TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY

Transcription

1 TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY PRELIMINARY: 01/07/2013 Federal Emergency Management Agency COMMUNITY NUMBER V000A

2 NOTICE TO FLOOD INSURANCE STUDY USERS Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS) may not contain all data available within the repository. It is advisable to contact the community repository for any additional data. Selected Flood Insurance Rate Map panels for the community contain information that was previously shown separately on the corresponding Flood Boundary and Floodway Map panels (e.g., floodways, cross sections). In addition, former flood hazard zone designations have been changed as follows: Old Zone A1 through A30 V1 through V30 B C New Zone AE VE X X Part or all of this Flood Insurance Study may be revised and republished at any time. In addition, part of this Flood Insurance Study may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the Flood Insurance Study. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current Flood Insurance Study components. ii

3 TABLE OF CONTENTS 1.0 INTRODUCTION... 1 Page 1.1 Purpose of Study Authority and Acknowledgments Coordination AREA STUDIED Scope of Study Community Description Principal Flood Problems Flood Protection Measures ENGINEERING METHODS Hydrologic Analyses Hydraulic Analyses Vertical Datum FLOOD PLAIN MANAGEMENT APPLICATIONS Flood Boundaries Floodways INSURANCE APPLICATION FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES iii

4 TABLE OF CONTENTS (Cont) FIGURES Figure 1 - Floodway Schematic TABLES Page Table 1 Community Map History... 2 Table 2 Summary of Discharges... 7 Table 3 Floodway Data EXHIBITS Exhibit 1 - Flood Profiles Fish River Perley Brook St. John River Panels 01P-03P Panel 04P Panels 05P-10P Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map iv

5 1.0 INTRODUCTION FLOOD INSURANCE STUDY TOWN OF FORT KENT, AROOSTOOK COUNTY, MAINE 1.1 Purpose of Study This Flood Insurance Study investigates the existence and severity of flood hazards in the Town of Fort Kent, Aroostook County, Maine, and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of This study has developed flood risk data for various areas of the community that will be used to establish actuarial flood insurance rates and to assist the community in its efforts to promote sound floodplain management. Minimum floodplain management requirements for participation in the National Flood Insurance Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR, This Flood Insurance Study (FIS) revises and updates a previous FIS/Flood Insurance Rate Map (FIRM) for the Town of Fort Kent, Aroostook County, Maine (Federal Emergency Management Agency, 1984). The 1984 study was based heavily off of the December 1979 FIS that is referred to throughout this FIS. This information will be used by the Town of Fort Kent to update existing floodplain regulations as part of the Regular Phase of the National Flood Insurance Program (NFIP). The information will also be used by local and regional planners to further promote sound land use and floodplain development. In some States or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than the minimum Federal requirements. In such cases, the more restrictive criteria take precedence, and the State (or other jurisdictional agency) will be able to explain them. 1.2 Authority and Acknowledgments The sources of authority for this FIS report are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of Information on the authority and acknowledgments for each of the previously printed FISs and FIRMs for community of Fort Kent has been compiled, and is shown below. For the 1979 FIS report (Federal Emergency Management Agency, 1979) the hydrologic and hydraulic analyses were performed by the New England Division of the U.S. Army Corps of Engineers for the Federal Emergency Management Agency (FEMA), under Inter-Agency Agreement No. IAA-H-7-76 and Project order No. 29 and IAA-H-10-77, Project Order No. 4. This work, which was completed in September of 1978, covered all significant flooding sources in the Town of Fort Kent. For the 1984 FIS report (Federal Emergency Management Agency, 1984) the hydrologic and hydraulic analyses were not redone. This study was completed in September of For this update new hydrologic and hydraulic analysis for the Fish and St. John Rivers was performed by the U.S. Geological Survey (USGS), for the Federal Emergency Management Agency (FEMA), under Interagency Agreement No. HSFE01-09-X This study was completed in June,

6 Basemap information for the accompanying Flood Insurance Rate Maps (FIRMs) is from the Maine Office of GIS (MEGIS). Orthophotos are precise to a scale of 1:2400 and 1: Coordination The purpose of an initial Consultation Coordination Officer's (CCO) meeting is to discuss the scope of the FIS. A final CCO meeting is held to review the results of the study. There were three CCO meetings held for the effective study: the initial on December 15, 1975, an intermediate in September, 1978, and the final on June 12, For this FIS, no initial CCO meeting was held; however, the Town of Fort Kent was informed of the scope of the FIS in October 2009 by the USGS. The results of the study were reviewed at the final CCO meeting held in on and attended by representatives of the Town of Fort Kent, FEMA and the USGS. All problems raised at that meeting have been addressed in this study. 2.0 AREA STUDIED 2.1 Scope of Study This FIS report covers the incorporated area of Fort Kent, Maine. The history of flood insurance mapping in Fort Kent is included in Table 1. Table 1. Community Map History Community Name Community Number Initial NFIP Map Date Initial FIRM Date Most Recent FIRM Panel Date Fort Kent, Town of June 12, 1979 February 15, 1984 April 18, 2012 For this revision, the rivers restudied include the St. John River from 1000 ft upstream from the International Bridge to 13,000 ft downstream from the International Bridge in the Town of Fort Kent, ME; and for the Fish River from the mouth to 2 miles upstream from its confluence with the St. John River. Streams that were studied with detailed methods for the 1979 FIS and that were not restudied as part of this revision, but that were converted from the National Geodetic Vertical Datum of 1929 (NGVD29) to the North American Vertical Datum of 1988 (NAVD88) and then redelineated on improved mapping for this revision, include the remaining portions of the St. John and Fish Rivers in Fort Kent, and Perley Brook from its confluences with the Fish River to the confluences with its north and south branches about 10,000 feet upstream from the Fish River. Approximate analyses were used to study those areas having a low development potential or minimal flood hazards. Streams studied by approximate methods for 2

