Scientific Investigations Map 3157
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 April-May, 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 water-surface 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.
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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 sheets, scale 1:17,500.
Purpose and Scope
Study Area Description
Constructing Water-Surface Profiles
Hydrologic and Steady Flow Data
Energy Loss Factors
Model Calibration and Performance
Development of Water-Surface Profiles
St. John and Fish Rivers, Fort Kent, Maine, Flood-Inundation Maps on the Internet
Uncertainty Associated with Inundation Maps