Presentation Transcript

1. Floodplain Mapping Update December 3, 2013 Robert Billings, PE, PH, CFM
2. Why are we here? The Purpose of this meeting: To update flood hazard data in Mecklenburg County Explain the FEMA floodplain mapping process Discuss the Impact of New Maps Discuss Floodplain Management Standards
3. Cooperating Technical Partner - CTP FEMA’s Cooperating Technical programs North Carolina is a Cooperating Technical State Mecklenburg County is a Cooperating Technical Partner
4. Floodplain Statistics: 320 miles of streams 4000+ structures in the floodplain Average Precipitation: 40 inches per year Record Maximum Precipitation: 22 inches in 24 hours (1916 estimate) Current 100-Year Precipitation is 7.29 inches Probable Maximum Precipitation: About 33 inches
5. What is a Floodplain ? Floodplains are those areas commonly inundated by flooding. Floods result when water runoff exceeds the capacity of stream and river channels or lake basins. FEMA Map Drains One Square Mile Area
6. Floodplains vsBuffers Buffer - Improve Water Quality - Limit Impervious Areas - Limit Vegetation/Tree Removal - Zoning Floodplain - Safety From Flood Damage - Restrict Placement of Fill In Floodway - Ensure Buildings are Elevated
7. DEFINITIONS Digital Flood Insurance Rate Map (DFIRM) A digitally-produced FIRM, whether viewed in hardcopy or in digital form Flood Insurance Study (FIS) Details the examination, evaluation, and determination of flood hazard areas FIRMs are part of the FIS Base Flood Elevation (BFE) As shown on the FIRM, represents whole-foot elevations of the 1% annual chance flood Regulated to the nearest tenth of a foot; detailed information provided in the FIS
8. Flood Plain Mapping Floodplain Mapping is regulated by FEMA if the community participates in the NFIP Floodplain Mapping must follow a regimented process Floodplain Maps generally progress through three levels: Draft, Preliminary, and Effective Floodplain Maps may take as long a five years to progress from terrain data acquisition to Effective
9. PURPOSE OF NFIP To make flood insurance available Flood insurance is a requirement if there is a mortgage on the home To identify floodplains and areas at risk of flooding To provide standards, guidance, and a framework to help communities manage floodplains
10. Floodplain Mapping History Protecting Life and Property Community Sustainability & Resiliency Communicate& Reduce Flood Risk Why are “Floodplains” Mapped? Uses for Flood Risk Information Flood Preparedness Flood Insurance Regulate New Development Planning Mitigation And more…..
11. Background: Floodplains Evolution of Floodplain Maps & Regulations 1978 – First Charlotte Ordinance and Maps 2002 -NC Floodplain Mapping – 99 Counties 2004– FEMA published updated Maps 2009 – Charlotte maps reformatted to meet NC Mapping Grid 2012 and beyond – New Floodplain Maps
12. Why Floodplain Maps Change Flood Risk Changes Over Time Climatological Changes Natural & Man Made Land Changes Technological Advancements Better Data Improved computer models Enhanced Map Products Extended Historic Rainfall Records Changes in Rain Intensity, Duration, Frequency, etc. Natural Geomorphic Stream Changes Development within the Watershed
13. NC – CTS Panel Zone X Zone AE NGS Benchmark BFE Floodway (white hatched area) Stream Name Cross Section
14. Floodplains Community (Future Conditions) Floodplain FEMA (Existing Conditions) Floodplain FEMA Floodway Community Encroachment Area
15. Floodplain Regulations and the Flood Insurance Rate Map (FIRM) FEMA Floodplain Area Community Floodplain Area
16. 2016 2014 February 19, 2014
17. Phase 1 Mapping UPPER LITTLE SUGAR BRIAR LOWER LITTLE SUGAR BACK REEDY McKEE CALDWELL McALPINE CLEAR GOOSE McMULLEN CROOKED FOUR MILE TWELVE MILE SIX MILE CLEM
18. Phase 2 Mapping Watersheds along and west of I-77: McDowell Upper Mtn Island Gar Long Lower MtnIsland Irwin Paw Catawba Sugar Beaverdam Steele Does not include Lake Norman or Lake Wylie
19. POST-PRELIMINARY PROCESSING Preliminary panels are issued 2 notices in local newspaper 90-day Appeal/Protest Period Educational Meetings Resolution of Appeals and Protests The 6-month Compliance Period Letter of Final Determination from FEMA Map Adoption and Update of Flood Damage Prevention Ordinance
20. CMSWS Recognition of Preliminary FIRM FEMA requires maps to be released as Preliminary for a period of about one year prior to the final approval by FEMA. The Preliminary maps may show increased flood elevations along some streams MCSWS regulates construction of new buildings using the preliminary elevations, but only if the new elevations are higher than the flood elevations shown on the current flood maps.
21. Regulate Where Floodplains are Increasing On Preliminary Maps
22. Cannot Use Preliminary Maps Where Floodplains Decreasing
23. DEVELOPMENT Development means any man-made change to improved on unimproved real estate, including, but not limited to: Buildings or other structures Mining Dredging Filling Grading Paving Excavating or drilling operations Storage of equipment or materials
24. NO IMPACT CERTIFICATION A no-impact certification is required for any proposed development in the floodway or community encroachment area. A professional engineer must conduct a study and certify that the proposed development will have no impact on flood elevations. Community can issue a Floodplain Development Permit only after receiving the engineer’s certification.
25. IMPACT ON DEVELOPMENT REQUIREMENTS When FEMA publishes new flood maps or new regulations are adopted, any existing compliant development is grandfathered based on the flood maps and regulations that were in effect at the time of the building permit was issued, the date of construction, or the date of last substantial damage and/or substantial improvement – whichever is later
26. USE OF PRELIMINARY DATA The use of Preliminary Data will be treated on a case by case process: Because Preliminary Data is the best available data, it may be used in some circumstances: Because Preliminary Data is not recognized by FEMA until it becomes Effective, it cannot be used in certain LOMC applications If communities wish to enforce more stringent data, they are encourage to adopt the Preliminary data
27. Online Flood Map Review http://mapserver.mecklenburgcountync.gov/fmr/ ftp://ftp1.co.mecklenburg.nc.us/luesa/stormwater/Floodplain%20Mapping/
28. What is Flood Risk
29. What is Changing
30. Using New Flood Map Products Knowing your flood risk is the first step intaking actions toward Reducing your risk.
31. Useful Information Mecklenburg County’s Flood Map Review Application: http://mapserver.mecklenburgcountync.gov/fmr/ Mecklenburg County’s Flood Map Review Application: http://maps.co.mecklenburg.nc.us/website/floodzone/ Mecklenburg County’s ftp site: ftp://ftp1.co.mecklenburg.nc.us/luesa/stormwater/Floodplain%20Mapping/ North Carolina Flood Map Application: http://floodmaps.nc.gov/fmis/ North Carolina DOT GIS: http://www.ncdot.org/it/gis/
32. Robert Billings, PE, PH, CFM Floodplain Mapping Project Manager (704) 432-0907 Robert.Billings@ MecklenburgCountyNC.gov Thank You