[Storm Water Management]

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CHAPTER 1: INTRODUCTION

Once solely a local government function, urban stormwater management is beginning to attract the attention of state water resources policy makers. In this article, we use data from two recent national surveys of state and local officials to demonstrate that the states do have a role to play in stormwater management for flood hazard mitigation and that state intervention can be effective. In addition, by describing and comparing stormwater management programs adopted by three pioneering states, we offer some guidance to other states that want to initiate their own stormwater programs.

Stormwater management describes measures used by property owners and local governments to limit the amount of stormwater runoff from urban development and to control the path of runoff through space and time. Traditionally, curbs, gutters, and underground pipes have been provided to remove storm water from developed property as quickly as possible to minimize the possibility of localized flooding. That approach has come under attack, however, because while avoiding flooding in a single subdivision, it sometimes shifts flooding downstream by increasing total flows, peak flows, and velocities in downstream channels (Urban Land Institute, et al., 1975). Hence, it is not surprising that in a recent survey of metropolitan counties (Platt, 1985) urban drainage overflow outranked rivcrine flooding (54 percent to 4 percent of the counties reporting) in the amount of property damage caused over the past ten years.

As the failures of traditional approaches have become better understood, recommended objectives and approaches to stormwater management have expanded to include the mitigation of downstream flooding by maintaining natural predevelopment runoff characteristics from developed sites and reserving the natural channels for what were once the "natural" amounts of stormwater runoff (Sheaffer, et a!., 1982; Whipple, et a!., 1983). Techniques for doing that indude measures to preserve the ability of rain water to infiltrate the soil (limitations on impervious surfaces such as driveways and streets, for example) and temporary stormwater storage in streets and parking lots, behind road fills, and in ponds located both on and off the site.

The newer view of stormwater management also recommends that localities undertake comprehensive drainage planning for entire watersheds. Such plans provide a means of identifying and justifying the acquisition of needed storm drainage easements, assigning responsibility for building and maintaining storm drainage infrastructure, and determining regulations needed to control various aspects of watershed development, such as the density of development, amount of impervious surfaces, setbacks from streams, site design, and engineering and construction practices (Sheaffer, et a!., 1983). Finaily, stormwater management is also beginning to ...