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Home My WebLink AboutLick Creek Watershed Flood Insurance RE-studyLick Creek Watershed Flood Insurance Re-study City of College Station, Texas 480083 Brazos County, Texas 481195 Request of Letter of Map Revision Case Number 00-06- July 2000 Prepared by: City of College Station, Development Engineering P.O. Box 9960 1101 Texas Avenue College Station, Texas 77842 Phone: (979) 764-3570 Fax: (979) 764-3496 Lick Creek Flood Insurance Re-Study July 2000 Page I Table of Contents 1.0 INTRODUCTION .............................................................................................. .4 1.1 BACKGROUND ................................................................................................................................. 4 1.2 BASIS FOR RE-STUDY ...................................................................................................................... 4 1.3 SITE L OCATION ............................................................................................................................... 6 1.4 WATERSHED DESCRIPTION .............................................................................................................. 6 1.5 LIMITS OF RE-STUDY ....................................................................................................................... 8 1.6 EXISTING STUDIES ........................................................................................................................... 8 2.0 FEMA LOMR FORMS MT-2 ................................................................................. 10 3.0 HYDROLOGIC ANALYSIS .................................................................................. 28 3.1 RAINFALL DISTRIBUTION .............................................................................................................. 28 3.2 INFILTRATION Loss RATE ............................................................................................................. 28 3.3 WATERSHED SUB -AREAS ............................................................................................................... 29 3.4 WATERSHED CHARACTERISTICS .................................................................................................... 30 3.5 CHANNELROUTING ....................................................................................................................... 31 3.6 HEC-1 RESULTS ............................................................................................................................ 32 4.0 FLOODPLAIN ANALYSIS ................................................................................. 33 4 .1 HYDRAULIC ANALYSIS .................................................................................................................. 33 4 .2 DUPLICATE EFFECTIVE MODEL ..................................................................................................... 33 4 .3 CORRECTED EFFECTIVE MODEL .................................................................................................... 34 4.4 EXISTING OR PRE-PROJECT CONDITIONS MODEL .......................................................................... 34 4 .5 REVISED OR POST-PROJECT CONDITIONS MODEL ......................................................................... 34 4 .6 MODEL RESULTS AND COMPARISON ............................................................................................. 35 5.0 FLOODPLAIN MAPPING ................................................................................... 41 6.0 NEED FOR ADDITIONAL STUDIES ..................................................................... 43 7.0 CONCLUSIONS ................................................................................................ 44 8.0 BIBLIOGRAPHY .............................................................................................. 45 Lick Creek Flood Insurance Re-Study July 2000 Page 2 List of Exhibits Exhibit 1 ............................ Watershed Area Map and Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Exhibit 2 ............................ Proposed Annotated FIRM Map..................................... 42 List of Appendixes Appendix 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Soil Maps Appendix 2 ..................................................... Duplicate Effective Hydrology Model Appendix 3.................................................... Corrected Effective Hydrology Model Appendix 4 ..................................................... Need to Re-study Letters Appendix 5..................................................... Effective Flood Insurance Rate Map Appendix 6 ..................................................... New Hydrology Drainage Area Map Appendix 7..................................................... Spring Creek Support Information Appendix 8................................................... .. CN Calculations Appendix 9..................................................... Lag Time Calculations Appendix 10 ..................................................... Proposed Hydrology Model HEC-1 Appendix 11 ..................................................... FEMA Effective HEC-2 Model Appendix 12 ..................................................... Duplicate Effective HEC-2 Model Appendix 13 ..................................................... Hydraulic Analysis Summary Table Appendix 14 ..................................................... "Corrected" Converted HEC-RAS Model Appendix 15A-F... .. . . .. . .. . .. . . .. . . ... ............. .. . . .. . ... Bridge Construction Plans Appendix 16 ................................................... Pictures of Existing Bridge Structures Appendix 17 ..................................................... Proposed HEC-RAS Model Appendix 18 .................................................... Floodplain Work Maps Appendix 19 ................................................... Proposed Floodplain Profiles Lick Creek Flood Insurance Re-Study July 2000 Page 3 1.0 INTRODUCTION 1.1 Background The initial Flood Insurance Study for the incorporated areas of Brazos County (College Station and Bryan) was completed by Turner, Collie, & Braden in March 1979. At the time of this initial study, the Lick Creek watershed was located entirely outside of any corporate city limits. The City of College Station began annexing areas within the Lick Creek drainage basin and it's tributaries in 1982 and continued annexations through 1996. Currently, almost fifteen of the twenty square miles of the Lick Creek watershed are located within the corporate limits of the City of College Station. This area now comprises much of the southern one-third of the City and is experiencing rapid growth. Most of this growth is concentrated in the area upstream of State Highway 6 due to the availability of sanitary sewer service. The city will begin construction to extend a major sewer trunk line along Lick Creek within the next year. In September 1988, the Fort Worth District of the U.S. Army Corps of Engineers (COE) completed a countywide Flood Insurance Study of Brazos County for FEMA. The COE produced a detailed study of Lick Creek downstream of State Highway 6. 1.2 Basis fo r Re-study The 1987 Brazos County Limited Detail Flood Insurance Study of Lick, Wickson, and Carter's Creeks prepared by the Fort Worth District of the U.S. Army Corps of Engineers utilized the Nu-Dallas computer program to generate the hydro logic data for the study. A copy of the input data was obtained and reviewed by City of College Station staff. This review revealed that the soil condition parameter used throughout the study area was "ninety percent (90%) sand". Based upon local knowledge of soil conditions, staff was concerned that the value of this parameter was grossly inaccurate and consequently consulted the USDA Soil Conservation Service Soil Survey for Brazos County. The Soil Survey indicates that the primary soils within this watershed are Type D soils having high runoff potential, unlike a "ninety percent sand" soil. A draft copy of the new Brazos County Soil Survey (to be published next year) was obtained from the local branch office of the Natural Resources Conservation Service. The draft publication indicated that the typical soils for this watershed are generally classified as "fine sandy loams" with shallow hard clay pans. The soil profiles indicate the top horizon, six to eight inches, contains approximately fifty-percent sand while the second soil horizon, twelve to eighteen inches thick, typically contains less than twenty-five- percent sand. Tabl e 1.1 below is taken from the USDA NRCS Draft Brazos County Soil Survey. Excerpts from these maps are located in Appendix I. Table 1.1 Soil Information From Final Draft of NRCS Brazos County Soil Survey dated March 3, 1995 Soils by decreasing percentage of the Lick Creek Drainage Basin Horizon USDA % Sand Map Soil Depth Texture (not passing Symbol Name (inches) By Horizon 200 sieve) 0-9 Fine Sandy Loam 40-60 SnB Singleton 9-17 Clay 5-25 Lick Creek Flood Insurance Re-Study July 2000 H)·drologic %Clay Group 5-20 D 35-50 Page4 0-8 Fine Sandy Loam 40-60 5-15 BwC Burlewash D 8-24 Clay, Sandy Clay 10-50 40-55 0-5 Fine Sandy Loam 40-60 4-12 ZuB Zulch D 5-13 Clay Loam 5-25 35-50 0-15 Fine Sandy Loam 45-70 8-20 TuA Tabor D 15-28 Clay 10-60 40-50 0-17 Fine Sandy Loam 35-60 5-15 BoA Boonville D 17-24 Clay, Clay Loam 10-30 35-55 0-15 Fine Sandy Loam 60-85 5-12 SkB Shiro c 15-24 Clay, Sandy Clay 5-49 35-45 0-6 Loam 20-55 15-25 Sa Sandow c 6-72 Fine Sandy Loam/Loam 10-60 15-35 0-6 Loam 10-45 8-20 DeA Derly D 6-16 Clay Loam 5-30 27-40 The Fort Worth District of the COE has, as a replacement for the Nu-Dallas Program, created the SWF-HYD program using identical variables as input data. The Flood Insurance Study (FIS) model for Lick Creek was re-coded and run on the SWF-HYD computer program. The output of this Duplicate Effective Model matched the data published in the original FIS within one-tenth of a percent (0.1 %) and is included in Appendi x 2. Subsequently, an assumption was made that the ninety-percent (90%) sand parameter should be modified to forty percent (40%) sand. This change was made and the Corrected Effective Model re-run. The output of this model is included in Appendi x 3. This new run produced flows at the given locations within the model approximately forty-percent ( 40%) higher than the adopted FIS. Tabl e 1.2 compares the flows reported in the adopted FIS to the flows produced by the corrected effective model for Lick Creek for the 100-year storm. Table 1.2 Comparison of Flows Effective FIS to Corrected Effective Models Location Arca FIS Discharge Corrected Discharge (sq-mi) (cfs) (cfs) At confluence with Navasota River 20.57 11 ,500 15,039 At Rock Prairie Road 18.28 12,300 15,798 At confluence of Alum Creek 14.45 11 ,500 14,878 Approx. 