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Flood Hazard Mitigation Appropriate for: Modifications to farming practices are most effective on steeper slopes where the most runoff and erosion occurs. Preserving storage areas is most effective in flat areas with natural depressions. Problems: Modified farming practices must be implemented by owners of propeny far from the flood problem, usually at their expense. For more information: Soil and Water Conservation Districts and their Natural Resources Conservation Service staff have both the expertise in watershed measures and the contacts with watershed landowners. Figure 2-3 Preserving Storage in the Butterfield Creek watershed Flood Storage Enhancement Opportunilies mn. Nilh.....l flood SIOllg./W,U4It'llh RUIOlalrion rLLf1 Compl... @9 ~j- Weiland I Flood SIorege 51"""" Source: A Vision for Butterfield Creek, Butterfield Creek Steering Committee, p. 9 A study of the Butterfield Creek watershed in southern Cook Cou nty showed that while 50% of the watershed had been developed, the flat up- land undeveloped portion contained natural ponding areas that stored over 1700 acre-feet of water during a 100-year rain, If these areas were to be developed, the 100-year flood discharge of Butterfield Creek would increase by as much as 100% in some locations. Accordingly, the communities in the Butterfield Creek water- shed are purchasi ng and otherwise reserving these areas so they won't be developed. 2.1.8 Soil erosion and sediment control Floodplain regulations control major development projects in floodplains to preserve the carrying capacity of the channel and the floodplain. However, sedimentation can obstruct channels and is often caused by erosion from outside the floodplain. As rain hits the ground, especially where there is bare dirt, as on farm fields and construction sites, soil is picked up and washed downstream. Sediment tends to settle where the river slows down and will gradually fill in the channel.