This chapter's protection standard is based on August 19, 2008, Cook County FIS prepared by FEMA.
If a base flood elevation or 100-year frequency flood elevation is not available for a particular site, then the protection standard shall be according to the best existing data available in the Illinois state water survey's floodplain information repository or from federal, state, or other sources.
When a party disagrees with the best available data, they shall submit a detailed engineering study needed to replace existing data with better data and submit it to IDNR/OWR and FEMA for review and consideration prior to any development of the site.
A. The base flood or 100-year frequency flood elevation for the SFHAs of the Des Plaines River, Prairie Creek, Farmers Creek, Willow Creek, Weller Creek, Higgins Creek, and Feehanville Ditch shall be as delineated on the 100-year flood profiles in the countywide flood insurance study of Cook County prepared by FEMA dated August 19, 2008, and such amendments to such study and maps as may be prepared from time to time.
B. The base flood or 100-year frequency flood elevation for the SFHAs of those parts of unincorporated Cook County that are within the one and one-half (11/2) mile extraterritorial jurisdiction of the city of Des Plaines or that may be annexed into the city of Des Plaines shall be as delineated on the 100-year flood profiles in the countywide flood insurance study of Cook County prepared by FEMA and dated August 19, 2008, and such amendments or revisions to such study and maps may be prepared from time to time.
C. The base flood or 100-year frequency flood elevation for each SFHA delineated as an AH zone or an AO zone shall be that elevation (or depth) delineated on the flood insurance rate map of the city.
D. The base flood or 100-year frequency flood elevation for each of the remaining SFHAs delineated as an A zone on the flood insurance rate map of the city shall be according to the best existing data available in the Illinois state water survey's floodplain information repository. The 100-year frequency flood event is that event which has a one percent (1%) statistical chance of occurring in any given year. When no base flood or 100-year frequency flood elevation data is available for a riverine SFHA, the 100-year frequency elevation shall be determined using hydrologic and hydraulic calculations as appropriate for the analysis circumstance that have been approved by FEMA or those models commonly used in this geographic area such as HEC-RAS, HEC-HMS, SWMM, TR-20, and Hydroflow. Flood flows should be based on anticipated future land use conditions in the watershed as determined from adopted local and regional land use plans. Along any watercourses draining more than one square mile, the above analyses shall be submitted to OWR for approval, once approved it must be submitted to the Illinois state water survey floodplain information repository for filing. For a nonriverine SFHA, the base flood elevation shall be the historic flood of record plus three feet (3'), unless calculated by a detailed engineering study and approved by the Illinois state water survey.
E. Prior to issuing a development permit the community development director or his designee shall determine the location of the subject property with respect to flood zones using the best information available. (Ord. M-15-16, 6-6-2016)