St. John River 

River

Fish

MARKET STREET Fort Kent AVENUE DES ÉRABLES

New Brunswick MAINE

CANADA

UNITED STATES

01014000

01013500

W MAIN STREET

International

Bridge

BRIDGE ST

MILLS RD

Old USGS streamgage

11

11 161

161

161

1

1

Prepared in cooperation with the Federal Emergency Managment Agency, Region 1

Flood-Inundation Maps for the St. John and

Fish Rivers in Fort Kent, Maine

U.S. Department of the Interior

U.S. Geological Survey

Pamphlet to accompany

Scientific Investigations Map 3157
Cover: Image of Fort Kent, Maine, from Global Relief Technologies, 2008.
Flood-Inundation Maps for the St. John and 

Fish Rivers in Fort Kent, Maine

By Pamela J. Lombard

Prepared in cooperation with the Federal Emergency Management Agency, 

Region 1

Pamphlet to accompany

Scientific Investigations Map 3157

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Lombard, P.J., 2011, Flood-Inundation maps for the St. John and Fish Rivers in Fort Kent, Maine: U.S. Geological 

Survey Scientific Investigations Map 3157, 8 p. pamphlet, 29 map sheets, scale 1:17,500.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Study Area Description........................................................................................................................3

Previous Studies ...................................................................................................................................3

Methods...........................................................................................................................................................3

Constructing Water-Surface Profiles................................................................................................4

Topographic/Bathymetric Data ..........................................................................................................4

Hydrologic and Steady Flow Data......................................................................................................4

Energy Loss Factors .............................................................................................................................4

Model Calibration and Performance .................................................................................................4

Development of Water-Surface Profiles...........................................................................................4

Flood-Inundation Maps.................................................................................................................................5

St. John and Fish Rivers, Fort Kent, Maine, Flood-Inundation Maps on the Internet ...............5

Uncertainty Associated with Inundation Maps...............................................................................6

Acknowledgments.........................................................................................................................................7

Summary..........................................................................................................................................................7

References Cited............................................................................................................................................8

Figures

1. Location of study reach for the St. John and Fish Rivers and location of USGS 

streamgage and National Weather Service forecast sites...................................................2

2. Blue squares show the identification number of the correct flood-inundation map 

to choose from the 29 available maps according to current or forecast gage height 

at two USGS streamgages at Fort Kent, Maine; St. John River below Fish River 

(01014000), and Fish River (01013500)........................................................................................7

Tables

1. USGS streamgage information for sites in Fort Kent, Maine ................................................3

2. Comparison of hydraulic-model output and surveyed high-water mark elevations 

from the flood of April–May, 2008, St. John and Fish Rivers, Fort Kent, Maine .................5

3. Discharge in cubic feet per second (cfs) for corresponding gage height estimates 

at selected locations for the St. John River, Fort Kent, Maine, for simulated watersurface profiles .............................................................................................................................6

4. Discharge in cubic feet per second (cfs) for corresponding gage height estimates 

at selected locations for the Fish River, Fort Kent, Maine, for simulated watersurface profiles .............................................................................................................................6
iv

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square foot (ft2

) 0.0929 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
Flood-Inundation Maps for the St. John and Fish Rivers in 

Fort Kent, Maine

By Pamela J. Lombard

Abstract

Digital flood-inundation maps for a 2.5-mile reach of 

the St. John River and a 2-mile reach of the Fish River were 

created by the U.S. Geological Survey (USGS) in cooperation 

with the Federal Emergency Management Agency (FEMA). 

The St. John River reach extends from 1,000 feet (ft) upstream 

from the International Bridge in Fort Kent, Maine, to 5,000 

ft downstream from the International Bridge. The 2-mile 

reach of the Fish River extends from just upstream from 

Mills Road to its confluence with the St. John River in Fort 

Kent. The inundation maps, which can be accessed through 

the USGS Flood Inundation Mapping Science Web site at 

http://water.usgs.gov/osw/flood_inundation/ depict estimates 

of the areal extent and depth of flooding corresponding to 

selected water levels (gage heights) at the USGS streamgage, 

St. John River below Fish River at Fort Kent, Maine (station 

01014000) and the USGS streamgage, Fish River near Fort 

Kent, Maine (station 01013500). Current gage heights at these 

USGS streamgages may be obtained on the Internet at http://

waterdata.usgs.gov/me/nwis/current/?type=flow The National 

Weather Service (NWS) forecasts flood hydrographs at places 

that are often collocated at USGS streamgages, such as the 

two gages mentioned above. Forecasted peak-gage-height 

information, also available on the Internet, may be used in 

conjunction with the maps developed during this study to 

show predicted areas of flood inundation.

