Text

Shine Medical Technologies, Inc., Application for Construction Permit Response to Environmental Requests for Additional Information, Enclosure 2, Attachment 23 - Preliminary Hydrological Analyses (Janesville) Rev 3, Part 2 of 2
	ML13309B624
Person / Time
Site:	SHINE Medical Technologies
Issue date:	08/03/2012
From:	; Golder Associates, SHINE Medical Technologies
To:	; Office of Nuclear Reactor Regulation
Shared Package
ML13303A887	List: ML13302C044; ML13309A984; ML13309A987; ML13309A988; ML13309A989; ML13309A990; ML13309A991; ML13309A992; ML13309A993; ML13309A994; ML13309A995; ML13309A996; ML13309B005; ML13309B006; ML13309B007; ML13309B008; ML13309B009; ML13309B010; ML13309B012; ML13309B013; ML13309B014; ML13309B016; ML13309B032; ML13309B033; ML13309B034; ML13309B035; ML13309B036; ML13309B037; ML13309B038; ML13309B039; ML13309B040; ML13309B041; ML13309B618; ML13309B619; ML13309B621; ML13309B622; ML13309B623; ML13309B624; ML13309B625; ML13309B626; ML13309B627; ML13309B628; ML13309B629; ML13309B630; ML13309B631; ML13309B632; ML13309B633; ML13309B634;
References
	SMT-2013-034
	Download: ML13309B624 (142)
	v • d • e

APPENDIX A FEMA FIS (ABBREVIATED SECTIONS FOCUSED ON ROCK RIVER AND TRIBUTARY NO. 1 TO THE ROCK RIVER FROM REPORT AND SUPPORTING FLOOD PROFILES)

ROCK COUNTY, WISCONSIN AND INCORPORATED AREAS VOLUME 1 OF 2 Community Name Community Number BELOIT, CITY OF 555544 BRODHEAD, CITY OF 550160 CLINTON, VILLAGE OF 550067 EDGERTON, CITY OF 550365 EVANSVILLE, CITY OF 550366 FOOTVILLE, VILLAGE OF 550575 JANESVILLE, CITY OF 555560 MILTON, CITY OF 550026 ORFORDVILLE, VILLAGE OF 550369 ROCK COUNTY (UNINCORPORATED AREAS) 550363 August 19, 2008 Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER 55105CV001A

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.

Effective Date: August 19, 2008 Revised Dates:

TABLE OF CONTENTS VOLUME 1

1.0 INTRODUCTION

...............................................................................................................1 1.1 Purpose of Study............................................................................................................1 1.2 Authority and Acknowledgments ..................................................................................1 1.3 Coordination ..................................................................................................................2 2.0 AREA STUDIED .................................................................................................................4 2.1 Scope of Study ...............................................................................................................4 2.2 Community Description.................................................................................................6 2.3 Principal Flood Problems...............................................................................................7 2.4 Flood Protection Measures ............................................................................................8 3.0 ENGINEERING METHODS .............................................................................................8 3.1 Hydrologic Analyses......................................................................................................8 3.2 Hydraulic Analyses........................................................................................................16 3.3 Vertical Datum...............................................................................................................21 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS ......................................................22 4.1 Floodplain Boundaries...................................................................................................22 4.2 Floodways......................................................................................................................23 5.0 INSURANCE APPLICATIONS ........................................................................................80 6.0 FLOOD INSURANCE RATE MAP ..................................................................................81 7.0 OTHER STUDIES...............................................................................................................81 8.0 LOCATION OF DATA.......................................................................................................81 9.0 BIBLIOGRAPHY AND REFERENCES ..........................................................................84 i

TABLE OF CONTENTS (Continued)

FIGURES Figure 1 - Floodway Schematic ........................................................................................................ 80 TABLES Table 1 - Summary of Discharges ............................................................................................... 11-15 Table 2 - Summary of Stillwater Elevations..................................................................................... 15 Table 3 - Floodway Data.............................................................................................................. 24-79 Table 4 - Community Map History................................................................................................... 83 VOLUME 2 EXHIBITS Exhibit 1 - Flood Profiles Allen Creek 01P-05P Bass Creek 06P-12P Blackhawk Creek 13P-14P East Fork Raccoon Creek 15P-16P Fisher Creek 17P-21P Greenbelt Tributary 1 22P-23P Greenbelt Tributary 2 24P Greenbelt Tributary 3 25P Greenbelt Tributary 4 26P-27P Greenbelt Tributary 5 28P-29P Markham Creek 30P-33P Marsh Creek 34P-36P Morningside Tributary 37P-38P Otter Creek 39P-42P Raccoon Creek 43P-46P Rock River 47P-70P Saunders Creek 71P-74P Spring Brook (Beloit) 75P-79P Spring Brook (Janesville) 80P-81P Sugar River 82P-86P Turtle Creek 87P-97P Unnamed Tributary 1 to Raccoon Creek 98P-99P Unnamed Tributary 2 to Raccoon Creek 100P-102P Unnamed Tributary 1 to Rock River 103P Unnamed Tributary 1 to Turtle Creek 104P Unnamed Tributary 2 to Turtle Creek 105P-106P Unnamed Tributary to Blackhawk Creek 107P-108P Unnamed Tributary to East Fork Raccoon Creek 109P-112P Unnamed Tributary in Turtle Township 113P-115P Yahara River 116P-119P Exhibit 2 - Flood Insurance Rate Map Index & Flood Insurance Rate Map ii

FLOOD INSURANCE STUDY ROCK COUNTY [AND INCORPORATED AREAS]

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 Rock County, including the Cities of Beloit, Brodhead, Edgerton, Evansville, Janesville and Milton; the Villages of Clinton, Footville and Orfordville; and the unincorporated areas of Rock County (referred to collectively herein as Rock County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. 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, 60.3.

Please note that the City of Edgerton is geographically located in Rock and Dane Counties. Also, the City of Brodhead is geographically located in Rock and Green Counties. The City of Edgertons special flood areas are included in its entirety in this FIS report. The flood-hazard information for the City of Brodhead is for information purposes only. See separately published FIS report and Flood Insurance Rate Map.

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 are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973.

