CEDAR FALLS COMPREHENSIVE PLAN


TMDL goal established for Dry Run Creek was to have less than 10 percent of each subwatershed in connected impervious cover (CIC). Achieving this goal would low- er flow rates as well as associated erosion and sedimentation. The TMDL report es- timated it will take 5-10 years to implement BMPs to achieve this goal, and 10 years thereafter for the biological community to recover. Five BMPs were specified: green roofs, cisterns, permeable pavement, bioretention, and dry swales. These reduced runoff volume by 40-80 percent, depending on type and situation.


In 2008, the University of Northern Iowa conducted a survey of residents within the Dry Run Creek watershed (University of Northern Iowa, 2008). In brief, the study found that nearly 38 percent of watershed residents agree that water quality in Dry Run Creek is declining, largely due to fertilizers and runoff from paved surfaces and new construction and development sites. However, at least half of landowners are not certain that water quality is actually declining in the creek. Seventy-five percent of residents agree that runoff from paved surfaces is a significant cause of pollution, but about a quarter of landowners don’t believe that rural and urban land use af- fects the water quality of Dry Run Creek. These survey results underscore the oppor- tunity to inform the public about water quality issues, causes, and solutions.


Black Hawk Creek


Several tributaries of Black Hawk Creek flow east and southeast in the southeast por- tion of the planning area. The creek’s mainstem touches the planning area’s south- east corner (Figure 3.3). A 2010 draft impaired waters document (IADNR 2011) lists Black Hawk Creek as impaired in the planning area. The impaired uses are “aquatic life” and “primary contact recreation” due to low biotic integrity and elevated bacte- ria levels. In 2006 a TMDL study was completed and approved to address these im- pairments. The issues and solutions in Black Hawk Creek are similar to those in Dry Run Creek, but significant improvement in the mainstem itself requires collabora- tion with upstream communities.


Protecting and enhancing surface waters can be accomplished with watershed planning and effective stormwater management. Watersheds are the catchments that feed and sustain our surface water resources. Understanding watersheds is critical to managing rivers, streams, wetlands, and other surface waters in Cedar Falls. In the last two decades, significant advances have been made in stormwater BMPs, which are practical tools for improving stormwater runoff quality and flow regulation. Sustainable stormwater management entails the use of nature-based elements (e.g., vegetated swales, infiltration basins, treatment wetlands), often in a treatment sequence, or train, to effectively treat targeted pollutants. This storm- water treatment train approach can be customized for any area and designed at different scales, from an individual site to an entire watershed. Their goal too is to reduce costs by capturing, treating, and conveying smaller amounts of runoff near its source. Low impact development (LID) practices can be used during land devel- opment to protect surface waters. If Iowa continues to experience climate trends as predicted (including more extreme events, both storms and droughts), ecological- ly-designed stormwater management systems will be even more important in miti- gating adverse impacts to Cedar Falls’ natural and built environment.


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