2009 - Illinois DNR - State of Illinois

STRUCTURE MODIFICATIONSThe implementation of any non-structural flood mitigation measures to reduce flooddamages in Farmers or Prairie Creek floodplain must be considered on a building bybuilding basis. Implementation of any of these measures would require the approval andparticipation of each individual property owner of a floodprone building, and would notreduce flood discharges through the watershed. This section is intended to address thegeneral feasibility of structure modifications to reduce flood damages.The success of most of these non-structural flood mitigation measures depends on thestructural condition of the building, local soil types, and the depth and speed at whichflooding occurs. Therefore, implementation of any such non-structural mitigationmeasures should be done in consultation with an engineer who is knowledgeable in theseareas. Additional information on non-structural mitigation can be obtained from theIllinois Department of Natural Resources, Office of Water Resources and/or the USArmy Corps of Engineers.Acquisition/DemolitionAcquisition and demolitions (also known as buy-outs) include removing the impactedstructures and converting the property into public open space that can flood withoutadverse consequences. This approach is often used for buildings that are difficult torelocate, buildings located in the 10-year floodplain, and buildings that are located alongthe stream channel and/or in the stream floodway where flooding is frequent and/orlikely to cause substantial damage (more than 50% of the structure value) to the building.Eleven structures within the Farmers and Prairie Creek floodplain are impacted by the10-year frequency flood event. Of these structures, 5 are detached garages, 5 arecondominiums and one is a single family residence. None of the 11 structures located inthe 10-year floodplain suffer average annual damages that are estimated to exceed 50%of the value of the structure.Removal of buildings from the floodway may also improve floodway conveyancethrough a community and reduce flood profile elevations. Demolition of all structures(17 buildings) in the Prairie Creek Floodway within 150 feet of the south bank of thechannel, between Rancho Lane and the Lutheran General Hospital pond, lowers floodelevations in that reach up to 0.16 feet. When multiple adjacent structures are acquired,demolished and the land converted to open space uses such as greenways or parks, a128