7 the 1979 FIS and redelineated here include Camel Brook, Pinette Brook and its tributary, Regiest Daigle Brook, Audibert Brook, upstream portions of Perley Brook, North Branch Perley Brook, South Branch Perley Brook and various unnamed streams. In areas where the flood plain width was less than 200 feet, negligible flood hazards were found to exist and no flood boundaries were mapped. Limits of detailed study are indicated on the Flood Profiles and on the Flood Insurance Rate Map (FIRM). The areas studied by detailed methods were selected with priority given to all known flood hazard areas and areas of projected development and proposed construction. The scope and methods of study were proposed to, and agreed upon, by FEMA and representatives from the Town of Fort Kent. FIS studies typically incorporate the determinations of letters issued by FEMA resulting in map changes. No Letters of Map Revision (LOMRs) were incorporated into this FIS as none have occurred within the Town to date. 2.2 Community Description The Town of Fort Kent is located in north-central Aroostook County in northern Maine, on the south bank of the St. John River, which in this area forms the United States-Canada border. The town s location at approximately latitude 47ºN is the most northern extremity of the continental United States, east of the Mississippi River. The Fish River flows north into the St. John River in the town center of Fort Kent. The area is rural. The total land area within the town limits of Fort Kent is 55 square miles. The region was originally settled in the 1780s by people primarily of Acadian background. Canadians also immigrated to the area, and in the early years of settlement following the American Revolution, loyalists to the British crown sought refuge in the region. The population of Fort Kent peaked around 1940, when it reached 5,363. A gradual decline then set in and the most recent estimate of population was 4,097 in 2010 (U.S. Census Bureau, 2010). 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. Fort Kent s climate is characteristic of northerly regions with cold winters and cool summers. The average annual temperature is 38 degrees Fahrenheit (ºF), with monthly averages varying from a high of 65ºF in July to a low of 6ºF in January. Extremes in temperature vary from approximately 97ºF to -42 ºF. The average growing season between killing frosts is 100 days, extending from the end of May to mid-september. The average annual precipitation is 37 inches and is distributed fairly uniformly throughout the year. Most of the precipitation from November to March occurs as snow, and the average annual snowfall in the 3

8 region is about 100 inches. The average snowpack reaches a maximum of about 9 inches water equivalent near the end of March. Extreme snowpacks have reached water equivalents of as high as 18 inches. St. John watershed is one of the largest in North America and drains into the Atlantic Ocean. Its headwaters arise from the south, resulting in ice and snow upriver melting sooner than downriver, sending ice jams and heavier flows north and downriver to Fort Kent along the international border. The basin is relatively undeveloped and has no dams upstream from Fort Kent. 2.3 Principal Flood Problems Historically, floods in the Fort Kent area have occurred primarily in April and May during periods of spring snowmelt. The top twelve peaks from 1933 to 2008 all occurred between April 22 and May 16. The greatest floods have resulted from snowmelt alone or from snowmelt and heavy rain, but rarely from rain alone. The flood of record on the St. John River occurred on either April 30 or May 1, 2008 and had a discharge of 183,000 cubic feet per second (cfs) at the USGS streamflow gaging station, St. John River below Fish River at Fort Kent, Maine (gaging station ). This flood resulted from up to 4 inches of rain falling on a late heavy snowpack that melted in the last two weeks of April, contributing up to 8 inches of water equivalent from snowmelt. Water came within inches of the top of the 30-foot high earthen levee constructed to protect the downdown area of Fort Kent and hit the low steel of the International Bridge connecting Fort Kent to New Brunswick. Ice jams can contribute significantly to floods, as they did for the flood of May 1974 (148,000 cfs). In May 1961, a large flood occurred which was the result almost entirely of snowmelt (131,000 cfs). In August 1976, tropical Storm Belle dumped 3-4 inches causing flood conditions. Other large floods on the St. John River occurred in April 1973 (136,000 cfs), and May 1933 (121,000 cfs). Flood losses in Fort Kent were relatively high compared to other communities in the St. John River basin before the installation of the levee. This is because the central business district of Fort Kent lies within the flood plain. 2.4 Flood Protection Measures In 1977, the U.S. Army Corps of Engineers (USACE) completed construction of an earth levee designed to protect the commercial center of Fort Kent from the flood with a 1-percent annual chance of exceedance. The levee extends downstream from the International Bridge for a distance of 3,250 feet to an area near the Fort Kent Blockhouse. The levee is currently provisionally accredited. Temporary sandbag installations at the east end of the levee and East Main Street along the Fish River are built into the plan for times of flood. The intent of the temporary sandbags was for flood protection while preserving the historic context of the blockhouse. 4

