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TRANSCRIPT
1/23/2017
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Floodplain Updates For Surveyors
Ceil Strauss – MN State Floodplain Manager
February 9, 2017
Floodplain Update For Surveyors
•Finding FEMA Maps & Data
•Map / Data Updates & Status
•Other useful resources
•Letters of Map Change (review)
• - LOMAs
• - LOMR-Fs
Sample FEMA Map with SFHA
National Standard of “100-year flood”
chosen
High Flood Risk
Medium Flood Risk
Low Flood Risk
Zone A & AE (old)
Zone A & AE (new)
Zone B (old maps)
Zone X (shaded)
Zone C (old maps)
Zone X (unshaded)
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SYNONYMOUS TERMS
•One-Percent (1%) Chance Flood
•100-Year Flood
•Base Flood Elevation, or BFE (FEMA)
•Regional Flood (MN DNR)
•Special Flood Hazard Area, or SFHA (FEMA)
•High Flood Risk Area
Status of FEMA Flood Insurance Rate Maps (FIRMs) in MN
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• DFIRM – Digital Flood Insurance Rate Map
• Preliminary DFIRMs • Other paper FIRMs
County-Specific
Status Updates
http://files.dnr.state.mn.us/waters/watermgmt_section/floodplain/map_update_process_county_timing.pdf
Or go to mndnr.gov & search “FEMA map update status”
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Preliminary & Effective DFIRMs
• DNR Eco/Waters posts electronic copies at:
ftp://ftp.dnr.state.mn.us/pub/waters/floodplain/County_data/
Can view:
• FIRM panels as pdfs (FIRM)
• FIS as pdf (FIS)
• GIS files (DFIRM_DB)
Documenting As Built Elevations
• FEMA Elevation Certificate (EC)
• DNR Sample “As-Built” form
• Link to both at MnDNR site
• Current FEMA EC has signature block on same page as elevations!
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Latest FEMA
Elevation Certificate
July 2015
Expires 11/30/2018
Types of Floodplain Delineation
• Zone AE or Zone A1-A30, AO, AH:
Detailed engineering analysis supports BFEs shown on maps, profiles, floodway data tables
• Zone A:
Approximate delineations without BFEs on the map and no profiles or data tables in the report
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Red=AE Blue=A
FEMA Mapped Floodplains
APPROXIMATE DELINEATIONS Zone A Areas
• Little or no field work conducted
• Older FIRMs use existing data such as FHBM, USGS Flood Prone Quadrangle Maps
• Newer Digital FIRMs have supporting documentation for estimated Base Flood Elevations
• Where no existing data is available, appropriate methods for approximating floodplain boundaries must be selected and applied
New FEMA Approximates
• In Map Modernization - zone A delineations will have an estimated BFE supporting the delineation
• Most have simple HEC-RAS models for support
• Data not on maps, but provided to zoning officials
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MN Geo Commons - https://gisdata.mn.gov/
Search “FEMA
floodplain” or “DFIRM”
MN GeoCommons Site
MnGEO
• Scroll halfway down and download the “ESRI File Geodatabase”
MnGEO
• Import the layer files into your ArcMap document
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MnGEO
• Database contains effective data: BFEs, DFIRM Cross-Sections, Flood Hazard Zones, DFIRM Panels
Clay County
DFIRM data available
MnGEO
• Database also includes the “pink lines”, which are the elevations associated with Zone A areas or the best available data in areas that are not yet effective
Polk County, No floodplain delineated (not effective yet)
Mahnomen County Zone A delineated (effective)
MnGEO
• Unmodernized floodplain information is also included for non-DFIRM counties (if available)
Aitkin County No pink lines or DFIRM data yet
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FEMA Hydraulic Model Download Application
• DNR website where you can download models used for FEMA maps
• A work in progress, not all models have been uploaded
• http://arcgis.dnr.state.mn.us/ewr/hydra_model_download/index.html
FEMA Hydraulic Model Download Application
Model Availability
FEMA Hydraulic Model Download Application
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Check the Datum!
• New Maps are in NAVD, 1988 Datum
• Old Data in:
• NGVD, 1929
• 1912
• Local
• Assumed
• There can be several feet of difference!
NGVD, 1929 versus NAVD 1988 To convert vertical or horizontal datums you may
obtain USACE's Corpscon Convers ion Program
Version 5.11 or newer
NAVD88 - Conversion = NGVD29
1.20
1.20
1.20
1.10
1.00
.90
.80
.80
.80
.70
.60
.50
.40
.30
.20
.10
.00
.00
.10
.20
.30
.40
.50
.60.70.80
.90
1.001.
