MARQUETTE COUNTY, MICHIGAN

Transcription

1 Marquette County MARQUETTE COUNTY, MICHIGAN (ALL JURISDICTIONS) COMMUNITY NAME COMMUNITY NUMBER COMMUNITY NAME COMMUNITY NUMBER *CHAMPION, TOWNSHIP OF * NEGAUNEE, CITY OF CHOCOLAY,CHARTER TOWNSHIP OF * NEGAUNEE, TOWNSHIP OF ELY, TOWNSHIP OF POWELL, TOWNSHIP OF *EWING, TOWNSHIP OF * REPUBLIC, TOWNSHIP OF *FORSYTH, TOWNSHIP OF * RICHMOND, TOWNSHIP OF *HUMBOLDT, TOWNSHIP OF * SANDS, TOWNSHIP OF *ISHPEMING, CITY OF SKANDIA, TOWNSHIP OF *ISHPEMING, TOWNSHIP OF * TILDEN, TOWNSHIP OF MARQUETTE, CITY OF * TURIN, TOWNSHIP OF MARQUETTE, CHARTER TOWNSHIP OF * WELLS, TOWNSHIP OF *MICHIGAMME, TOWNSHIP OF WEST BRANCH, TOWNSHIP OF *NO SPECIAL FLOOD HAZARD AREAS IDENTIFIED Preliminary: FLOOD INSURANCE STUDY NUMBER 26103CV000A

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) report may not contain all data available within the Community Map Repository. Please contact the Community Map Repository for any additional data. The Federal Emergency Management Agency (FEMA) may revise and republish part or all of this FIS report at any time. In addition, FEMA may revise part of this FIS report by the Letter of Map Revision process, which does not involve republication or redistribution of the FIS report. Therefore, users should consult with community officials and check the Community Map Repository to obtain the most current FIS report components. Selected Flood Insurance Rate Map panels for this 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(s) Al through A30 B C New Zone AE X X Initial Countywide FIS Effective Date: To Be Determined

3 TABLE OF CONTENTS 1.0 INTRODUCTION 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 FLOODPLAIN MANAGEMENT APPLICATIONS Floodplain Boundaries Floodways INSURANCE APPLICATIONS FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES i

4 TABLE OF CONTENTS (Continued) FIGURES Figure 1 - Floodway Schematic TABLES Table 1 Streams Studied by Detailed Methods... 3 Table 2 - Summary of Discharges... 7 Table 3 Manning s n Values... 9 Table 4 Vertical Datum Conversions Table 5 Floodway Data Tables EXHIBITS Exhibit 1 - Flood Profiles Carp River Panel 01P Chocolay River Panels 02P-04P Silver Creek Panels 05P-06P Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map ii

5 FLOOD INSURANCE STUDY MARQUETTE COUNTY, MICHIGAN (ALL JURISDICTIONS) 1.0 INTRODUCTION 1.1 Purpose of Study This Flood Insurance Study (FIS) revises and updates information on the existence and severity of flood hazards in the geographic area of Marquette County, including the Cities of Ishpeming, Marquette, and Negaunee; the Charter Townships of Chocolay and Marquette; and the Townships of Champion, Ely, Ewing, Forsyth, Humboldt, Ishpeming, Michigamme, Negaunee, Powell, Republic, Richmond, Sands, Skandia, Tilden, Turin, Wells, and West Branch (referred to collectively herein as Marquette County), 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, Please note that the Cities of Ishpeming and Negaunee and Townships of Champion, Ewing, Forsyth, Humboldt, Ipsheming, Michigamme, Negaunee, Republic, Richmond, Sands, Tilden, Turin, and Wells have no mapped special flood hazard areas. 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. The Digital Flood Insurance Rate Map (DFIRM) and FIS report for this countywide study have been produced in digital format. Flood hazard information was converted to meet the Federal Emergency Management Agency (FEMA) DFIRM database specifications and Geographic Information System (GIS) format requirements. The flood hazard information was created and is provided in a digital format so that it can be incorporated into a local GIS and be accessed more easily by the community. 1.2 Authority and Acknowledgments The sources of authority for this FIS are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of