The hydrologic analyses for Saunders Creek, Fisher Creek, Markham Creek, Greenbelt Tributaries 1-5, Morningside Tributary, Blackhawk Creek, Unnamed Tributary to Blackhawk Creek, Unnamed Tributary 1 to Rock River, Spring Brook (Beloit), Unnamed Tributary in Turtle Township, Bass Creek above Footville Road, Lenigan Creek, Lenigan Creek Tributaries 1 & 2, Unnamed Clinton Tributary, Unnamed Tributary in Union Township, Philhower Road Tributary, Unnamed Tributary 2 to Rock River, and Milton Ditch was performed 1

by Wisconsin DNR. The hydraulic analyses for these same streams in addition to Rock River, Raccoon Creek, Unnamed Tributaries 1 & 2 to Raccoon Creek, East Fork Raccoon Creek, Unnamed Tributary to East Fork Raccoon Creek was performed by Gannett Fleming, for the Federal Emergency Management Agency (FEMA), under Contract No. NMF00000316. Mapping done countywide was performed by Gannett Fleming. This work was completed in May 2006.

The hydrologic and hydraulic analyses for the following streams were done by Owen Ayres and Associates, Inc., for FEMA under Contract H-3805 completed in May 1979: Yahara River, Otter Creek, Marsh Creek, Sugar River, Turtle Creek, Unnamed Tributary 1 and 2 to Turtle Creek, Spring Brook (Janesville) and Bass Creek from Footville Road to its mouth. The hydrologic analyses for the Rock River, Raccoon Creek, Unnamed Tributary 1 & 2 to Raccoon Creek, East Fork Raccoon Creek, Unnamed Tributary to East Fork Raccoon Creek done under this same contract was incorporated into the new 2006 hydraulic study.

The hydrologic and hydraulic analyses for Allen Creek above the Lake Leota Dam were performed by the U.S. Department of Agriculture, Soil Conservation Service (SCS), as reported in a Flood Hazard Study, City of Evansville, Rock County, Wisconsin in January 1984. The hydrologic analysis done in that study was used in the 2006 hydraulic study.

The projection used in the preparation of this map was Universal Transverse Mercator (UTM) zone 16. The horizontal datum was NAD83, GRS1980 spheroid. Differences in datum, spheroid, projection or UTM zones used in the production of FIRMs for adjacent jurisdictions may result in slight positional differences in map features across jurisdiction boundaries. These differences do not affect the accuracy of this FIRM.

1.3 Coordination Information on the coordination for each jurisdiction included in this countywide FIS, as compiled from their previously printed FIS reports, is shown below.

Beloit, City of: Streams requiring detailed and approximate study were identified at an initial coordination and time and cost meeting attended by representatives of FEMA, the Study Contractor, and the City of Beloit on February 2, 1977. Base maps were obtained from the U.S. Army Corps of Engineers (COE), Rock Island District; and the City of Beloit. Flood elevations, flood boundaries, and floodway delineations were determined by the Wisconsin Department of Natural Resources, the Rock Island District COE, and the U.S. Geological Survey (USGS).

2

On October 16, 1980, the results of the work by the Study Contractor were reviewed and accepted at a final coordination meeting attended by representatives of FEMA, the Study Contractor, and the City of Beloit.

Edgerton, City of: Streams requiring detailed study were identified at a meeting attended by representatives of the Study Contractor, FEMA, the Wisconsin Department of Natural Resources and representatives of the City of Edgerton on June 6, 1979. Results of the hydrologic analyses were coordinated with the Wisconsin Department of Natural Resources, Flood Plain Management Section, and the Engineering Department of the City of Edgerton.

On March 31, 1981, the results of the study were reviewed and accepted at a final meeting attended by representatives of the Study Contractor, FEMA and community officials.

Evansville, City of: On February 21, 1983, the results of this study were reviewed and accepted at a final coordination meeting attended by representatives of the community and FEMA.

Janesville, City of: At a time and cost meeting on August 6, 1980 with representatives of the Wisconsin Department of Natural Resources (WDNR), FEMA, the Study Contractor, and the City Engineer, the limits of detailed and approximate study were determined.

The hydrology and hydraulics for the Rock River and Spring Brook and the floodway were coordinated with the WDNR.

On January 18, 1984, the results of the work by the Study Contractor were reviewed and accepted at a final coordination meeting attended by representatives of the Study Contractor, FEMA, and the community.

Rock County (Unincorporated Areas): A search for basic data was made at all levels of government. County officials, local residents, the U.S. Army Corps of Engineers (COE), the U.S.

3

Geological Survey (USGS) and the State of Wisconsin were contacted to obtain data on land use and other available data within the county.

Discharges were coordinated with the COE, the USGS, and the States of Illinois and Wisconsin.

An initial coordination meeting was held on February 21, 1975, to define study procedures and establish detailed study areas. This meeting was attended by representatives of FEMA, the State of Wisconsin, Rock County, and the Study Contractor.

During the course of the work by the Study Contractor, flood elevations, flood boundaries, and floodway delineations were reviewed with community officials and with officials from the Wisconsin Department of Natural Resources.

On October 14, 1980, the results of the work by the Study Contractor were reviewed and accepted at a final coordination meeting attended by personnel of FEMA, the State of Wisconsin, the county, and the Study Contractor.

2.0 AREA STUDIED 2.1 Scope of Study This FIS covers the geographic area of Rock County, Wisconsin, including the incorporated 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 September 2006.