9 3.0 ENGINEERING METHODS For the flooding sources studied by detailed methods in the community, standard hydrologic and hydraulic study methods were used to determine the flood-hazard data required for this study. Flood events of a magnitude that is expected to be equaled or exceeded once on the average during any 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected as having special significance for floodplain management and for flood insurance rates. These events, commonly termed the 10-, 50-, 100-, and 500-year floods, have a 10-, 2-, 1-, and 0.2-percent chance, respectively, of being equaled or exceeded during any year. Although the recurrence interval represents the long-term, average period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than 1 year are considered. For example, the risk of having a flood that equals or exceeds the 1-percent-annual-chance flood in any 50-year period is approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in the community at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish peak discharge-frequency relationships for each flooding source studied by detailed methods affecting the community. The St. John River watershed has a drainage area of 5,680 square miles at the USGS streamgaging station, St. John River below Fish River at Fort Kent, ME (gaging station ). Continuous data have been collected at this station from 1926 through the present (2010). Data from this streamgaging station was used for a Log Pearson Type III (LPIII) frequency analysis to determine streamflows with 10-, 2-, 1-, and 0.2 percent annual exceedance probabilities. These exceedance probabilities were updated after the 2008 flood in northern Maine (Lombard, 2010). The drainage area of the St. John upstream from the Fish River is 4782 square miles. To determine streamflows with 10-, 2-, 1-, and 0.2 percent annual exceedance probabilities on the St. John upstream from the Fish River, statistically expected flows on the Fish River at the mouth (see below) at the time of the St. John peaks were subtracted from streamflows on the St. John at the gage. The Fish River watershed has a drainage area of 867 square miles at the USGS streamflow gaging station Fish River near Fort Kent, ME (gaging station ). Continuous data have been collected at this station from 1929 through the present (2010). Data from this streamgaging station was used for a Log Pearson Type III (LPIII) frequency analysis to determine 10-, 2-, 1-, and 0.2 percent annual exceedance probabilities. These exceedance probabilities were updated after the 2008 flood in northern Maine (Lombard, 2010). Drainage area adjustments were computed to determine streamflows with 10-, 2-, 1-, and 0.2 percent annual exceedance probabilities on the Fish River at the mouth just downstream from Rte 1 by use of the following equation: Q ungaged = Q gaged (DA ungaged /DA gaged ) b ; where Q ungaged is the unknown flow at a location upstream or downstream from the gage in cubic feet per second, Q gaged is the flow at the gage in cubic feet per second, DA is the drainage area in square miles, and b is a coefficient that depends on the exceedance 5

10 probability (Hodgkins, 1999). Drainage areas were calculated by use of a Geographic Iinformation System (GIS) and are based on a USGS watershed boundary data layer at a scale of 1:24,000. USGS gaging stations and are 3 miles apart near the confluence of the Fish and St. John Rivers in Fort Kent, Maine. Their interaction is unusual in that the annual peakflow of the tributary river almost always occurs after that of the main branch. In general, rivers with small drainage areas can be expected to peak more quickly after precipitation or snowmelt events than those with large drainage areas. However, the Fish and St. John Rivers are an exception to this principle because the Fish River basin contains a large number of lakes. Lakes retard the drainage process by retaining runoff for longer timespans. The Fish River peaked after the St. John River in 69 of 80 years of annual peakflow record. In three of the other eleven years, the St. John River peaked more than 10 days after the Fish River indicating that the peakflow was probably caused by a different event. The time difference in the remaining eight years was only one day. The lake effect on the Fish River delays its peakflow response to runoff events by as much as several days. Due to this effect, the annual peakflows of the two basins regularly occur within a short time of each other. Air temperature and precipitation are similar enough across the two basins such that annual peak flow (usually a combination of snowmelt and rainfall) generally occurs around the same time for both. Although peak flows occur at close to the same time on the two rivers, the relative magnitudes of the two peak flows are not necessarily the same (when the St. John River experiences a flow with an annual exceedance probability of 1 percent, the peak flow that may be occurring at the same time on the Fish River may only have an annual exceedance probability of 10 percent). The hydrologic analyses include development of two separate flow relations; one when the St. John River peaks and one when the Fish River peaks. To accomplish this, the flow at the Fish River was determined for each annual peak on the St. John River, and these ordered pairs were plotted for the entire periods of record. The same was done for the flow of the St. John River for each annual Fish River peakflow. The linear correlation predicting flow on the St. John River when the Fish River peaked (r 2 = 0.78) was better than the predicting flow on Fish River when the St. John River peaked (r 2 = 0.54). The hydraulic model includes both the Fish River and the St. John River and the interaction between them, but it is run with two different scenarios. It was first run with the flows corresponding to annual exceedance probabilities of 10-, 2-, 1-, and 0.2- percent on the St. John River, and expected (corresponding) flows that would occur at the same time on the Fish River (the St. John model) according to the above mentioned correlation. Then it was run with the flows corresponding to annual exceedance probabilities of 10-, 2-, 1-, and 0.2- percent on the Fish River, and expected (corresponding) flows that would occur at the same time on the St. John River (the Fish model). Since the downstream end of the Fish is significantly affected by backwater from the St. John, the St. John model resulted in higher water surface elevations on the Fish River from the mouth upstream to Bridge Rd than did the Fish model. Thus the results of the two models are combined in the mapping and the profiles. Peak water surface elevations from the St. John model are used for mapping the St. John River and for mapping the Fish River from the mouth upstream to Bridge St; and peak water surface elevations from the Fish model are used for mapping the Fish River from Bridge Rd upstream to the Fish River streamflow gage. 6

