NFIP Mapping Issues. Wendy Lathrop, PLS, CFM. Cadastral Consulting, LLC

Transcription

1 NFIP Mapping Issues Cadastral Consulting, LLC NFIP Basic Objectives: Reduce the exposure to flood damages through the use of minimum standards for the placement and design of structures located in flood hazard areas. NFIP Purposes (42 USC 4001) Identify and map flood hazard areas Provide a framework for floodplain management regulations Make flood insurance available in communities participating in the NFIP Why mapping matters Inaccurate map = improper insurance and regulation No map = insurance and/or regulatory repercussions NFIP Regulations Title 44 CFR - Part 59 - General Provisions Definitions Program description Eligibility requirements Terminology Flood Flood frequency Floodplain Flood fringe Floodway Base flood elevation Floodplain management Flooding types Three main categories: Riverine flooding Coastal flooding Shallow flooding 1

2 NFIP Zones: 44 CFR 64.3 Zone A Zones A1 - A30, AE Zones AO, AH Zones A99, AR Zones B, Shaded X Zones C, Unshaded X Zone V Zones V1 - V30, VE Zone VO Zone D Zone E Zone M Riverine Watershed and Floodplain Floodway / Flood Fringe 2

3 Coastal Hazards 3

4 Other Unique Flood Hazards Alluvial Fans Migrating streams Mud Flows Ice/debris Jams Dam Failures Tsunamis Legacy sediments Map evolution Flood Hazard Boundary Maps (FHBM) Flood Insurance Rate Maps Flood Boundary/Floodway Maps (FBFW) Digital format Digital Flood Insurance Rate Maps (DFIRM) The birth of a map Mapping needs assessment Determination of resources Scoping Data Collection Data Analysis and compilation How to make a FIRM/DFIRM 44 CFR 65: Identification and Mapping of Special Hazard Areas The purpose of this part is to outline the steps a community needs to take in order to assist the Agency's effort in providing up-to-date identification and publication, in the form of the maps described in part 64 Guidelines and Standards: Master Index Guidelines and Specifications for Flood Hazard Mapping Partners A compilation of resources 3 volumes, 14 appendices Some items marked superseded but not fully replaced; use as background The multiple purposes of FIRMs Insurance rating Lender compliance with NFIP Eligibility for disaster assistance Land use regulation Planning Emergency management Land development Appraisal 4

5 Approaches to mapping floodplains Approximate methods Limited study methods Detailed methods Limited map maintenance projects Restudies What a FIRM / DFIRM tells us Flood risk levels Flood protection Flood containment Level of detail Limit of detail Refer to FIS Flood Insurance Study Report - The details Map Mod is Dead, Long Live Risk MAP to deliver quality data that increases public awareness and leads to action that reduces risk to life and property. Digital mapping Digital mapping may or may not be of better quality than non-digital versions Scanned paper maps Field data converted to digital files for analysis and digital map creation Field data collected as digital files for analysis and digital map creation Digital photography 3-D Laser scanning Procedure Memorandum 38 Data consistency standard, not accuracy standard 5

6 Look at the metadata Base Map Source: 1:100,000 USGS Digital Line Graphs. Map users should be aware that this base map source causes road alignment distortions at and near road intersections. These alignment problems have been corrected in the vicinity of identified floodplains. The adoption of a map Preliminary mapping Public hearings FEMA review of appeals Letter of Final Determination NFIP Regulations - Title 44 CFR, Part 67 Appeals from Proposed Flood Elevation Determinations Right of appeal Types of appeals Appeal procedures Keeping maps current Original lack of mapping detail Topographic changes Impervious cover changes Structural changes Hydrologic and hydraulic changes Jurisdictional changes Remember - the map is a snapshot of conditions at a given time Responsibility for mapping 44 CFR 65.3 Requirement to submit new technical data not later than six months after the date such information becomes available, a community shall notify [FEMA] of the changes by submitting technical or scientific data 6

7 Future conditions Advisory mapping The volatility of erosion (and/or subsidence and/or sea level rise) LOMCs Officially amend or revise the Flood Insurance Rate Map (FIRM) Why LOMCs? Less expensive than republishing the maps Faster than republishing the maps Scale limitations Time and notice considerations Elevation matters! Where is zero? Height of floor Height of water Inherent uncertainties Benefits / costs Key Terms for LOMCs Lowest Adjacent Grade (LAG) Highest Adjacent Grade (HAG) in Zone AO Base Flood Elevation (BFE) Fill Lowest Floor Basement 7