The flooding sources studied by detailed methods are listed below:

1. Allen Creek, from 450 ft below State Highway 213 to about 6500 ft above City of Evansville Corporate Limits;

2. Bass Creek, from its mouth at the Rock River to W. Dorner Road;

3. Blackhawk Creek, from its confluence with Spring Brook (Janesville) to about 500 ft. above S. Milton Shopiere Road;

4. East Fork Raccoon Creek, from the state boundary to Spring Creek Road;

5. Fisher Creek, from its mouth at the Rock River to about 2100 ft. above N.

Little Road;

6. Greenbelt Tributary 1, from its mouth at Blackhawk Creek to Sandhill Drive;

7. Greenbelt Tributary 2, from its mouth at Greenbelt Tributary 4 to about 600 feet above E. Milwaukee Street; 4

8. Greenbelt Tributary 3, from its mouth at Greenbelt Tributary 1 to about 1400 ft. above City of Janesville Corporate limits;

9. Greenbelt Tributary 4, from its mouth at Greenbelt Tributary 1 to about 350 ft.

above E. County Highway A;

10. Greenbelt Tributary 5, from its mouth at Greenbelt Tributary 4 to about 650 ft.

above N. State Highway 14;

11. Markham Creek, from its mouth at the Rock River to about 2200 ft. above W.

Hanover Road;

12. Marsh Creek, from its mouth at the Rock River to County Highway H;

13. Morningside Tributary, from its mouth at Spring Brook (Janesville) to State Highway 14 (Humes Road);

14. Otter Creek, from the county boundary to Bowers Road;

15. Raccoon Creek, from the downstream county boundary to State Highway 81;

16. Rock River, within the county boundaries;

17. Saunders Creek, within the county boundaries;

18. Spring Brook (Beloit), from its mouth at Turtle Creek to 100 ft. above S.

Clinton Corners Road;

19. Spring Brook (Janesville), from its mouth at the Rock River to the confluence with Blackhawk Creek;

20. Sugar River, within the county boundaries;

21. Turtle Creek, from its confluence with the Rock River to about 2 miles upstream of Johnson Road;

22. Unnamed Tributary 1 to Raccoon Creek, from its mouth at Raccoon Creek to Beloit-Newark Road;

23. Unnamed Tributary 2 to Raccoon Creek, from its mouth at Unnamed Tributary 1 to Raccoon Creek to Beloit-Newark Road;

24. Unnamed Tributary 1 to Rock River, from its mouth at the Rock River to County Highway G;

25. Unnamed Tributary 1 to Turtle Creek, from its mouth at Turtle Creek to Elm Drive;

26. Unnamed Tributary 2 to Turtle Creek, from its mouth at Turtle Creek to County Highway J;

27. Unnamed Tributary to Blackhawk Creek, from its mouth at Blackhawk Creek to N. Tarrant Road;

28. Unnamed Tributary to East Fork Raccoon Creek, from its mouth at East Fork Raccoon Creek to Beloit-Newark Road;

29. Unnamed Tributary in Turtle Township, from the state boundary to about 400 ft below S. Clinton Corners Road;

30. Yahara River, within the county boundaries.

The flooding sources studied by limited detailed methods are listed below:

1. Lenigan Creek, from its mouth at the Rock River to about 0.9 mile above City of Beloit Corporate limits;

2. Lenigan Creek Tributary 1, from its mouth at Lenigan Creek to about 250 ft.

below the City of Beloit Corporate limits; 5

3. Lenigan Creek Tributary 2, from its mouth at Lenigan Creek to about 0.6 mile above McKinley Avenue;

4. Milton Ditch, from W. High Street to State Highway 26;

5. Philhower Road Tributary, from its confluence with the Rock River to its confluence with Turtle Creek;

6. Unnamed Clinton Tributary, from about 700 ft. above Village of Clinton Corporate limits to confluence with Southern Branch at railroad tracks;

7. Unnamed Clinton Tributary Southern Branch, from about 150 ft. above Village of Clinton Corporate limits to confluence with Clinton Tributary at railroad tracks;

8. Unnamed Tributary 2 to Rock River, from its mouth at the Rock River to W.

High Street;

9. Unnamed Tributary in Union Township, from Union Township southern limits to just south of County Highway C Approximate analyses were used to study those areas having low development potential or minimal flood hazards. This was done by overlaying effective zone A floodplains over 10-foot contours to approximate flood elevations. These approximated elevations were then laid over year 2000 terrain data for a revised flood boundary. The scope and methods of study were proposed to, and agreed upon, by FEMA and the various affected communities.

2.2 Community Description Rock County, located in south-central Wisconsin, is bordered on the west by Green County, on the north by Dane and Jefferson Counties, on the east by Walworth County, and on the south by Winnebago and Boone Counties in Illinois. Rock County includes the incorporated areas of Footville, Evansville, Beloit, Janesville, Edgerton, Clinton, and Milton. Rock County's present boundaries were established in 1838. Prior to 1836 the county was a portion of Milwaukee County. Rock County derived its name from the Rock River which the French named Riviere de la Roche.

Rock County has experienced a general increase in population since 1850 when there were 20,750 residents. By 1880 there were 43,220 residents, 113,913 by 1960, 131,970 by 1970, 140,103 in 1990 and 152,307 residents in 2000. Interstate Highway 90 is the major north-south highway.

Joseph Thiebeau, a French-Canadian fur trader, was the first white man to come to the county in 1824. The Rock River valley was under control of a number of Indian tribes until the end of the Black Hawk War in 1832. Following the end of Indian control, permanent settlement began to appear with all the present towns being organized by 1849. Wheat was the first stable crop to be grown in the county; however, due to disease and soil depletion the wheat production decreased, with increased acreage being devoted to oats, hay, and corn. The main farm enterprise in Rock County is dairying with the raising of beef cattle becoming increasingly 6

important. Important crops in the county are field and sweet corn, hay, oats, soybeans, and peas. In addition to farming, Janesville and Beloit have become manufacturing centers for machinery and automobiles.

The climate of Rock County is classified as continental, with long cold winters and warm humid summers. The county has recorded an average annual precipitation of 33 inches, which includes a moderate winter snowfall. Approximately 60 percent of this precipitation occurs within the five month period from May to September.

Thunderstorms occur on the average of 40 times a year. The total annual snowfall has ranged from less than 10 inches to more than 65 inches. Prevailing winds are from the south in the summer and from the west during the winter months. The average wind speed during the windiest months (March, April, and November) is 12 miles per hour. The extreme temperatures recorded are -27 degrees Fahrenheit (F.) and 100 degrees F., exhibiting extreme seasonal variations.

