CHAMBERS COUNTY MASTER DRAINAGE PLAN Volume I: Report Prepared for Chambers County, Texas
November 2014
Texas PE Firm Reg. #F-929
Project No. 1057.002.000
November 24, 2014
The Honorable Jimmy Sylvia, Chambers County Judge The Honorable Mark Huddleston, County Commissioner The Honorable David ‘Bubba’ Abernathy, County Commissioner The Honorable Gary R. Nelson, County Commissioner The Honorable Rusty Senac, County Commissioner
Chambers County Courthouse 404 Washington St. Anahuac, Texas 77514
Attention: Mr. Bobby Hall, Chambers County Engineer Subject: Final Chambers County Master Drainage Plan
Klotz Associates is pleased to submit to you this final version of the Chambers County Master Drainage Plan. The attached report summarizes our findings of the current and ultimate drainage conditions across the western half of Chambers County.
The Master Drainage Plan was developed to identify current drainage and flooding problems and provide recommendations for solutions for the future build-out of the study area. The study area focuses on approximately 100 square miles on the western edge of the county, bound by Harris County to the west, IH-10 to the north, Trinity River to the east and Galveston Bay to the south.
We have identified several key areas that would benefit from drainage improvements. Section 9.0 of this report includes conclusions and recommendations. The County can use this information to develop an initial prioritization of projects however preliminary engineering reports will be needed to provide sufficient details for use in prioritization ranking for inclusion into the County’s capital improvement plan.
Klotz Associates sincerely appreciates the opportunity to have prepared this plan for Chambers County. We look forward to continuing to provide our services to you.
Yours truly,
Gary l. Struzick, P.E., CFM Vice President
VOLUME I: REPORT
TABLE OF CONTENTS
EXECUTIVE SUMMARY ...... ES-1
1. INTRODUCTION ...... 1-1
1.1 Authorization ...... 1-1 1.2 Background ...... 1-1 1.3 Objectives ...... 1-1 1.4 Scope of Chambers County Master Drainage Plan...... 1-1 1.4.1 Coordination and Interaction: Tasks 1 and 3 ...... 1-2 1.4.2 Data Collection and Review, Inventory, Field Survey: Tasks 2, 4, 5, 6, 7 ...... 1-2 1.4.3 Existing Conditions, Future Growth, Levels of Service: Tasks 8, 9, 10, 11 ...... 1-2 1.4.4 Proposed Remedies and Future Infrastructure: Tasks 12 and 13 ...... 1-2 1.5 Study Focus………………...... 1-2 1.5.1 Study Area ...... 1-2 1.5.2 Scale of Problems and Problem Resolution ...... 1-2 1.5.3 Non-Hurricane Conditions ...... 1-3 1.5.4 Date of Information...... 1-3 1.6 Structure of CCMDP Report ...... 1-3
2. DESCRIPTION OF STUDY AREA ...... 2-1
2.1 Chambers County…………...... 2-1 2.2 Study Area Boundary……… ...... 2-1 2.3 Working Study Area………...... 2-1 2.4 General Physiographic Characteristics ...... 2-1 2.4.1 Topography ...... 2-1 2.4.2 Soils and Geology ...... 2-2 2.4.3 Watersheds, Subwatersheds and Study Drainage Areas ...... 2-2 2.4.4 Water Bodies…… ...... 2-3
2.4.5 Undevelopable Swamplands, Wetlands, Refuge Areas ...... 2-3 2.4.6 Well Known Chambers County Conservation Areas near Study Area ...... 2-4 2.4.7 Floodplains ...... 2-4 2.5 Significant Anthropogenic Features ...... 2-4 2.5.1 Political and Administrative Boundaries ...... 2-4 2.5.2 Population and Communities in the Study Area ...... 2-5 2.5.3 Major Transportation Arteries ...... 2-6 2.5.4 Petrochemical Pipelines ...... 2-6 2.5.5 Land-use………...... 2-6