500 feet US of Alum Creek 10.05 7,900 10,001 At confluence of Spring Creek 8.17 8,300 10,513 Approx. 500 feet US of Spring Creek 4.43 4,500 5,739 Approx. 1.29 miles DS of Highway 6 3.25 4,900 6,139 Approx. 1.19 miles DS of Highway 6 1.72 2,500 3,162 Lick Creek Flood Insurance Re-Study July 2000 Page 5 These findings were reported to Mr. Jack Quarles, P.E., Civil Engineer with FEMA Region VI (see letter in Appendi x 4). Mr. Quarles advised City staff that a re-study would be appropriate. He also stated that only limited federal funding was available for such re-studies. As such, it may be several years before FEMA could complete such a study. Based on this conversation, City staff chose to complete this re-study before substantial development accrued adjacent to the subject floodplain. Due to the fact that local soil conditions contain a shallow clay pan horizon, which can not accurately be modeled in the Nu-Dallas or SWF-HYD programs, and the nature of the available data, City staff determined that the re-study should use the standard conventional US Army Corps of Engineer's HEC- 1 program. This aspect of the re-study is discussed further in Secti on 3 of this report. 1.3 Site Location The Lick Creek watershed is located in south central Brazos County, Texas. The re-study area is bounded approximately by Rock Prairie Road to the north, Wellborn Road to the west, Peach Creek Cut-off to the south, and the Navasota River to the east as shown in Exh ibit I . The watershed drains the southern one-third of the corporate limits of the City of College Station. Three major tributaries contribute to the Lick Creek watershed: Spring Creek, Alum Creek, and Peach Creek. The confluence of Peach Creek with Lick Creek is located at a point where backwater from the Navasota River controls the floodwater surface elevation. Based on this fact, the Peach Creek Drainage basin was not included in the current FIS or within this re-study. The re-study area is depicted on FEMA Flood Insurance Rate Map (FIRM) panels 48041C0182C, 48041C0201D, and 4841C0205D in Appendix 5. 1.4 Watershed Description Lick Creek flows generally from west to east to its confluence with the Navasota River. The ground elevation at the headwaters near the intersection of Rock Prairie Road and Wellborn Road is 333 feet ms] and drops to an elevation of 185 feet msl within the Navasota River floodplain. The watersheds of the north and south forks of Lick Creek, upstream of State Highway 6, are experiencing rapid development. Nearly half of this area has been platted for single-family residences along with some mixed-use/commercial development. Another quarter of this area has been preliminary platted generally employing the same uses. Numerous detention ponds have been constructed within the area. In this re-study, this upper one-third of the watershed, bounded at the downstream end by State Highway 6, is assumed as fully developed. The middle one third of the watershed is primarily undeveloped, due to the unavailability of economical sanitary sewer service at this time. The City will be extending service to this area within the next year and this will undoubtedly attract growth. However, based upon FEMA guidelines, this area is assumed as primarily undeveloped; bounded by Greens Prairie Road on the downstream end. The Spring Creek watershed drains to the Lick Creek watershed in this section. The effective Spring Creek flood study was prepared by LJA Engineering and submitted to FEMA in I 999 as LOMR case number 99-06-1336P. Currently, Master Development Plans (MDPs) have been approved for two- thirds of the Spring Creek drainage basin, but very little has been completed. The approved MDPs call for construction of several major detention ponds to offset the effects of development. One such pond is currently being reviewed by FEMA under CLOMR case number 00-06-844R. The upper portion of the lower one third of the Lick Creek watershed is experiencing rapid growth consisting of one-half acre and smaller single-family lots being built by the Pebble Creek developers. Lick Creek Flood Insurance Re-Study July 2000 Page 6 Insert Exhibit 1 Lick Creek Flood Insurance Re-Study July 2000 Page 7 An MDP has been approved for this area and is approaching the point of 50% completion. Based on this premise, this re-study assumes this area as fully developed. The lower portion of the lower one- third of Lick Creek consists of sporadic low destiny development and large amounts of floodplain. In accordance with FEMA guidelines, this area is modeled as having limited development. The Alum Creek drainage basin flows into Lick Creek in this lower one-third of the watershed. Much of the upper half of the Alum Creek drainage basin, bounded by State Highway 6, is developed as low density single-family, and is modeled as such in this re-study. Tributary AC-1 drains into Alum Creek drainage basin downstream of Highway 6. The drainage area to this tributary is nearly fully developed and consists of the College Station Business Park to the west, and single family development to the east. Currently, the lower half of the Alum Creek basin is experiencing single-family development to the north and no development to the south. The Lick Creek stream channel flows out of the corporate limits of College Station 22,000 feet upstream of the confluence with the Navasota River. Based on the current effective FIS, backwater from the Navasota River controls the 100-year flood elevation at 206 feet ms! for the lower 20,000 feet of Lick Creek. 1.5 Limits of Re-study This re-study of Lick Creek extends from the point were backwater from the Navasota River controls the flood elevation, as mentioned above, to the upstream limits of the existing adopted study. This portion of the re-study uses new hydrology with existing hydraulic information imported into HEC- RAS. This re-study also extends to the North Fork of Lick Creek 6,050 feet to the Park Meadows Development. The re-study also includes the South Fork of Lick Creek from its confluence with the main branch 9,278 feet upstream of the proposed Victoria Road extension. 1.6 Existing Studies In September 1988, the Fort Worth District of the U.S. Army Corps of Engineers (COE) completed a countywide Flood Insurance Study for FEMA, which included a detailed study of Lick Creek downstream of State Highway 6. City staff re-coded the hydraulic HEC-2 model from paper copies and used it as the basis for the new hydraulic model downstream of State Highway 6. Chapter 13, Section 5.F of the City of College Station Code of Ordinances (in accordance with FEMA minimum requirements) requires that developments greater than 50 lots or 5 acres establish base flood elevations. Because of this requirement, several studies have been generated to map the floodplain along the upper branches of Lick Creek. This re-study incorporates several of the hydraulic models from these small limited studies. Robertson Consulting Engineers conducted a limited study in April, 2000 as part of the City of College Station Graham Road Rehabilitation Project. This study extends along the North Branch from the limits of the existing study upstream for approximately 3,830 feet. This study was used to size the culvert crossing for Graham Road and utilized the HEC-RAS program. Three studies have been produced along the south fork of Lick Creek. Two of these studies were produced by McClure Engineering for the Springbrook-Oakgrove and Alexandria Subdivisions. The first of these was completed in May 1994 to map the floodplain, and established minimum finished floor elevations. A second study was completed in November 1999 extending the previous study, and was used to map the floodplain and size the on-line detention pond. This second study, which utilized Lick Creek Flood Insurance Re-Study July 2000 Page 8 HEC-RAS, is incorporated into this re-study. Morrison Hydrology produced a third study for the Westfield Subdivision in October 1999. This study mapped the floodplain and determined the size of the proposed on-line detention pond. This study was completed using the HEC-2 program and City staff converted it to HEC-RAS through the HEC-RAS import routine. Electronic copies of these four studies were provided to the City of College Station from their respective creators. Lick Creek Flood Insurance Re-Study July 2000 Page 9 I FEDERAL EMERGENCY MANAGEMENT AGENCY O.M.B No. 3067-0148 REVISION REQUESTER AND COMMUNITY OFFICIAL Expires April 30, 2001 Public reporting burden for this form is estimated to average 2.13 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington DC 20472; and to the Office of Management and Budget, Paperwork Reduction Project (3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. 1. REQUESTED RESPONSE FROM FEMA This request is tor a: D CLOMR A letter from FEMA commenting on whether a proposed project, if built as proposed, would justify a map revision, or proposed hydrology changes (See 44 CFR Ch. 1, Parts 60,65 & 72). LOMR A letter from FEMA officially revising the current NFIP map to show the changes to floodplains, floodway or flood elevations. LOMRs typically decrease flood hazards. (See 44 CFR Ch. 1 Parts 60 & 65.) D Other Describe: 2. OVERVIEW 1. The basis tor this revision request is (are): (check all that apply) D Physical Change 1:8] Improved Methodology/Data D Floodway Revision D Other Describe: Note: A photograph is not required, but is very helpful during review. 