Coastal Flood Mapping Using
Customized GIS Layers
by Jeff Zanotti
National Flood Insurance Program
 NFIP established in 1968
 Community participation is
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voluntary
Participation allows for chance
to buy federal flood insurance in
exchange for community
floodplain management
regulations
Buildings constructed in
compliance with NFIP standards
suffer around 80% less damage
annually
Over 350 communities in
Alabama participate
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Map Modernization
 Majority of Flood Insurance Rate Maps (FIRMs) have become

outdated in Alabama
FEMA assumes primary ownership of creation of the new flood maps
with Alabama’s Office of Water Resources (OWR) being responsible
for the Alabama Flood Map Modernization Program
“The mission of the program is to make Alabama and its citizens less
vulnerable to the impact of flooding through statewide floodplain
management and provide local communities with the tools and
resources for managing, assessing and planning for development in
flood prone areas to reduce the loss of life and property”
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Coastal Issues
 Storm surge plays an important


role in controlling flooding along
the coast
Unlike riverine flooding, coastal
flooding also takes into account
the impact of waves in
designated special flood hazard
areas
The impact of waves can be
affected by numerous variables:
sand dunes, barrier islands,
type of vegetation, buildings, etc
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AMEC Tool
 AMEC created a tool that would efficiently and accurately take into
account those variables while modeling
 Developed using VB.NET
 Works as a toolbar within ESRI’s ArcGIS Desktop 9.3
 Utilizes WHAFIS 4.0 and RUNUP 2.0 which are required to be
installed on the computer running the Coastal Tool
 Requires a combination of customized GIS layers
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GIS Layers
 Transects
 Survey Points
 PFD Crest
 PFD Heel
 Buildings
 Vegetation
 Surface DEM
 Surge DEM
 Over Water Fetch
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Transects
 Polylines that run from the body
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of water inland
Drawn from scratch in GIS by
engineers and water resource
specialists
Similar to cross sections in
riverine studies
Evenly spaced throughout the
entire study area
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Survey Points
 Point survey data containing
ground elevation
 Also can be coded for toe, peak,
and heel of dune
 Points are taken along transects
 This layer is optional dependent
upon the quality of the surface
DEM
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PFD Crest and PFD Heel
 Polylines of the primary frontal
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dune’s crest and heel
These will not always be used
as not all coastal areas have
dunes
Assist in profiling the level of
dune erosion and whether or
not that will affect wave impact
These lines can be constructed
using survey, obtained from
data of local gov’t, or made from
high resolution Lidar
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Buildings
 Polygons of buildings digitized
from aerial imagery
 Not individual buildings; groups
of buildings with similar
attributes (i.e. width, layout,
spacing, etc)
 Calculations are made or
estimated (based on quality of
aerial and size of the structures)
to assess the “open space ratio”
of each polygon
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Buildings (continued)
 Calculations involving row width