Rock County is underlain entirely by sedimentary sandstones and limestone. The county is divided into three physiographic regions. The northern region is composed of hills and kettles, the result of glacial deposition. The central and southeastern portions of the county are typified by a flat glacial outwash plain. The southwestern corner of the county experienced less glacial activity, which is evidenced by deep valleys cut in sandstone ridges. A majority of the county's river and stream valleys are filled with thick deposits of alluvial sand and gravel. A majority of the soils in Rock County are a result of glacial activity. The county is generally typified by a surface layer of silt loam or loam underlain by glacial till or stratified sand and gravel outwash materials. The exception is the southwest region where shallow surface layers of loam or sandy loam overlay the bedrock Rock County is drained entirely by the Rock River and its tributaries. The Rock River's major tributaries are the Yahara River, the Sugar River, Raccoon Creek and Turtle Creek. The Yahara River and its major tributary, Badfish Creek, drain the northwestern corner of the county along Allen and Marsh Creeks. The Sugar River, Raccoon Creek, and their tributaries drain the southwestern region of the county.

Raccoon Creek confluences with the Sugar River in Illinois which in turn empties into the Rock River. The southeastern portion of the county is drained by Turtle Creek, which confluences with the Rock River in South Beloit.

The floodplains include residential, commercial, industrial, recreational, and agricultural developments. The river floodplains, in general, follow the natural valley limits.

2.3 Principal Flood Problems The streams and rivers in Rock County are subject to flooding throughout the year; however, most flooding has occurred in the spring. These spring floods, the result of a combined snowmelt with moderate amounts of precipitation, can cause 7

flooding which is aggravated due to ice jams throughout the stream reaches. March is the most common month for peak annual discharges based on USGS stream flow records. Even though early spring is the most common time for flooding, the most severe flood on record occurred on Turtle Creek in late April 1973. This flood was due to an intense period of rainfall over the Turtle Creek basin. It had an estimated return period of 150 years.

2.4 Flood Protection Measures There are a number of dams on the rivers and creeks in Rock County; however, none of these dams were designed as flood control structures. The Rock Island COE has published a Phase I General Design Memorandum for a flood damage reduction project on Turtle Creek. That project was terminated due to a lack of economic justification. Rock County originally adopted a state approved floodplain zoning ordinance in November 1974. This Flood Insurance Study is expected to provide data that will be used to update the existing zoning ordinance. A levee system is located on the southwest flood plain of the Sugar River from the State Boundary to about one mile upstream of Nelson Road and on the northeast side from about two miles downstream of Nelson Road to about one mile upstream of Nelson Road. These levees will not provide any protection from the 100-year flood.

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-, 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 (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 8

Hydrologic analyses were carried out to establish peak discharge-frequency relationships for each flooding source studied by detailed methods affecting the community.

Precountywide Analyses Discharge values for the Yahara River at the Rock-Dane county line were taken from the discharge-frequency curve for the Stebbinsville Dam supplied by the USGS. Discharges downstream of the dam to the Badfish Creek confluence were based on a drainage area-discharge relationship for the Stebbinsville Dam. An analysis of Badfish Creek was made to determine its impact on Yahara River flood flows. The discharge-frequency curve for Badfish Creek was based on a statistical analysis of 11 years of record for the nonrecording USGS gage (No. 5-4301) located four miles southwest of Stoughton using a log-Pearson Type III distribution, and on Conger's method. Final values indicated that Badfish Creek controls the flood discharges on the Yahara River downstream of its confluence.

Discharges used in this study are a combination of peak discharges on Badfish Creek plus a portion of the Yahara River flow.

The Rock River was previously studied in Rock County by various governmental agencies. The discharges used in these reports were not adopted due to updated methods of determining discharges. Frequency-discharge relationships for the USGS gage at Afton (No. 543001) with a record from 1914 to present, located on the right bank in Afton and 1.1 miles upstream of Bass Creek, were computed by the log-Pearson Type III distribution. Discharges used were the result of coordination between the States of Wisconsin and Illinois and FEMA. Frequency-discharge curves for other locations on the Rock River were determined by a drainage area comparison to the Afton gage.

Discharge values for Otter, Marsh, and Bass Creek downstream of S. Footville Road were determined by procedures set forth in Project Formulation Hydrology, Technical Release No. 20 (TR-20). Supporting computations were made using Conger's method and a peak discharge-drainage area comparison to Turtle Creek.

Discharges for Allen Creek were computed using the TR-20 method as reported in a Flood Hazard Study for the City of Evansville, Wisconsin.

Flood discharges for Turtle Creek are based on a statistical analysis of the USGS recording station (No. 5-4315) with a period of record from 1939 to the present, located on the left bank of Turtle Creek immediately downstream of the State Highway 140 bridge, 2.7 miles north of Clinton. This analysis, using the log-Pearson Type III distribution, was the result of coordination between the States of Wisconsin and Illinois and was accepted by FEMA. The resulting discharge does not agree with previously accepted values due to the different methodology used and the inclusion of the April 1973 flood. Discharge-frequency curves at other locations were based on a drainage area comparison to the Clinton gage.

9

Unnamed Tributary No. 1 to Turtle Creek and Unnamed Tributary No. 2 to Turtle Creek were studied by Conger's method, TR-20, and discharge-drainage area comparisons. The final discharge-frequency curves are a composite of these three methods.

Discharges for the Sugar River are based on a statistical analysis of the USGS recording station (No. 5-4365) with a period of record from 1914 to the present, located on the left bank of the Sugar River, 1.2 miles southwest of Brodhead. The adopted discharge-frequency relationship was the result of coordination between Wisconsin and Illinois and was accepted by FEMA. Discharges for the study were based on a drainage area-discharge comparison to the Brodhead gage.

Discharges for Raccoon Creek and its two unnamed tributaries were determined by a TR-20 model. Supporting calculations were made by Conger's method and a discharge-drainage area comparison.

Discharges for the East Fork Raccoon Creek and its unnamed tributary were based on a TR-20 model. Supporting computations included a drainage area comparison to a USGS gage (No. 5-4372) with a period of record from 1958 to the present located on the unnamed tributary and Conger's method.

Flood discharges for Spring Brook Beloit and Spring Brook Janesville were based on the results of Conger's method, a drainage comparison, and the U.S. Department of Agriculture, Soil Conservation Service (SCS) method.

