R2008-87 AUTHORIZING AGREEMENT - Laserfiche WebLink

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Top Issues and Concerns in the Big and Long Creek Watershed ...as identified by the Planning Committee. • Soil Erosion and Sedimentation � Stormwater and Water Quality Management • Education and Outreach • Wildlife Technical Advisory Committee Following the identification of the top issues and concerns in the Watershed,a technical advisory committee composed of professionals from several resource agencies was formed to provided insight and expertise to the committee's concerns. The combined efforts of the following individuals have made this document possible: City of Decatur Keith Alexander Illinois Department of Natural Resources Carl Handel Macon County Soil and Water Conservation District Shannon Allen,Tim McMahon USDA Natural Resources Conservation Service Annette Holmes, Justin Massie,Jeff Hyett, Karen Brinkman, Roger Windhorn, Paul Krone, Sharon Santure Illinois State Water Survey Laura Keefer Resources Problem: Soil Erosion and Sedimentation Goal: Reduce the total amount of erosion occurring in Big and Long Creek watershed and as a result reduce the amount of sediment deposited in Lake Decatur. Action: Identify the types of erosion occurring and inventory the extent they are contributing to Lake Decatur and Big and Long Creeks. Action: Recommend alternatives to address the types of erosion present. Findings: • Erosion is occurring from three distinct areas: streambank, cropland,and urban sites under construction. • Annually, the average total sediment load delivered from all land uses to Lake Decatur is 47,250 to 49,500 tons. (See separate text box, page 14 ) • National estimates indicate that uncontrolled erosion from construction activities can generate enormous quantities of sediment ranging from 20 to 200 tons per acre per year. Figure 1 shows the high sediment loads produced by areas under development as compared to other land uses. • Average annual erosion rates from cropland in Big and Long Creek watersheds range from 1 to 15 tons per acre. • The total sediment load delivered to Lake Decatur comes from four types of erosion. The distribution of how much each contributes to the total is as follows: roughly 50%from sheet and rill erosion, 36% from ephemeral erosion, 3% gully erosion, and 11% streambank erosion. The sheet and rill sediment is coming from the watershed of 32,800 acres while the other three types of erosion are coming from concentrated areas. 5