6 Precountywide Analyses Information on the authority and acknowledgements for each jurisdiction included in this countywide FIS, as compiled from their previously printed FIS reports, is shown below: Chocolay, Charter Township of: The hydrologic and hydraulic analyses for Chococlay River and Silver Creek, for the May 4, 1987 FIS Report were performed by STS Consultants, Ltd, for FEMA, under Contract No. EMW-83-C The work was completed in August 1985 (FEMA, 1987). The Cities of Ishpeming, Marquette, and Negaunee; the Charter Township of Marquette; and the Townships of Champion, Ely, Ewing, Forsyth, Humboldt, Ishpeming, Michigamme, Negaunee, Powell, Republic, Richmond, Sands, Skandia, Tilden, Turin, Wells, and West Branch have no previously printed FIS reports. This Countywide FIS Report The hydrologic and hydraulic analyses for all areas studied by approximate methods for this countywide study and the redelineation of Carp River were performed by Atkins, for FEMA, under contract number HSFE05-05-D-0023, Task Order 30. The work was completed in July Flooding effects from Lake Superior were redelineated by Atkins, for FEMA, under contract number HSFE05-05-D-0023, Task Order 30. using elevation data from the Revised Report on Great Lakes Open-Coast Flood Levels, Phase I, prepared by the U.S. Army Corps of Engineers (USACE) (USACE, 1988). The work was completed in July Base map information shown on the Flood Insurance Rate Map (FIRM) was derived from the National Agricultural Imagery Program produced at a scale of 1:12,000, from imagery dated 2010 or later. The projection used in the preparation of this map is Universal Transverse Mercator (UTM) Zone 16, and the horizontal datum used is North American Datum of 1983 (NAD83), Geodetic Reference System (GRS) 1980 spheroid. 1.3 Coordination An initial meeting is held with representatives from FEMA, the community, and the study contractor to explain the nature and purpose of a FIS, and to identify the streams to be studied or restudied. A final meeting is held with representatives from FEMA, the community, and the study contractor to review the results of the study. 2

7 Precountywide Analysis The initial and final meeting dates for previous FIS reports for Marquette County and its communities are listed in the following table: Community FIS Date Initial Meeting Final Meeting Chocolay, Township of May 4, 1987 April 22, 1983 June 11, 1986 This Countywide FIS Report The initial meeting was held on May 29, 2008, and attended by representatives of FEMA, Atkins, Michigan Department of Natural Resources (MDNR), and Marquette County. The results of the study were reviewed at the final meeting held on, and attended by representatives of. All problems raised at that meeting have been addressed. 2.0 AREA STUDIED 2.1 Scope of Study This FIS covers the geographic area of Marquette County, Michigan, including all communities listed in Section 1.1. The areas studied by detailed methods were selected with priority given to all known flood hazards and areas of projected development or proposed construction through the time of the study. The following streams in and lakes in Table 1 are studied by detailed methods in this FIS report: Table 1 Streams Studied by Detailed Methods Carp River Chocolay River Lake Superior Silver Creek The limits of detailed study are indicated on the Flood Profiles (Exhibit 1) and on the FIRM (Exhibit 2). 3