2. Flooding Source: Lick Creek 3. Project Name/Identifier: Lick Creek Re-study and Extension 4. FEMA zone designations affected: X and AE (example: A, AH, AO, A 1-A30, A99, AE, V, V1-V30, VE, B, C, D, X) 5. The NFIP map panel(s) affected tor all impacted communities is (are): Community No. Community Name State Map No. 480083 48041C 481195 Brazos County TX 48041C 6. The area of revision encompasses the following types of flooding and structures. Check all that apply. 1:8] D D D D D Riverine Coastal Alluvial fan Types of Flooding Shallow Flooding (e.g. Zones AO and AH) Lakes Other (describe) D D 1:8] D D D Channelization Levee/Floodwall Bridge/Culvert Dam Fill Other (describe) Structures Panel No. 02010 02050 0182C 02050 PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS Effective 02109100 02109100 07102192 02109100 FEMA Form 81-89 Revision Requester and Community Official Form MT-2 Form 1 Page 1 of 2 I I 4. ENCROACHMENT INFORMATION 1. Does the State have jurisdiction over the floodway or its adoption by communities participating in the NFIP? D Yes ~ No .'Yes, attach a copy of a letter notifying the appropriate State agency of the floodway revision and documentation of the approval of the revised floodway by the appropriate State agency. 2. Does the development in the floodway cause the 1 % annual chance (base) elevation to increase at any location by more than 0 .000 feet? 0 Yes D No ~ N/A 3. Does the cumulative effect of all development that has occurred since the effective SFHA was originally identified cause the base flood elevation to increase at any location by more than one foot (or other increase limit if community or state has adopted more stringent criteria -even if a floodway has not been delineated by FEMA)? 0 Yes ~ No If the answer to either items is Yes, please attach documentation that all requirements of Section 65.12 of the NFIP regulations have been met, regarding evaluation of alternatives, notice to individual legal property owners, concurrence of CEO, and certification that no insurable structures are impacted. 5. MAINTENANCE RESPONSIBILITY The community is willing to assume responsibility for D performing ~ overseeing compliance with the maintenance and operation plans of the ____ _ (Name) flood control structure. If not performed promptly by an owner other than the community, the community will provide the necessary services without cost to the Federal government. Operation and maintenance plans are attached. 0 Yes 0 No ~ N/A 6. REVIEW FEE The review fee for the appropriate request category has been included. 0 Yes Fee amount: $ ____ _ OR This request is based on a federally sponsored flood-control project where 50 percent or more of the project's cost is federally sponsored, or the request is based on detailed hydrologic and hydraulic studies conducted by Federal, State, or local agencies to replace approximate studies conducted by FEMA and shown on the effective FIRM; thus the project is fee exempt. ~ Yes Please see Instructions for Fee Amounts 7. SIGNATURE Note: I understand that my signature indicates that all information Note: Signature indicates that the community understands, from the submitted in support of this request is correct revision requester, the impacts of the revision on flooding conditions in the community. Signature of Revision Requester Signature of Community Official Jeffrey S. Tondre, P.E., Civil Engineer Ted Mayo, P.E., Asst. City Engineer Printed Name and Title of Revision Requester Printed Name and Title of Community Official City of College Station, Develo12ment Services City of College Station Company Name Community Name Teleohone No.: 979-764-3570 Date: Telephone No.: 979-764-35 70 Date: CERTIFICATION BY REGISTERED PROFESSIONAL ENGINEER Check which forms have been included with this request AND/OR LAND SURVEYOR This certification is in accordance with 44 CFR Ch. 1, Sect 65.2 Form Name and jNumber) Required if ...... 181 Hydrologic (3) new or revised discharges 181 Hydraulic (4) new or revised water-surface elevations Signature 181 Mapping (5) floodplain/floodway changes D Channelization (6) channel is modified Jeffrey S. Tondre, P.E., Civil Engineer 181 Bridge/Culvert (7) addition/revision of bridge/culvert Printed Name and Title of Revision Requester D Levee/Floodwall (8) addition/revision of levee/floodwall D Coastal (9) new or revised coastal elevations .egistr No. 85609 Expires (Date) 06/30/01 State Texas D Coastal Structures ( 1 0) addition/revision of coastal structure D Dam ( 1 1) addition/revision of dam Type of License/Expertise: Civil I Drainage and Land Develo12ment D Alluvial Fan ( 1 2) structures proposed on alluvial fan FEMA Form 81 -89 Revision Requester and Community Official Form MT-2 Form 1 Page 2 of 2 /0 FEDERAL EMERGENCY MANAGEMENT AGENCY O.M.B No. 3067-0148 HYDROLOGIC ANALYSIS Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE 'ublic reporting burden for this form is estimated to average 3.67 hours per response. The burden estimate .ncludes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington DC 20472; and to the Office of Management and Budget, Paperwork Reduction Project (3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Note: Fill out one form for each flooding source studied Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1 . REASON FOR NEW HYDROLOGIC ANALYSIS 0 No existing analysis ~ Improved data ~ Changed physical condition of watershed 0 Alternative methodology 0 Proposed Conditions (CLOMR) D Other For the reason stated above, please attach a detailed explanation. If a computer program/model was used in revising the hydrologic analysis, please provide a diskette with the input files for the same flood recurrence intervals contained in the FIS for that stream; and at least for the 1 % annual chance (base) flood where no detailed study exists. Explanation provided: ~ Yes 0 No Diskettes provided: ~ Yes D No Indicate Method 0 Statistical Analysis of Gage Records 0 Regional Regression Equations ~ Precipitation/Runoff Model 0 Other 2. METHODOLOGY FOR NEW ANALYSIS Required Data Form 3 -Attachment A Form 3 -Attachment C Form 3 -Attachment D Back-up computations and supporting data 3. APPROVAL OF ANALYSIS Data Included D Yes ~ No D Yes ~ No ~ Yes 0 No D Yes ~ No The hydrologic analysis has already been approved by a local, state, or Federal Agency. 0 Yes 0 No ~ Not Required If Yes, attach evidence of approval. 0 Approval attached. If No, attach explanation. 0 Explanation attached. 4. COMPARISON OF BASE FLOOD DISCHARGES Location: Drainage Area (SqMi) FIS(cfs) Revised (cfs) See table 3.3 in section 3.6 of report Note: When revised discharges are not significantly different than the FIS discharges, FEMA may require a confidence limits analysis (see attachment BJ at a later date to complete the review. If only a portion of a detailed study area was revised please attach an explanation describing the transition from the proposed discharges to the effective discharges. 0 Explanation Included ~ Explanation Not Required 5. HISTORICAL FLOODING INFORMATION ,f historical data are available for the flooding source please provide: Location, peak discharges/water-surface elevations and dates, and source of information. D Data Attached ~ Data Not Available PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81 -898 Hydrologic Analysis Form MT-2 Form 3 Page 1 of 5 ,, '1... 2. 3. 4. 5. 6. 7. 8. 9. 10. . 1 . 12. 13. 14. ATTACHMENT D: PRECIPITATION/RUNOFF MODEL Method or model used: Version: Date: Source of rainfall depth: Source of rainfall distribution: Rainfall duration: Areal adjustment to precipitation (%): Maximum overland flow length Hydrograph development method: Loss rate method: Source of soils information: Source of land use information: Channel routing method: Reservoir routing: Baseflow considerations: If Yes, explain below how baseflow was determined: Snowmelt considerations: Model calibration: If Yes, explain below how calibration was performed Future land use condition: If Yes, explain .why below FIS: Nu Dallas unknown unknown unknown unknown unknown 0 Yes 0 Yes 0 Yes 0 Yes 0 Yes [8J No [8J No [8J No [8J No [8J No Revised: June 1998 SCS Type Ill NRCS/SCS Soil Surveys City of College Station Muskingum-Cunge 0 Yes 0 Yes 0 Yes 0 Yes [8J Yes [8J No [8J No [8J No [8J No [8J No Upper portion of drainage basin is master planned and currently being platted. It was considered to be built out. 15. Attach precipitation/runoff model, hydrologic model schematic, curve number calculations, time of concentration calculations, and supporting maps, delineating the watershed boundary and drainage area divides. Information and Maps provided? [8J Yes [8J No NOTE: FEMA policy is to base flooding on existin conditions. FEMA Form 81 -898 Hydrologic Analysis Form MT-2 Form 3 Page 5 of 5 FEDERAL EMERGENCY MANAGEMENT AGENCY O .M.B No. 3067-0148 RIVERINE HYDRAULIC ANALYSIS Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2.25 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and wiewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W ., Washington DC 20472; and to the Office of Management and Budget, Paperwork Reduction Project (3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Note: Fill out one form for each floodin source studied Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1 . REACH TO BE REVISED Describe the limits of the revision OR submit a copy of the FIRM with the revision area clearly highlighted. Copy of FIRM(s) attached depicting area of the revision (highlighted, or circled)? C8J Yes Downstream Limit: Backwater of Navasota River Upstream Limit: beyond current FIS 2. MODELS SUBMITTED Requirements: for areas which have detailed flooding: Full input and output listings along with files on diskette for each of the models listed below (items 1-4) and a summary of the source of input parameters used in the models must be provided. The summary must include a description of any changes made from model to model (e.g., Duplicate Effective model to Corrected Effective model). At a minimum, the Duplicate Effective (item 1) and the Revised or Post-Project Conditions (item 4) models must be submitted. See ·,structions for directions on when other models may be required. for areas which do not have detailed flooding: Only the 100-year (Base) flood profile is required. A hydraulic model is not required for areas which do not have detailed flooding; however, BFEs may not be added to the revised FIRM. If a hydraulic model is developed for the area, items 3 and 4 described below must be submitted. If hydraulic models are not developed, hydraulic analyses {including all calculations) for existing or pre-project conditions and revised or post-project conditions must be submitted. 