3. DATA COLLECTION AND REVIEW ...... 3-1
3.1 Purposes of Data Collection and Review...... 3-1 3.2 Data Sources and Collection ...... 3-1 3.2.1 Prior Studies and Reports...... 3-1 3.2.2 Floodplain Data ...... 3-1 3.2.3 Databases ...... 3-1 3.2.4 Critical Facilities ...... 3-2 3.2.5 Land-use ...... 3-2 3.2.6 Other Miscellaneous Technical Data ...... 3-2 3.3 Hydraulic and Hydrologic Models ...... 3-2 3.4 Discussions with Chambers County and Others ...... 3-2
4. FACILITIES, LAND-USE AND DRAINAGE ISSUES ...... 4-1
4.1 Introduction ...... 4-1 4.2 Land-use ...... 4-1 4.2.1 Land-use and Imperviousness ...... 4-1 4.2.2 Existing Land-use ...... 4-2 4.2.3 Ultimate Land-use ...... 4-3 4.2.4 Historical Development and Land-use ...... 4-3 4.2.5 Estimation of Planning Time Horizon ...... 4-5 4.3 C&I and Roadway Development Planned or Underway ...... 4-5 4.4 Facilities ...... 4-7
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4.4.1 Inventory of Bridges, Major Culverts and Siphons ...... 4-7 4.4.2 Inventory of Critical Facilities ...... 4-8 4.5 Sources of Drainage and Flooding Problems...... 4-8 4.5.1 Repetitive Losses ...... 4-8 4.5.2 Excessive Ponding ...... 4-9 4.5.3 Local Street and Property Flooding ...... 4-10 4.5.4 Coastal Flooding ...... 4-10 4.5.5 Riverine Flooding ...... 4-11 4.5.5.1 Common Causes of Riverine Flooding ...... 4-11 4.5.5.2 Flooding Problem Areas ...... 4-13 4.5.5.3 Types of Infrastructure Remedies for Riverine Flooding ...... 4-13
5. MODELING METHODOLOGY ...... 5-1
5.1 Purpose of This Section ...... 5-1 5.2 Modeling Timeframes ...... 5-1 5.2.1 Existing and Revised Existing Condition Models ...... 5-1 5.2.2 Future Condition Models ...... 5-2 5.3 Input Parameters for HMS Models ...... 5-2 5.3.1 General Drainage Topography and Drainage Areas ...... 5-3 5.3.2 Drainage Topography with Development Projects ...... 5-3 5.3.3 Rainfall for Hydrologic Modeling ...... 5-3 5.3.4 Soil Moisture and Rainfall Excess ...... 5-3 5.4 Runoff Discharges for Hydrologic Modeling ...... 5-4 5.4.1 Drainage Area Runoff ...... 5-4 5.4.2 Flood Routing Down a Channel ...... 5-4 5.5 Types of Mitigation and Flood Control Storage ...... 5-5 5.6 Hydrologic Determination of Storage for Mitigation and Flood Control ...... 5-6 5.6.1 Off-line Detention ...... 5-6 5.6.2 On-line Detention...... 5-7 5.6.2.1 Calculation of On-line Storage ...... 5-8 5.6.2.2 Detention Rate Method ...... 5-8 5.6.2.3 Detention Mitigation Rates ...... 5-8
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5.7 Applying Storage Sizing Equations ...... 5-9 5.7.1 Mitigation to Reduce Increased Runoff Due to Development...... 5-9 5.7.2 Reduction of Large Flood Flows ...... 5-9 5.7.3 Mitigation of Increased Conveyance ...... 5-9
6. FRAMEWORK FOR DEVELOPING DRAINAGE REMEDIES ...... 6-1 6.1 Purpose ...... 6-1 6.2 Design Criteria ...... 6-1 6.2.1 Capacity-Based Design ...... 6-1 6.2.2 Design Frequencies ...... 6-1 6.2.3 Design Criteria and Requirements for Modeling ...... 6-1 6.2.3.1 Chambers County Public Infrastructure Design Standards ...... 6-1 6.2.3.2 Chambers County Drainage Criteria Manual Impact Criteria ...... 6-1 6.2.3.3 Chambers County Drainage Criteria Manual Physical Criteria ...... 6-2 6.2.3.4 Chambers County Drainage Criteria Manual Hydraulic Criteria .... 6-2 6.3 Environmental and Preservation Issues ...... 6-2 6.3.1 Site Specific Permitting ...... 6-2 6.3.2 Wetland Determination and Impact Mitigation ...... 6-3 6.3.3 Section 404 Permit for Fill or Excavation ...... 