8 This Countywide FIS Report The Carp River was redelineated based on updated topography and all areas studied by approximate methods were either newly studied or revised based on updated hydrologic and hydraulic models. Lake Superior was delineated using the Stillwater elevation of feet, NAVD, from the USACE report on open-coast flood levels of the Great Lakes (USACE, 1988). For this countywide FIS, the FIS report and FIRM were converted to countywide format, and the flooding information for the entire county, including both incorporated and unincorporated areas, is shown. Also, the vertical datum was converted from the National Geodetic Vertical Datum of 1929 (NGVD) to the North American Vertical Datum of 1988 (NAVD). In addition, the UTM coordinates, previously referenced to the North American Datum of 1927, are now referenced to the NAD83. Approximate analyses were used to study those areas having low development potential or minimal flood hazards. The scope and methods of study were proposed to and agreed upon by FEMA and Marquette County. The following tabulation presents Letters of Map Change (LOMCs) incorporated into this countywide study: LOMC Case Number Date Issued Project Identifier P February 28, 2005 Whetstone Brook 2.2 Community Description Marquette County is located in Michigan s Upper Peninsula on the south shore of Lake Superior. It is bordered by Alger and Delta Counties to the East; Dickinson and Menominee Counties to the South; and Baraga and Iron Counties to the West. Marquette County covers an area of about 1,870 square miles. The population of Marquette County was 67,077 in The City of Marquette is the county seat and has a population of 20,780 (U.S. Census Bureau, 2011). Marquette County is served by U.S. Highway 41, State Highways 35 and 95, and the Lake Superior and Ishpeming Railroad. Approximately 89-percent of the county is forested, with only about 2-percent of the county classified as farmland. Forestry, mining, and recreation are the major 4

9 land uses within the county based on the Soil Conservation Service (SCS) soil survey of Marquette County (SCS, 2007). The climate of Marquette County is influenced to a considerable extent by its proximity to Lake Superior. Temperatures in the county range from an average high of 73 degrees Fahrenheit ( F) to an average low of 55 F in the summer, and from an average high of 28 F to an average low of 14 F in the winter. Annual average precipitation in the region is 30.0 inches (The Weather Channel, 2011). The Carp River flows approximately 12 miles, from Deer Lake, to its confluence with Lake Superior in the southern portion of the City of Marquette. The Chocolay River watershed encompasses approximately 159 square miles. The majority of the watershed, which originates in southeastern Marquette County, consists of wooded and undeveloped land. However, the lower reaches of the watershed include some residential and commercial development in addition to a few small farms. Silver Creek is a tributary to Chocolay River. The Silver Creek watershed is mainly rural with some residential developments. 2.3 Principal Flood Problems Flood conditions on the Chocolay River are generally caused by an increase in river flows that are a result of major rainstorm events within the watershed, or increased runoff due to snowmelt during the spring season. The resulting increase in flood elevations has an impact on developments that have been constructed in the floodplains adjacent to these river systems. There have been many flood events in the Chocolay River watershed but the only documented event occurred in April At that time, a spring rainfall combined with extensive snowmelt and a dambreak at Lake LeVasseur resulted in flood conditions along the lower reaches of the Chocolay River. High-water marks were reported by the MDNR to fall between the 1- and 0.2-percent- annual-chance flood events. The estimated 1- and 0.2-percent-annual-chance flood discharges for the Chocolay River are 2,350 and 3,550 cubic feet per second (cfs). Structural damage to homes in the Fernwood subdivision resulted from this flood event and several culverts along Mangum Road and Green Garden Road were washed out. Flooding that occurs on Silver Creek is often elevated by flooding from the Chocolay River due to backwater effects. A sudden downpour, however, can cause Silver Creek to flood independently of the Chocolay River. 2.4 Flood Protection Measures There are 57 dams in Marquette County. Most of them were constructed for hydroelectric power, lake development, and fish and wildlife habitat projects. 5

10 These structures contribute to flood control by storing and gradually releasing large stream flows. 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 are expected to be equaled or exceeded once on the average during any 10%, 2%, 1%, or 0.2% 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 (100-year) 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. Precountywide Analyses For the Chocolay River, a regression analysis methodology developed by the MDNR and U.S. Geological Survey (USGS) to compute discharge-frequency relationships at the confluence with Lake Superior (USGS, 1984). This method incorporates basin characteristics such as drainage area, stream slope, ground cover, geological make-up, channel geometry, and climate characteristics in the development of discharges. The SCS computer program, TR-20, (SCS, 1965) was used to simulate the hydrologic processes that occur in the Silver Creek watershed and the approximate study areas. This program computes the storm water runoff that would result from a given rainstorm event, taking into consideration parameters such as precipitation, land use, topography, time of concentration, and drainage area. The TR-20 program also routes flood hydrographs through detention and retention areas. This feature accounts for the attenuation of flood peaks that occur when portions of the storm water are stored in ponds or swampy areas. 6

