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SENT BY:DPRA St.Paul, MN t-12-99 i 3:30AM ; 612 22V -522- 612 407 4131;# 2 i Planners concerned with wear co- source procecdon in urbanbing areas must deal -ich the advent Impacts of polluted runoff. impervious surface coverage is a quantifiable land -use in- dicator that comeintes closely with those impacts. Once the role and dis. tribudon of impervious coverage are understood, a udde range of strategies to mduca impervious surfatea.and „- t6ek impacts m water msoun pn be applied as community planning, site -level planning and design, and land use regulation. Those stmcesies rFhimmplemenc manly Current trends In planning, mning, and landscape do, ylgs: that go beyond water pollution 'ryr,.+:•:mntestec ea. address the quality of Gfe }"+ in a community. s... . rr•.7.;:,-Arnold is a Wamt Quality Educator, and Gibbons a Natural Resource Plan- .ning Eduatsar, at rht University of C,,nt d ut Cooperative Extension System. They am correctly principals .... is the NEMo Preleer, which uses geo- graphic infcnnation syso-m technol- ogy to educate munioipol land -use Tt+i, deaslon-maloets about nonpoint .source water pollution. , foomil of he Amorie0n Planning . A,,60a0. W I. 62, No, 2, Spring 1996. -American Pl• ning . 'Nsouatian, Chicago, IL. Impervious Surface Coverage The Emergence of a Key Environmental Indicator Chester L. Arnold, Jr. and C. James Gibbons mpervious land cover has long been characteristic of urban areas, but has only recently emerged as an environmental indicator. Natural re- source planning using impervious surface coverage as a framework can be a pragmatic and effecrive way of addressing a host of complex urban environmental issues, particularly those related co die health of water re- sources. Water resource protection at the local level is getting more compli- cated, largely due cc the recognition of nonpoint source pollution, or pol- luted runoff, as a major problem. This diffuse form of pollution, now the nation's leading threat to water quality (Environmental Protection Agency 1994), is derived from contaminants washed off the surface of the land by stormwater runoff, and carried either directly or indirectly into waterways or groundwater. As programs directed at nonpoint source con- trol cascade down from federal to $race to local governments, the techni- cal complexities involved wirh such control are further complicated by regulatory and management considerations. Scormwater runoff problems are nothing new to local land -use decision -makers. However, the principal concern about runoff has always been safety, with the focus on directing and draining water off of paved surfaces as quickly and efficiently as possible. Once off the road and out of sight, stormwater has been largely out of mind —downstream conse- quences be damned (or dammed). Regulations have been expanded in re- cent years to include consideration of flooding and erosion, yet these factors fall far short of a comprehensive and effective approach ca midgat- ing the water quality impacts of development. How do planners and ocher local officials get a handle on protecting their local water resources? While no magic bullet exists to simplify all the complexities involved, an indicator is emerging from the scientific literature, that appears to have all the earmarks of a useful tool for local planners —the amount of impervious, or impenetrable, surface. This ar- ticle reviews the scientific underpinning, usefulness, and practical appli- APAJODUNAL•SPYLENG 1996 243