Coastal Flood Mapping Using Customized GIS Layers by Jeff Zanotti.
-
Upload
davion-costello -
Category
Documents
-
view
233 -
download
0
Transcript of Coastal Flood Mapping Using Customized GIS Layers by Jeff Zanotti.
Coastal Flood Mapping Using Customized GIS Layers
by Jeff Zanotti
2
National Flood Insurance Program
NFIP established in 1968
Community participation is 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
3
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Majority of Flood Insurance Rate Maps (FIRMs) have become outdated in Alabama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”
4
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
5
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
6
GIS Layers
Transects
Survey Points
PFD Crest
PFD Heel
Buildings
Vegetation
Surface DEM
Surge DEM
Over Water Fetch
7
Transects
Polylines that run from the body 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
8
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
9
PFD Crest and PFD Heel
Polylines of the primary frontal 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
10
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
11
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
12
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
13
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
14
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
15
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
16
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
17
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
18
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
19
Surge DEM
Raster DEMs
10 year surge
100 year surge with wave setup
100 year surge without wave setup
20
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
21
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
22
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
23
Coastal Inspection Data Entry
24
Coastal Inspection Data Entry/Viewing
25
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
26
Step 1
Create Transect Database(s) Sets up individual databases for
each transect Requires Surface and Transects
shapefile
27
Step 2
Integrate Survey Optional step Set Search Radius for distance
from transects Requires Survey Points
28
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
29
Step 3 (continued)
30
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
31
Step 5
Generate WHAFIS Input Transforms data into a WHAFIS
models
32
Step 6
Run WHAFIS WHAFIS input and output files
are placed in the transect databases
33
Step 7
Generate RUNUP Input Creates RUNUP model User chooses a roughness
coefficient
34
Step 8
Run RUNUP Models Puts outputs into transect
databases
35
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
36
Questions?