Fort Kent - USGS

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					Flood Inundation Modeling and Mapping Pilot Project for Fort Kent,
Maine
Co-Investigators:
Pamela J. Lombard, Hydrologist, Maine Water Science Center, USGS
Phone: (207) 622-8201 x130 email: plombard@usgs.gov

Lance J. Ostiguy, Physical Scientist, Massachusetts Water Science Center, USGS
Phone: (508) 490-5052           email: lostiguy@usgs.gov

Daniel Walters, Geospatial Liaison for Maine, USGS NSDI Partnership Office
Phone: (207) 776-1293           email: danwalters@usgs.gov

Gregory J. Stewart P.E., Data Section Chief, Maine Water Science Center, USGS
Phone: (207) 622-8201 x118 email: gstewart@usgs.gov

Background/Problem –
The town of Ft. Kent, Maine has a levee that was nearly overtopped by significant flooding that occurred in 2008.
Both the Fish River and the St John River had streamflows with annual exceedance probabilities less than 1
percent during this event. Following the April/May 2008 flood, FEMA initiated a project to update the hydrologic
and hydraulic analyses for peak water surface elevations having a 1% and a 0.2 percent chance of being equaled
or exceeded annually for the Fish River and the St. John River in Fort Kent, and to delineate the revised peak
water surface analyses on new topographic mapping developed from LIDAR. The USGS Maine Water Science
Center is in the process of completing the hydrologic and hydraulic analyses and mapping of Fort Kent for FEMA
and drafting Digital Flood Insurance Rate Maps (DFIRMs) that will be available by the end of the fiscal year. See
figure 1 for the region that will be mapped.

Although DFIRMS allow users to see which areas of the town are affected by floods with a 1% and 0.2% chance
of being equaled or exceeded any given year, they do not show the extent and depth of flood inundation that
would occur for a forecast stage during a flooding event in real time. Flood inundation mapping, however, could
show the extent and depth of flooding that would result from incremental increases in stage at a local gage. This
would give state emergency responders and the public a series of maps-- available via the internet--that would
indicate what was inundated at the current time and what the forecasted flow would inundate.

Existing 10%, 2%, 1%, and 0.2% exceedance probability flood flows are determined statistically for a specific site
on a river, and serve as a planning tool for emergency response officials as a part of FEMA’s flood insurance
program. These are statistical flows and do not necessarily reflect actual forecast flood discharges. The National
Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS) forecast and model
precipitation to estimate flood discharges associated with specific storms. These forecasts take the form of peak
flows, peak flood elevations, or plots of one or both of these over time. The forecasts, however, are restricted to
the immediate proximity of the streamflow stations used in the predictions; no flood elevations are predicted for
areas between the stations, and elevations are not mapped to show the region that will be influenced. The
proposed work will address the gap between the availability of flood maps for planning purposes, and the
availability of maps for forecast flood flows.


Objectives and Scope –
The objective of this work is to generate flood-inundation maps for the Fish River and the St John River in Fort
Kent Maine. Maps will be tied to real time data from the USGS streamflow gages, flood forecast information, and
delivered to the public via the Internet. The maps will be created by the Massachusetts Water Science Center on
LIDAR and will depict the approximate area that would be inundated at selected water levels in increments of 1
foot at the nearest streamgage, ranging from approximately top-of-bank to the maximum observed water level.
Maps will be referenced to stream stage at two USGS long-term streamflow gages in Fort Kent and to mean sea
level relative to North American Vertical Datum of 1988.
Figure 1. Portion of Fort Kent, Maine for which flood inundation mapping is being proposed (southeast
US side of the Saint John River only.


Relevance/Benefits/Federal Role –
The Saint John and Fish Rivers in Fort Kent Maine are ideal for a flood inundation modeling and mapping pilot
project. Almost all of the tools necessary for this work are already in place including LIDAR maps for the region,
up-to-date hydrologic and hydraulic analyses for the Fish River and the Saint John River, and active streamflow
gages on both the Fish and Saint John Rivers with over 80 years of record in both cases. Furthermore, Fort Kent
is protected by a levee--creating a need for complex mapping. All work can be calibrated to the stream gage
elevations and high water marks collected by the USGS during the 2008 flood. A small amount of additional work
would leverage all the work that has been done in this region in the last 2 years and provide the local, state, and
federal emergency managers with state of the art flood inundation maps that would serve as a pilot for other
similar projects to be completed in the state and in the northeast.

Emergency management workers will be able to access flood inundation maps that are tied to National Weather
Service flood forecasts during an event. Interactive maps will show them at a glance the roads that are
inaccessible, the properties that are most at risk, and the areas of the town that are unlikely to be affected.

USGS Maine and Massachusetts Water Science Centers are in a unique position to complete this work, as the
Maine Water Science Center has recently surveyed high water marks, natural cross sections and structures on
these rivers, are currently building hydraulic models for the St John and Fish Rivers in Fort Kent, and will be
creating and providing DFIRMs for this region. The Massachusetts-Rhode Island Water Science Center has
extensive GIS and LIDAR mapping capabilities and will be able to apply the work to create a library of real-time
interactive maps. This work will provide a template for future flood inundation maps in New England and the
northeast.
Approach –
All of the relevant existing data will be compiled. This includes up-to-date hydraulic river models for the St. John
River and the Fish River in Fort Kent, LIDAR maps for the river corridors in Fort Kent, and stream gaging data for
the two USGS gages with long-term data in the region (Fish River near Fort Kent, Maine (USGS station number
01013500) and the St. John River below Fish R, at Fort Kent, Maine (USGS station number 01014000).

The hydraulic models will be calibrated for all river stages from bank-full to the 0.02 percent chance of
exceedance flow at 1-foot increments at each gage. Streamflows and their associated stream stages will be
compiled and linked to NWS flood forecast data that is available on the internet in real time.

One foot increments in stage will be mapped in GIS and output into tiled overlays for google map at selected
zoom intervals. The State of Maine Office of GIS will serve these images that will be tied to the flood forecast
website. All images will be available via the internet for the forecast stage for a region during high water events.
Images for other stages will be available by user selection.

Products and Audience –
The planned products include an internet application for Fort Kent Maine that displays a flood inundation map for
any flood forecast for the region. The applicable map as well as all other maps will be available to emergency
management workers and the public for safety and planning purposes. In addition, a report outlining the
methodology used to develop this pilot product will be published.

Personnel –
USGS Maine Water Science Center
Pamela J. Lombard, Hydrologist-GS12
Phone: (207) 622-8201 x130 email: plombard@usgs.gov

USGS Massachusetts Water Science Center
Lance J. Ostiguy, Physical Scientist, GS-9
Phone: (508) 490-5052           email: lostiguy@usgs.gov

Budget –
Funding request to support USGS staff
USGS MeWSC             $30,000
USGS MaWSC             $30,000

Total request            $60,000

In-kind services:
FEMA region 1; LiDAR data for the study area ($55,000)
State of Maine OGIS; Web hosting maps and serving them to the public ($12,000)
FEMA/USGS MeWSC existing hydraulic and hydrology study ($90,000)

				
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posted:11/11/2011
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