1. Duplicate Effective Model [8J Natural File Name LCdupEFF.ih2 0 Floodway File Name ____ _ Copies of the hydraulic analysis used in the effective FIS, referred to as the effective models ( 10-, 50-, 100-, and 500-year multi-profile runs and the floodway run) must be obtained and then reproduced on the requester's equipment to produce the Duplicate Effective model. This is required to assure that the effective models input data has been transferred correctly to the requester's equipment and to assure that the revised data will be integrated into the effective data to provide a continuous FIS model upstream and downstream of the revised reach. 2. Corrected Effective Model C8J Natural File Name LCconvert.prj 0 Floodway File Name ____ _ The Corrected Effective model is the model that corrects any errors that occur in the Duplicate Effective model, adds any additional cross sections to the Duplicate Effective model, or incorporates more detailed topographic information than that used in the currently effective model. The Correctly Effective model must not reflect any man-made physical changes since the date of the effective model. An error could be a technical error in the modeling procedures, or any construction in the floodplain that occurred prior to the date of the effective model but was not incorporated into the effective model. 3. Existing or Pre-Project Conditions Model 0 Natural File Name _ _ _ _ _ 0 Floodway File Name ____ _ The Duplicate Effective model or Corrective Effective model is modified to produce the Existing or Pre-Project Conditions model to reflect any modifications that have occurred within the floodplain since the date of the Effective model but prior to the construction of the project for which the revision is being requested. If no modification has occurred since the date of the effective model, then this model would be identical to the Corrected Effective model or Duplicate Effective model. 4. Revised or Post-Project Conditions Model C8J Natural File Name LC2000f.prj 0 Floodway File Name ____ _ The Existing or Pre-Project Conditions model (or Duplicate Effective model or Corrected Effective model, as appropriate) is revised to reflect revised or post-project conditions. This model must incorporate any physical changes to the floodplain since the effective model was produced as well as the effects of the project. When the request is for the proposed project this model "TIUSt reflect proposed conditions. 5. Other -Please attach a sheet describing all other models submitted along with the file names. 0 Natural 0 Floodway PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81 -89C Riverine Hydraulic Analysis Form MT-2 Form 4 Page 1 of 2 I~ 3. STARTING WATER-SURFACE ELEVATIONS Explain how they were determined. Explanation Attached? [8] Yes 0No NOTE: If the effective study is an approximate study, the slope/area method is recommended. For detailed analysis studies, usin a known water-surface elevation is recommended. 4. RESULTS (from the model used to revise the 100-year water surface elevations) If the results indicate any of the following, attach an explanation -to this form, or to the hydraulic model printout-as to the reasonableness of the situation. 0 Supercritical depth 0 Critical Depth 0 Drawdowns 0 Negative Floodway Surcharges 0 Floodway Surcharges Greater Than Maximum Allowed by Community/State 0 Water surface elevations higher than the end points of cross sections. 0 Floodway discharge is different than the Natural 1 00-year (base) flood discharge. [8] Project causes 100-year floodplain or flood way elevations to increase (state if increases are located off the requester's property) Explanation attached with Form 0 Explanation provided on attached printout [8] If Hydraulic model used is HEC-2, has it been checked with FEMA'S CHECK-2 computer program? 0 Yes (see instructions for information on how to obtain CHECK-2) 5. REVISED FIRM/FBFM AND FLOOD PROFILES 1. Profile Transition [8J No a. 100-Year Water-Surface Elevations -indicate the difference in water surface elevations where the project 1 00-year elevations tie into the existing 100-year water surface elevations at each end of the project. Downstream End ~ within _ _ _ _ _ (feet) Cross-Section # Upstream End ~ within _ _ _ _ _ (feet) Cross-Section # b. Floodway Elevations -indicate the difference in water surface elevations where the project floodway elevations tie into the existing floodway water surface elevations at each end of the project. Downstream End ~ within Cross-Section # (feet) Upstream End ~ within _ _ _ _ _ (feet) Cross-Section # c. Floodway widths -indicate the difference in floodway widths where the project floodway widths tie into the existing floodway width at each end of the project. Downstream End lli2_ within Cross-Section # (feet) Upstream End ~ within _ _ _ _ _ (feet) Cross-Section # 2. Profile Checklist (check box if information has been provided on profile) The following information (unless in parentheses) must be included at the same scale as the existing profiles for this project: [8] Stream Name [8] Community Name [8] Corporate Limits labeled 0 Study limits labeled [8] Confluences labeled [8] Channel Stationing [8] Streambed profiled [8] Cross Sections labeled [8] HorizontalNertical Scales indicated [8] 100-year elevs profiled* [8] Road Crossings [8] Labeled [8] Low Chord Elevations [8] Top of Road Elevations *All recurrence intervals in the effective study must also be profiled. Floodway Data Table Attach a Floodway Data Table for each cross section listed in the published Floodway Data table in the FIS report. Floodway Data Table Attached 0 Yes [8] Not Required FEMA Form 81-89C Riverine Hydraulic Analysis Form MT-2 Form 4 Page 2 of 2 I FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B. Burden No. 3067-0148 BRIDGE/CULVERT Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington, DC 20472; and to the Office of Manage- ment and Bud!=!et, Paperwork Reduction Project (3067-0148), Washinmon, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1. IDENTIFIER 1. Name of structure (roadway, railroad, etc.): State Highway 6 North Fork Bridge #1 2. Location of bridge/culvert along flooding source (in terms of stream distance or cross-section identifier): cross-section 641 + 58 on North Fork Main 3. This revision reflects (check one of the following): C8J New bridge/culvert not modeled in the FIS D Modified bridge/culvert previously modeled in the FIS D New analysis of bridge/culvert previously modeled in the FIS 4. Hydraulic model used to analyze the structure {e.g., HEC-2 with special bridge routine, WSPRO, HYB) HEC-RAS If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze the structure(s). {Attach justification) Justification attached D Yes D No C8J N/A PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 1 of 2 I 2. DRAWING CHECKLIST Attach plans of the structure(s) certified by a registered professional engineer. The plan detail and information should include the following (check the boxes if the information has been provided): [8J Dimensions (height, width, span, radius, length) t8J Shape (culverts only) t8J Material D Bevelihg or Rounding D Wing Wall Angle t8J Low Chord Elevations -Upstream and Downstream [8J Top of Road Elevations -Upstream and Downstream [8J Structure Invert Elevations -Upstream and Downstream t8J Stream Invert Elevations -Upstream and Downstream t8J Skew Angle [8J Cross-Section Locations [8J Distances Between Cross Sections D Erosion Protection 3. SEDIMENT TRANSPORT CONSIDERATIONS If there is any indication from historical records that sediment transport (including scour and deposition) can affect the 1 00- year (base flood) water-surface elevations; and/or based on the stream geomorphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including sewer and deposition) to affect the base flood elevations, then provide the following information (Check the box if provided): D Estimated sediment load D Method used to estimate sediment transport D Method used to estimate scour and/or deposition D Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 2 of 2 7 I FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B. Burden No. 3067-0148 BRIDGE/CULVERT Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington, DC 20472; and to the Office of Manage- ment and Budget, Paperwork Reduction Project (3067-0148), Washinqton, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1 . IDENTIFIER 1. Name of structure (roadway, railroad, etc.): Graham Road Culvert of North Fork Bridge #2 2. Location of bridge/culvert along flooding source (in terms of stream distance or cross-section identifier): cross-section 660 + 37 on North Fork Main 3. This revision reflects (check one of the following): 181 New bridge/culvert not modeled in the FIS D Modified bridge/culvert previously modeled in the FIS D New analysis of bridge/culvert previously modeled in the FIS 4. Hydraulic model used to analyze the structure (e.g., HEC-2 with special bridge routine, WSPRO, HYBJ HEC-RAS If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze the structure(s). (Attach justification) Justification attached D Yes D No 181 N/A PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81-89F