ENVIRONMENTAL PROFILE | CHAPTER 3


Table 3.3 Subwatershed analy sis of imper v ious cover Subwatershed Name


Black Hawk Park-Cedar River (North) Black Hawk Park-Cedar River (South) Dry Run Creek (SUB-1A) Dry Run Creek (SUB-1B) Dry Run Creek (SUB-2) Dry Run Creek (SUB-3) Dry Run Creek (SUB-4) Dry Run Creek (SUB-5) Dry Run Creek (SUB-6) Dry Run Creek (SUB-7) Dry Run Creek (SUB-8) Dry Run Creek (SUB-9)


Hammers Creek-Beaver Creek Prescotts Creek-Black Hawk Creek Waterloo Municipal Airport Totals


Dry Run Creek (all subwatersheds)


Subwatershed Size (ac) within Project Area


4,627.3 3,055.5 1,323.3 972.4


1,761.0 551.7 615.6 655.1


2,076.5 1,094.6 1,666.4 368.3


1,329.1 2,748.2 58.1


22,903.2 11,084.9


Impervious cover (ac) 545.6


878.9 814.9 308.0 603.9 264.2 241.8 54.3 95.0 15.5


300.2 0.5 6.9


530.7 6.6


4,666.9 2,698.2


Watersheds can be defined and assessed at a variety of scales. For example, the Mis- sissippi River watershed and the watershed of a small headwater stream are quite different in scale and issues. For the purposes of this comprehensive plan, 15 sub- watersheds were delineated within the Cedar Falls planning area based on USGS hydrologic units and City-provided subwatersheds for Dry Run Creek (Figure 3.4):


• Black Hawk Park-Cedar River (divided into 2 subwatersheds, north and south of the River) • Dry Run Creek (consisting of 10 subwatersheds) • Hammers Creek-Beaver Creek subwatershed • Prescotts Creek-Black Hawk Creek subwatershed • Waterloo Municipal Airport subwatershed


Due to variations in soils, topography, hydrology and land use throughout the proj- ect area, there is considerable variation among these 15 subwatersheds. All these factors affect surface water runoff, which in turn influences water quality. Using im- pervious cover mapping (available within the City limits only), subwatersheds with- in the planning area were analyzed for their impervious cover (Table 3.3). Note that available data do not differentiate between directly connected impervious cover (i.e., contiguous to a receiving water via a conveyance system) and disconnected ones (e.g., isolated or draining to pervious areas).


Studies have found that beginning at 8-12 percent connected impervious cover (CIC), small increases in the urban area produce dramatic changes in stream insects


59


Impervious Cover 12%


29% 62% 32% 34% 48% 39% 8% 5% 1%


18% 0% 1%


19% 11% 20% 24%


Impervious Cover Category medium


high high high high high high low low low


medium low low


medium medium


high


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