11 Hydrologic and hydraulic analyses were performed for Perley Brook as a part of the 1979 study. Since Perley Brook is an ungaged stream with no discharge records available, the adopted discharge frequencies were developed using a report entitled, Technique for Estimating the Magnitude and Frequency of Floods in Maine prepared by the USGS in cooperation with the Maine State Department of Transportation and the Federal Highway Administration (Morrill, 1975). This report was a precursor to the report, Estimating the Magnitude of Peak Flows for Streams in Maine for Selected Recurrence Intervals (Hodgkins, 1999), and was in use at the time of the 1979 report. The estimating technique requires determination of the size of the drainage area, main channel slope and percentage of storage (lakes and ponds) in the basin. Once these parameters are determined, discharge frequencies are calculated by empirical formulas and nomagraphs. In calculating the discharge frequencies for Perley Brook, the following parameters were used: drainage area = 20.4 square miles, main channel slope = 42 feet per mile, and the percentage of storage in the basin = 5 percent. Since the length of Perley Brook within the study limit is only two miles, with little hydraulic effect from any tributaries, the discharge remained constant throughout the entire Perley Brook reach. A summary of the drainage area-peak discharge relationships for flooding sources in the Town of Fort Kent is shown in Table 1, Summary of Discharges. Table 2. Summary of Discharges Flooding Source Drainage Area PEAK DISCHARGES (cfs) and Location (square miles) 10-Percent- Annual- Chance 2-Percent- Annual- Chance 1-Percent- Annual- Chance 0.2-Percent- Annual- Chance St. John River At International Bridge- Fort Kent 4, , , , ,800 At gage (below Fish River) 5, , , , ,900 Fish River At gage (near Fort Kent) ,000 15,100 16,300 19,300 At mouth ,200 15,400 16,700 19,600 Perley Brook At mouth ,000 1,900 2,000 4, Hydraulic Analyses Analyses of the hydraulic characteristics of flooding from the sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that flood elevations shown on the Flood Insurance Rate Map (FIRM) represent rounded whole-foot elevations and may not exactly reflect the elevations shown on the Flood Profiles or in the Floodway Data table in the FIS report. Flood elevations shown on the FIRM are primarily intended for flood insurance rating purposes. For construction and/or floodplain management purposes, users are cautioned to us the flood elevation data presented in this FIS report in conjunction with the data shown on the FIRM. Cross-section data and structure elevations for the St. John River from 1000 ft upstream from the International Bridge to 13,000 ft downstream from the International Bridge 7

12 (including the International Bridge structure); and for the Fish River from the mouth to 2 miles upstream from its confluence with the St. John River (including three bridge structures) were obtained from field surveys in October and November of Field data included elevation data collected with a total station theodolite, and underwater depths collected with an Acoustic Doppler Current Profiler (ADCP) referenced to the elevation of the water surface at the time of the survey. Underwater and channel bank field survey data were merged with Light Detection and Ranging (LIDAR) data for the elevations of the overbanks. LIDAR data were collected and post processed into a digital elevation model (DEM) in 2009 by The Sanborn Map Co., Inc. The DEM data have a contour interval of 2 ft and were collected and processed to meet 3.3-ft (root-meansquared error) horizontal accuracy and a vertical accuracy of 0.6 ft The computer program HEC-RAS 4.0 (U.S. Army Corps of Engineers, 2008) was used to model stream profiles with 10-, 2-, 1-, and 0.2 percent annual exceedance probabilities for the St. John and Fish Rivers. The model was run with the levee in place to determine the area protected by the levee and without the levee to determine the levee protected zone. The starting water surface elevations for the 10-, 2-, 1-, and 0.2 percent annual exceedance probability flow profiles downstream from the St. John gage were estimated from normal depth slope calculations. The starting water surface elevations for the 10-, 2-, 1-, and 0.2 percent annual exceedance probability flow profiles at the mouth of the Fish River were taken from the St. John model profiles at the location of the confluence of the Fish River. All of the warnings in the models have been reviewed and found acceptable. The 1- and 0.2-percent-annual-chance flood boundaries were drafted with a GIS using LIDAR data collected specifically for this project with 2-ft contour intervals. LIDAR data were verified and adjusted based on digital orthophoto quads and field surveys. All Maine LIDAR mapping data and surveyed cross sections reference NAVD88. The n-values were determined by field observations and by use of publications; USGS Water-Supply Papers 2339 and 2441 (USGS, 1989; USGS, 1998). The n-values for the main channel of the St. John River range from to 0.049, and n-values for overbanks range from.07 to N-values for the main channel of the Fish River range from to 0.05, and n-values for overbanks range from to 0.1. Roughness coefficients and losses in the model were calibrated using flows and high water marks collected along the St. John and Fish Rivers following the 2008 flood in Fort Kent. For Perley Brook, all work was completed as a part of the 1979 FIS. Cross sections were surveyed above and below bridges, culverts, and other hydraulic structures. Channel cross sections were taken from photogrammetric maps (U.S. Army Corps of Engineers, unpublished). The ACOE HEC-2 step-backwater computer program (Army Corps of Engineers, 1973) was used for the Perley Brook model. Manning's "n" roughness coefficients for Perley Brook were in the channel and for the overbanks. Starting water surface elevations were determined through normal depth calculations. The hydraulic analyses for this FIS were based on unobstructed flow. The flood elevations shown on the profiles are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail 8