6-3 6.3.4 Section 10 of the Rivers and Harbors Act of 1899 ...... 6-4 6.3.5 Threatened or Endangered Species ...... 6-4 6.3.6 Historical Preservation ...... 6-4 6.3.7 Archeological Review ...... 6-4 6.3.8 Other Environmental Regulation Constraints ...... 6-5 6.3.9 Costs of Environmental Review and Permitting ...... 6-5 6.4 Hydrologic (HMS) Models ...... 6-5 6.4.1 Cedar Bayou Watershed ...... 6-5 6.4.1.1 Hickory Island Gully...... 6-6 6.4.1.2 Smith Gully ...... 6-6 6.4.1.3 Horsepen Gully ...... 6-6 6.4.1.4 Sawpit Gully ...... 6-6 6.4.1.5 Sutton Gully ...... 6-7 6.4.1.6 Ijams Gully and Water Oak Gully ...... 6-7
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6.4.2 Cotton Bayou and Hackberry Gully ...... 6-7 6.4.3 Beach City and Environs ...... 6-7 6.4.4 Cherry Point Bayou...... 6-8 6.4.5 Old River Ditch ...... 6-8 6.4.6 Areas Outside Chambers County ...... 6-9 6.5 Hydraulic (RAS) Modeling...... 6-9 6.5.1 Channel Capacity ...... 6-9 6.5.2 Channel Conveyance Improvement ...... 6-9 6.6 RAS Models ...... 6-10 6.6.1 Source Models for RAS Modeling ...... 6-10 6.6.2 Cedar Bayou Watershed ...... 6-10 6.6.2.1 Smith Gully ...... 6-11 6.6.2.2 Horsepen Bayou ...... 6-11 6.6.2.3 Sawpit Gully ...... 6-11 6.6.3 Cotton Bayou and Hackberry Gully Watershed ...... 6-11 6.6.3.1 Hackberry Gully and Cotton Bayou ...... 6-11 6.6.3.2 Cotton Bayou-Cove Tributary ...... 6-12 6.6.3.3 Langston Road ...... 6-13 6.6.3.4 Unnamed (McAdams) Stream Crossed by SH 565 and SH 99 ...... 6-13 6.7 Cherry Point Gully Watershed ...... 6-13 6.8 Old River Ditch Watershed ...... 6-13 6.9 Beach City and Environs Watershed ...... 6-13 6.10 Tailwater Conditions for RAS Modeling ...... 6-14 7. REMEDIES AND PROJECTS ...... 7-1 7.1 Introduction ...... 7-1 7.2 Types of Projects...... 7-1 7.2.1 Channel Conveyance Improvements: Standard Option 1 ...... 7-1 7.2.2 Detention Ponds for Flood Mitigation: Standard Option 2 ...... 7-3 7.2.3 Diversions ...... 7-3 7.2.4 Channel Hydraulic Structures Modification ...... 7-4 7.3 Methods for Estimating Project Costs ...... 7-4 7.3.1 Direct Construction Costs ...... 7-4
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7.3.2 Other Construction Related Costs ...... 7-5 7.3.3 ROW ...... 7-5 7.3.4 Environmental Protection Costs ...... 7-6 7.4 Conveyance Improvement and Flood Control Projects ...... 7-6 7.4.1 Smith Gully ...... 7-7 7.4.2 Horsepen Gully Improvements ...... 7-7 7.4.3 Sawpit Gully ...... 7-8 7.4.4 Ijams and Water Oak Gullies ...... 7-9 7.4.5 Sutton Gully ...... 7-9 7.4.6 Cotton Bayou and Hackberry Gully Upstream of IH-10 ...... 7-9 7.4.7 Cotton Bayou and Hackberry Gully Downstream of IH-10 ...... 7-10 7.4.8 McAdams Ditch Improvements ...... 7-12 7.4.9 SH 99 Segment Completion South of IH-10 ...... 7-12 7.5 Cherry Point Watershed ...... 7-12 7.6 Old River Ditch Watershed ...... 7-12 7.7 Beach City Area ...... 7-13 7.7.1 Watercourses within Beach City ...... 7-13 7.7.1.1 Cedar Creek ...... 7-13 7.7.1.2 Skylane ...... 7-13 7.7.1.3 Point Barrow Gully ...... 7-14 7.7.1.4 Tri-City Gully ...... 7-14 7.7.2 Spring Creek ...... 7-14 7.8 Future Projects ...... 7-15 8. PROGRAMMATIC IMPROVEMENTS AND FUNDING ...... 8-1 8.1 Complementary Roles ...... 8-1 8.2 Programmatic Improvements for Chambers County ...... 8-1 8.2.1 Regulation and Criteria ...... 8-1 8.2.2 Coastal Flood Protection ...... 8-1 8.2.3 Sheet Flow Management...... 8-2 8.2.4 Use of Regional Detention ...... 8-2 8.2.5 Tracking Growth and Drainage Issues ...... 8-2 8.3 Funding Strategies ...... 8-2