For this study, flood profiles were computed for the 

stream reach by means of a one-dimensional step-backwater 

model. The model was calibrated using gage height-discharge 

relations at USGS streamgages 01014000 and 01013500, 

and documented high water marks from a flood in AprilMay, 2008. The hydraulic model was then used to determine elevations throughout the study reaches for nine gage 

heights at streamgage 01014000, and for seven gage heights 

at streamgage 01013500. Flood-inundation maps for this 

report include 29 combinations of gage heights at the two 

streamgages. Gage heights are referenced to the streamgage 

datums and range from bankfull to approximately the highest 

recorded water level at the streamgages. The simulated watersurface profiles were then combined with a geographic information system (GIS) digital elevation model (derived from 

Light Detection and Ranging (LiDAR) data having a 0.6-ft 

vertical and 3.3-ft horizontal resolution) in order to delineate 

the area flooded at each water level.

Flood inundation maps and current gage heights from 

USGS streamgages and forecasted stream gage heights from 

the NWS are all available on the internet. These data provide 

emergency management personnel and residents from Fort 

Kent with information that is critical for flood-response activities such as evacuations, road closures, emergency shelter 

location, disaster declarations and postflood recovery efforts.

Introduction

The town of Fort Kent, Maine, is a small urban community with an estimated population of 4,300 (Maine Register, 

2009). Fort Kent has experienced severe flooding numerous 

times, most notably in 1974, 1979, and 2008. The majority of 

flood damages have occurred in Fort Kent at the confluence of 

the St. John and Fish Rivers (fig. 1).

Prior to this study, Fort Kent officials have relied on 

several information sources to make decisions on how best 

to alert the public and mitigate flood damages. One source is 

the Federal Emergency Management Agency (FEMA) Flood 

Insurance Study (FIS) for Fort Kent dated February, 1984 

(Federal Emergency Management Agency, 1984). A second 

source of information is the USGS streamgages on the St. 

John and Fish Rivers in Fort Kent (table 1) from which current or historical water levels (gage height) can be obtained 

at http://waterdata.usgs.gov/me/nwis/current/?type=flow. A 

third source is the National Weather Service (NWS) forecast 

of peak gage height at the USGS streamgages through the 

Advanced Hydrologic Prediction Service (AHPS) website at 

http://www.erh.noaa.gov/nerfc/index.shtml. Although FEMA 

flood-insurance studies provide maps of theoretical floods for 

given exceedance probabilities, these maps do not necessarily correspond to current or forecast flood elevations and do 

not indicate how deep the water is at locations other than near 

USGS streamgages or NWS flood-forecast points. USGS current gage height and NWS forecast gage height information is 

useful for residents in the immediate vicinity of a streamgage, 

but is of limited use to residents upstream or downstream of 

the streamgage because the water-surface elevations are not 

constant along the stream channel. 
St. John River 

River

Fish

MARKET STREET

Fort Kent AVENUE DES ÉRABLES

New Brunswick MAINE

CANADA

UNITED STATES

01014000

01013500

W MAIN STREET

International

Bridge

BRIDGE ST

MILLS RD

Old USGS streamgage

MAINE

Study

area

Orthography from Global Relief Technologies, 2008. National boundary from U.S. Geological Survey National Map available at 

http://viewer.nationalmap.gov/viewer. Position of boundary on this map is approximate and for informational purposes only.

EXPLANATION

Flow arrow—Indicates

direction of water flow

National Boundary

USGS streamgage and number

State route marker

U.S. route marker

Old USGS streamgage (no longer in use)

01014000

11

11

161

161

161

1

1

161

1

47°14’

47°15’

47°16’

47°17’

68°37’ 68°36’ 68°35’

0 .5 1 KILOMETERS

0 .5 1 MILES

Figure 1. Location of study reach for the St. John and Fish Rivers and location of USGS 

streamgage and National Weather Service forecast sites.