13 3.3 Vertical Datum All FIS reports and FIRMs are referenced to a specific vertical datum. The vertical datum provides a starting point against which flood, ground, and structure elevations can be referenced and compared. Until recently, the standard vertical datum used for newly created or revised FIS reports and FIRMs was NGVD29. With the completion of the NAVD88, many FIS reports and FIRMs are now prepared using NAVD88 as the referenced vertical datum. Flood elevations shown in this FIS report and on the FIRM are referenced to NAVD88. These flood elevations must be compared to structure and ground elevations referenced to the same vertical datum. Ground, structure, and flood elevations may be compared and/or referenced to NGVD29 by applying a standard conversion factor (approximately +0.4 ft). For more information on NAVD88, see the FEMA publication entitled Converting the National Flood Insurance Program to the North American Vertical Datum of 1988 (FEMA, June 1992), or contact the Vertical Network Branch, National Geodetic Survey, Coast and Geodetic Survey, National Oceanic and Atmospheric Administration, Silver Spring, Maryland (Internet address Qualifying benchmarks within a given jurisdiction that are cataloged by the National Geodetic Survey (NGS) and entered into the National Spatial Reference System (NSRS) as First or Second Order Vertical and have a vertical stability classification of A, B, or C are shown and labeled on the FIRM with their 6-character NSRS Permanent Identifier. Benchmarks cataloged by the NGS and entered into the NSRS vary widely in vertical stability classification. NSRS vertical stability classifications are as follows: Stability A: Monuments of the most reliable nature, expected to hold position/elevation well (e.g., mounted in bedrock) Stability B: Monuments which generally hold their position/elevation well (e.g., concrete bridge abutment) Stability C: Monuments which may be affected by surface ground movements (e.g., concrete monument below frost line) Stability D: Mark of questionable or unknown vertical stability (e.g., concrete monument above frost line, or steel witness post) Temporary vertical monuments are often established during the preparation of a flood hazard analysis for the purpose of establishing local vertical control. Although these monuments are not shown on the FIRM, they may be found in the Technical Support Data Notebook associated with the FIS report and FIRM for this community. Interested individuals may contact FEMA to access these data. The base flood elevations (BFEs) shown on the FIRM represent whole-foot rounded values. For example, a BFE of will appear as 102 on the FIRM and will appear as 103. Therefore, users who wish to convert the elevations in this FIS to 9