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8.3.1 Project Phasing and Project Decomposition ...... 8-3 8.3.2 Developing Additional Internal Funding ...... 8-3 8.3.3 Joint and Cooperative Funding of Projects ...... 8-4 8.3.4 Joint Funding of Projects in Coordination with Private Developers ...... 8-4 8.3.5 Impact Fees ...... 8-5 8.3.6 Utility or Special Districts ...... 8-5 8.3.7 External Funding ...... 8-6 8.4 External Funding for Drainage and Flood Control Projects ...... 8-6 8.4.1 FEMA Grants ...... 8-6 8.4.2 Texas Water Development Board Loans ...... 8-7 8.4.3 Amenity Funding by Texas Department of Parks and Wildlife ...... 8-7 8.4.4 State Administered Grant Programs ...... 8-8 8.4.4.1 Texas Coastal and Estuarine Land Conservation Program ...... 8-8 8.4.4.2 Texas Department of Rural Affairs ...... 8-8 8.4.5 U.S. Army Corps of Engineers Project Monies ...... 8-9 8.4.6 Multi-Purpose Detention Systems to Access Other Program Funds ...... 8-9 9. RECOMMENDATIONS ...... 9-1 9.1 Conclusions ...... 9-1 9.2 Major Projects ...... 9-1 9.2.1 Conveyance Improvements ...... 9-1 9.2.2 Diversions ...... 9-1 9.2.3 Flood Mitigation Ponds ...... 9-1 9.2.4 Optimal Combinations of Conveyance Improvements and Flood Mitigation Storage ……...... 9-2 9.2.5 Cost for Major Projects ...... 9-2 9.3 Issues in Project Options & Their Selection ...... 9-2 9.3.1 Issues in Costs ...... 9-3 9.3.2 Other Alternatives ...... 9-3 9.4 Infrastructure Improvement Recommendations ...... 9-4 9.4.1 Project Rank by Cost ...... 9-4 9.4.2 Factors for Project Ranking ...... 9-4 9.5 Recommendations for Programmatic Improvements ...... 9-5
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LIST OF TABLES
2-1 Summary Characteristics of WSA Drainage Areas 2-2 Primary Water Bodies in WSA 2-3 Study Area Community Characteristics 2-4 Major Roadways in WSA 4-1 Imperviousness and Land-use Categories 4-2 Critical Facilities 5-1 HEC-RAS and HEC-HMS Models 5-2 Hydrologic Loss and Infiltration Parameters Used for All Hydrologic Models 5-3 Time of Concentration and Storage Factor for Working Study Area Drainage Areas 6-1 Design Storm Frequencies for Infrastructure 6-2 Design Criteria for Conveyance and Storage Facilities 6-3 Hydraulic Properties for New Models 7-1 Project Channel Conveyance and Flow Reduction Goals 7-2 Unit Costs for Project Construction and Implementation 7-3 Representative Environmental Permitting Costs 7-4a Beach City Area- HMS Input 7-4b Beach City Area- HMS Output 7-4c Cotton Bayou and Hackberry Gully Watershed – HMS Input 7-4d Cotton Bayou and Hackberry Gully Watershed – HMS Output 7-4e Cedar Bayou Watershed – HMS Input 7-4f Cedar Bayou Watershed – HMS Output 7-5a Summary of Channel Conveyance Improvements and Costs 7-5b Summary of Flood Mitigation Features and Costs 7-5c Notes for Table 7-5a and Table 7-5b 7-7a Summary of Features of Cotton Bayou Diversion South of IH-10 7-7b Summary of Features of Spring Creek Diversion 7-7c Proposed Approximate Alignment of Cotton Bayou and Spring Creek Diversion 9-1 Summary of Mitigation Features and Cost
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LIST OF FIGURES
(Figures are found in text where they are first introduced) 1-1 Work Flow for Development of CCMDP 4-1 Correlation of Development with Imperviousness 5-1 Definition Sketch for Offline and Online Storage Design
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EXHIBITS