Bridge/Culvert Form MT-2 Form 7 Page 1 of 2 I 2. DRAWING CHECKLIST Attach plans of the structure(s) certified by a registered professional engineer. The plan detail and information should include the following (check the boxes if the information has been provided): 181 Dimensions (height, width, span, radius, length) 181 Shape (culverts only) 181 Material D Beveling or Rounding 0 Wing Wall Angle 181 Low Chord Elevations -Upstream and Downstream 181 Top of Road Elevations -Upstream and Downstream 181 Structure Invert Elevations -Upstream and Downstream 181 Stream Invert Elevations -Upstream and Downstream 181 Skew Angle 181 Cross-Section Locations 181 Distances Between Cross Sections 0 Erosion Protection 3. SEDIMENT TRANSPORT CONSIDERATIONS If there is any indication from historical records that sediment transport (including scour and deposition) can affect the 1 00- year (base flood) water-surface elevations; and/or based on the stream geomorphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including sewer and deposition) to affect the base flood elevations, then provide the following information (Check the box if provided): 0 Estimated sediment load 0 Method used to estimate sediment transport 0 Method used to estimate scour and/or deposition 0 Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 2 of 2 I FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B. Burden No. 3067-0148 BRIDGE/CULVERT Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington, DC 20472; and to the Office of Manage- ment and BudQet, Paperwork Reduction Project (3067-01 48), WashinQton, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1 . IDENTIFIER 1. Name of structure (roadway, railroad, etc.): Utility Service Center Driveway Culvert of North Fork Bridge #3 2. Location of bridge/culvert along flooding source (in terms of stream distance or cross-section identifier): cross-section 670 + 49 on North Fork Main 3. This revision reflects (check one of the following): [gl New bridge/culvert not modeled in the FIS 0 Modified bridge/culvert previously modeled in the FIS 0 New analysis of bridge/culvert previously modeled in the FIS 4 . Hydraulic model used to analyze the structure (e.g., HEC-2 with special bridge routine, WSPRO, HYBJ HEC-RAS If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze the structure(s). (Attach justification) Justification attached 0 Yes 0 No [gj N/A PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 1 of 2 I 2. DRAWING CHECKLIST Attach plans of the structure(s) certified by a registered professional engineer. The plan detail and information should include the following (check the boxes if the information has been provided): ~ Dimensions (height, width, span, radius, length) ~ Shape (culverts only) ~ Material 0 Beveling or Rounding 0 Wing Wall Angle ~ Low Chord Elevations -Upstream and Downstream ~ Top of Road Elevations -Upstream and Downstream ~ Structure Invert Elevations -Upstream and Downstream ~ Stream Invert Elevations -Upstream and Downstream ~ Skew Angle ~ Cross-Section Locations ~ Distances Between Cross Sections 0 Erosion Protection 3. SEDIMENT TRANSPORT CONSIDERATIONS If there is any indication from historical records that sediment transport (including scour and deposition) can affect the 1 00- year (base flood) water-surface elevations; and/or based on the stream geomorphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including sewer and deposition) to affect the base flood elevations, then provide the following information (Check the box if provided): 0 Estimated sediment load 0 Method used to estimate sediment transport 0 Method used to estimate scour and/or deposition 0 Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport FEMA Form 81-89F Bridge/Culvert Form MT-2 Form 7 Page 2 of 2 I FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B. Burden No. 3067-0148 BRIDGE/CULVERT Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington, DC 20472; and to the Office of Manage- ment and Budqet, Paperwork Reduction Project (3067-0148), Washinmon, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1 . IDENTIFIER 1. Name of structure (roadway, railroad, etc.): State Highway 6 South Fork Bridge #4 2. Location of bridge/culvert along flooding source (in terms of stream distance or cross-section identifier): cross-section 23 + 75 on South Fork Main 3. This revision reflects (check one of the following): [gl New bridge/culvert not modeled in the FIS D Modified bridge/culvert previously modeled in the FIS D New analysis of bridge/culvert previously modeled in the FIS 4. Hydraulic model used to analyze the structure (e.g., HEC-2 with special bridge routine, WSPRO, HYBJ HEC-RAS If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze the structure(s). (Attach justification) Justification attached D Yes D No [gl N/A PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 1 of 2 I 2. DRAWING CHECKLIST Attach plans of the structure(s) certified by a registered professional engineer. The plan detail and information should include the following (check the boxes if the information has been provided): 181 Dimensions (height, width, span, radius, length) 181 Shape (culverts only) 181 Material 0 Beveling or Rounding 0 Wing Wall Angle 181 Low Chord Elevations -Upstream and Downstream 181 Top of Road Elevations -Upstream and Downstream 181 Structure Invert Elevations -Upstream and Downstream 181 Stream Invert Elevations -Upstream and Downstream 181 Skew Angle 181 Cross-Section Locations 181 Distances Between Cross Sections 0 Erosion Protection 3. SEDIMENT TRANSPORT CONSIDERATIONS If there is any indication from historical records that sediment transport (including scour and deposition) can affect the 1 00- year (base flood) water-surface elevations; and/or based on the stream geomorphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including sewer and deposition) to affect the base flood elevations, then provide the following information (Check the box if provided): 0 Estimated sediment load 0 Method used to estimate sediment transport 0 Method used to estimate scour and/or deposition 0 Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 2 of 2 ..,.., I FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B. Burden No. 3067-0148 BRIDGE/CULVERT Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington, DC 20472; and to the Office of Manage- ment and BudQet, Paperwork Reduction Project (3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1. IDENTIFIER 1. Name of structure (roadway, railroad, etc.): Longmire Drive culvert of South Fork Bridge #5 2 . Location of bridge/culvert along flooding source (in terms of stream distance or cross-section identifier): cross-section 35 + 67 on South Fork Main 3. This revision reflects (check one of the following): ~ New bridge/culvert not modeled in the FIS 0 Modified bridge/culvert previously modeled in the FIS 0 New analysis of bridge/culvert previously modeled in the FIS 4. Hydraulic model used to analyze the structure (e.g., HEC-2 with special bridge routine, WSPRO, HYBJ HEC-RAS If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze the structure(s). (Attach justification) Justification attached 0 Yes 0 No ~ N/A PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81-89F Bridge/Culvert Form MT-2 Form 7 Page 1 of 2 I z 2. DRAWING CHECKLIST Attach plans of the structure(s) certified by a registered professional engineer. The plan detail and information should include the following (check the boxes if the information has been provided): ~ Dimensions (height, width, span, radius, length) ~ Shape (culverts only) ~ Material D Beveling or Rounding D Wing Wall Angle ~ Low Chord Elevations -Upstream and Downstream ~ Top of Road Elevations -Upstream and Downstream ~ Structure Invert Elevations -Upstream and Downstream ~ Stream Invert Elevations -Upstream and Downstream ~ Skew Angle ~ Cross-Section Locations ~ Distances Between Cross Sections D Erosion Protection 3. SEDIMENT TRANSPORT CONSIDERATIONS If there is any indication from historical records that sediment transport (including scour and deposition) can affect the 1 00- year (base flood) water-surface elevations; and/or based on the stream geomorphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including sewer and deposition) to affect the base flood elevations, then provide the following information (Check the box if provided): D Estimated sediment load D Method used to estimate sediment transport D Method used to estimate scour and/or deposition D Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport FEMA Form 81-89F Bridge/Culvert Form MT-2 Form 7 Page 2 of 2 I FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B. Burden No. 3067-0148 BRIDGE/CULVERT Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington, DC 20472; and to the Office of Manage- ment and Budget, Paperwork Reduction Project (3067-0148), Washinmon, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Community Name: City of College Station and Brazos County, Texas Flooding Source: Lick Creek Project Name/Identifier: Lick Creek Re-study and Extension 1 . IDENTIFIER 1. Name of structure (roadway, railroad, etc.): Alexandira Avenue culvert of South Fork Bridge #6 2. Location of bridge/culvert along flooding source (in terms of stream distance or cross-section identifier): cross-section 67 + 30 on South Fork Main 3 . This revision reflects (check one of the following): [8J New bridge/culvert not modeled in the FIS 0 Modified bridge/culvert previously modeled in the FIS 0 New analysis of bridge/culvert previously modeled in the FIS 4. Hydraulic model used to analyze the structure (e.g., HEC-2 with special bridge routine, WSPRO, HYB) HEC-RAS If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze the structure(s). (Attach justification) Justification attached 0 Yes D No [8J N/A PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 1 of 2 I 2. DRAWING CHECKLIST Attach plans of the structure(s) certified by a registered professional engineer. The plan detail and information should include the following (check the boxes if the information has been provided): ~ Dimensions (height, width, span, radius, length) ~ Shape (culverts only) ~ Material D Beveling or Rounding D Wing Wall Angle ~ Low Chord Elevations -Upstream and Downstream ~ Top of Road Elevations -Upstream and Downstream ~ Structure Invert Elevations -Upstream and Downstream ~ Stream Invert Elevations -Upstream and Downstream ~ Skew Angle ·~ Cross-Section Locations ~ Distances Between Cross Sections D Erosion Protection 3. SEDIMENT TRANSPORT CONSIDERATIONS If there is any indication from historical records that sediment transport (including scour and deposition) can affect the 1 00- year (base flood) water-surface elevations; and/or based on the stream geomorphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including sewer and deposition) to affect the base flood elevations, then provide the following information (Check the box if provided): D Estimated sediment load D Method used to estimate sediment transport D Method used to estimate scour and/or deposition D Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport FEMA Form 81 -89F Bridge/Culvert Form MT-2 Form 7 Page 2 of 2 3.0 HYDRO LOGIC ANALYSIS As previously discussed in Section I .2, it was decided that a new hydrologic model should be utilized to replace the existing Nu-Dallas Model. This new hydro logic analysis of the Lick Creek watershed uses the U.S. Army Corps of Engineers HEC-1 computer program in accordance with the City of College Station Drainage Policy and Design Standards (DP/DS). This model is further described in this section. 3.1 Rainfall Distribution The rainfall depth data obtained from the DP/DS are based on isohyetal charts found in the National Weather Service's Technical Paper 40 (TP-40). Table 3.1 contains the rainfall depth for different frequency events. Table 3.1 24-Hour Rainfall Depths for Selected Storm Return Periods Storm Return Period 24 Hour Rainfall Depth (yrs) (in) 2 4.5 5 6.2 IO 7.4 25 8.8 50 9.8 100 11.0 Rainfall distribution was modeled using the SCS Type III rainfall ratios which were developed for areas of the United States east of the Cascade and Sierra Nevada Mountains. This distribution assumes the greatest 30-minute depth to occur at approximately the middle of the 24-hour period. 3.2 Infiltration Loss Rate Infiltration loss is the quantity of rainfall expected to be absorbed into the soil throughout the duration of the runoff. The precipitation losses due to infiltration and land surface interception are dependent on factors such as rainfall volume, rainfall density, antecedent soil moisture, depression storage, interception, infiltration and evaporation. In tum, these factors are dependent on soil type, land use, vegetative cover, topography and time of year. For this re-study, the Soil Conservation Service (SCS) Curve Number method was used to determine the infiltration losses. The U.S. Department of Agriculture -Soil Conservation Service, has instituted a soil classification system for use in soil survey maps across the country. Based on experimentation and experience, the Lick Creek Flood Insurance Re-Study July 2000 Page 28 agency has related drainage characteristics of the soil groups to a Curve Number, CN, as a function of soil cover, land use type and antecedent moisture conditions. Precipitation loss is calculated in HEC-1 based on user supplied CN values and initial abstraction estimates. Initial abstraction (IA) is the surface moisture storage capacity at the beginning of the storm event, in inches. Values for CN and IA are related to a total runoff depth for a storm by the following equations: and: In which: Q-(P-IA)2 (P-IA+S) S= 1000 -lO CN CN SCS Curve Number, percent of runoff IA initial abstraction Q accumulated excess (runoff) in inches P accumulated rainfall depth in inches S soil moisture storage deficit (maximum retention) available at the beginning of the storm, in inches If a value of zero (0) is entered for IA in the HEC-1 model, a default value is computed as: IA=0.2S This relationship is based on empirical evidence established by the SCS. Since the SCS method gives total excess for a storm, the incremental excess (the difference between rainfall and precipitation loss for a time period) is computed as the difference between the accumulated excess at the end of the current period and the accumulated excess at the end of the previous period. The SCS soil classifications and hydrologic soil groups used to determine CN are further discussed in Section 3.4. 3.3 Watershed Sub-areas The Lick Creek watershed was divided into the sub-areas shown on Appendix 6. Subareas were determined using City of College Station aerial topography maps. Topographic data was obtained by photogrammetric methods from aerial photographs taken February and March 1994 using the following datum: • North American Datum, 1983 Adjustment Lick Creek Flood Insurance Re-Study July 2000 Page 29 • Texas State Plane Coordinate System, Central Zone • National Geodetic Vertical 1929 Mean Sea Level Datum Sub-areas for Spring Creek were taken directly from LOMR case number 99-06-1336R. These areas are shown as Appendix 7. 3.4 Watershed Characteristics The DP/DS requires the use of the SCS Dimensionless Unit Hydrograph option in HEC-1 to determine the rainfall runoff. Input data for this method consists of a single parameter, TLag, which is equal to the lag time, in hours, between the center of mass of excess rainfall and the peak of the unit hydro graph. TLag is computed using the SCS Curve Number Method as published in the National Engineering Handbook Section 4 (NEH-4). The SCS Curve Number Method uses the following equation to estimate lag times: Where TLag L y s Lo.s (S+l)°'1 (1900 )Y0·5 basin lag time hydraulic length in feet the watershed slope in percent maximum retention as described in Section 2.2 As previously discussed in Section 1.2, the Soil Conservation Service Soil Survey for Brazos County dated 1958 and the draft Natural Resource Conservation Service Soil Survey for Brazos County, due to be published next year, were reviewed by City staff. These documents clearly show that the predominate hydro logic soil classification of the watershed area is Group D. Appendix I contains the 1958 and Draft 2001countywide soil survey maps with an overlay of the drainage basins. Also included in this exhibit is the detailed soil map from the draft soil survey for the majority of the study area. These Group D soils consist of soils having very slow infiltration rates when thoroughly wetted. They consist chiefly of clay soils with high swelling potential, a permanent high water table, clay pan or clay layer at or near the surface, shallow soils over nearly impervious material, and certain saline soils. These soils have very low infiltration rates. The weighted CN for each sub-area was calculated using the land-use CN for Group D soils with antecedent soil condition II. CN and lag times computations for each subarea are shown in Appendi x 8 & 9. Table 3.2 summarizes these values for each area. Lick Creek Flood Insurance Re-Study July 2000 Page 30 Table 3.2 Watershed Characteristics Summary Sub-Arca Name Drainage Arca CN T(Lag) (sq-mi) (hrs) NF.l 0.2941 89.8 0.67 NF.2 0.3343 87.7 1.17 NF.3 0.3931 94.0 0.91 NF.4 0.2195 91.9 1.16 SF.l 0.5610 88.1 0.64 SF.2 0.2927 87.8 0.77 SF.3 0.4175 87.4 1.33 SF.4 0.2080 91.9 1.05 LM.l 0.9642 83 . l 2.56 LM.2 0.7490 83 .8 1.78 LM.3 1.1478 87.0 1.91 LM.4 0.6198 75 .0 2.45 LM.5 1.5620 75.0 3.52 AL.l 2.1493 84.0 2.08 AL.2 0.7863 75.0 2.34 AL.3 1.5539 75.0 1.85 ACl.l 0.8551 90.5 1.56 Note --Spring Creek data from LOMR case number 99-06-1336P 3.5 Channel Routing Flow routing (or reach routing) in the HEC-1 model used the eight-point cross-section option of the Muskingum-Cunge channel routing method. The City DP/DS states that the "normal depth" option should be used. At the time the DP/DS was published, the Muskingum-Cunge method was not available in HEC-1. Today, this method has "largely eliminated the need for kinematic wave and normal depth storage routing." The Muskingum-Cunge method requires nearly the identical information with the exception of no longer requiring the number of routing steps. As such, normal depth channel routing is no longer supported, nor is it expected to be in the future, within the next generation software package HEC-Hydrologic Modeling System (HEC-HMS); the replacement for HEC-1 . Lick Creek Flood Insurance Re-Study July 2000 Page 31 3.6 HEC-1 Results The final HEC-1 Model is included as Appendix I 0. Results from this hydrologic re-study are summarized below in Table 3.3. As can be seen from Table 3.3, the HEC-1 resultant flows are similar to the flows reported in the existing FIS. Flows are generally slightly less than the existing FIS in the upper reaches of Lick Creek, and slightly more in the lower reaches of Lick Creek. All flows are within ten percent of the existing FIS. However, this study includes additional flow point locations in the upper branches. This model produces one uniform model for the entire drainage basin, and we therefore request that it be used to replace the existing FIS Study. Table 3.3 Summary of HEC-1 Results Main Branch At Co orate Limits 16.01 12,730 11 ,500 10.06 9,161 7,900 8.29 9,153 8,300 4.43 5,324 4,500 8,000 Feet U stream of Green Prairie Rd 3.68 4,905 4,900 At Confluence of North & South Forks 2.72 4,589 4,900 North Fork Down Stream of H 6 1.24 2,301 2,500 AtH 6 1.02 1,980 n/a 0.63 1,201 n/a At Victoria Ave 0.29 677 n/a South Fork 6 1.48 2,297 n/a 1.27 2,025 n/a At Alexandria Ave 0.85 1,352 n/a At Westfield Drive 0.56 990 n/a Lick Creek Flood Insurance Re-Study July 2000 Page 32 4.0 FLOODPLAIN ANALYSIS 4.1 Hydraulic Analysis As previously discussed in Section 1.6, this hydraulic model is a geometric composition of the FEMA effective model and several other existing models used to map floodplains surrounding approximate "A" flood zones for subdivision development. New base flood elevations along the Lick Creek study reach were computed using the U.S. Army Corps of Engineers HEC-RAS