2 Flood-Inundation Maps for the St. John and Fish Rivers in Fort Kent, Maine
Methods 3

Purpose and Scope

The purpose of this report is to describe the development 

of a series of flood-inundation maps for the St. John and Fish 

Rivers near Fort Kent, Maine, and to make these maps available to emergency workers and the public on the USGS Flood 

Inundation Mapping Science Web site available at http://water.

usgs.gov/osw/flood_inundation/. The purpose is to (1) provide 

users with a library of flood inundation maps that correspond 

to a range of flood elevations on the two rivers that come 

together in Fort Kent, Maine, and (2) provide links between 

NWS forecasted peak stage at streamgages during times of 

flood and the corresponding flood inundation map that shows 

what that forecast stage will look like on the ground.

Study Area Description

The Fish and St. John Rivers are in northern Maine in 

Aroostook County. The St. John River has a drainage area 

of 4,782 mi2 at the International Bridge above the Fish River 

in Fort Kent, and a drainage area of 5,680 mi2 at streamgage 

01014000. The St. John River forms part of the United States–

Canada border before flowing to New Brunswick, Canada, 

and draining into the Atlantic Ocean. It flows northeastward 

in Maine, resulting in ice and snow upriver melting sooner 

than downriver, sending ice jams and heavier flows north and 

downriver to Fort Kent. The river basin is relatively undeveloped and has no dams for most of its length. The Fish River 

has a drainage area of 873 mi2 at streamgage 01013500, and 

a drainage area of 890 mi2 at the mouth. The Fish River flows 

generally northward before entering the St. John River in Fort 

Kent. The flood inundation maps include the St. John River 

from between 1,000 ft upstream from the International Bridge 

in Fort Kent and 5,000 ft downstream from the International 

Bridge; and the Fish River from just upstream from Mills 

Road to its confluence with the St. John River in Fort Kent, 

Maine (fig. 1).

The economy of Fort Kent is diverse, but is centered 

on agriculture (primarily potato crops) and forestry. Nearly 

80 percent of the manufacturing is in wood and paper products. 

Previous Studies

The previous FIS for Fort Kent (Federal Emergency 

Management Agency, 1984) was completed by New England 

Division of the U.S. Army Corps of Engineers for the Federal 

Insurance Administration in September, 1984. That study 

covered the 1.0 and 0.2 percent annual exceedance probability 

water-surface profiles and associated flood-plain maps for all 

significant flooding sources in the town of Fort Kent. A flooddocumentation study of the 2008 flood in northern Maine 

(Lombard, 2010) provided many of the high water marks used 

to calibrate models for this flood-inundation work.

Methods

Tasks specific to development of the maps were (1) 

examination of data from streamgages on the St. John River 

and the Fish River (table 1); (2) collection of topographic 

data and geometric data (for structures/bridges) throughout 

the study reach; (3) determination of energy-loss factors 

(roughness coefficients) in the stream channel and flood 

plain, and steady-flow data; (4) computation of watersurface profiles using the U.S. Army Corps of Engineers 

(USACE) HEC–RAS computer program (U.S. Army Corps 

of Engineers, 2010); (5) production of estimated floodinundation maps corresponding to targeted water surface 

elevations at the gages (gage heights) using the USACE 

HEC–GeoRas computer program (U.S. Army Corps of Engineers, 2009) and a Geographic Information System (GIS); 

and (6) development of an Internet interface that links to 

USGS real-time streamgage information and (or) NWS 

forecasted peak gage height to facilitate the display of userselected flood-inundation maps on the Internet.

Maps were produced for inundation levels referenced to 

gage heights at the USGS streamgage, St. John River below 

Fish River at Fort Kent, Maine (station 01014000), and the 

USGS streamgage, Fish River near Fort Kent, ME (station 

01013500) and range from approximately bankfull to the 

maximum recorded water level at each streamgage. 

Table 1. USGS streamgage information for sites in Fort Kent, Maine.