The hydrologic analyses for Allen Creek to establish the peak discharge relationships for floods of the 10-, 50-, 100-, and 500-year recurrence intervals were made utilizing the SCS hydrology computer program TR-20. The principal factors considered in this method are soil types, land use, slope of terrain, channel length and rainfall distribution. Four rainfalls were used in the model. Rainfall data for the 10-, 500, 100-, and 500-year return frequency storms were obtained from the U.S. Weather Bureau Technical Paper No. 40. The resulting flows computed in the TR-20 model were compared to U.S. Geological Survey (USGS) gauged watersheds of similar characteristics and were determined to match reasonably well.

Revised Analyses for this Countywide FIS The hydrologic analyses for Bass Creek upstream of S. Footville Road, Blackhawk Creek upstream of State Highway 14, Fisher Creek, Greenbelt Tributaries 1-5, Markham Creek, Morningside Tributary, Saunders Creek, Spring Brook (Beloit),

Unnamed Tributary 1 to Rock River, Unnamed Tributary to Blackhawk Creek and Unnamed Tributary in Turtle Township and all limited detail studies (outlined in section 2.1) were done using the Wisconsin DNR Hydrology Tool extension in ArcView 3.2 and HEC-HMS 2.2.2.

10

The Loss rate method/abstraction used was SCS CN. CN data was based on WiscLand grid. The SCS Unit hydrograph/TR-55 flow path segment method was used. Channel properties were estimated from the 2000 digital terrain model (DTM). Mannings N values were derived from the 2000 orthophoto. Muskingum Cunge was used for routing and channels were based off of the 2000 DTM.

Rainfall distribution curve was developed by SEWRPC for all southeast Wisconsin Counties. Rock County was on the fringe of this region, but it was determined that the curve still applied as the curve included gauge data from Rock County.

24-, 12-, 6- and 3-hour storm durations were run in HEC-HMS to determine the storm with the highest peak flow. The 24-, 12-, 6- and 3-hour rainfall for 10-, 50-and 100-year storms were obtained from the U.S. Weather Bureau Technical Paper No. 40. The 500-year rainfall total was extrapolated based on the previous totals.

There was a storm on August 5, 1998 that approximately measured as a 1 percent annual chance rainfall event. This event was entered into the HEC-HMS models to compare the flow to the 1 percent annual chance peak flow. The values compared favorably.

The stream gauge on a tributary to Fisher Creek (#5430403) was used to verify Fisher Creeks peak value. This was the only stream gauge on any of the studies were new hydrology was performed.

Peak discharge-drainage area relationships for Rock County are shown in Table 1.

Table 1 - Summary of Discharges Peak Discharges (cubic feet per second)

Drainage Area 10-Percent- 2-Percent- 1-Percent- 0.2-Percent-Flooding Source and Location (square miles) Annual-Chance Annual-Chance Annual-Chance Annual-Chance ALLEN CREEK Downstream of North State Highway 213 795 1,340 1,600 2,300 Approximately 1 mi. above North State Highway 213 765 1,290 1,545 2,230 Approximately 2.3 mi. above North State Highway 213 730 1,230 1,475 2,150 Halfway between E Church St. & Water St. 675 1,145 1,375 2,050 At Lake Leota Dam 590 1,010 1,215 1,770 BASS CREEK State Highway 11 14.0 2,225 3,537 4,362 6,283 Old State Highway 11 13.3 2,169 3,439 4,240 6,097 Dorner Road 9.3 1,705 2,649 3,234 4,553 11

Table 1 - Summary of Discharges - continued Peak Discharges (cubic feet per second)

Drainage Area 10-Percent- 2-Percent- 1-Percent- 0.2-Percent-Flooding Source and Location (square miles) Annual-Chance Annual-Chance Annual-Chance Annual-Chance BLACKHAWK CREEK State Highway 14 32.7 2,457 4,126 5,152 7,042 Confluence with Unnamed Trib to Blackhawk Creek 31.6 2,409 4,037 5,035 6,868 250' upstream of County Highway MM 14.2 1,132 1,899 2,364 3,205 1/2 mile upstream of Milton Shopeire Road at Tributary 12.5 995 1,675 2,081 2,819 E FORK RACCOON CREEK Wisconsin-Illinois State line 17.0 2,150 3,450 4,100 5,700 Above Unnamed Tributary to East Fork Raccoon Creek 10.8 1,450 2,300 2,750 3,900 Spring Creek Road 6.6 1,050 1,650 1,920 2,700 FISHER CREEK At mouth 5.9 861 1,491 1,817 2,831 Upstream of Unnamed Trib. 4.0 621 1,047 1,270 1,935 Rockport Road 3.5 540 914 1,099 1,646 State Highway 11 2.6 535 890 1,074 1,577 Downstream of Mineral Point Road 1.7 408 656 774 1,112 Upstream of Mineral Pt. Rd. 0.8 206 331 390 560 GREENBELT TRIBUTARY 1 Confluence with Greenbelt Tributary 4 4.5 804 1,212 1,453 1,983 Confluence with Unnamed 0.7 129 195 234 319 Tributary State Highway 14 0.4 61 93 112 154 GREENBELT TRIBUTARY 2 At mouth 0.8 140 214 258 356 GREENBELT TRIBUTARY 3 At mouth 0.4 76 113 135 181 GREENBELT TRIBUTARY 4 At mouth 2.9 516 778 934 1,278 Below confluence with Greenbelt Tributary 2 1.9 336 509 612 838 Above confluence with Greenbelt Tributary 2 1.0 213 320 383 522 GREENBELT TRIBUTARY 5 At mouth 1.1 183 277 333 456 MARKHAM CREEK At mouth 10.2 1,210 1,922 2,374 3,409 Confluence with Unnamed Tributary 8.8 1,158 1,811 2,230 3,187 Railroad Bridge 5.8 846 1,315 1,620 2,288 State Highway 11 3.8 583 898 1,087 1,496 N. Willowdale Road 2.7 387 604 734 1,015 Mineral Point Road 1.1 201 304 366 501 12

Table 1 - Summary of Discharges - continued Peak Discharges (cubic feet per second)