computer program. HEC-RAS was developed as a part of the Hydrologic Engineering Center's "Next Generation" of hydro logic engineering software. The HEC- RAS program will ultimately be able to analyze steady flow water surface profiles, unsteady flow simulations and movable boundary sediment transport computations. However, the current version only supports Steady Flow water surface profile calculations, like HEC-2 but with some major differences. HEC-RAS is a completely new program. None of the hydraulic routines from HEC-2 were used in HEC-RAS. Even though both programs compute one-dimensional water surface profiles, the results may differ. For example, the default method in HEC-RAS computes overbank conveyance by subdividing flow in the overbank areas using the input locations where n-values change. The program sums the incremental conveyances in the overbanks to obtain a conveyance for the left overbank and the right overbank. The method used in HEC-2 is to calculate conveyance between every coordinate point in the overbanks. The conveyance is then summed to get the total left overbank and right overbank values. The two methods for computing conveyance will produce different results whenever portions of the overbanks have ground sections with significant vertical slopes. In general, the HEC-RAS default approach will provide a lower total conveyance for the same water surface elevation. The current version of HEC-RAS can calculate water surface profiles for steady, gradually varied flow. The system can handle a full network of channels, dendritic systems, or a single river reach., Subcritical, supercritical and mixed flow regime water surface profiles can be modeled . • The basic computational procedure is b.ased on the solution of the one-dimensional energy equation. Energy losses are evaluated by friction (Manning s equation) and contraction/expansion (coefficient multiplied by the change in velocity head). The momentum equation is used in situations where flow is rapidly varied such as hydraulic jumps, bridge hydraulics and str am junctions. In HEC-RAS either the energy equation or the momentum equation cari model a junction. The energy • equation does not take into account the angle of the branch entering or exiting, while the momentum equati'on does., Normally, the amount of energy lost due to the angle of the tributary is insignificant. For this re-study, all junctions were modeled using the energy equation. . . 4.2 Duplicate Effective Model ~ A paper copy of the FEMA Effective Model was received from Michael Baker, Jr., Inc. A copy of the effective model is included in Append'ix 11. Using this paper copy, a HEC-2 Duplicate Effective Model was created and results from this model were compared to the Effective Model. The Duplicate Effective Model is contained in Appendix 12. A comparison of the FEMA Effective Model and the Lick Creek Flood Insurance Re-Study July 2000 Page 33 HEC-2 Duplicate Effective Model matched water surface elevations within one inch as shown in Appendix 13. Due to legibility of the paper copy, closer matches could not be obtained. 4.3 Corrected Effective Model The HEC-2 Duplicate Effective Model was then imported into HEC-RAS using the import sub- routine. Bridges were re-coded to match the HEC-2 study, as required. This "Corrected" HEC-RAS Duplicate Effective Model is contained in Appendix 14. The "Corrected" HEC-RAS Duplicate Effective Model was run and compared to the Effective Model as also shown in Appendix 13 . The corrected model produced results within nine (9) inches of the FEMA Effective Model, with most cross-sections matching the Effective Model with an increase of less than six (6) inches. 4.4 Existing or Pre-Project Conditions Model No changes between the Corrected Effective Model and the Existing Conditions Model are proposed. Therefore. an Existing or Pre-Project Conditions Model is not being submitted. 4.5 Revised or Post-Project Conditions Model The purpose of the Revised Model is to extend this re-study upstream along the North Fork of Lick Creek, to provide a detailed study of the South Fork of Lick Creek, and to include the new hydrology data. To create this model, the "Corrected" Duplicate Effective Model was used as the base model. A junction was added between cross-sections S86+00 and S99+00 at the confluence of the North and South Forks of Lick Creek. 4.5.1 Extension of North Fork The HEC-RAS geometry data of the as-built model of the Graham Road Rehabilitation Study was reviewed for accuracy and omissions. Upon completion of this review, it was imported directly into the revised model and connected at the upstream limits of the effective study. This section includes the culvert crossings of State Highway 6 and of Graham Road. As-built bridge plans of these crossings are contained in Appendi ces I SA and I SB. Original cross-sectional data in this model was obtained from 1994 City of College Station aerial topography unless otherwise noted. City staff extended the study to the Park Meadows Development by adding ten additional cross- sections upstream of the limits of the Graham Road study. This cross-sectional data was obtained from 1994 City of College Station aerial topography. This stream section includes the City of College Station Utility Customer Service Center driveway culvert. No as-built plans exist of this driveway, however, construction plans are included in Appendix I SC. Construction plans were reviewed, but did not appear to match what was constructed with regard to size and elevation. Field surveys were completed to establish actual culvert size and flow line elevations. 4.5.2 Creation of South Fork Lick Creek Flood Insurance Re-Study July 2000 Page 34 City staff has added one new cross-section ( 10+60) between the downstream confluence junction and the Alexandria studies. 1994 City of College Station aerial topographic data was used to create this additional cross-section. The HEC-RAS geometry data from the Alexandria Subdivision floodplain study was reviewed for accuracy and omissions. The coding of the low cord of the roadway deck for the State Highway 6 crossing of the South Fork was corrected. All cross-sections within the Alexandria study were re- numbered by adding a distance of l 9+SO to each cross-section to denote the actual distance upstream of the confluence. Cross-sectional data for the Alexandria study was obtained from 1994 City of College Station aerial topography unless otherwise noted. Along with these corrections, the geometry file from the Alexandria study was imported into the base model. This segment includes the culvert crossings of State Highway 6, Longmire Drive, and Alexandria Avenue. As-built construction plans for these roadway crossings are included in Appendices l SD, l SE, and lSF. One additional new cross-section (90+88) was added between the Alexandria and Westfield floodplain studies. 1994 City of College Station aerial topographic data was used to create this additional cross- section. The HEC-2 file for the Westfield floodplain study was imported by City staff into HEC-RAS. The imported model was run and the results compared with the Westfield study. This section included the proposed (permitted) pedestrian bridge aligned with Westfield Drive. Manning's roughness coefficients were adjusted to values that appear more representative of the study reach. Cross-sectional data for the Alexandria study was obtained from 1994 City of College Station aerial topography. 4.5.3 Review, Adjustment, and Insertion of New Hydrology into Proposed Model The new study sections were reviewed and adjusted to bring uniformity to the Manning's roughness coefficients along the different stream segments. Manning's "n" values for the channels and overbanks were determined through field observation and examination of photogramrnetric maps. The "n" values ranged from 0.04 to 0.07 for the channels to 0.06 to 0.09 for the overbanks with some variations near bridges. The roughness values from the Effective Model were also reviewed. No adjustment was deemed necessary. Pictures of the all bridge crossing are contained in Appendix 16 . New hydrologic data from Section 3.6 were coded into the model to complete the hydraulic element of the re-study. To finalize the model, a new starting water surface condition was coded to reflect the backwater conditions of the Navasota River as recorded in the current FIS. 4.6 Model Results and Comparison The final proposed conditions model is included in Appendix 17. The results of the computed 100- year water surface elevations for Lick Creek are shown in Appendix 13 and Table 4. l. Due to the coding of the backwater effect from the Navasota River, rather than using the slope/area method, the water surface elevation up to cross-section 201 +8S was increased within the model. However, the backwater effect is taken into account within the FIRM and therefore will not increase the base flood elevation (BFE) by more than one ( 1) foot. Lick Creek Flood Insurance Re-Study July 2000 Page 35 From cross-section 207+90 to 459+80 the new BFE matches the current BFE within one (1) foot. This change is generally caused by computational differences between HEC-2 and HEC-RAS. From cross-section 459+80 to 497+30, flow rates are reduced within the model. As such, base flood elevations decrease by approximately one ( 1) foot. Between cross-sections 504+64 and 599+00, base flood elevations increase by Jess than one-half (112) foot. Base Flood Elevations decrease by less than one (1) foot for cross-sections 612+00 and 627+20 as a result of reductions of flows. For the remainder of the North Fork and all of the South Fork of Lick Creek the new base flood elevations match generally within one foot of the small limited studies previously conducted. These variations are a result of the changes in flow rates and starting water surface conditions. Table 4.1 Results and Comparison of Water Surface Elevations to Effective FIS Main Branch 8750 194.97 205.00 10.03 Main Branch 10815 197.22 205.03 7.81 Main Branch 12880 199.42 205.10 