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CEDAR FALLS COMPREHENSIVE PLAN


FUTURE STORMWATER Future development, existing water body impairments, and ambitious conservation goals necessitate more effective and sustainable stormwater management in Ce- dar Falls. Opportunities for improved stormwater management should be sought in new developments and existing facilities. Surface water impairments in the region suggest that emphasis should be placed on reducing sediment in the streams. A va- riety of approaches are available to reduce erosion and sedimentation.


It is highly recommended that the Iowa Department of Natural Resources’ current Soil and Water Assessment Tool (SWAT) be used to model future land planning con- siderations. SWAT estimates sediment and pollutant loadings given land use, soils, slope, and historic weather conditions. By considering the downstream water qual- ity impacts of land use decisions during the planning stage, more holistic stormwa- ter management measures will be taken that promote economic, social and envi- ronmental sustainability.


In conjunction with the SWAT analysis, the stormwater management system should be considered from a comprehensive perspective. Grey, green and blue stormwater conveyance systems work in conjunction by watershed, not by neighborhood, sub- division, business, or other land use. Hence, the use of natural hydrologic features should be promoted over that of highly modified stormwater systems. Furthermore, any opportunities to retrofit existing man-made systems with natural ones should be capitalized upon.


NEW DEVELOPMENT


New development presents a unique opportunity to maintain, and even improve, the City’s stormwater management system and water resources. The Iowa Storm- water Management Manual (ISMM) illustrates many best management practices (BMPs) tailored to Iowa’s soils and climate. The most effective BMPs for reducing runoff volume and velocity as well as promoting water quality should be selected and designed appropriately for each development site. Existing impairments of Ce- dar Falls’ surface waters throughout the planning area underscore the importance of effective stormwater management. The completed TMDL (Total Maximum Dai- ly Load) studies and identified target pollutants (e.g., suspended solids) should be used in the selection and design of BMPs.


A proven technology for stormwater management in new development is a storm- water treatment train. This approach would therefore be applicable for the west- ern growth area as detailed in Chapter 9. This is a series of naturalized stormwater management elements, such as rain gardens, vegetated swales, infiltration basins and treatment wetlands. These are integrated into a development’s design, provid- ing effective, sustainable stormwater management while also creating wildlife habi- tat, places for trails and nature education, and open space for the local community. Stormwater treatment trains are customized for each site’s soils, runoff volume and rate, and target pollutants. This type of approach directly addresses impaired wa- ters and can greatly accelerate their de-listing. Proper construction and perpetual management of BMPs is needed to ensure that performance levels are maintained in the long run. This is accomplished in different ways. Home-owner associations can be made responsible for long term operations under covenants enforced by the


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