11 The previous hydrologic analysis for Carp River is not available. Peak discharge-drainage area relationships for each flooding source studied in detail are shown in 2. Table 2 - Summary of Discharges Peak Discharges (cfs) Flooding Source and Location Drainage Area (square miles) 10-Percent- Annual-Chance 2-Percent- Annual-Chance 1-Percent- Annual-Chance 0.2-Percent- Annual-Chance CARP RIVER * * * * * CHOCOLAY RIVER At confluence with Lake Superior SILVER CREEK At confluence with Chocolay River ,900 4,100 4,600 5, *Data Not Available This Countywide FIS Report For the streams studied by approximate methods, peak discharges were derived using USGS stream gage data (Sorrell, 2008), USGS regression equations, and the Michigan Department of Environmental Quality (MDEQ) SCS procedures (Sorrell 2008;USGS, 1984). Regression equations estimate peak discharges for ungaged streams based on characteristics of nearby gaged streams. The hydrologic analyses for Lake Superior was taken from the USACE report on Open-Coast Flood Levels of the Great Lakes (USACE, 1988). Stillwater elevations for Marquette County are shown in Table 1. Table 1 - Summary of Stillwater Elevations Water Surface Elevations (Feet NAVD 1 ) Flooding Source 10-Percent- Annual-Chance 2-Percent- Annual-Chance 1-Percent- Annual-Chance 0.2-Percent- Annual-Chance LAKE SUPERIOR North American Vertical Datum of

12 3.2 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 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 use the flood elevation data presented in this FIS report in conjunction with the data shown on the FIRM. Precountywide Analyses Cross sections for the backwater analyses of the Chocolay River and Silver Creek were obtained by field survey in November All bridges and culverts were field surveyed to obtain elevation data and structural geometry. Aerial survey maps and USGS topographic maps were used to supplement the field survey data for overbank elevations in some areas (Marquette County Planning Commission, 1955; USGS, various dates). Water-surface elevations (WSELs) for floods of the selected recurrence intervals were computed through use of the USACE, Hydrologic Engineering Center (HEC) computer program, HEC-2 (HEC, 1982). Starting WSELs for the Chocolay River were established based on the mean annual elevation of Lake Superior. The starting conditions for the Silver Creek backwater analysis were established based on the mean annual flood elevation of the Chocolay River at the confluence of these two streams. These elevations were obtained from a stage-frequency curve developed for the Chocolay River and Lake Superior. The previous hydraulic analysis for Carp River is not available. This Countywide FIS Report For the approximately studied streams, cross section data was obtained from the topography. Roads were modeled with available bridge and culvert inventory data or as weirs, using elevation from the topography. The studied streams were modeled using the USACE, HEC computer program, HEC-RAS, Version 4.1 (HEC, 2010). Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed (Section 4.2), selected cross section locations are also shown on the FIRM (Exhibit 2). 8

13 The profile baselines depicted on the FIRM represent the hydraulic modeling baselines that match the flood profiles on this FIS report. As a result of improved topographic data, the profile baseline, in some cases, may deviate significantly from the channel centerline or appear outside the Special Flood Hazard Area. Channel roughness factors (Mannings n ) used in the hydraulic computations were chosen by engineering judgment and based on field observations of the streams and overbank areas. The Manning s n values for all detailed studied streams are listed in Table 3: Table 3 Manning s n Values Manning's "n" Values Stream Channel n Overbank n Carp River * * Chocolay River Silver Creek * Data Not Available The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the Flood Profiles (Exhibit 1) are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail. 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 in use for newly created or revised FIS reports and FIRMs was NGVD. With the finalization of NAVD, many FIS reports and FIRMs are being prepared using NAVD as the referenced vertical datum. All flood elevations shown in this FIS report and on the FIRM are referenced to NAVD. Structure and ground elevations in the community must, therefore, be referenced to NAVD. It is important to note that adjacent communities may be referenced to NGVD. This may result in differences in Base Flood Elevations (BFEs) across the corporate limits between the communities. Some of the data used in this study were taken from the prior effective FIS reports and adjusted to NAVD. The average conversion factor that was used to convert the data in this 9