Station name Station

number

Drainage

area

(mi2

)

Latitude Longitude Period of record Maximum flood elevation 

(ft above NAVD 88)

and date

St. John River 

below Fish 

River at Fort 

Kent, Maine

01014000 5,680 47°15'29" 68°35'45" Oct., 1926 to 2010 517.64 ft1

April 30, 2008

Fish River near 

Fort Kent, 

Maine

01013500 873 47°14'15" 68°34'58" Sept., 1929 to 2010 524.60 ft

April 30, 2008

1

Corresponds to an approximate elevation of 512.1 ft NAVD88 or a gage height of 27.7 ft at current (2010) location of gage (latitude 47°16'59.9", longitude 

68°35'6.6")
Constructing Water-Surface Profiles

The water-surface profiles used to produce the floodinundation maps in this study were computed using 

HEC–RAS, version 4.1.0 (U.S. Army Corps of Engineers, 

2010). HEC–RAS is a one-dimensional step-backwater 

model for simulation of water-surface profiles with steadystate (gradually varied) or unsteady-state flow computation 

options. The HEC–RAS analysis for this study was done 

using the steady-state flow computation option.

Topographic/Bathymetric Data

Global positioning system (GPS) static surveys were 

used to establish a local control network at locations near the 

streams studied. All topographic data are referenced horizontally to the North American Datum of 1983 (NAD 83) and to 

the North American Vertical Datum of 1988 (NAVD 88), and 

are projected in Maine State Plane East coordinates in feet.

Streambank elevations and hydraulic structure geometries 

were obtained from USGS field surveys using differential 

leveling techniques to tie elevations to the local control network described above. Structural dimensions for four bridges 

were measured and surveyed in the field concurrently with the 

stream-channel surveys. Underwater depths were determined 

using hydroacoustic instrumentation to profile the channel 

bottom in relation to the water surface. A detailed description 

of the methods used to acquire and process the topographic and 

bathymetric data can be found in Bales and others (2007).

Light Detection and Ranging (LiDAR) data were collected and post processed in 2009 by The Sanborn Map 

Co., Inc. Using a Geographic Information System (GIS), a 

Triangular Irregular Network (TIN) was developed from the 

digital grids provided by The Sanborn Map Co. to supplement 

surveyed cross-sectional data and provide digital elevation 

data for mapping. Selected data collected during the GPS field 

surveys were used by the USGS to perform quality-control 

checks of the LiDAR mapping data.

Hydrologic and Steady Flow Data

The study area hydrologic network consists of two 

streamgages, both with more than 80 years of record (fig. 1; 

table 1). Gage height is measured continuously at the two sites 

from which continuous records of streamflow are computed. 

All water-surface elevations are referenced to gage datum and 

to NAVD 88. The streamgages are equipped with satellite radio 

transmitters that allow data to be transmitted routinely to the 

Internet within an hour of collection. Data can be accessed 

at http://waterdata.usgs.gov/me/nwis/current/?type=flow by 

clicking on the appropriate station number.

Energy Loss Factors

Field observations and high-resolution aerial photographs were used to select initial (pre-calibration) Manning’s 

roughness coefficients (“n” values) for energy (friction) loss 

calculations. Initial values of n were adjusted as part of the 

calibration process. The n-values for the main channel of 

the St. John River range from 0.023 to 0.049, and n-values 

for overbanks range from 0.07 to 0.09. For the main channel of the Fish River, n-values range from 0.048 to 0.05 and 

n-values for overbanks range from 0.085 to 0.1.

Model Calibration and Performance

The hydraulic model was calibrated to the gage 

height-discharge relations at the St. John and Fish River 

streamgages in Fort Kent and high-water marks from the 

flood in 2008 (Lombard, 2010). The estimated peak discharge for the April-May 2008 flood was 183,000 ft3

/s 

with an estimated gage height of 517.64 ft at streamgage 

01014000. The estimated peak discharge for the 2008 flood 

was 18,300 ft3/s, with an estimated gage height of 524.6 ft at 

streamgage 01013500. Model calibration was accomplished 

by adjusting Manning’s n-values and loss coefficients until 

the results of the hydraulic computations closely agreed with 

the known flood discharge and gage height values. Differences between measured and simulated gage heights for 

models calibrated to high-water marks were less than 0.2 ft 

except at the mouth of the Fish River which is affected by 

backwater from the St. John River (table 2). In this case 

modeled gage height is 0.74 feet lower than gage height 

observed during the April-May 2008 flood. The model 

reflects backwater from the St. John River at this location. 

