Slide 2 Managing Zone A Floodplains Jana Green, CFM Kim Dunn,
P.E., CFM RAMPP FEMA Region III National Flood Insurance Program
Essentials and Best Practices Slide 3 Topics of Discussion Overview
of Zone A Floodplains Permitting Development in Zone A Floodplains
Estimating Flood Elevations in Zone A Flood Insurance Implications
Letters of Map Change Zone A Floodplains Resources for more
information 2 Slide 4 What is a Zone A Floodplain? Area of the 1%
annual-chance floodplain Boundaries have been determined using
approximate methodologies No published Base Flood Elevations (BFEs)
on Flood Insurance Rate Map (FIRM) or in the Flood Insurance Study
(FIS) report 3 Slide 5 Zone A Challenges Without defined Base Flood
Elevations: Lowest floor elevations must be determined for
permitting Flood insurance rates may be higher based on unknown
risk Benefit-cost ratios for mitigation projects may be more
difficult to calculate Water surface elevation needs to be
estimated 4 Slide 6 Delineating A Zones The paper FIRMs used:
topographic maps soils analysis and mapping historical information
and high water marks studies not completed by FEMA More recently,
Zone As are supported by automated hydrologic and hydraulic
analyses Not a detailed hydrologic and hydraulic study 5 Slide 7
Zone A Regulatory Requirements Reasonably obtain and utilize any
flood elevation data when reviewing and issuing permits If the
automated hydrologic and hydraulic analysis (model- backed Zone As)
are available, use that as best available data Use studies
conducted by other federal or state agencies Check to see if
elevations have been determined for nearby development Subdivision
requirements: Base Flood Elevations must be determined through a
detailed study for proposed development larger than 5 acres or 50
lots, whichever is lesser 6 Permits are required for all
development Slide 8 Obtaining Estimated Elevations 1.Automated
hydrologic and hydraulic (H&H) analyses 2.Other sources of data
3.Simplified methodologies Contour interpolation
(point-on-boundary) Data extrapolation Remember, the floodplain
administrator can always require a detailed study to establish a
true Base Flood Elevation 7 Slide 9 Automated H&H analyses were
run for Zone As Elevation information exists in the model Not
detailed enough to be included on the FIRM Can be used to estimate
a 1% chance flood elevation Floodplain Administrators can use this
as best available data for permitting in Zone A Zone A cross
sections will soon be available online! 8 Automated H&H Data
Slide 10 9 www.Riskmap3.comwww.Riskmap3.com or FEMA Engineering
Library Availability of Automated H&H Slide 11 State Sources
for Automated H&H Currently Region III hosts the data at
www.Riskmap3.comwww.Riskmap3.com Data will be transitioned to State
websites: Maryland website: www.mdfloodmaps.com www.mdfloodmaps.com
West Virginia website: www.mapwv.gov/flood/ www.mapwv.gov/flood/
Pennsylvania: www.pafloodmaps.com www.pafloodmaps.com 10 Slide 12
Other Sources of Data When automated H&H unavailable, check for
other sources of elevation data: Community Records Development
plans Letters of Map Amendment (LOMA) for neighboring property
State or County agencies Departments of Transportation (plans for
nearby bridges) Departments of the Environment (Stream restoration
/ erosion control projects) Federal Agencies Unpublished USACE,
NRCS, or USGS studies Preliminary FIRM data from FEMA 11 Slide 13
Simplified Methodologies Contour Interpolation Method Based on an
overlay of FIRM on topographic map Estimate water surface elevation
at the intersection of the contour Confirm accuracy is acceptable
12 Slide 14 Simplified Methodologies Data Extrapolation Method
Extend water surface profile at the same slope Transfer that
elevation to the map view Relevant within 500 feet of detailed
study No hydraulic structures (e.g. bridges, culverts) between end
of detailed study and site 13 Slide 15 Using Elevation Data Once
the BFE is established, development is required to comply with
Section 60.3(c) of the NFIP regulations. 14 Residential: elevate
lowest floor to the BFE Non-residential: elevate or dry floodproof
to BFE Manufactured homes: elevate and anchor to BFE Enclosures
below BFE, must have adequate flood openings and be used only for
parking, access, or storage. Openings Elevation of utilities and
mechanicals Lowest Floor above BFE Yardley Borough, Bucks County,
PA (from PEMA) Slide 16 Flood Insurance Implications Mandatory
flood insurance purchase requirements: applies for all structures
in or touching the floodplain that carry a federally-backed
mortgage 15 Slide 17 Elevation Certificate An Elevation Certificate