14 FIS report to NAVD was calculated using the National Geodetic Survey s (NGS) VERTCON online utility (NGS, 2009). The data points used to determine the conversion for each stream studied by detailed methods are listed in 4. Table 4 -Vertical Datum Conversions Location Latitude Longitude Conversion from NGVD to NAVD CARP RIVER At downstream end Approximate Middle At upstream end Average: CHOCOLAY RIVER At downstream end Approximate Middle At upstream end Average: LAKE SUPERIOR West extent of Marquette County boundary Approximate Middle East extent of Marquette County boundary Average: SILVER CREEK At downstream end Approximate Middle At upstream end Average: For additional information regarding conversion between NGVD and NAVD, visit the NGS website at or contact the NGS at the following address: Vertical Network Branch, N/CG13 National Geodetic Survey, NOAA 10

15 Silver Spring Metro Center East-West Highway Silver Spring, Maryland (301) 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. 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. Therefore, each FIS provides 1-percent-annual-chance (100- year) flood elevations and delineations of the 1- and 0.2-percent-annual-chance (500- year) floodplain boundaries and 1-percent-annual-chance floodway to assist communities in developing floodplain management measures. This information is presented on the FIRM and in many components of the FIS report, including Flood Profiles, Floodway Data Table, and Summary of Stillwater Elevations Table. Users should reference the data presented in the FIS report as well as additional information that may be available at the local 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-percentannual-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 Carp River, the 1- and 0.2-percent-annual-chance floodplain boundaries were redelineated using 2-foot contours for the City of Marquette (Ayres Associates, 2002). For Chocolay River and Silver Creek, 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 at a scale of 1:62,500, with a contour interval of 20 feet (USGS, various dates). 11

16 For Lake Superior, within the City of Marquette, the 1-percent-annual-chance and 0.2 percent-annual-chance floodplain boundaries were delineated using 2- foot contours for the City of Maquette (Ayres Associates, 2002). For Lake Superior, outside of the City of Marquette, the 1- and 0.2-percentannual-chance floodplain boundaries were delineated using topographic maps at a scale of 1:62,500, with a contour interval of 20 feet (USGS, various dates). 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 and AE), 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-annualchance 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 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 1- percent-annual-chance 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. In Michigan though, under Michigan Act 245, Public Acts of 1929, as amended by Act 167, Public Acts of 1968 (State of Michigan, 1968), encroachment in the floodplain is limited to that which will cause only an insignificant increase in flood heights. Thus, at the recommendation of the Bureau of Water Management, a floodway having no more than a 0.1-foot surcharge has been delineated for this study. 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. 11

17 The floodways presented in this FIS report and on the FIRM were computed for certain stream segments 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 have been tabulated for selected cross sections (Table 5). In cases where the floodway and 1-percent-annual-chance floodplain boundaries are either close together or collinear, only the floodway boundary has been shown. 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 WSEL of the 1-percent-annual-chance 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 No floodway was computed for Carp River. 13

18 FLOODING SOURCE CROSS SECTION DISTANCE 1 WIDTH (FEET) CHOCOLAY RIVER FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) A B C 1, , D 2, , E 3, F 5, , G 6, , H 8, , I 10, , J 13, , K 15, , L 16, , M 18, , N 19, , O 20, , P 21,650 1,013 4, Q 22, , R 23,880 1,268 5, S 25,260 1,125 5, T 26,250 1,034 4, U 27,920 1,730 8, V 29,670 1,448 7, W 30,820 1,408 6, Feet above confluence with Lake Superior TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY MARQUETTE COUNTY, MI (ALL JURISDICTIONS) FLOODWAY DATA CHOCOLAY RIVER