ES-1 Chambers County Master Drainage Plan Study Area ES-2 Anticipated Major Commercial and Industrial Developments ES-3 Proposed Improvements Options ES-4 Drainage Improvement Options Ranked by Estimated Costs 2-1 Vicinity Map with Study Area and Working Study Area 2-2 Topography of Study Area 2-3 Watersheds, Drainage Areas and Major Water Bodies 2-4 100-Year Floodplains 2-5 Administrative and Political Boundaries 2-6 2010 Population Distribution 2-7 Petrochemical Pipelines 4-1 Existing Land-use 4-2 Projected Ultimate Land-use 4-3 Major Transportation and Commercial &Industrial Development 4-4 Bridges, Major Culverts and Siphons 4-5 Critical Facilities 4-6 Repetitive Loss Density 4-7 Identified Drainage and Flooding Problem Areas 4-8 Coastal Surge Conditions 5-1 HMS Hydrologic and RAS Hydraulic Modeling Locations 7-1 Key Map for Channel Improvements and Diversions 7-1a-p Channel Improvements and Diversions 9-1 Drainage Improvement Options Ranked by Estimated Costs
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VOLUME II:
APPENDICES
APPENDIX A. BRIDGE INVENTORIES APPENDIX B. SUMMARIES OF SELECTED REPORTS APPENDIX C. SELECTED PHOTOGRAPHS AND FEMA INDICES APPENDIX D. HYDROLOGIC METHODS APPENDIX E. PERCENT DEVELOPMENT AS FUNCTION OF PERCENT IMPERVIOUSNESS APPENDIX F. DEVELOPMENT RATES APPENDIX G. HYDROLOGICAL MODELING SYSTEM (HEC-HMS) RESULTS APPENDIX H. DETENTION RATES APPENDIX I ASSESSED PROPERTY VALUES APPENDIX J. RAS MODELING RESULTS APPENDIX K. SELECTED PORTIONS OF THE MONT BELVIEU MASTER DRAINAGE PLAN APPENDIX L. ELECTRONIC COPIES OF MODELS APPENDIX M. FUTURE PROJECTS
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ABBREVIATIONS
Brackets ([ ]) are used to denote standard units if not apparent from abbreviation * indicates that abbreviation is used only in tables, figures and/or exhibits
-A- -D- ac acre DCC % channel conveyance ac-ft acre foot (acre feet) DCI % channel improvement aka also known as DET % of detention controlled approx *approximate, approximately drainage area ASFPM American Society of Floodplain DFund Texas Water Development Managers Board fund DLU % urban development -B- DS *downstream
BCA benefit cost analysis -E- BNSF Burlington Northern-Santa Fe Railroad ea *each elev *elevation -C- ETJ Extraterritorial Jurisdiction Ext * existing, existing condition ca. approximately (in time) CCID Chambers County Improvement -F- District CCMDP Chambers County Master FEMA Federal Emergency Drainage Plan Management Agency CCPID Chambers County Public FHWA Federal Highway Infrastructure Design Administration CD compact disk FIRM Flood Insurance Rate Map cfs cubic feet per second FIS Flood Insurance Study C&I commercial and industrial FM farm to market comm *commercial FMA flood mitigation assistance grant CFR Code of Federal Regulations fps *foot (feet) per second CN (SCS) Curve Number ft foot (feet) Cty *(Chambers) county fut-im *improved future, improved cy cubic yard future condition CWA Coastal Water Authority fut-un *unimproved future, CWSRF Clean Water State Revolving unimproved future condition Fund