5.68 Main Branch 13856 199.63 205.12 5.49 Main Branch 13857 199.56 205.11 5.55 Main Branch 13904 199.63 205.11 5.48 Main Branch 13905 199.88 205.12 5.24 Main Branch 14280 199.98 205.14 5.16 Main Branch 14780 200.11 205.15 5.04 Main Branch 15280 200.33 205.18 4.85 Main Branch 15780 200.82 205.22 4.40 Main Branch 16280 201 .61 205.27 3.66 Main Branch 17930 203.64 205.58 1.94 Main Branch 19580 205.21 206.12 0.91 Main Branch 20185 206.04 206.56 0.52 Main Branch 20790 207.42 207.64 0.22 Main Branch 22640 209.97 210.14 0.17 Main Branch 24490 212.02 212.29 0.27 Main Branch 26340 214.09 214.40 0.31 Main Branch 27210 215.00 215.32 0.32 Main Branch 28080 215.72 216.07 0.35 Lick Creek Flood Insurance Re-Study July 2000 Page 36 Main Branch 28690 216.15 216.53 0.38 Main Branch 29300 217.09 217.45 0.36 Main Branch 29910 218.42 218.74 0.32 Main Branch 30520 219.78 219.92 0.14 Main Branch 31130 220.81 220.83 0.02 Main Branch 31744 221.66 222.11 0.45 Main Branch 32358 223.22 223.86 0.64 Main Branch 32972 224.45 225.13 0.68 Main Branch 33586 225.52 226.28 0.76 Main Branch 34200 226.51 227.30 0.79 Main Branch 35280 227.11 227.93 0.82 Main Branch 35446 227.15 227.96 0.81 Main Branch 35612 227.19 228.01 0.82 Main Branch 35778 227.24 228.06 0.82 Main Branch 35944 227.30 228.13 0.83 Main Branch 36110 227.38 228.21 0.83 Main Branch 36276 227.48 228.31 0.83 Main Branch 36442 227.60 228.43 0.83 Main Branch 36608 227.75 228.58 0.83 Main Branch 36774 227.95 228.75 0.80 Main Branch 36940 228.19 228.97 0.78 Main Branch 37106 228.46 229.22 0.76 Main Branch 37272 228.79 229.52 0.73 Main Branch 37438 229.16 229.89 0.73 Main Branch 37604 229.56 230.24 0.68 Main Branch 37770 229.99 230.63 0.64 Main Branch 37936 230.42 231 .02 0.60 Main Branch 38012 230.84 231.41 0.57 Main Branch 38268 231.26 231.80 0.54 Main Branch 38434 231 .66 232.18 0.52 Main Branch 38600 232.06 232.55 0.49 Main Branch 39222 233.75 234.20 0.45 Main Branch 39844 235.20 235.65 0.45 Main Branch 40466 236.58 237.03 0.45 Main Branch 41088 237.91 238.37 0.46 Main Branch 41710 239.26 239.70 0.44 Main Branch 42440 241.34 241.68 0.34 Main Branch 42539 241 .81 242.22 0.41 Main Branch 42540 241 .75 242.24 0.49 Main Branch 42584 242.15 242.54 0.39 Main Branch 42680 243.46 243.99 0.53 Main Branch 43850 243.63 244.18 0.55 Lick Creek Flood Insurance Re-Study July 2000 Page 37 Main Branch 45020 244.87 245.01 0.14 Main Branch 45980 246.89 245.84 -1.05 Main Branch 46940 250.43 249.26 -1.17 Main Branch 47900 251 .79 250.63 -1 .16 Main Branch 48510 252.53 251 .37 -1 .16 Main Branch 49120 253.69 252.57 -1.12 Main Branch 49730 254.43 253.72 -0.71 Main Branch 50464 254.92 255.21 0.29 Main Branch 51198 256.54 257.37 0.83 Main Branch 51932 258.69 259.38 0.69 Main Branch 52666 260.71 261 .30 0.59 Main Branch 53400 262.51 263.09 0.58 Main Branch 54700 265.26 265.73 0.47 Main Branch 56000 267.27 267.68 0.41 Main Branch 57300 269.07 269.50 0.43 Main Branch 58600 270.66 271.12 0.46 North Fork 59900 272.19 272.36 0.17 North Fork 61200 273.87 273.05 -0.82 North Fork 61960 274.90 274.11 -0.79 North Fork 62720 276.49 276.68 0.19 North Fork 62721 n/a 276.60 North Fork 63220 n/a 278.62 North Fork 63470 n/a 280.32 North Fork 63770 n/a 282.26 North Fork 63870 n/a 282.44 North Fork 63920 n/a 282.29 North Fork 64395 n/a 284.57 North Fork 64500 n/a 284.89 North Fork 64800 n/a 285.25 North Fork 65050 n/a 285.92 North Fork 65250 n/a 286.80 North Fork 65500 n/a 287.41 North Fork 65700 n/a 287.97 North Fork 65950 n/a 288.31 North Fork 65969 n/a 288.59 North Fork 65970 n/a 288.59 North Fork 65980 n/a 288.59 North Fork 66000 n/a 288.43 North Fork 66075 n/a 288.92 North Fork 66090 n/a 289.15 North Fork 66105 n/a 289.10 Lick Creek Flood Insurance Re-Study July 2000 Page 38 North Fork 66150 n/a 289.06 North Fork 66215 n/a 289.19 North Fork 66216 n/a 289.23 North Fork 66300 n/a 289.40 North Fork 66550 n/a 290.01 North Fork 66850 n/a 290.81 North Fork 66940 n/a 290.99 North Fork 66970 n/a 291 .17 North Fork 66980 n/a 291 .21 North Fork 67050 n/a 292.02 North Fork 67060 n/a 292.01 North Fork 67075 n/a 292 .03 North Fork 67300 n/a 292.24 North Fork 67680 n/a 292.99 North Fork 68025 n/a 293.60 North Fork 68410 n/a 294.20 North Fork 68770 n/a 294.66 South Fork 1060 n/a 272.43 South Fork 2050 n/a 272.99 South Fork 2210 n/a 272.82 South Fork 2540 n/a 273.89 South Fork 2560 n/a 274.3 South Fork 2880 n/a 274.67 South Fork 3200 n/a 275.26 South Fork 3410 n/a 275.96 South Fork 3467 n/a 276.02 South Fork 3520 n/a 275.96 South Fork 3538 n/a 275.64 South Fork 3596 n/a 277.25 South Fork 3610 n/a 277.35 South Fork 3665 n/a 277.32 South Fork 3860 n/a 277.52 South Fork 4310 n/a 279.25 South Fork 4580 n/a 280.02 South Fork 4810 n/a 280.40 South Fork 4930 n/a 280.58 South Fork 5050 n/a 280.93 South Fork 5200 n/a 281 .51 South Fork 5320 n/a 281 .8 South Fork 5616 n/a 282.19 South Fork 5827 n/a 282.42 Lick Creek Flood Insurance Re-Study July 2000 Page 39 Reach Cross-Section 1988 FIS 2000 FIR-s Change in WSel South Fork 5943 n/a 282.81 South Fork 6050 n/a 283.12 South Fork 6175 n/a 283.63 South Fork 6266 n/a 283.7 South Fork 6423 n/a 283.78 South Fork 6612 n/a 284.06 South Fork 6632 n/a 284.11 South Fork 6675 n/a 283.37 South Fork 6698 n/a 283.79 South Fork 6784 n/a 287.13 South Fork 6825 n/a 287.26 South Fork 7137 n/a 287.31 South Fork 7435 n/a 287.41 South Fork 7612 n/a 287.51 South Fork 7815 n/a 287.67 South Fork 7993 n/a 287.78 South Fork 8354 n/a 287.93 South Fork 8750 n/a 288.21 South Fork 9088 n/a 288.67 South Fork 9343 n/a 288.92 South Fork 9458 n/a 289.03 South Fork 9568 n/a 289.18 South Fork 9688 n/a 289.95 South Fork 10018 n/a 291 .12 South Fork 10058 n/a 290.87 South Fork 10138 n/a 292.20 South Fork 10208 n/a 291 .70 South Fork 10338 n/a 293.25 South Fork 10518 n/a 293.85 South Fork 10628 n/a 294.21 South Fork 10758 n/a 294.41 South Fork 10978 n/a 295.96 South Fork 11228 n/a 297.53 Lick Creek Flood Insurance Re-Study July 2000 Page 40 5.0 Floodplain Mapping A cross-section location map of the FEMA Effective Study was obtained through Wallace Group from the Ft Worth District of the COE. These locations were transposed onto 1994 City of College Station aerial topography. Cross-section locations from the various other floodplain studies were also transposed onto the topographic map. With the cross-sections located and the result of water surface elevations from Section 4.6, the floodplain boundary was drawn onto the map. This floodplain boundary is presented on the work map in Exhibit 18. Profile sheets for Lick Creek are shown in Appendix 19. The Proposed "annotated" FIRM is included in Exhibit 2. Lick Creek Flood Insurance Re-Study July 2000 Page 41 Exhibit 2 Lick Creek Flood Insurance Re-Study July 2000 Page 42 6.0 Need for Additional Studies An additional study of the Alum Creek Watershed and floodplain is needed prior to any substantial development of Pebble Creek or other developments near the floodplain . This is primarily needed due to the undefined flat topography of the lower end of this watershed. Additional refinement of the floodplain boundary is needed in the lower end of the Lick Creek Basin. No newer topography exists than what was used to create the existing FEMA. As a result the floodplain boundary was not revised in this lower section. That topography was USGS 10-foot contour Quarter Quads, which is generally inadequate for these flat wooded areas. A LOMR should be submitted at the time the Brazos Valley Land Fill completes the channel re- alignment upstream of Greens Prairie Road. This work was permitted under a FEMA CLOMR 95-06- 160R. Based upon field observations, this work is nearing completion. Updates will be needed as development continues in the area of the watershed between State Highway 6 and Greens Prairie Road. Lick Creek Flood Insurance Re-Study July 2000 Page 43 7.0 Conclusions This study updates the existing floodplain shown on the Flood Insurance Rate Map for the Lick Creek Watershed in Brazos County. Generall y the flood plain increases by less than one foot as a result of this study. The study also extends the Flood Hazard Boundary upstream into an area of rapid development. This extension will assist in ensuring that that adjacent property owners are aware of the hazards of flooding in this area. The flood hazard boundary is rectified by this study to more detailed topography currently being used by the City of College Station. It also imports a unified Hydrauli cs model into the latest computer model, HEC-RAS 2.2 and a unified hydrology model into HEC-1. This HEC-1 model is compatible with the latest model, HEC-HMS 2.0, and can be imported into that program. This program was not used due to limited ability to produce output data. Lick Creek Flood Insurance Re-Study July 2000 Page 44 8.0 Bibliography Drainage, Water and Sewer Report of Alexandria Subdivision Phases One Through Five, McClure Engineering, November 1999 Drainage Report-Graham Road Rehabilitation Project, Robertson Consulting Engineers, April 2000 Hydrologic Analysis Study for a Portion of the South Fork Lick Creek Tributary through the Westfield Addition, Morrison Hydrology Engineering, Inc, October 1, 1999 Flood Insurance Study for Brazos County, Texas and Incorporated Areas, Federal Emergency Management Agency, Revised February 9, 2000 City of College Station Stormwater Design Policy and Design Standards, City of College Station, Revised through December 1997 National Engineering Handbook Section 4 -Hydrology, USDA SCS, March 1985 ProHEC-1 Users Manual and Program Reference, Dodson & Associates, Inc, April 1991 ProHEC-2 Users Manual and Program Reference, Dodson & Associates, Inc, April 1991 HBC-River Analysis System Users Manual version 2.0, US Army Corps of Engineers Hydrologic Engineering Center, April 1997 HBC-River Analysis System Hydraulic Reference Manual version 2.0, US Army Corps of Engineers Hydrologic Engineering Center, April 1997 Brazos County Soil Survey, UDSA Soil Conservation Service, May 1958 Brazos County Soil Survey, UDSA Natural Resource Conservation Service, Draft 2001 Lick Creek Flood Insurance Re-Study July 2000 Page 45