19 FLOODING SOURCE CROSS SECTION DISTANCE 1 WIDTH (FEET) SILVER CREEK FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) A B 1, C 1, D 2, E 3, F 4, G 4, H 5, I 6, , J 7, K 7, L 8, M 8, Feet above confluence with Chocolay River 2 Elevation computed without consideration of backwater effects from Chocolay River TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY MARQUETTE COUNTY, MI (ALL JURISDICTIONS) FLOODWAY DATA SILVER CREEK

20 5.0 INSURANCE APPLICATIONS 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 risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no BFEs or base flood depths are shown within this zone. Zone AE Zone AE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by detailed methods. In most instances, wholefoot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Zone X Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percentannual-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, and areas protected from the 1-percent-annual-chance flood by levees. No BFEs or base flood depths are shown within this zone. The FIRM for Marquette County includes areas designated by Congress as units of the Coastal Barrier Resources System (CBRS), where federally backed flood insurance is not available. The Coastal Barrier Resources Act of 1982 and the Coastal Barrier Improvement Act of 1990 define and establish a system of protected coastal areas (including the Great Lakes) known as the CBRS. The Acts define areas within the CBRS as depositional geologic features consisting of unconsolidated sedimentary materials; subject to wave, tidal, and wind energies; and protecting landward aquatic habitats from direct wave attack. The Acts further define coastal barriers as all associated aquatic habitats, including the adjacent wetlands, marshes, estuaries, inlets and nearshore waters, but only if such features and associated habitats contain few manmade structures and these structures and man s activities on such features, and within such habitats do not significantly impede geomorphic and ecological processes. The Acts provide protection to CBRS areas by prohibiting most expenditures of Federal funds within them. These prohibitions refer to any form of loan, grant, guarantee, insurance, payment, rebate, subsidy or any other form of direct or indirect Federal assistance, with specific and limited exceptions. The 16

21 CBRS boundaries depicted on the FIRM for Marquette County were adopted into public law by Acts of Congress and are, therefore, considered final and not subject to appeal. In addition to the CBRS, the Coastal Barrier Improvement Act of 1990 established Otherwise Protected Areas (OPAs). OPAs are undeveloped coastal barriers within the boundaries of an area established under Federal, State, or local law, or held by a qualifying organization, primarily for wildlife refuge, sanctuary, recreational, or natural resource conservation purposes. Congress designated the initial CBRS areas in Subsequent modifications of the CBRS are introduced as legislation to be acted on by Congress, and originate from State and local requests, as well as recommendations made by the U.S. Fish and Wildlife Service. After Congress approves additions to the CBRS, the new areas are assigned a unique effective date, after which Federal assistance prohibitions apply. In cooperation with the U.S. Department of the Interior, FEMA transfers CBRS boundaries to FIRMs using Congressionally adopted source maps titled Coastal Barrier Resources System. FIRMs clearly depict the different CBRS areas and their effective dates with special map notes and symbols. It should be noted that although FEMA shows CBRS areas on FIRMs, only Congress may authorize a revision of CBRS boundaries. Within CBRS boundaries, Federal flood insurance is not available for structures built or substantially improved on or after the date that the subject area was added to the CBRS. To assist map users in determining the correct insurance prohibition date in CBRS areas, each separate CBRS unit is clearly identified on the FIRM. It is important to note that insurance for structures in OPAs may be obtained if written documentation is provided, which certifies that the structures are used in a manner consistent with the purpose for which the area is protected. 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 risk 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 the 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. The countywide FIRM presents flooding information for the entire geographic area of Marquette County. Previously, FIRMs were prepared for each incorporated community 17

