5. 114
Identifying and Funding Studies
Identify Priorities
• Utilize FEMA’s Community Needs Management System (CNMS) to
identify age and validity of study
• Incorporate information contained within Hazard Mitigation Plans
Funding allocation
• FEMA Region I receives some of the lowest funding from FEMA HQ
• Funding is provided in Allocation Buckets that have to be used on
projects pertaining to that Bucket
i.e., funding for a Coastal Study cannot be used to fund a Riverine
Study
Receive final PALT
9. 118
Level of Study
Coastal Zones AE and VE
Riverine Zone AE (Detail Study)
Riverine Zone AE (Limited Detail Study)
Riverine Zone A (Approximate Study)
Redelineation (Zone AE or Zone A)
10. 119
Riverine Zone A (Approximate Study)
Example: Pawcatuck/Wood Watershed, RI
11. 120
New Method: Example Reach
The watershed area for the
selected reach is 8.8 mi2
which is within the
acceptable range for Rhode
Island State Regression (4
to 404 mi2)
12. 121
Old Two Point Method
Cross sections are
drawn and elevations
are picked from both
sides of the floodplain.
The water surface
elevation is the average
of the two points.
327.5
329.6
13. 122
Two Point Method Issue
• This method really
breaks down when
the old effective
floodplain is shifted
or does not conform
to the LiDAR
topography at all.
• At this point it is
even more of an art
and completely
dependent on what
we see on the
LiDAR.
15. 124
Calculating Hydrology
Points are generated
along the reach
centerline at all
confluence nodes and
hydrology is
calculated 20 feet
below and above the
confluence to
determine drainage
area difference. If the
drainage area is less
than 50% of a
downstream flow
change location then
it is kept as a flow
change location.
16. 125
Flow Change Locations
For this reach, the
only points kept for
calculating flow is
the most
downstream point
and one flow change
location seen as a
black triangle.
The table below
shows the calculated
flows for both points
using Rhode Island
State Regression.
18. 127
Reach with drawn cross sections
Cross sections are
drawn
at elevation
changes, upstream
and downstream of
structures, and
directly downstream
of flow change
locations.
19. 128
HEC-GeoRAS Export
• We have incorporated the MA bankfull
equations for estimating depth
• The cross sections are export from HEC
GeoRAS for HEC-RAS modeling.
22. 131
New and Old Floodplain boundaries
Old floodplain (transparent green)
over the new approximate modeled
floodplain (dark blue)
23. 132
Summary
New Zone A with hydrology and hydraulic
information to back up the flood lines.
• No BFE available
Structures are not included
Hydrology assumptions (outside the bounds of equations)
Many hydraulic assumptions must be made (channel depth, n-values)
without field data
• Data will be uploaded and stored in the MIP
Questions?
27. 136
Components of a Flood Insurance
Study
Hydrologic study
How much water will there be?
Hydraulic study
How high will the water get?
Topographic analysis
What areas will the water cover?
28. 137
Order of Importance – Coastal
Study
Flood Insurance Rate Map
• Some Special Flood Hazard Areas are risk based
• Some Special Flood Hazard Areas include wave action
Summary of Stillwater Elevations table in FIS
29. 138
Risk Based Special Flood Hazard
Areas
Primary Frontal Dunes
• Identification of a geomorphologic feature on the profile
• Base Flood Elevation associated with flood zone may be lower than actual ground
elevation
Wave overtopping
• Primarily occurs in areas of coastal structures
• Mapping is associated with a distance back from the slope break
30. 139
Wave Action Inclusive Special
Flood Hazard Areas
In areas of overland wave propagation
Topographic limit of Special Flood Hazard associated with SWL and
wave setup
Flood zones at the boundary may contain wave action
‘Hidden AE’ zones
31. 140
Limit of Moderate Wave Action
LiMWA
• Areas subject to wave
heights greater than 1.5 feet
• Defines Coastal A Zone
• Recommendation of building
to V zone standards
• It is regulatory in Rhode
Island
32. 141
Coastal A Zones
Portion of the coastal AE Zone located between the VE Zone and the
LiMWA, where the waves are between 1.5 and 3 feet
Also known as the Moderate Wave Action or MoWA
33. 142
FEMA Standard 614
FEMA will only use whole foot BFEs for LOMA or CLOMA
determinations where effective flood hazard areas are the result of
coastal flood hazard analysis.
For example:
• SWEL – 8.8 feet NAVD 88
• BFE shown on map is AE EL 9
• LAG is 8.9 feet NAVD 88
• Structure would not be removed from SFHA as 8.9 is lower than 9
34. 143
NGS Benchmarks
• Obtained from National Geodetic Survey website: http://www.ngs.noaa.gov/
• FEMA requires that Benchmarks possess stability of C or higher
• Benchmarks shown on old FIRMs may not possess stability of C or higher and
thus will not be shown on the new DFIRMs
35. 144
Contact Information
Kerry Bogdan, Kerry.Bogdan@fema.dhs.gov
Greg Stewart, gstewart@usgs.gov
Brian Caufield, CaufieldBA@cdmsmith.com
Links:
FEMA Map Service Center: https://msc.fema.gov
National Geodetic Survey website: http://www.ngs.noaa.gov/
More information is available on line at: http://www.fema.gov/flood-hazard-
mapping-frequently-asked-questions