SCOTT AIR FORCE BASE, Ill. -- Base and community leaders, along with representatives from the U.S. Army Corps of Engineers and the U.S. Geological Survey met on Oct. 7 to discuss regional storm water management and the impact of the Aug. 12 flash floods to the base and the surrounding communities.
Storm water management is an ongoing initiative under Scott Air Force Base’s Community Partnership Public-Public, Public-Private, or P4, Program. Base subject matter experts with the 375th Civil Engineer Squadron and federal agencies such as the U.S. Fish and Wildlife meet regularly with leaders in the industry, as well as local officials, to identify opportunities to improve water flow and mitigate flood risks throughout the region.
“Scott is not immune to flooding,” said Joe Weber, 375th CES’s Water Quality Program Manager. “We have several flood prone areas due to the natural geography of the base. There are communities near us and south of us who also have areas that flood during heavy rains.
“It’s important for all of us to come together to talk about this issue and having a Storm Water Management Working Group under the base’s P4 Program allows us to do that,” said Weber.
On Aug. 12, 5.9” of rain fell on Scott AFB in six hours causing an estimate $3.26 million damage to facilities as well as government property. More rain fell during this August flash flood than the previous significant rain event, which was in April 2013. In 2013, 4.5” of rain fell throughout the day on base.
“There isn’t an easy fix to prevent flooding,” said Weber. “We made some improvements from the April 2013 base flood to this year’s in August. We built a detention basin over by the dormitories and we fixed the drainage lines around Ward Drive. These actions helped to lessen the damage.”
Heartlands Conservancy, a non-profit organization that works with land owners and community leaders to protect and preserve natural and cultural resources, is a member of the Storm Water Management Working Group. In 2018, they completed the Lower Silver Creek Watershed Plan. Scott AFB sits within this watershed, which has 454 miles of streams that drains about 126,000 acres of land. The Lower Silver Creek Watershed Plan identified several factors that contribute to regional flooding.
Mary Vandevord, CEO of Heartlands Conservancy, said, “Storm water management is complicated. There are many elements that cause flooding, but two of them are logjams and sediment build up from soil erosion of streams and agricultural lands.
“It’s a repeating cycle of events,” said Vandevord. “Floods weaken the root systems of large trees like oaks. Then, the oaks die and create logjams. The logjams create soil erosion, which leads to an excessive accumulation of sediment in drainage ditches, for example, impeding the natural flow of water. Unable to flow, the water becomes stagnant, kills trees, creates more logjams and the cycle begins again.”
The U.S. Geological Survey – Central Midwest Water Science Center has collected data from the August rains as an initial step in collating data from Silver Creek streamgage locations to pursue a regional-scale watershed analysis. This watershed analysis will incorporate current and projected land-use change in nine smaller sub-watersheds, representing communities proximal to Scott AFB that provides an evaluation of ‘cause and effect’ storm water management practices to enhance integration.
Based upon the results of the watershed analysis, the USGS-CMWSC proposes to conduct detailed hydraulic and storm water analysis within the installation at Scott AFB. Analysis by the USGS will allow managers to identify problem areas for retrofit in existing storm water infrastructure, areas for accommodating storage, and a roadmap for regulatory flood insurance compliance and future development given our changing climate and resulting precipitation.
Paul Rydlund, Surface Water Hydraulics and Modeling Section Chief for USGS-CMWSC said, “Storm water management is about developing resiliency within the watershed, where the management thereof transcends jurisdictional boundaries.
“Although periodic heavy rains are of significant concern, the design of current storm water infrastructure, future development practices and allowances for adequate storage are just as crucial,” said Rydlund. “Design storms and frequency estimates that define regulatory flows change over time, requiring an evaluation of future hydrology based on changing climatic conditions as well as land use. The 100-year flood estimate today could be much more significant in terms of impact in the future.”
Combined with the 2018 Lower Silver Creek Watershed Plan, the Storm Water Management Working Group intends to use the data collected by the U.S. Geological Survey to better understand the region’s storm water capacity. The working group is also researching resources to fund projects to clear the logjams and clean up the buildup of sediment.
“Through the Storm Water Management Working Group, the base, community leaders, and subject matter experts are coming together to tackle this regional issue,” said Weber.
The Lower Silver Creek Watershed Plan is available to the public on Heartlands Conservancy’s on line library at www.heartlandsconservancy.org.