Drainage Area 10-Percent- 2-Percent- 1-Percent- 0.2-Percent-Flooding Source and Location (square miles) Annual-Chance Annual-Chance Annual-Chance Annual-Chance MARSH CREEK At mouth 30.8 1,800 2,900 3,470 4,900 State Highway 184 22.0 1,550 2,500 2,950 4,150 MORNINGSIDE TRIBUTARY At mouth 14.8 2,023 3,109 3,799 5,319 Confluence with Unnamed Tributary 6.2 891 1,412 1,738 2,444 Confluence with Unnamed Tributary 5.8 812 1,315 1,614 2,260 Mt. Zion Avenue 4.8 666 1,069 1,305 1,823 State Highway 14 2.8 388 608 738 1,025 OTTER CREEK At Rock County limits 50.3 2,150 3,550 4,250 6,000 RACCOON CREEK Wisconsin-Illinois State line 27.8 2,750 4,500 5,350 7,700 Approximately 1.3 miles above County Highway H 16.4 1,600 2,600 3,150 4,400 State Highway 81 12.1 1,400 2,300 2,700 3,900 ROCK RIVER Wisconsin-Illinois State line 3,450 11,500 15,300 16,900 20,100 At Afton Gage 3,340 10,900 14,500 16,000 19,000 At Monterey Dam 3,310 10,800 14,300 15,800 18,800 Above confluence with Markham Creek 3,280 10,600 14,100 15,600 18,500 At Centerway Dam 3,240 10,400 13,800 15,300 18,200 West State Highway 14 3,190 10,200 13,500 14,900 17,800 Approximately 3.7 miles above W State Highway 14 3,170 10,100 13,400 14,800 17,600 Below confluence with Yahara River 3,120 9,970 13,100 14,500 17,200 Above confluence with Yahara River 2,580 7,480 9,950 11,000 13,000 Outlet of Lake Koshkonong 2,500 7,140 9,500 10,500 12,400 SAUNDERS CREEK At mouth 42.0 918 1,580 2,016 2,930 Edgerton Southern Corporate Limits 41.7 919 1,582 2,018 2,934 Confluence near Stoughton Road 38.3 937 1,615 2,059 3,005 Dane - Rock County line 26.8 828 1,382 1,751 2,548 SPRING BROOK (BELOIT)

At mouth 15.0 1,280 1,933 2,332 3,227 550' above E. Lawn Rd. 14.2 1,235 1,864 2,227 3,145 Interstate Highway 90 9.1 752 1,309 1,644 2,388 Railroad at corporate limits 7.3 691 1,221 1,536 2,245 At trib 1/4 mile below Gustafson Road 5.3 586 1,072 1,320 1,911 At trib 0.65 mile below Gustafson Road 3.8 521 906 1,094 1,517 13

Table 1 - Summary of Discharges - continued Peak Discharges (cubic feet per second)

Drainage Area 10-Percent- 2-Percent- 1-Percent- 0.2-Percent-Flooding Source and Location (square miles) Annual-Chance Annual-Chance Annual-Chance Annual-Chance SPRING BROOK (JANESVILLE)

At mouth 48.74 3,165 5,250 6,075 7,300 Downstream of East Racine Street 46.26 3,080 4,960 5,920 7,125 Upstream of East Racine Street 44.06 2,950 4,760 5,675 6,840 At Ruger Avenue 42.83 2,900 4,700 5,590 6,740 SUGAR RIVER Wisconsin-Illinois State line 696 11,400 20,600 25,500 39,000 Below confluence with Taylor Creek 658 10,800 19,500 24,100 36,900 Above confluence with Taylor Creek 605 10,500 18,900 23,400 35,800 TURTLE CREEK At mouth 247 6,500 12,400 15,400 24,500 State Highway 15 217 5,980 11,400 14,200 22,500 Above Unnamed Tributary 1 to Turtle Creek 210 5,860 11,200 13,900 22,100 USGS gage at Clinton 202 5,730 10,900 13,600 21,600 Below Little Turtle Creek 184 5,220 9,900 12,400 19,700 Above Little Turtle Creek 116 3,290 6,300 7,800 12,400 UNNAMED TRIBUTARY 1 TO RACCOON CREEK At mouth 6.1 1,300 2,160 2,580 3,700 At State Highway 81 3.3 730 1,200 1,450 2,050 At Beloit-Newark Road 1.0 330 560 670 980 UNNAMED TRIBUTARY 2 TO RACCOON CREEK At mouth 2.4 580 960 1,150 1,650 UNNAMED TRIBUTARY 1 TO ROCK RIVER At mouth 18.4 2,255 3,473 4,205 5,813 Above State Highway 51 17.9 2,232 3,415 4,129 5,692 Field crossing 1/4 mile above State Highway 51 17.2 2,170 3,308 3,992 5,492 450' below County Highway G 16.7 2,113 3,214 3,876 5,331 County Highway G 15.8 2,000 3,038 3,662 5,036 UNNAMED TRIBUTARY 1 TO TURTLE CREEK At mouth 7.8 840 1,380 1,650 2,350 Town Road, S25 T2N R13E 4.7 620 1,100 1,330 2,000 14

Table 1 - Summary of Discharges - continued Peak Discharges (cubic feet per second)

Drainage Area 10-Percent- 2-Percent- 1-Percent- 0.2-Percent-Flooding Source and Location (square miles) Annual-Chance Annual-Chance Annual-Chance Annual-Chance UNNAMED TRIBUTARY 2 TO TURTLE CREEK At mouth 3.8 490 840 1,000 1,500 Above confluence with Unnamed Southern Trib. 2.4 360 575 680 950 At dam upstream of Buss Rd 1.2 230 420 520 810 UNNAMED TRIBUTARY TO BLACKHAWK CREEK Below Milton Shopiere Road 15.8 1,212 2,026 2,530 3,462 South of County Highway A 14.9 1,134 1,902 2,377 3,259 500' below Tarrant Rd 12.6 1,001 1,647 2,052 2,807 UNNAMED TRIBUTARY TO E FORK RACCOON CREEK At mouth 4.8 820 1,310 1,550 2,200 At Beloit-Newark Road 1.6 400 640 760 1,060 UNNAMED TRIBUTARY IN TURTLE TOWNSHIP Wisconsin-Illinois State line 6.5 643 1,051 1,307 1,908 East County Highway P 5.8 604 990 1,230 1,781 Confluence with Tributary 4.8 537 859 1,057 1,518 Confluence with Tributary 4.0 490 762 925 1,313 East County Highway P 3.3 424 643 795 1,126 East County Highway P 1.4 239 376 455 630 S. Clinton Corners Road 0.6 117 178 214 293 YAHARA RIVER At mouth 537 2,200 3,800 4,700 7,000 Dane-Rock County line 430 710 910 990 1,180 The City of Janesville Flood Insurance Study Hydrologic Summary produced by Owen Ayers & Associates in 1981 has flow values for portions of Fisher Creek, Markham Creek, Morningside Tributary and Greenbelt Tributaries 1-5 because they were previously approximate zones. These values compared favorably to the HEC-HMS peak flow values attained in 2005.

