08/30/2000 Env Bd Packet - Laserfiche WebLink

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Dakota County Soil and Water Conservation District Fact Sheet Environmental Impacts of Urban Development Urban development causes an overall imbalanr•e in the hydrology of a watershed. As sidewalks, roads, parking lots, rooftops, and other hard surfaces that inhibit water from infiltrating into the ground are constructed, more water runs off the land and less water is incorporated into groundwater. During storms, the rainwater flows off impervious areas very quickly into stormsewers that often discharge directly into natural streams, wetlands, and lakes. Decreased flow during dry weather periods and increased flow during storms have an adverse impact on local surface waters. What is Low Impact Development? Low impact development (LID) integrates ecological and environmental considerations into all phases of urban planning, design, and construction. The goal of low impact development is to eliminate or minimize the impacts of urbanization on the natural water processes occurring within the watershed. Components of Low Impact Development I. Urban Planning: Integration of the soil, biological, and hydrological characteristics are considered while designing the site so that environmentally fragile areas (steep slopes, wetlands, natural depressions, aquifer source areas ) are not developed or encroached II. Decreasing Runoff Volume: The goal of LID is to decrease runoff volumes by increasing runoff infiltration and maximizing evapotranspiration (evaporation and uptake of water by plants). Use of water permeable materials for sidewalks and parking areas, reduction of sidewalk and street widths in low traffic areas, reductions in building setbacks from roads to reduce driveway lengths, routing water from rooftops and driveways to lawns, and eliminating conventional curbs and storm- drains on streets will all decrease overall runoff volumes III. Promoting Natural Processes: Inclusion of wetlands, grassed swales, natural vegetation, detention ponds, bioretention and infiltration devices are all effective in reducing runoff volumes and increasing infiltration. Bioretention practices are designed to mimic naturally vegetated areas that naturally control hydrology through infiltration and evapotranspiration. Bioretention is well suited for -residential lots. Dry wells, or infiltration basins, are small excavated areas backfilled with stone and are used to control rooftop or pavement runoff. The use of open vegetated watercourses and swales are more desirable than storm drain systems because of their ability to slow water movement and decrease runoff volumes. Regional detention basins can also help alleviate peak runoff volumes. The. Dakota SWCD is committed to working with land owners, developers, and local units of government to promote LID concepts in Dakota County. In addition to technical assistance, financial incentives may be available to qualified projects. Contact our office for more information. Roof Grains to Parking Lot Sturm Saar (Typindi Comm., l Lot Mice Hat f Paved f+ \Pardee `av •.nra Conventional Development Landscape „ Area (N chi ` _. MUM r' J +1 +,. ,, r l iiMa \ • N Sidawotit ∎ Z �Ziiparpgr N )t..1 ` • Street l Mono saver We t .Cstarm Germ Gullet ".• Nanttote tit Low Impact Development Noe: Unlined= cd Nam sem spawn and Ineteasel seals wow Manse ttis to taw 3. Graphic modified from Texas Nonpoint SourseBOOK web page DAKOTA COUNTY SOIL 8 WATER CONSERVATION DISTRICT Dakota County Extension and Conservation Center 4100 220th Street West, Suite 102 Farmington, MN 55024 Phone: (651) 480 -7777 Fax: (651) 480 -7775 Primary Coptact Jay Riggs, Urban Conservationist (651) 480-7779 jay.riggs@co.dakota.mn.us