This chapter's protection standard is based on the countywide flood insurance study for Cook County. 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. When a party disagrees with the best available data, he/she may finance the detailed engineering study needed to replace existing data with better data and submit it to DWR and FEMA. (Ord. 0-00-27, 10-16-2000, eff. 10-26-2000)
A. The base flood or 100-year frequency flood elevation for the SFHAs of McDonald Creek and its tributaries and the Des Plaines River shall be as delineated on the 100-year flood profiles in the flood insurance study of Cook County prepared by FEMA dated August 19, 2008, and such amendments to the 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 extraterritorial jurisdiction of the city or that may be annexed into the city shall be as delineated on the 100-year flood profiles in the flood insurance study of Cook County prepared by FEMA and dated August 19, 2008, and such amendments or revisions to such study and maps as may be prepared from time to time. (Ord. 0-08-27, 7-8-2008, eff. 7-19-2008)
C. The base flood or 100-year frequency flood elevation for each SFHA delineated as an "AH zone" or "AO zone" shall be that elevation (or depth) delineated on the countywide flood insurance study for Cook County prepared by the federal emergency management agency and dated November 6, 2000, and such amendments to such study and maps as may be prepared from time to time.
D. The base flood or 100-year frequency flood elevation for each of the remaining SFHAs delineated as an "A zone" on the countywide flood insurance study for Cook County prepared by the federal emergency management agency and dated November 6, 2000, shall be according to the best existing data available in the Illinois state water survey flood plain information repository.
When no base flood or 100-year frequency flood elevation exists, the base flood or 100-year frequency flood elevation for a riverine SFHA shall be determined from a back water model, such as HEC-II, WSP-2, or a dynamic model such as HIP. The flood flows used in the hydraulic models shall be obtained from a hydrologic model, such as HEC-I, TR-20, or HIP, or by techniques presented in various publications prepared by the United States geological survey for estimating peak flood discharges. 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 analysis shall be submitted to DWR for approval, once approved it must be submitted to the Illinois state water survey flood plain information repository for filing. For a nonrivering SFHA, the base flood elevation shall be historic flood of record plus three feet (3') unless calculated by a detailed engineering study and approved by the Illinois state water survey. (Ord. 0-00-27, 10-16-2000, eff. 10-26-2000)