Stillwater elevations for Lake Koshkonong are shown in Table 2.

Table 2 - Summary of Stillwater Elevations Water Surface Elevations (Feet NGVD291) 10-Percent- 2-Percent- 1-Percent- 0.2-Percent-Flooding Source Annual-Chance Annual-Chance Annual-Chance Annual-Chance Lake Koshkonong 781.8 783.6 784.6 785.8 1

National Geodetic Vertical Datum of 1929 15

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 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 use the flood elevation data presented in this FIS report in conjunction with the data shown on the FIRM.

Precountywide Analyses UNINCORPORATED AREAS There were 471 field measured cross sections for the Rock County study, of which 183 were supplied by the COE and the USGS.

The distances between cross sections were obtained from enlarged 1:24000 scale USGS quadrangle maps.

Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles. For stream segments for which a floodway was computed (Section 4.2), selected cross section locations are also shown on the Flood Boundary and Floodway Map.

The channel and overbank roughness factors (Manning's n) were assigned on the basis of field inspection. These range from 0.028 to 0.05 in the channel and 0.04 to 0.15 in the overbanks.

The hydraulic model for Yahara River reflects existing conditions. The powerhouse and dam on the Yahara River, near Fulton, are presently being modified or have future plans for modification. The 18 wicket gates at the powerhouse are operable; however, they are blocked off from flow and were not considered in developing outflow rating curves from the lake. The powerhouse may be fully functional within a year's time, thus affecting the water-surface upstream of the dam. An area of divided flow exists at the Fulton Dam. A small portion of the 100-year flow separates from the main flow and is diverted east of the Fulton Dam through a divergence channel and then back into the Yahara River.

Flows through the divergence channel were taken into account in the hydraulic model. A levee located along the northern side of the channel prevents the diverging flow from overflowing into the flood plain. Hydraulic data upstream of the Stebbinsville Dam were obtained from the Dane County Flood Insurance Study. The river miles for the Yahara River do not agree with previous studies due to updated mapping.

16

Water-surface elevations were computed using the COE HEC-2 step-backwater computer program. Profiles were determined for the 10-, 50-, 100-, and 500-year floods. Water-surface elevations for the other detailed study streams were started at bank full elevations at the main stem.

Starting water-surface elevations on Blackhawk Creek are the corresponding elevations of Spring Brook at the confluence point.

The starting water-surface elevations for Sugar River match the elevations at the upstream limit of the Winnebago County, Illinois, Flood Insurance Study.

Turtle Creek was studied in combination and coordinated with the Beloit and South Beloit Flood Insurance Studies. Starting water surface elevations were taken from the Beloit Flood Insurance Study. Hydraulic data were also coordinated with the Rock Island COE. Due to the level of detail and lack of data, a possible overflow bypass across Creek Road to the Rock River was not studied by detailed methods.

All flow was assumed to continue downstream on Turtle Creek. Flood profiles were drawn showing computed water-surface elevations for floods of the selected recurrence intervals.

Hydraulic characteristics of stream reaches studied by approximate methods were determined from flood prone area maps and by normal depth analysis.

The hydraulic analyses for Allen Creek were taken from the Flood Hazard Study for the City of Evansville. The flood profiles taken from the report were computed using the SCS WSP-2 computer program.

CITY OF JANESVILLE Cross section data and structure data necessary for this analysis were developed by field survey and bridge data from the COE, Rock Island District, files, City of Janesville data, and use of topographic maps at a scale of 1:2400 with a contour interval of 2 feet for overbank areas.

The procedures used for calculating head losses through bridges and other structures causing constrictions to flow allowed the identification of significant backwater producing structures.

Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles. For stream segments for which a floodway was computed (Section 4.2), selected cross section locations are also shown on the Flood Boundary and Floodway Map.

Overbank roughness factors (Manning's n) for the streams were estimated using engineering judgment and high water data from photographs taken at cross section locations and field observations. Channel roughness factors were estimated by 17

comparison with table values and the step-by-step procedure for channel n values in Chow's text on open-channel hydraulics and historical high water data. These ranged from 0.028 to 0.033 for channel and 0.04 to 0.09 for overbanks on the Rock River. For Spring Brook and Blackhawk Creek, which are hydraulically continuous, these values varied from 0.035 to 0.070 in the channel and 0.050 to 0.14 for overbanks.

Starting water-surface elevations on Spring Brook were determined using the corresponding 10-year frequency water surface on the Rock River. Starting water-surface elevations on Blackhawk Creek are the elevation of Spring Creek at the confluence point. Water surface elevations were computed using the COE HEC-2 step-backwater computer program CITY OF BELOIT Stream cross sections and structural data for all streams studied in detail were obtained from field survey and the Rock Island District COE.

Roughness coefficients (Manning's n), used in the hydraulic analyses, were based on field observations and engineering judgment, and were provided by the Rock Island District COE. The n values for the Rock River channel range from 0.03 to 0.045 and the overbanks range from 0.055 to 0.085. The n value for the Turtle Creek channel is 0.035 and the overbanks range from 0.05 to 0.075. The n' values for the Spring Brook channel range from 0.03 to 0.07 and the overbanks range from 0.06 to 0.16.

Hydraulic information for Spring Brook was obtained from the Rock County, Wisconsin Flood Insurance Study.

Starting water-surface elevations for the Rock River and Turtle Creek were based on downstream flood profiles obtained from the South Beloit Flood Insurance Study. Starting water surface elevations for Spring Brook were obtained using the slope-area method. Water surface profiles for the various discharge-frequencies were determined using the COE HEC-2 computer program. Flood profiles were drawn showing computed water-surface elevations for floods of the selected recurrence intervals.