8 Map updates amendments Letter of Map Amendment site specific Inadvertent inclusions to floodplain Structures or legally defined parcels Do not involve hydrologic or hydraulic analyses (unless Zone A) Use MT-1 (or MT-EZ) e-loma considerations NFIP Regulations - Title 44 CFR, Part 70 - Procedure for Map Correction Mapping Deficiencies Unrelated to Community-Wide Elevation Determinations Right to submit technical information Letters of Map Amendment Review of proposed projects The FIRM takes precedence over elevation. If the grade is above BFE, request a LOMA. 44 CFR 70.3 LOMA Data in the application may include: Topographic mapping No topography needed if a plot on the FIRM shows out as shown LAG (including attached decks, garages) Map showing location of structure Curvilinear line representing area subject to inundation by the base flood Homeowner can submit application Cross Sectional View of a LOMA Request 8

9 Typical Sources of BFEs FEMA Flood Insurance Study Report profile FEMA Flood Insurance Rate Map Other 1% annual-chance Flood Study FEMA Quick-2 software Stream gauge data Extrapolation of detailed study upstream New detailed study No BFE now what? FEMA Publication 265 (1995): Managing Floodplain Development in Approximate Zone A Areas: A Guide for Obtaining and Developing Base (100-Year) Flood Elevations" Approximate BFE methods Historical high water marks + safety factor Water control structure + freeboard Match topography Contour method (a.k.a. point on boundary ) LOMA in Zone A MAY be able to complete LOMA without engineer: o Include all available information regarding structure location, topography, FIRMs. If too close to call, consider other approaches: o Extrapolation of BFEs from nearby locations If none of the simplified methods are appropriate, surveyed cross sections and engineering methods are required. Applying for a LOMA Outcome (what is removed from SFHA) Building 200 Flood Zone BFE LAG LFE Lowest Lot Elevation X (unshaded) 13.8 feet 21.8 feet 23.3 feet - Outcome (what is not removed from SFHA) Flood Zone BFE LAG LFE Lowest Lot Elevation Structure AE

10 Outcome (what is outside SFHA) Residential structure Flood Zone BFE LAG LFE Lowest Lot Elevation C e-loma On-line application Restrictions: no fill; BFE available Auditing Implications for local communities and others who utilize LOMAs Differs from online LOMC application Map updates revisions Engineered changes o Letter of Map Revision o Letter of Map Revision based on Fill o Physical map revisions More complex than amendments Not usually lot or structure specific Typically involve hydrologic and/or hydraulic analyses Require submittal of MT-2 forms NFIP Regulations - Title 44 CFR, Part 65 Identification and Mapping of Special Flood Hazard Areas Requirement to submit technical data (65.3) Right to submit new technical data Map revisions Floodways Levees 44 CFR LOMR-F Requestor must submit: Copies of recorded deed and plats Topographic map indicating present ground elevations and fill Location of structure and LAG elevation BFE data from authoritative source Community acknowledgement form (MT-1) Definition of Lowest Floor... the lowest floor of the lowest enclosed area, including basement. An unfinished or flood resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other than a basement area is not considered a building s lowest floor; provided that 10

11 such enclosure is not built so as to render the structure in violation of the applicable nonelevation design requirements of Sec Definition of Basement That portion of a building having its floor subgrade (below ground level) on all sides. Cross-Sectional View of a LOMR-F Request LOMR-F Why did this application fail? Outcome (what is not Flood Zone BFE LAG LFE Lowest Lot Elevation removed from SFHA) Structure AE 63.3 feet 62.3 feet 60.5 feet - New map now what? Incorporated? OR Revalidated and reauthorized? OR Superseded? Conditional Letters Review of proposed projects CLOMA: 44 CFR 70.9 CLOMR: 44 CFR 65.8 No effect on insurance Final LOMC requires as-built certification 11

12 NFIP Regulations - Title 44 CFR, Part 72 Procedures and Fees for Processing Map Changes Defines CLOMA, CLOMR, CLOMR-F, LOMR, LOMR-F, PMR Fee schedule Submittal and payment procedures Fee exemptions Resubmittals Ms. Alpha Her house is a wood-frame structure with FFE of NGVD, a basement elevation of 702.8, LAG is Fill was placed for construction in The flood insurance map (then a FHBM) was first printed 1997, but Walnut Creek (flooding source) wasn t shown as a flood hazard until New study will include a restudy of Walnut Creek. Current BFE is 710.5, while restudy shows Which LOMC? Should it be approved? What about after the new study is published? Mr. Beta His house is a brick structure with a FFE of NGVD, a crawl space elevation of , and LAG is Engineered fill was placed during construction of the home in The FIRM for this community is dated 1995, and it is the first NFIP map showing SFHAs in this area. Mr. Beta previously submitted and received a conditional letter in Should his house be removed from SFHA? What type of letter should he apply for? 12