14 NGVD29 should apply the stated conversion factor to elevations shown on the Flood Profiles and supporting data tables in the FIS report, which are shown at a minimum to the nearest 0.1 foot. To obtain current elevation, description, and/or location information for benchmarks shown on this map, please contact the Information Services Branch of the NGS at (301) , or visit their website at FLOODPLAIN MANAGEMENT APPLICATIONS The NFIP encourages State and local governments to adopt sound floodplain management programs. To assist in this endeavor, each FIS report provides 1-percent-annual-chance floodplain data, which may include a combination of the following: 10-, 2-, 1-, and 0.2-percent-annual-chance flood elevations; delineations of the 1- and 0.2-percent-annual-chance floodplains; and a 1-percent-annual-chance floodway. This information is presented on the FIRM and in many components of the FIS report, including Flood Profiles, Floodway Data tables, and Summary of Stillwater Elevation tables. Users should reference the data presented in the FIS report as well as additional information that may be available at the local community map repository before making flood elevation and/or floodplain boundary determinations. 4.1 Floodplain Boundaries To provide a national standard without regional discrimination, the 1-percent-annual-chance flood has been adopted by FEMA as the base flood for floodplain management purposes. The 0.2-percent-annual-chance flood is employed to indicate additional areas of flood risk in the community. For each stream studied by detailed methods, the 1- and 0.2-percent-annual-chance floodplain boundaries have been delineated using the flood elevations determined at each cross section. Between cross sections, the boundaries were interpolated using topographic maps developed from LIDAR, with a contour interval of 2 feet and at a scale of 1:1,000. The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the FIRM (exhibit 2). On this map, the 1-percent-annual-chance floodplain boundary corresponds to the boundary of the areas of special flood hazards (Zones A, AE, X), and the 0.2-percent-annual-chance floodplain boundary corresponds to the boundary of areas of moderate flood hazards. In cases where the 1- and 0.2-percent-annual-chance floodplain boundaries are close together, only the 1-percent-annual-chance floodplain boundary has been shown. Small areas within the floodplain boundaries may lie above the flood elevations, but cannot be shown due to limitations of the map scale and/or lack of detailed topographic data. For the streams studied by approximate methods, only the 1-percent-annual-chance floodplain boundary is shown on the FIRM (exhibit 2). 4.2 Floodways Encroachment on floodplains, such as structures and fill, reduces flood-carrying capacity, increases flood heights and velocities, and increases flood hazards in areas beyond the encroachment itself. One aspect of floodplain management involves balancing the economic gain from floodplain development against the resulting increase in flood hazard. For purposes of the NFIP, a floodway is used as a tool to assist local communities 10

15 in this aspect of floodplain management. Under this concept, the area of the 1-percent-annual-chance floodplain is divided into a floodway and a floodway fringe. The floodway is the channel of a stream, plus any adjacent floodplain areas, that must be kept free of encroachment so that the base flood can be carried without substantial increases in flood heights. Minimum Federal standards limit such increases to 1 foot, provided that hazardous velocities are not produced. The floodways in this study are presented to local agencies as minimum standards that can be adopted directly or that can be used as a basis for additional floodway studies. Floodways were recomputed for the river reaches that were restudied by detailed methods as a part of this revision. The remaining floodways presented in this study were computed as a part of the 1979 FIS, converted from NGVD29 to NAVD88 and redelineated here. Floodways were calculated on the basis of equal-conveyance reduction from each side of the floodplain. Floodway widths were computed at cross sections. Between cross sections, the floodway boundaries were interpolated. The results of the floodway computations are tabulated for selected cross sections (Table 2, Floodway Data). In cases where the floodway and 1-percent-annual-chance floodplain boundaries are either close together or collinear, only the floodway boundary is shown. The regulatory floodway widths at all cross-sections of the St. John River extend beyond the corporate boundary into New Brunswick, Canada, and are not show entirely on the Flood Insurance Rate Maps. The area between the floodway and 1-percent-annual-chance floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the water-surface elevation (WSEL) of the base flood more than 1 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 1. Figure 1. Floodway Schematic 11

16 FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER-SURFACE ELEVATION (FEET NAVD88) CROSS SECTION DISTANCE 1 (feet) WIDTH (feet) SECTION AREA (square feet) MEAN VELOCITY (feet per second) REGULATORY WITHOUT FLOODWAY WITH FLOODWAY INCREASE Fish River A , B 1, , C 1, , D 2, , E 2, , F 3,809 1,195 16, G 4, , H 5, , I 6, , J 6, , K 7, , L 8, , M 8, , N 9, , O 9, , upstream from mouth 2 controlled by backwater from the St. John River TABLE 3 FEDERAL EMERGENCY MANAGEMENT AGENCY TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY 12 FLOODWAY DATA FISH RIVER

17 FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER-SURFACE ELEVATION (FEET NAVD88) TABLE 2 CROSS SECTION DISTANCE 1 (feet) WIDTH (feet) SECTION AREA (square feet) MEAN VELOCITY (feet per second) REGULATORY WITHOUT FLOODWAY WITH FLOODWAY INCREASE Fish River (continued) P 9, , Q 10, , R 10, , S 10, , T 11, , U 12, , V 15, , W 16, , X 18, , Y 21, , Z 23, , AA 25, , AB 27, , AC 29, , AD 30, , upstream from mouth 2 controlled by backwater from the St. John River TABLE 3 FEDERAL EMERGENCY MANAGEMENT AGENCY TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY 13 FLOODWAY DATA FISH RIVER

18 FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER-SURFACE ELEVATION (FEET NAVD88) CROSS SECTION DISTANCE (feet) WIDTH (feet) SECTION AREA (square feet) MEAN VELOCITY (feet per second) REGULATORY WITHOUT FLOODWAY WITH FLOODWAY INCREASE Perley Brook A B 1, C 2, D 3, E 4, F 7, G 9, St. John River A 2, , B 4, , C 6, , , D 9, , , E 14, , , F 16, , , G 19, , H 22, , upstream from mouth 2 upstream from corporate limit 3 width extends beyond corporate limits TABLE 3 FEDERAL EMERGENCY MANAGEMENT AGENCY TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY 14 FLOODWAY DATA PERLEY BROOK AND ST. JOHN RIVER