Details on techniques used in model development and calibration can be found in Bales and others (2007).

Development of Water-Surface Profiles

Profiles were developed for nine gage heights at 1-ft 

intervals between 20.6 ft and 28.6 ft as referenced to a local 

gage datum at streamgage 01014000, corresponding to 

elevations of between 505 and 513 ft NAVD88. In addition, 

profiles were developed for seven gage heights at 1-ft intervals 

between 8.3 ft and 14.3 ft as referenced to a local gage datum 

at station 01013500—corresponding to elevations of between 

519 and 525 ft NAVD 88.

Models on the Fish River and the St. John River were 

calibrated to produce the selected profile elevations at the 

streamgages (tables 3 and 4). Discharges at the mouth of the 

Fish River were determined by drainage-area adjustment 

calculations by using the following equation:

4 Flood-Inundation Maps for the St. John and Fish Rivers in Fort Kent, Maine
Flood-Inundation Maps 5

 Qungaged = Qgaged(DAungaged/DAgaged)b

where

Qungaged is the unknown flow at a location upstream or 

downstream from the streamgage in cubic feet per 

second (cfs),

Qgaged is the flow at the gage in cfs,

DA is the drainage area in square miles,

and b is a coefficient that depends on the exceedance 

probability (Hodgkins, 1999).

Discharges on the St. John River upstream from the confluence of the Fish River were determined by subtracting the 

discharge of the Fish River at the mouth from the discharge 

of the St. John River at the streamgage downstream from the 

Fish River confluence. Drainage areas were calculated in GIS 

and are based on a USGS watershed boundary data layer at a 

scale of 1:24,000.

Flood-Inundation Maps

Flood-inundation maps were created for 29 combinations 

of profiles at the two USGS streamgages, both of which are 

NWS flood-forecast points (fig. 2). The maps were created in a 

GIS by combining the water-surface profiles and digital elevation model data. The digital elevation model data were collected and processed to meet 3.3-ft (root-mean-squared error) 

horizontal accuracy and a vertical accuracy of 0.6 ft. Estimated 

flood-inundation boundaries for each simulated profile were 

developed with HEC–GeoRAS software (U.S. Army Corps 

of Engineers, 2009). HEC–GeoRAS is a set of procedures, 

tools, and utilities for processing geospatial data in ArcGIS 

by use of graphical user interface (Whitehead and Ostheimer, 

2009). The interface allows the preparation of geometric data 

for import into HEC–RAS and processes simulation results 

exported from HEC–RAS (U.S. Army Corps of Engineers, 

2010). The HEC–GeoRAS results at the cross sections were 

adjusted to ensure a hydraulically reasonable transition of 

the boundary between modeled cross sections relative to the 

contour data for the land surface (Whitehead and Ostheimer, 

2009). The maps show estimated flood-inundation areas overlaid on high-resolution, georeferenced, aerial photographs of 

the study area for each of the water-surface profiles that were 

generated by the hydraulic model.

St. John and Fish Rivers, Fort Kent, Maine, 

Flood-Inundation Maps on the Internet

A USGS Flood Inundation Mapping Science World Wide 

Web portal has been established by the USGS at url http://

water.usgs.gov/osw/flood_inundation/ to provide floodinundation information to the public. The maps and data 

from this study showing the extent of inundated areas can be 

downloaded in three electronic file formats from that portal; 

(1) GIS shapefile format (2) kmz file format, and (3) Portable 

Document (PDF) Format. Users can print out formatted maps 

quickly or create a customized map using available GIS data 

layers. In addition, downloadable GIS raster files and kmz 

map files showing the depth of flooded areas are available at 

the web portal. All pdf and kmz maps show aerial photography 

beneath the flood layers. The estimated flood-inundation maps 

are displayed in sufficient detail to note the extent of flooding with respect to individual structures so that preparations 

for flooding and decisions for emergency response can be 

performed efficiently.