CITY OF EDGERTON The cross sections used for the study were obtained from 2-foot contour maps made available by the City.

All bridge elevation data and structural geometry for the backwater analyses of the flooding source studied were obtained by field surveys by the Study Contractor.

The channel soundings were also obtained by field measurement.

Channel roughness factors (Manning's n) used in the hydraulic computations were chosen by engineering judgment and based on field observations of the 18

streams and floodplain areas. Roughness values for the main channel of Saunders Creek range from 0.035 to 0.04 with floodplain roughness values ranging from 0.06 to 0.11 for all floods.

CITY OF EVANSVILLE Cross section data for Allen Creek were obtained from field survey measurements.

All bridges and culverts were field surveyed to obtain elevation data and structural geometry.

Comparing the 100-year flood elevation with the contour maps, it was discovered that flow would occur over the Chicago and North Western railroad tracks toward the east in an area downstream of Main Street. The water that flows over the tracks does not re-enter Allen Creek until it joins the flow from a drainage basin from the east and enters Allen Creek south of the city. The divided flow was subtracted from the main flow in the channel.

Revised Analyses for this Countywide FIS All new hydraulic models were done by Gannett Fleming using HEC-RAS 3.1.3.

County-wide floodplain delineations were also created by Gannett Fleming using year 2000 Rock County digital terrain data and ArcGIS 9.1.

The distances between all cross sections were obtained by calculating the distance along the stream centerline digitized from the 2000 Rock County orthophoto.

Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles. For stream segments for which a floodway was computed (Section 4.2), selected cross section locations are also shown on the Flood Insurance Rate Map.

The channel and overbank roughness factors (Manning's n) for new studies were assigned on the basis of inspection of the 2000 Rock County orthophoto.

All studies that were redelineated used the previous models n values.

For all new detailed studies (Fisher Creek, Markham Creek, Morningside Trib, Greenbelt Tribs 1-5, Unnamed Trib to Blackhawk Creek, Unnamed Trib 1 to Rock River, Unnamed Trib in Turtle Township and portions of Saunders Creek, Spring Brook-Beloit, Bass Creek and Blackhawk Creek) all bridges and culverts were field surveyed to obtain elevation data and structural geometry. For the following redelineated studies, all bridges in the existing model were verified as the current existing bridges and the 2000 orthophoto was inspected to search for new bridges since the model was created: Rock River, Raccoon Creek, East Fork Raccoon Creek, Unnamed Tribs 1 & 2 to Raccoon Creek, Unnamed Trib to East Fork Raccoon Creek and the remaining portions of Saunders Creek, Spring Brook-Beloit 19

and Allen Creek. If the DOT had plans for a new bridge, it was entered into the HEC-RAS 3.1.3 model and re-run to get new water surface elevations.

There were no new hydraulic models created for; Yahara River, Otter Creek, Marsh Creek, Turtle Creek, Unnamed Tribs 1 & 2 to Turtle Creek, Sugar River, Spring Brook-Janesville, the downstream-most 1.25 miles of Blackhawk Creek, upstream of the Lake Leota Dam on Allen Creek and below S. Footville Rd. on Bass Creek. The old FIS profile was taken as is and those elevations were mapped on new terrain data. This was done largely for the fact that the original model could not be located on most of these. On the few that an original model could be found, complications including matching the cross sections to new terrain and time constraints were used as the reason why the model was not updated. The only exception to this is that Fulton Dam was taken out of the profile of Yahara River since it has been removed since the last FIS.

The limited detail studies on Lenigan Creek, Lenigan Creek Tribs. 1 & 2, Philhower Road Trib., Unnamed Clinton Trib., South Branch Unnamed Clinton Trib., Unnamed Trib. in Union Township, Milton Ditch and Unnamed Trib. 2 to Rock River were done in the same manner in HEC-RAS 3.1.3 as the new detailed studies. The difference between these two types of studies was that the limited detail studies bridges were not surveyed into mean sea level (MSL). The bridges were measured in relative distances from the top of road.

The 10-year frequency water surface of the Rock River was used as the starting water surface for the following studies: Unnamed Trib. 1 to Rock River, Markham Creek, Fisher Creek and Saunders Creek.

The 100-year frequency water surface elevation at the upstream end of the redelineate reach of Blackhawk Creek was used as the starting water surface elevation for the new detailed reach of Blackhawk Creek.

The 100-year frequency water surface elevation at the upstream end of the redelineate reach of Bass Creek was used as the starting water surface elevation for the new detailed reach of Bass Creek.

The 10-year frequency water surface of Blackhawk Creek was used as the starting water surface for Greenbelt Trib. 1 and Morningside Trib. Greenbelt Tribs. 1-5 were all entered in the same HEC-RAS model and Tribs. 2-5 starting water surface elevations are equal to the 100-year frequency water surface of its receiving stream.

The Unnamed Trib. to Blackhawk Creek was included in the same HEC-RAS model as Blackhawk Creek, so its starting water surface elevation is equal to the 100-year frequency water surface of Blackhawk Creek at the confluence.

20

Spring Brook (Beloit) has a starting water surface elevation equal to the 10-year frequency water surface of Turtle Creek.

Starting water surface elevation for Unnamed Trib. in Turtle Township was done by normal depth calculation.

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).

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 the National Geodetic Vertical Datum of 1929 (NGVD29). With the finalization of the North American Vertical Datum of 1988 (NAVD88), many FIS reports and FIRMs are being prepared using NAVD88 as the referenced vertical datum.

All flood elevations shown in this FIS report and on the FIRM are referenced to NGVD29. Structure and ground elevations in the community must, therefore, be referenced to NGVD29. It is important to note that adjacent communities may be referenced to NAVD88. This may result in differences in Base Flood Elevations (BFEs) across the corporate limits between the communities.

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 20910 (Internet address http://www.ngs.noaa.gov).

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 21

for this community. Interested individuals may contact FEMA to access these data.

4.0 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-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 delineated based on the 2000 Rock County digital terrain model.

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. 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).

22

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. 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.

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 (Table3).

23