and building width are done in
GIS and reflective to properties
perpendicular to the coast line
Polygons must be a certain
length, dependent upon the
spacing of the transects in that
area
Google Street View and in field
data collection allowed for the
percentage of houses on stilts
to be taken into account
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Vegetation
 Polygons representing areas of
similar vegetation type
 These polygons were
determined by using a
combination of online datasets
from gov’t agencies, remote
sensing data, and aerial
photography
 Data had to be put into a format
that WHAFIS could read
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Vegetation - Reclassification
 Land use reclassification values
 Marsh Vegetation
– Herbaceous Wetlands
 Rigid Vegetation
– Deciduous Forest
– Evergreen Forest
– Mixed Forest
– Woody Wetland
– Shrubland
 Other
– Agriculture
– Barren
– Urban
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Vegetation - GAP
 GAP national land cover data
was used as a helpful tool in
reclassifying land use into
WHAFIS accepted values
 Pixel resolution was too low to
be able to use in its current
 Digitization had to be done to
make smoother polygons that
more effectively matched aerial
photography
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Vegetation - FIA
 From WHAFIS model input parameters similar plant characteristics
included:
 Drag coefficient
 Mean wetted height
 Mean effective diameter
 Mean horizontal spacing
 Spatial join with Forest Inventory and Analysis (FIA) data was
performed on the reclassified polygons to get a representation
average for each of the sub groups
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Vegetation – Marsh Grass
 WHAFIS input model
incorporates information based
on marsh grass type
 2 main marsh grass types on
the Alabama coast
 Spartina alterniflora
 Juncus roemerianus
 A guiding shapefile was used
from the U.S. Fish & Wildlife
Service’s National Wetland
Inventory
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Vegetation – Marsh Grass (continued)
 National Wetland Inventory’s
(NWI) habitat shapefile came
with various extraneous
polygons as well that had to be
weeded out
 Areas associated with marsh
grass were determined by the
corresponding habit based on
Cowardin classification
 NWI’s shapefile needed to be
reshaped to match up with
aerial photography
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Surface DEM
 Digital Elevation Model depicting the topography of the study area
 The better the DEM the more accurate the model will be
 AMEC obtained local Lidar as well as detailed coastline Lidar from
NOAA’s Digital Coast website
 There was a concern of edge matching the DEM and Finite Mesh
Development for storm surge modeling by FEMA and the Northwest
Florida Water Management District
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Surge DEM
 Raster DEMs
 10 year surge
 100 year surge with wave setup
 100 year surge without wave
setup
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Over Water Fetch
 Fetch is area of open water over
which wind can blow (i.e.
sounds, oceans, bays, etc)
 Transfer of energy from the
wind to the water caused by
frictional drag
 Larger the fetch the bigger the
waves that can be generated by
the wind
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Data QA/QC
 Field visits were made to select
transects for data verification
 Data and photos were recorded
from these locations using a
smart phone application
 Many transect locations
required coordination with other
local and state agencies in
order to record field data
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Advantages of Smart Phone App
 Data is uploaded immediately to server
 No need to unload and then sort through large amounts of data once
returning from the field
 Data can be used instantaneously
 If the phone is damaged or broken the data is not lost
 Less equipment needed out in the field
 Can be more efficient
 Can go more places
 Utilizes a variety of tools normally inaccessible out in the field
 Data is uniform regardless of who is sent out in the field
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Coastal Inspection Data Entry
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Coastal Inspection Data Entry/Viewing
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Ready to Run the Coastal Tool
 Data is formatted and compiled, now we are ready to run the Coastal
Tool
 9 steps to the tool
 Tool guides you step by step
 Some of the 9 steps are optional dependent on the study area
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Step 1
 Create Transect Database(s)
 Sets up individual databases for
each transect
 Requires Surface and Transects
shapefile
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Step 2
 Integrate Survey
 Optional step
 Set Search Radius for distance
from transects
 Requires Survey Points
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Step 3
 Dune Erosion
 User chooses method of erosion:
Retreat or Removal
 Step is dependent on the
presence of dunes in the study
area
 Requires PFD Crest, PFD Heel,
and Surge DEMs
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Step 3 (continued)
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Step 4
 Populate Transect Nodes
 This step utilizes the most
customized GIS layers
 Loads layer data into transect
databases
 Requires vegetation, buildings,
over water fetch, PFD Crest, and
Surge DEM layers
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Step 5
 Generate WHAFIS Input
 Transforms data into a WHAFIS
models
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Step 6
 Run WHAFIS
 WHAFIS input and output files
are placed in the transect
databases
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Step 7
 Generate RUNUP Input
 Creates RUNUP model
 User chooses a roughness
coefficient
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Step 8
 Run RUNUP Models
 Puts outputs into transect
databases
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Step 9
 Generate Summary Transects
 Integrates all the previous
modeling steps to generate a
summary of all relevant locations
along each transect
 This step analyzes where to
determine zone breaks for
mapping
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Questions?
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