Each stream reach displayed on the Web portal contains links to USGS graphs of the current gage height and 

Table 2. Comparison of hydraulic-model output and surveyed high-water mark 

elevations from the flood of April–May, 2008, St. John and Fish Rivers, Fort Kent, 

Maine. [ft, feet]

River station High-water 

mark elevation 

(ft) ( NAVD88)

Model water-surface 

elevation (ft)

Elevation 

difference (ft)

St. John River

Old streamgage in New 

Brunswick, Canada 517.64 517.63 –0.01

International Bridge 520.53 520.54 +0.01

Fish River

Route 1 Bridge 520.04 519.3 –0.74

350 ft downstream from 

Bridge Street 521.67 521.67 0

Streamgage 01013500 524.6 524.5 -0.1
6 Flood-Inundation Maps for the St. John and Fish Rivers in Fort Kent, Maine

Table 3. Discharge in cubic feet per second (cfs) for corresponding gage height estimates at selected locations for the St. John 

River, Fort Kent, Maine, for simulated water-surface profiles.

Gage height in feet 

above gage datum 

(parentheses 

reference NAVD 88)

20.6

(505)

21.6

(506)

22.6

(507)

23.6

(508)

24.6

(509)

25.6

(510)

26.6

(511)

27.6

(512)

28.6

(513)

Streamgage no. 

01014000

101,500 108,800 117,600 128,700 140,000 152,900 166,400 180,500 195,000 

Upstream from Fish 

River confluence

92,600 99,300 107,400 117,600 128,000 139,900 152,400 165,400 178,700 

Table 4. Discharge in cubic feet per second (cfs) for corresponding gage height estimates at selected locations for the Fish River, 

Fort Kent, Maine, for simulated water-surface profiles.

Gage height in feet 

above gage datum 

(parentheses 

reference NAVD 88)

8.3

(519)

9.3

(520)

10.3

(521)

11.3

(522)

12.3

(523)

13.3

(524)

14.3

(525)

At mouth 7,500 9,400 11,000 14,000 15,100 16,300 19,600

Streamgage no.

01013500

7,300 9,200 10,800 13,800 14,800 15,900 19,200

streamflow at streamgages 01014000 and 01013500—to which 

the inundation maps are referenced. A link also is provided to 

the NWS Advanced Hydrologic Prediction Service (AHPS) 

site (http:/water.weather.gov/ahps/) so that the user can obtain 

applicable information on forecasted peak gage heights. 

Uncertainty Associated with Inundation Maps

Although the flood-inundation maps represent the 

boundaries of inundated areas with a distinct line, some 

uncertainty is associated with these maps. The flood boundaries shown were estimated based on gage heights at selected 

USGS streamgages. Water-surface elevations along the stream 

reaches were estimated by steady-state hydraulic modeling, 

assuming unobstructed flow and using discharges and hydrologic conditions anticipated at the USGS streamgage(s). The 

hydraulic model reflects the land-cover characteristics and any 

bridge, dam, levee, or other hydraulic structures existing in 

2010. Unique meteorological factors (timing and distribution 

of precipitation) may cause actual discharges along the modeled reach to vary from assumed conditions during a flood and 

lead to deviations in the water-surface elevations and inundation boundaries shown. Additional areas may be flooded due to 

unanticipated backwater from major tributaries along the main 

stem or from localized debris or ice jams. Inundated areas 

shown should not be used for navigation, regulatory, permitting, or other legal purposes. The USGS provides these maps 

as a quick reference and emergency planning tool but assumes 

no legal liability or responsibility for any direct, indirect, incidental, consequential, special, or exemplary damages or lost 

profit resulting from the use or misuse of this information.

If this series of flood-inundation maps will be used 

in conjunction with NWS river forecasts, the user should be 

aware of additional uncertainties. The NWS uses forecast 

models to estimate the quantity and timing of water flowing 

through selected stream reaches in the United States. These 

forecast models (1) estimate the amount of runoff generated by 

a precipitation or snowmelt event, (2) simulate the movement 

of floodwater as it proceeds downstream, and (3) predict the 

flow and gage height for the stream at a given location (AHPS 

forecast point) throughout the forecast period (every 6 hours 

over 3 to 5 days).
Summary 7

Figure 2. Blue squares show the identification number of the correct flood-inundation 

map to choose from the 29 available maps according to current or forecast gage 

height at two USGS streamgages at Fort Kent, Maine; St. John River below Fish River 

(01014000), and Fish River (01013500).