22 and the unincorporated areas of the County identified as flood-prone. Historical data relating to the maps prepared for each community are presented in Table OTHER STUDIES This report either supersedes or is compatible with all previous studies on streams studied in this report and should be considered authoritative for purposes of the NFIP. 8.0 LOCATION OF DATA Information concerning the pertinent data used in the preparation of this study can be obtained by contacting FEMA, Federal Insurance and Mitigation Division, 536 South Clark Street, Chicago, IL BIBLIOGRAPHY AND REFERENCES Ayres Associates, Digital Orthophotography Project, City of Marquette, Minnesota, April 1, Federal Emergency Management Agency, Flood Insurance Study, Township of Chocolay, Marquette County, Michigan, May 4, Hydrologic Engineering Center, HEC-2 Water Surface Profiles, U.S. Army Corps of Engineers, Davis, California, September Hydrologic Engineering Center, HEC-RAS River Analysis System, Version 4.1, U.S. Army Corps of Engineers, Davis, California, January Marquette County Planning Commission, Aerial Topography of Portions of Chocolay Township, Contour Interval 5 feet, obtained from Chocolay Township offices, National Geodetic Survey, VERTCON - North American Vertical Datum Conversion Utility. Retrieved June 25, 2009 from Soil Conservation Service, Computer Program for Project Formulation, Hydrology, Technical Release No. 20, U.S. Department of Agriculture, May Sorrell, Richard C. Computing Flood Discharges for Small Ungaged Watersheds, Michigan Department of Environmental Equality, Land and Water Management Division, June Retrieved on September 2008, from 17

23 COMMUNITY NAME INITIAL IDENTIFICATION FLOOD HAZARD BOUNDARY MAP REVISION DATE FIRM EFFECTIVE DATE FIRM REVISION DATE *Champion, Township of N/A None N/A None Chocolay, Charter Township of October 24, 1975 January 5, 1979 May 4, 1987 None Ely, Township of May 20, 1977 February 13, 1981 August 1, 1988 None *Ewing, Township of N/A None N/A None *Forsyth, Township of N/A None N/A None *Humboldt, Township of N/A None N/A None *Ishpeming, City of N/A None N/A None *Ishpeming, Township of N/A None N/A None Marquette, City of September 30, 1988 None September 30, 1988 December 2, 1994 Marquette, Charter Township of To Be Determined None To Be Determined None *Michigamme, Township of N/A None N/A None *Negaunee, City of N/A None N/A None *Negaunee, Township of N/A None N/A None *No special flood hazard areas indentified TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY MARQUETTE COUNTY, MI (ALL JURISDICTIONS) COMMUNITY MAP HISTORY

24 COMMUNITY NAME INITIAL IDENTIFICATION FLOOD HAZARD BOUNDARY MAP REVISION DATE FIRM EFFECTIVE DATE FIRM REVISION DATE Powell, Township of November 20, 2000 None November 20, 2000 None *Republic, Township of N/A None N/A None *Richmond, Township of N/A None N/A None *Sands, Township of N/A None N/A None Skandia, Township of To Be Determined None To Be Determined None *Tilden, Township of N/A None N/A None *Turin, Township of N/A None N/A None *Wells, Township of N/A None N/A None West Branch, Township of To Be Determined None To Be Determined None *No special flood hazard areas indentified TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY MARQUETTE COUNTY, MI (ALL JURISDICTIONS) COMMUNITY MAP HISTORY

25 Soil Conservation Service, Soil Survey of Marquette County, Michigan, Department of Agriculture, U.S. State of Michigan, Act 25, Public Acts of 1929, as amended by Act 167, Public Act of U.S. Army Corps of Engineers, Revised Report on Great Lakes Open Coast Flood Levels, Phase 1, Detroit, Michigan, February U.S. Geological Survey, Statistical Models for Estimating Flow Characteristics of Michigan Streams, Water Resources Investigations Report , U.S. Department of the Interior, U.S. Geological Survey, Water-Resources Investigations Report , Statistical Models for Estimating Flow Characteristics of Michigan Streams, D.J. Holtschlag, and Hope M. Croskey, U.S. Geological Survey, 15-Minute Series Topographic Maps, Scale 1:62,500, Contour Interval 20 feet: quadrangles of Gwinn, Michigan, 1952; Skandia, Michigan, 1958 Marquette, Michigan, 1975; and Laughing Fish Point, Michigan, 1958, U.S. Department of the Interior, various dates. U.S. Census Bureau, America Fact Finder, Marquette County, Michigan, Retrieved July 20, 2011, from The Weather Channel, Monthly Averages for Marquette County, MI Fairgrounds. Retrieved July 20, 2011, from 21

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