19 FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER-SURFACE ELEVATION (FEET NAVD88) CROSS SECTION DISTANCE 1 (feet) WIDTH 2 (feet) SECTION AREA (square feet) MEAN VELOCITY (feet per second) REGULATORY WITHOUT FLOODWAY WITH FLOODWAY INCREASE St. John River (continued) I 25,610 1,328 25, J 28, , K 30, , L 33,460 1,883 32, M 35, , N 38, , O 41, , P 42, , Q 43, , R 45, , S 46, , T 47,428 1,215 26, U 48,815 1,016 24, V 49, , W 50, , X 51, , upstream from corporate limit 2 width extends beyond corporate limit TABLE 3 FEDERAL EMERGENCY MANAGEMENT AGENCY TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY 15 FLOODWAY DATA ST. JOHN RIVER

20 FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER-SURFACE ELEVATION (FEET NAVD88) CROSS SECTION DISTANCE 1 (feet) WIDTH 2 (feet) SECTION AREA (square feet) MEAN VELOCITY (feet per second) REGULATORY WITHOUT FLOODWAY WITH FLOODWAY INCREASE St. John River (continued) Y 52, , Z 54, , AA 56,915 1,034 22, AB 59, , AC 61, , AD 64,400 1,276 31, AE 66,285 2,060 39, AF 67,665 1, , AG 70, , AH 75,900 1, , upstream from corporate limit 2 width extends beyond corporate limit TABLE 3 FEDERAL EMERGENCY MANAGEMENT AGENCY TOWN OF FORT KENT, MAINE AROOSTOOK COUNTY 16 FLOODWAY DATA FISH RIVER ST. AND JOHN PERLEY RIVER BROOK

21 5.0 INSURANCE APPLICATION For flood insurance rating purposes, flood insurance zone designations are assigned to a community based on the results of the engineering analyses. These zones are as follows: Zone A Zone A is the flood insurance rate zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS report by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no base (1-percent-annual-chance) flood elevations (BFEs) or depths are shown within this zone. Zone AE Zone AE is the flood insurance rate zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS report by detailed methods. Whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Zone X Zone X is the flood insurance rate zone that corresponds to areas outside the 0.2-percent-annual-chance floodplain, areas within the 0.2-percent-annual-chance floodplain, areas of 1-percent-annual-chance flooding where average depths are less than 1 foot, areas of 1-percent-annual-chance flooding where the contributing drainage area is less than 1 square mile (sq. mi.), and areas protected from the base flood by levees. No BFEs or depths are shown within this zone. 6.0 FLOOD INSURANCE RATE MAP The FIRM is designed for flood insurance and floodplain management applications. For flood insurance applications, the map designates flood insurance rate zones as described in Section 5.0 and, in the 1-percent-annual-chance floodplains that were studied by detailed methods, shows selected whole-foot BFEs or average depths. Insurance agents use zones and BFEs in conjunction with information on structures and their contents to assign premium rates for flood insurance policies. For floodplain management applications, the map shows by tints, screens, and symbols, the 1- and 0.2-percent-annual-chance floodplains, floodways, and the locations of selected cross sections used in the hydraulic analyses and floodway computations. 7.0 OTHER STUDIES Information pertaining to revised and unrevised flood hazards in Fort Kent have been compiled in this FIS. Therefore, this FIS supersedes all previously printed FIS reports, FIRMs, and/or FHBMs and should be considered authoritative for the purposes of the NFIP. 17

22 8.0 LOCATION OF DATA Information concerning the pertinent data used in the preparation of this study can be obtained by contacting the Flood Insurance and Mitigation Division, FEMA Region I, 99 High Street, 6th Floor, Boston, MA BIBLIOGRAPHY AND REFERENCES Federal Emergency Management Agency, 1984, Flood Insurance Study, Town of Fort Kent, Aroostook County, Maine. Washington, D.C., 19 p. Federal Emergency Management Agency, 1979, Flood Insurance Study, Town of Fort Kent, Aroostook County, Maine. Washington, D.C., 19 p. Hodgkins, G, Estimating the Magnitude of Peak Flows for Streams in Maine for Selected Recurrence Intervals: U.S. Geological Survey Water-Resources Investigations Report , 45 p. Lombard, P.J., 2010, Flood of April and May 2008 in northern Maine: U.S. Geological Survey Scientific Investigations Report , 17 p. at Morrill, R.A., 1975, A Technique for Estimating the Magnitude and Frequency of Floods in Maine: U.S. Geological Survey Open-File Report , 44p. National Oceanic and Atmospheric Administration, 2002, Climatography of the United States no. 81, Monthly station normals of temperature, precipitation, and heating and cooling degree days, : Region 17, Maine, 16 p. U. S. Army Corps of Engineers, 1973, Hydrologic Engineering Center, HEC-2 Water Surface Profiles, Generalized Computer Program, Davis, California. U. S. Army Corps of Engineers, 1974, New England Division, Detailed Project Report, Fort Kent Local Flood Protection, Waltham, Massachusetts, November U. S. Army Corps of Engineers, 1977, New England Division, Water Control Branch, Flood Profile Computations, St. John River, Lincoln School downstream to Grand Falls, March U.S. Army Corps of Engineers, 2008, Hydrologic Engineering Center, HEC-RAS, River Analysis System, version 4.0 March

