This chapter's protection standard is based on the Countywide flood insurance study of Will County, Illinois, and incorporated areas, prepared by the Federal Emergency Management Agency, and dated September 6, 1995, and as modified or amended from time to time. If the 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 IDNR/OWR and FEMA. (Ord. 1630, 4-12-1999)
A. The base flood or 100-year frequency flood elevation for the SFHAs of Hickory Creek and East Marley Creek shall be as delineated on the 100-year flood profiles in the Countywide flood insurance study of Will County, Illinois, and incorporated areas, prepared by the Federal Emergency Management Agency, and dated February 15, 2019, 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 Will County that are within the extraterritorial jurisdiction of the Village or that may be annexed into the Village shall be as delineated on the 100-year flood profiles in the Countywide flood insurance study of Will County, Illinois, and incorporated areas, prepared by the Federal Emergency Management Agency, and dated February 15, 2019, and such amendments or revisions to such study and maps as may be prepared from time to time. (Ord. 2019-O-002, 1-28-2019)
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 of Will County, Illinois, and incorporated areas, prepared by the Federal Emergency Management Agency, and dated September 6, 1995. (Ord. 1630, 4-12-1999)
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 of Will County, Illinois, and incorporated areas, prepared by the Federal Emergency Management Agency, and dated February 15, 2019, shall be according to the best existing data available in the Illinois State Water Survey Floodplain 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 backwater 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 IDNR/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. (Ord. 2019-O-002, 1-28-2019)
E. For an unmapped extended SFHA (with drainage area less than 1 square mile) which has been identified by the Building and Zoning Administrator pursuant to subsection 11-1-3A of this chapter, the base flood elevation shall be determined by the applicant utilizing a method as approved in this section with concurrence of the IDNR/OWR or Village Engineer. (Ord. 1630, 4-12-1999)