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HomeMy WebLinkAboutFEMA Flood Insurance Rate Map Errors Commission Memorandum REPORT TO: Honorable Mayor and City Commission FROM: Brian Heaston, Project Engineer Debbie Arkell, Director of Public Services SUBJECT: FYI – FEMA Flood Insurance Rate Map (FIRM) Errors MEETING DATE: May 7, 2012 AGENDA ITEM TYPE: Special Presentation RECOMMENDATION: Consider the materials presented by Staff BACKGROUND: As the Commission may recall, the City’s Flood Insurance Study (FIS) and Flood Insurance Rate Maps (FIRMs) were recently revised by the Federal Emergency Management Agency (FEMA). The new FIS/FIRMs have an effective date of 9/2/2011 and replace the 7/15/1988 FIS/FIRMs in their entirety. The update occurred under FEMA’s Map Modernization program which aims to reduce the reliance on paper map products by implementing new digital map products. This is more commonly referred to as a dFIRM Update (digital flood insurance rate map update). FIRMs depict special flood hazard areas (SFHAs) established by hydraulic modeling and hydrologic study. The hydrologic study generally defines the magnitude of flood flows. The hydraulic modeling characterizes the general behavior of these flood flows by determining the base flood elevation (BFE) at any given point within the model. The FIS documents the means and methods employed in the hydrologic and hydraulic analyses including model outputs and summary tables. The BFEs, coupled with planimetric information (i.e. roads, streams, crossings, buildings, etc.) and topography, are used to delineate SFHAs upon the FIRMs. The FIS and FIRMs, although integral to one another, are separately utilized for land-use and flood insurance rating purposes. The city restricts land-uses in proximity to water courses with defined BFEs due to the health and safety hazard that flooding presents. The BFE is the regulatory device, as it is employed to delineate a building setback line where the ground contour coincides with it and is used to establish lowest-floor-level elevation relative to the BFE for new construction. Insurance companies use FIRMs to establish the flood risk of a property in order to determine the proper risk rating for policy premium purposes. Property owners of buildings located in SFHAs with a federally secured mortgage are required by federal law to carry a flood insurance policy. Owners of buildings outside of SFHAs may voluntarily purchase a flood insurance policy, or they may be required by their mortgage lender to obtain one as a condition of loan approval. 94 The City’s recent dFIRM update incorporated a new hydraulic model, and resulting BFEs, for the East Gallatin River, Rocky Creek and Bridger Creek. The model was prepared for the State Department of Natural Resources and Conservation (DNRC) by the firm of Anderson Engineering. Hydrologic data (i.e. flood flow magnitude) from the 1988 FIS was maintained in the new hydraulic model. SFHAs shown on the 9/2/2011 FIRMs for these water courses were revised accordingly to reflect the new BFEs. Significant changes to the mapped SFHAs present themselves through comparison of the old 7/14/1988 FIRMs and the new 9/2/2011 FIRMs. The dFIRM update did not revise the hydrologic analyses, or the hydraulic model, for Bozeman Creek, its tributaries (Mathew-Bird Creek, Nash-Spring Creek, Figgins Creek, and Flat Creek) and diversion (Mill Ditch). All that occurred with the recent dFIRM Update for these water courses was a conversion of the 7/15/1988 SFHAs to a digital Geographic Information System (GIS) format. The SFHAs mapped on the 7/15/1988 FIRMs are identical to the SFHAs mapped on the 9/2/2011 FIRMs for Bozeman Creek, its tributaries and diversion. GIS is a powerful mapping and visualization tool that gives the ability to easily determine mapped SFHAs to a high level of resolution using computer software. A similar order of resolution is simply impossible given paper FIRMs produced at a scale of 1”=500’. Given that SFHAs can easily be resolved using GIS at a small scale - such as that of single-family home for instance - the spatial accuracy of a water course and thus its corresponding SFHAs becomes extremely critical. Unfortunately, the conversion to GIS format exposed a spatial mapping error in the water course locations and SFHA of Bozeman Creek, its tributaries and diversion. The error was present in the 1988 FIRMs, it just could not be resolved at a scale of 1” = 500’. The degree of inaccuracy is not constant and varies along these water courses, upwards of 100’ at worst. The mapping error presents a hardship to property owners in two different capacities. First, many buildings are located in SFHAs that in actuality would not be if the maps were spatially accurate. These owners may be burdened with the expense of purchasing a mandatory flood insurance policy where the premium does not reflect the true actuarial risk for the property. There is a FEMA process available to correct the mapped SFHA on a case-by-case basis, with the onus falling upon the property owner to complete the process, despite the owner having no relationship to the event causing the hardship. The converse rings true as well, where many buildings that are not in a mapped SFHA would be if the mapping were accurate. Some of these buildings may not be insured against flooding, where this insurance would have been mandatory if the maps were correct. Exhibits are attached to this memorandum visually showing the SFHA mapping errors. This issue has been brought to the attention of FEMA and the DNRC. Currently, the DNRC is making application for a FEMA grant to re-study Bozeman Creek, its tributaries and diversion. New hydrologic analysis and hydraulic modeling will be completed if funding is received through the grant. The consent agenda for this 5/7/12 Commission meeting contains an item authorizing the Mayor to sign a letter of support addressed to DNRC in their efforts to procure grant funding for this restudy. 95 UNRESOLVED ISSUES: Many issues remain unresolved with this effort. The City in collaboration with DNRC is initializing steps to rectify these mapping errors. The ultimate goal is a new FIS and FIRMs that are spatially accurate and reflect current hydrology and flood behavior. Timeframe is unknown. ALTERNATIVES: As suggested by the City Commission. FISCAL EFFECTS: At this point, the City aims to assist DNRC with its efforts in procuring the FEMA grant and is providing in-kind support for data and staff time. Attachments: Various map error exhibits Report compiled on: April 26, 2012 96 . 010020030040050 Feet FIRM Error Exhibit Legend FIRM Streamline COB Lidar Streamline FIRM Flood Zones Zone AE Floodway Zone AE Zone A Zone X - Shaded Zone X - Unshaded Parcels Mathew-Bird Creek FIRM location 1:1,400 Mathew-Bird Creek ACTUAL Location Kagy Blvd. Hoffman Dr. Mason St. Figgins Creek ACTUAL Location Figgins Creek FIRM location 97 . 010020030040050 Feet FIRM Error Exhibit Legend FIRM Streamline COB Lidar Streamline FIRM Flood Zones Zone AE Floodway Zone AE Zone A Zone X - Shaded Zone X - Unshaded Parcels 1:1,400 Cambridge Dr. S. 11th Ave. Alder Creek Dr. Figgins Creek ACTUAL Location Figgins Creek FIRM location 98 . 09018027036045 Feet FIRM Error Exhibit Legend FIRM Streamline COB Lidar Streamline FIRM Flood Zones Zone AE Floodway Zone AE Zone A Zone X - Shaded Zone X - Unshaded Parcels 1:1,237 E. Babcock St. E. Olive St. Bozeman Creek ACTUAL Location Bozeman Creek FIRM location 99