23 U.S. Army Corps of Engineers, Hydrologic Engineering Center, 2002b, HEC-GeoRAS for ArcGIS 9.3, accessed on June 5, 2010, at URL U. S. Army Corps of Engineers, (unpublished), New England Division, Topographic Maps compiled from air photos, Scale 1:4,800, Contour Interval 5 Feet: Town of Fort Kent, Aroostook County, Maine, flown in May U.S. Census Bureau, 2010, Releases 2010 Census Demographic Profile for Maine accessed at on June 7, U.S. Department of the Interior, Geological Survey, 1989, Guide for Selecting Manning s Roughness Coefficients for Natural Channels and Flood Plains, Water-Supply Paper 2339, 38 p. U.S. Department of the Interior, Geological Survey, 1998, Estimation of Roughness Coefficients for Natural Stream Channels with Vegetated Banks, Water-Supply Paper 2441, 133 p 19

24 FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME AROOSTOOK COUNTY FLOOD PROFILES FISH RIVER S Q R T U C J O A B D E F G H I K L M N P CROSS SECTION LOCATION STREAM DISTANCE IN FEET ABOVE MOUTH 01P U.S. ROUTE 1 CONFLUENCE WITH REGIEST DAIGLE BROOK WALKING BRIDGE BRIDGE STREET CONFLUENCE WITH PERLEY BROOK LEGEND 0.2% ANNUAL CHANCE FLOOD 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED ELEVATION IN FEET (NAVD 88)

25 BANGOR AND AROOSTOOK RAILROAD FLOOD PROFILES FISH RIVER ELEVATION IN FEET (NAVD 88) LEGEND 0.2% ANNUAL CHANCE FLOOD 500 V W X Y STREAM DISTANCE IN FEET ABOVE MOUTH Z AA 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED CROSS SECTION LOCATION FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME 02P AROOSTOOK COUNTY

26 CORPORATE LIMITS FLOOD PROFILES FISH RIVER ELEVATION IN FEET (NAVD 88) LEGEND 0.2% ANNUAL CHANCE FLOOD 510 AB AC AD STREAM DISTANCE IN FEET ABOVE MOUTH 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED CROSS SECTION LOCATION FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME 03P AROOSTOOK COUNTY

27 FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME AROOSTOOK COUNTY FLOOD PROFILES PERLEY BROOK STREAM DISTANCE IN FEET ABOVE MOUTH 04P CONFLUENCE WITH FISH RIVER ROUTE 161 BANGOR AND AROOSTOOK RAILROAD LIMIT OF DETAILED STUDY LEGEND 0.2% ANNUAL CHANCE FLOOD 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED A B C D E F G CROSS SECTION LOCATION ELEVATION IN FEET (NAVD 88)

28 FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME AROOSTOOK COUNTY FLOOD PROFILES ST. JOHN RIVER STREAM DISTANCE IN FEET ABOVE CORPORATE LIMITS 05P CORPORATE LIMITS CONFLUENCE OF DAIGLE BROOK LEGEND 0.2% ANNUAL CHANCE FLOOD 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED A B C D CROSS SECTION LOCATION ELEVATION IN FEET (NAVD 88)

29 FLOOD PROFILES ST. JOHN RIVER ELEVATION IN FEET (NAVD 88) LEGEND 0.2% ANNUAL CHANCE FLOOD 450 E F G STREAM DISTANCE IN FEET ABOVE CORPORATE LIMITS H 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED CROSS SECTION LOCATION I FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME 06P AROOSTOOK COUNTY

30 CONFLUENCE OF AUDIBERT BROOK FLOOD PROFILES ST. JOHN RIVER ELEVATION IN FEET (NAVD 88) LEGEND 0.2% ANNUAL CHANCE FLOOD 460 J K L M STREAM DISTANCE IN FEET ABOVE CORPORATE LIMITS 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD N 10% ANNUAL CHANCE FLOOD STREAM BED CROSS SECTION LOCATION FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME 07P AROOSTOOK COUNTY

31 CONFLUENCE OF FISH RIVER INTERNATIONAL BRIDGE FLOOD PROFILES ST. JOHN RIVER ELEVATION IN FEET (NAVD 88) LEGEND 0.2% ANNUAL CHANCE FLOOD 470 O P Q R S T U STREAM DISTANCE IN FEET ABOVE CORPORATE LIMITS V W X 1% ANNUAL CHANCE FLOOD 2% ANNUAL CHANCE FLOOD 10% ANNUAL CHANCE FLOOD STREAM BED CROSS SECTION LOCATION FEDERAL EMERGENCY MANAGEMENT AGENCY FORT KENT, ME 08P AROOSTOOK COUNTY