10
1.2
01.30
1.401.30
Nort
h D
ako
taS
out
h D
ako
ta
St. Lou isItasc a
Lake
Ca ss
Polk Beltram i
Aitkin
Pine
Co ok
Koo chichin g
Otte r Ta il
Clay
Ro sea u
Marsh all
Becke r
To dd
Stea rns
Kittso n
Swif t
Lyon
Pop e
Morr ison
Re nville
W ilkin
Ca rlto n
Martin
Hu bba rd
Rice
No rm an
Fillmo re
W righ t
Mowe r
Crow W in g
Murray
No bles
Gra nt
Sibley
Brown
Clea rwa ter
Lake of th e W o od s
Ro ck
Re dwoo d
Kan diyoh i
Do ugla s
Jackso n
Mee ker
Goo dhu e
Isan ti
W in on a
Fa rib au lt
Da kota
Free bo rn
Olmste d
Linco ln
Blue Earth
Scot t
Stev ens
Ano ka
Mille L acs
Ho usto n
Stee le Do dge
Trav erse
W ade na
McL eod
He nne pin
Nico lle t
Kan abe c
Ch ip pe wa
Ben ton
W aba sha
Lac Qui P arle
Ca rve r
Pen ning ton
Co tto nwood
Big S ton eCh is ago
W aseca
Mah no me n
Le Sue ur
Yellow M edicin e
Pipest on e
Re d L ake
She rb urne
W ato nwan
W ashin gto n
Ra mse y
1.40
1988 – conversion = 1929
Get this map by searching “NAVD88 to NGVD29” at MnDNR site, or
http://files.dnr.state.mn.us/waters/watermgmt_section/floodplain/datum_conversion.pdf
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Who Determines BFE?
Resident contacts community
Community provides BFE to resident
NO YES Community
has BFE?
YES
NO
Community checks online resources
BFE available?
Community contacts DNR or watershed
BFE estimate made & given to community
How To Find Base Flood Elevation (BFE)
• Current detailed study area: Use your Flood Insurance Rate Map (FIRM) & Flood Insurance Study (FIS) - DNR can help you learn to interpret
• Current A Zone, but have Detailed Preliminary: Can use the preliminary FIRM & FIS as best available data
• Current A Zone:
• Limited detail available?
• Previous estimate determination? Check with watershed district & DNR; Previous LOMA?
• Have resident apply for LOMA & request BFE to be determined
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2017-2018 County Modernizations • A Zone models • 1% digitized • Will be able to use for
zoning & flood insurance appeal (Letter of Map Amendment - LOMA) decisions
• Official updated maps would be a future step
Sample of Effort Types in Each
County
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Find Current Effective Map
New Look as of December 2015
Enter address or city or county here
Toggle to
aerial
To see
panel
MSC – After Address (or city) Entered
Viewing Panels at FEMA’s Map Service Center (MSC)
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Make FIRMette
To see all
products,
including
when new
maps are
coming
Other Data at MSC
Get Effective, Preliminary, Pending and Historic files
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If DFIRM, will have this
icon to link to FEMA’s
National Flood Hazard
Data (NFHL) viewer
Link to FEMA’s National Flood Hazard Layer (NFHL) Viewer
FEMA’s National Flood Hazard Layer (NFHL) Viewer
If at city
level, may
need to
zoom in to
see other
layers
NFHL Viewer Background Options
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FEMA NFHL Viewer
Click on purple dot to see LOMA document
Even in non-DFIRM
Counties, LOMAs can be viewed!
To print
FEMA NFHL Viewer
Useful Tool
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Print from FEMA NFHL Viewer
DFIRM FIRMette – brand new! http://tinyurl.com/j4xwp5e
MnTOPO
• http://www.dnr.state.mn.us/maps/mntopo/index.html or search MNTOPO and proceed to viewer
• Use to view or download state LiDAR data
• Use to view FEMA floodplain data (not as up-to-date as MnGEO)
• Must be zoomed in or out to see certain layers
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Search MNTOPO
MnTOPO Site http://arcgis.dnr.state.mn.us/gis/mntopo/
MNTOPO Options
Zoom to your location
Download LiDAR products
Print a map
Get a point elevation or elevation along a line
Show map layers: • 50-, 10-, 2-foot contours • LiDAR flight lines • FEMA Flood Data
Change Basemap: • Road • Imagery • Color Terrain • B&W Terrain
Help PDF document
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MnTOPO
Download LiDAR products
“Unmodernized” – NOT official; Q3 layer (quick digitization)
“Modernized” – Final Digital Flood Insurance Rate Map (DFIRM) layer
Transparency
slider bar
Unmodernized Example
Modernized Example
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Lines and Point Elevations in MnTOPO
MnTOPO – Sample of “Line”
Letters of Map Change (LOMCs)
•Letters of Map Amendment (LOMAs)
•Letters of Map Revisions based on Fill (LOMR-Fs)
•Letters of Map Revisions (LOMRs)
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Floodplain Boundary Disputes
•Floodplain ordinance: community decides
•Lending/Flood Insurance: FEMA decides (LOMC):
•Letter Of Map Amendment (LOMA)
•Letter of Map Revision based on fill (LOMR-F)
•Letter of Map Revision (LOMR)
What’s the Option if House is Really High?
Location on FIRM for existing house
Zone AE
Lender must require flood insurance if they are “in” the Special Flood Hazard Area (Zone A) on the map, no matter how high they really are.
