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SEMI' BY:DPRA SS.Paul, MN ; 4-12-33 i 9:33AM 612 227 5522 CplEMR 4 ARNOLD, JR. AND C. JAM IBBONS 1 , 612 407 4191t# 9 Existing levels bated on satellite land cm r Paomt Impervious Om 14.9°.6 Q Local Basins 9356 tc 29.9% CJ Open Watts ® Greater than 3056 FIGURE 4. Impervious coverage analysis fur Old Saybrook, CT terms of impervious cover —and by inference, the health of their local water resources. The results of the impervious surface analysis can be used to help guide planning emphasis within each local basin area. For areas in the lower impervious zone, emphasis should be placed on preventive mea- sures that retain existing natural syscems, using tech- niques like open space planning and stream buffers. For areas that are in, or will be in, the `impacted" (10- 30%) zone, preventive planning should be accompa- nied by a focus on site design considerations that reduce runoff and imperviousness. Finally, for areas at (or climbing into) the "degraded" (over 30%) zone, the focus shifts ro remediation, through pollutant miriga- rion and resource restoration. NEMO is one example of the use of impervi- ousness for broad -based community or regional water resource planning. Similar approaches are beginning to spring up around the country. Schueler (1994a) rcc- ommends watershed -based zoning chat "is based on the premise chat impervious cover is a superior mea- sure to gauge the impacts of growth, compared to population density, dwelling units or other facmrs," In Alpine Township, Michigan, conccrn about the ef- fects of urbanization on a formerly pcoduccive cold. 250 APAIOUMAL-SPRING 1996 Prolectod k%vis beoW =zee g build -out analysis 1 a t Nfilc. water trout fishery has prompted researchers fn„, Grand Valley State Universiry to design a wacerslm,l based GIS decision support system for local land.,,.. authorities (Frye and Denning 1995). The xyst, 1,: makes use of a number of ihydrulogic and land -use L,- tors, including impervious surface estimates and , ing-based build-oucanalyses. In Montgomery Count, Maryland, a derailed planning study was done co 1„t mulate a land -use strategy to protect the wares t, sources of chc Paint Branch stream (Montgonw. County MD 1995). The study both measures and pi,,t ects future impervious surface coverage by subwm, t shed basin, and uses this information cc help guide- i t . recommendations for protective actions. Each of these efforts contains the elements of im pervious cover, subbasin-level analysis, and build -„tit projections. An even more comprehensive ctearmcm r chat undertaken by the City of Olympia, Washingi, m During 1993 and 1994, Olympia conducted their last pervious Surface Reduction Study (ISRS), from whi. I, information is cited repeatedly in this paper. The 1SI4:. Final Report (Gry of Olympia 1995) contains an in, pressive and comprehensive body of research, poll„ analysis, and build -out scenarios, culminating in P- specific acrion recommendadons. The study mncludr•.