- very large volumes -- becomes manifest.
|
From page 32... ...
Wastewater treatment plants manage a similarly broad range of pollutants, but stormwater flows have highly unsteady inflows and, when present, typically much greater volumes to treat. Industrial sources of stormwater pose a particularly challenging problem because potential generators of polluted or toxic runoff are widespread and are regulated under NPDES permitting by their activities, not by the specific category of industrial activity under which they fall.
|
From page 33... ...
Measures of size or complexity, particularly for stream channels, are particularly responsive to the changes in flow regime and discharge. Booth (1990)
|
From page 34... ...
. The CWA defined a list of priority pollutants, of which a subset is regularly measured in many urban streams (e.g., Field and Pitt, 1990)
|
From page 35... ...
As pollution control measures for industrial process wastewater and municipal sewage were implemented and refined during the 1970s and 1980s, more diffuse sources of water pollution have become the predominant causes of water quality impairment, including stormwater runoff. To address the role of stormwater in causing water quality impairments, Congress included Section 402(p)
|
From page 36... ...
Stormwater pollution prevention plans document the stormwater control measures (SCMs; sometimes known as best management practices or BMPs) that will be used to prevent or slow stormwater from quickly reaching nearby waterbodies and degrading their quality.
|
From page 37... ...
Monitoring data are minimal for most permittees, despite the fact that they are often the only indicators of whether an adequate stormwater program is being implemented. At the present time, available monitoring data indicate that many industrial facilities routinely exceed "benchmark values" established by EPA or the states, although it is not clear whether these exceedances provide useful indicators of stormwater pollution prevention plan inadequacies or potential water quality problems.
|
From page 38... ...
Chapter 2 presents the regulatory history of stormwater control in the United States, focusing on relevant portions of the CWA and the regulations that have been created to implement the Act. Federal, state, and local programs for or affecting stormwater management are described and critiqued.
|
From page 39... ...
Journal of the American Water Resources Association 37(2)
|
From page 40... ...
Water Resources Bul letin 23(5)
|
From page 41... ...
1992. Storm Water Management for Industrial Activities, Developing Pollution Prevention Plans and Best Management Practices.
|
From page 42... ...
Journal of the American Water Resources Association 39(1)
|
From page 43... ...
2002. The limitations of mitigation-based stormwater management in the pacific northwest and the potential of a con servation strategy based on low-impact development principles.
|
From page 44... ...
USGS Water Resources Investigations Report 86-4000, 85 pp. Puget Sound Action Team.
|
From page 45... ...
1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban Best Management Practices.
|
From page 46... ...
1989. Changes in urban stream channels in Zimbabwe.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.