Can only be changed by FEMA with Letter of Map Amendment (LOMA)
LOMA - Letter of Map Amendment
A letter from FEMA stating that an existing structure or parcel of land that has not been elevated by fill would not be inundated by the 100-year flood
The FEMA map is wrong – better topographic contour lines or a field survey shows site is above BFE
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BFE
LOMA
Lowest Adjacent Grade (LAG)
Natural Grade
BFE
LOMA
Lowest Adjacent Grade (LAG)
Natural Grade
LOMA - Cross Sectional View
LAG below BFE NOT REMOVED
Lowest Adjacent Grade (LAG) 600.0’
Lowest Floor 596.0’
BFE 602.0’
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Lower Garvin Brook at
Minnesota City
Why Attached Decks Matter to FEMA
BFE ~1128
Letter of Map Amendment (LOMA)
Owner contends FEMA map in error
Need: (1) Lowest adjacent grade (LAG)
(2) Base Flood Elevation (BFE), aka 100-year
• Survey of LAG required (exceptions noted later)
• No fee for FEMA’s review (will be cost for survey and maybe for preparing submittal)
• FEMA responds within 60 days
Forms: FEMA form MT-1 (multi-lot or single lot)
FEMA form MT-EZ (single lot only)
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Letter of Map Change (LOMC) Application Options
• Paper Application - with MT-EZ (for single lot LOMA) or MT-1 (for LOMR-Fs and multi-lot LOMAs or LOMR-Fs)
• Online Application – Submit same items as in paper, but in digital format. Search “FEMA online LOMC”
• eLOMA – Only available to licensed surveyors and PEs. Search “FEMA eLOMA application.” First one is audited, and then randomly. eLOMAs are processed in less than a day! Only for LOMAs & where there are detailed studies or certain A zone BFEs (based on the “pink lines” basic engineering, or have determination memo/letter from DNR, Corps, Watershed, or community).
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Letter of Map Amendment – Out as Shown (LOMA-OAS)
Provide better information on where STRUCTURE IS on the lot
Don’t need survey data
Need community logo / name
~ 15% of LOMA requests
LOMA & LOMA-OAS Guidelines
At MN DNR site, search for
LOMA or LOMA-OAS
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This abbreviated LOMA application process is intended for locations where it is clear that the entire building (or the entire lot) is above the base flood elevation (BFE) based on review of the LiDAR derived contour
elevations compared to the base flood elevation.
Only in Minnesota (and a few communities nationally)
Use of LiDAR for LOMAs
Search “LOMA with LiDAR” at MnDNR Site
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• Include everything on checklist
• Map prepared by city, county, surveyor or PE
• Include LiDAR certification letter (available on DNR site) for that county
When Can LOMA LiDAR Be Done?
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Calculating the Lowest Adjacent
Grade (LAG):
1. Determine the closest contour
lower than the building footprint.
NOTE: You must choose a contour
that does NOT go through the
building. Use the contour that is just
below or just barely touching the
structure (but not going through).
2. Subtract either ½ the contour
interval or 1 foot (whichever is
greater).
NOTE: Minnesota certified LiDAR contours
are 2 foot intervals, so subtract 1 foot.
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LiDAR Data Collected by Blocks
• SE Minnesota
• SW Minnesota
• Arrowhead Region
• Metro Area
• Individual Counties
• North Central MN
• Red River Valley
Can be done by city, county, surveyor or PE
In Anoka County Anoka County GIS staff prepared map “app” that can be used by local officials and other professionals (surveyors, engineers) http://gis.anokacountymn.gov/flood/
Nice features that others may want to use in their templates (i.e., disclaimer notes FEMA BFE and local regulation elevations different, still floods above BFE, etc.)
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Hennepin Co Natural Resources
https://gis.hennepin.us/naturalresources/map/
Hennepin Co Natural Resources
Hennepin Co Natural Resources
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LOMR-F Letter of Map Revision (Based on Fill)
A letter from FEMA stating that an existing structure or parcel of land that has been elevated by fill would not be inundated by the 100-year
flood
BFE
LOMR-F
Fill
LOMR-F Diagram
Part 65 of the NFIP Regulations requires that the following be equal to or higher than the BFE: • the lowest ground touching the structure; and • For existing structures, the lowest floor (including basement or crawl space) (this also
means that the community certifies the structure is complaint with Section 60.3 of the NFIP regulations)
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Community Acknowledgement Form (CAF)
Community signature – you are saying:
- Not in floodway
- Complies with Endangered Species Act
- Have all necessary Federal, State & Local permits (if
CLOMR, will obtain)
- Existing and proposed structures will be “reasonably safe
from flooding”
(NOTE: The supporting documentation must be available to
submit to FEMA upon request!)
In MN, LOMR-F Does Not Remove from Regulated Floodplain
Additional requirements to get removed:
• Meets MN Rules 6120.5800, subp. 2:
- filled above the Regulatory Flood Protection Elevation (RFPE), and
- contiguous to other lands lying outside the floodplain
OR flood control measures meeting 6120.5900 are constructed and operating
• Community amends ordinance and adopts the LOMR-F or LOMR
BFE
LOMA?
LOMR-F?