19

10 11 12

13 14

15 16

17

18

20 21

22 23

24 25 8

28 26 9

29 27

1 2 3

4 5

6 7

20.6 21.6 22.6 23.6 24.6 25.6 26.6 27.6 28.6

8.3

9.3

10.3

11.3

12.3

13.3

14.3

Gage height at USGS streamgage no. 01014000, St. John River below Fish River at Fort Kent (in feet)

Gage height at USGS streamgage no. 01013500,

Fish River near Fort Kent (in feet)

Choosing the Correct Map for Forecast Flood

Acknowledgments

The author thanks the many local, State, and Federal 

agencies that have cooperated in the funding for the operation 

and maintenance of the streamgages used for this study, especially the Maine Emergency Management Agency, the Maine 

River Flow Advisory Commission, the International Joint 

Commission, and the National Weather Service. 

Summary

A series of estimated flood-inundation maps were developed in cooperation with FEMA for the St. John and Fish 

Rivers in Fort Kent, Maine. These maps, available at a USGS 

Web portal, in conjunction with the real-time gage height 

data from USGS streamgages 01014000 and 01013500, and 

NWS flood forecasts, can help to guide the general public 

in taking individual safety precautions and can provide city 

officials with a tool to manage emergency flood operations 

and flood-mitigation efforts. 

The maps were developed using the U.S. Army Corps 

of Engineers’ HEC–RAS and HEC–GeoRAS programs to 

compute water-surface profiles and to delineate estimated floodinundation areas and depth of flooding for selected gage heights. 

The maps show estimated flood-inundation areas overlaid on 

a high-resolution georeferenced aerial photograph of the study 

area. Maps reflect profiles developed for nine gage heights 

between 20.6 ft and 28.6 ft at streamgage 01014000 (505 and 

513 ft NAVD88) and seven gage heights between 8.3 ft and 

14.3 ft at streamgage 01013500 (519 and 525 ft NAVD88). 
8 Flood-Inundation Maps for the St. John and Fish Rivers in Fort Kent, Maine

Publishing support provided by:

Denver Publishing Service Center

For more information concerning this publication, contact:

Director, Maine Water Science Center

U.S. Geological Survey

196 Whitten Road

Augusta, ME 04330

(207) 622-8201

Or visit the Maine Water Science Center

Web site at:

http://me.water.usgs.gov/

References Cited

Bales, J.D., Wagner, C.R., Tighe, K.C., and Terziotti, Silvia, 

2007, LiDAR-derived flood-inundation maps for realtime flood-mapping applications, Tar River Basin, North 

Carolina: U.S. Geological Survey Scientific Investigations 

Report 2007–5032, 42 p.

Federal Emergency Management Agency (FEMA), 1984, 

Flood insurance study, town of Fort Kent, Aroostook 

County, Maine. Washington, D.C., 19 p.

Hodgkins, G, 1999. Estimating the magnitude of peak flows 

for streams in Maine for selected recurrence Intervals: U.S. 

Geological Survey Water-Resources Investigations Report 

99–4008, 45 p.

Lombard, P.J., 2010, Flood of April and May 2008 in northern 

Maine: U.S. Geological Survey Scientific Investigations 

Report 2010–5003, 17 p. Available at http://pubs.usgs.gov/

sir/2010/5003/.

Maine Register, 2009, Maine register state yearbook and legislative manual no. 140: Standish, Maine, Tower Publishing 

Company.

U.S. Army Corps of Engineers, 2009, Hydrologic Engineering 

Center, HEC-GeoRAS, GIS Tools for Support of HEC–

RAS at http://www.hec.usace.army.mil/software/hec-ras/

hec-georas_downloads.html

U.S. Army Corps of Engineers, Hydrologic Engineering Center, 2010, HEC–RAS River Analysis System, version 4.1, 

at http://www.hec.usace.army.mil/software/hec-ras/hecrasdownload.html.

Whitehead, M.T., and Ostheimer, C.J., 2009, Development 

of a flood-warning system and flood-inundation mapping 

for the Blanchard River in Findlay, Ohio: U.S. Geological 

Survey Scientific Investigations Report 2008–5234, 9 p.
Lombard—Flood-Inundation Maps for the St. John and Fish Rivers in Fort Kent, Maine—U.S. Geological Survey Scientific Investigations Map 3157