is an administrative tool to provide elevation information
necessary to: record building elevations demonstrate compliance
with the NFIP support a Letter of Map Change (LOMC) determine
proper flood insurance premiums 16 Slide 18 Elevation Certificate
Section E Property owners can provide measurements that insurance
agents can use to rate a flood insurance policy in Zone A These
measurements are not informative of risk or water surface
elevations should not be used for permitting purposes 17 Slide 19
Post-FIRM Zone A Rating No Base Flood Elevation Provided Post-FIRM
rating considers the elevations of the structure to determine rates
Top of Bottom Floor - Highest Adjacent Grade = Elevation Difference
18 Borough of Olyphant, PA - Post-FIRM structure (FEMA Region III)
Slide 20 Post-FIRM Zone A Rating Base Flood Elevation Information
Available If a Base Flood Elevation is available from another
source, Lowest Floor Elevation Flood Elevation = Elevation
Difference Lowest Floor elevation is not an entry on the Elevation
Certificate It is determined by an insurance agent using
information provided on the Elevation Certificate 19 Slide 21
Letters of Map Change in a Zone A 20 If flood elevation data is
provided, FEMA will verify its reasonableness If elevation data
cannot be provided, FEMA will compute a flood elevation This
elevation determination may not be included on the determination
letter Slide 22 Reviewing Zone A LOMCs 21 If more detailed data is
needed, the applicant may be asked to provide data such as:
Culvert/bridge dimensions One or two cross sections If supporting
data is provided and is reasonable, it is incorporated into the
hydrologic and hydraulic evaluation If additional data is not
provided, the determination may be based on more conservative
methodology Slide 23 Providing Cross Sections For one lot, one
cross section is usually sufficient For a large lot or multiple
lots, a cross section should be surveyed at each end of the parcel
Perpendicular to flow path If property is upstream of a bridge, at
least 2 cross sections are required Should capture changes in
channel characteristics: slope, roughness, etc. Should reference
vertical datum 22 Slide 24 Zone A LOMA 23 Page 1Page 2 Slide 25
LOMC Determination Documents The flood elevation used to complete a
LOMC determination may or may not be displayed on the final letter.
Flood elevations are shown for: Conditional Letters of Map Change
Non-removal determinations Flood elevations are not shown for:
Removal determinations Out As Shown determinations 24
Considerations When Elevations are Displayed Slide 26 Zone A
Permitting Example One A resident enters the permitting office with
the intention to build a house on a riverfront plot of land. The
land is natural grade, and gently slopes down a hill from the main
road to the stream channel. The stream has a history of flooding
and its floodplain is mapped as Zone A. Suggestions Recommend
moving building site outside of the mapped Zone A floodplain If
possible, establish a flood elevation Automated H&H if
available, other sources of data, simplified methodologies,
detailed study Document how reasonably safe from flooding was
established Use high water elevations, add freeboard, use flood
resistant materials, etc. 25 Slide 27 Zone A Permitting Example Two
You are permitting development for a 60 lot subdivision. 15 of the
lots are located in a Zone A floodplain. 26 Slide 28 Zone A
Permitting Example Two Suggestions: Recommend altering plans so
houses will not be in the SFHA Remember: If the development in the
SFHA exceeds either 50 lots or 5 acres, flood elevation data is
required 27 Slide 29 Resources Visit the FEMA Library for: FEMA
1-98 Use of FIS Data as Best Available Data The Zone A Manual:
Managing Floodplain Development in Approximate Zone A Areas FEMA
Engineering Library for Models HEC-RAS:
www.hec.usace.army.milwww.hec.usace.army.mil USGS Stream Stats:
http://water.usgs.gov/osw/streamstats/
http://water.usgs.gov/osw/streamstats/ FEMA GeoPlatform:
www.riskmap3.comwww.riskmap3.com FEMA Map Information eXchange
(FMIX) (877) FEMA-MAP 28 Slide 30 Contacts 29 FEMA Region III
Floodplain Management and Insurance Branch:
[email protected] Washington, D.C. Phetmano Phannavong,
P.E., CFM 202-535-2248 [email protected] Delaware Michael
Powell, CFM 302-739-9921 [email protected] Maryland David
Guignet, P.E., CFM 410-537-3775 [email protected]
Pennsylvania Daniel Fitzpatrick, CFM 717-720-7445
[email protected] Virginia Charley Banks, CFM 804-371-6135
[email protected] West Virginia Kevin Sneed, CFM
304-957-2571 [email protected] Slide 31