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-G- LiDAR Light Detection and Ranging LOB *left over bank GIS geographic information system LWCF (Texas) Land and Water Conservation Fund GLO (Texas) General Land Office Google Earth Google Earth® -M- -H- main stem principal channel within a given drainage basin, and into which HCFCD Harris County Flood Control all of the tributary streams in a District drainage basin drain HEC-HMS Hydrologic Engineering Center max *maximum Hydrologic Modeling System mi *mile (miles) HEC-RAS Hydrologic Engineering Center mi/hr mile(s) per hour River Analysis System min *minimum HGAC Houston Galveston Area Council hr *hour(s) -N- HMGP (FEMA) Hazard Mitigation Grant Program n Manning’s n coefficient (n- HMS See HEC-HMS value) H:V horizontal to vertical (slope) n/a non-applicable NFIP National Flood Insurance -I- Program NOAA National Oceanic and Atmospheric Administration IDF Intensity-duration-frequency NWR National Wildlife Refugee [inches/hour-hours-years] NG *natural ground in *inch(es) NRCS National Resources in. inches Conservation Service (formerly ind industrial (for Tables only) SCS) IH-10 Interstate Highway 10 -O- -J- ORD Old River Ditch -K- -P-
-L- pg. page proj. project L length of longest stream Lca stream length to centroid of area
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-Q- evaluation Clark Hydrograph method TDRA Texas Department of Rural Q *discharge [cfs]; with subscripts Affairs or suffices to denote special discharge TNRIS Texas National Resources Information System TOB top of bank -R- TPWD (State of Texas) Parks and Wildlife Department R storage factor TRA Trinity River Authority RAS see HEC-RAS TxDOT Texas Department of Resid *residential Transportation River Sta *river station TWDB Texas Water Development ROB *right over bank Board ROW right-of-way (right of way) -U- -S- UPRR Union Pacific Railroad S flow line slope US *Upstream So watershed slope U.S. United States SCS (United States) Soil USACE United States Army Corps of Conservation Service (now Engineers NRCS) USFWS United States Fish and Wildlife SH state highway Service Shape file digital vector storage format for USGS United States Geological Survey storing geometric location and associated attribute information -V- sq-ft *square foot (square feet) sq-mi square mile Sta station -W- Study Area area in Chambers County west of Trinity River WSA Working Study Area WSE water surface elevation -T- -X- t time for various parameters
Tc, Tc time of concentration (minutes) TCELCP Texas Coastal and Estuarine -Y- Land Conservation Program TBCD Trinity Bay Conservation yr year(s) District Tc & R time of concentration and -Z- storage factor for hydrograph Klotz Associates Proj. 1057.002.000 Master Drainage Plan November 2014 Chambers County xiii
EXECUTIVE SUMMARY
This Chambers County Master Drainage Plan was developed to address existing drainage and flooding problems and to provide for drainage needs expected to occur in the coming years, particularly the coming decade, as development continues. The Chambers County Master Drainage Plan was developed for a Study Area encompassing Chambers County lying to the west of the Trinity River. The Study focuses upon the approximately 100 square miles (sq-mi) Working Study Area, a subset of the larger study area (see Exhibit ES-1).
The total Working Study Area is expected to approach ultimate development within approximately 20 to 25 years, with many areas in the western and central portions of the Working Study Area undergoing rapid development at an approximated 2 percent annual rate of increased cover over the next 5 to 10 years.
Commercial and Industrial development, as well as residential development, are growing at a rapid pace in much of the Working Study Area (see Exhibit ES-2). This development is a key factor in identifying potential drainage improvements and flood control needs. Land-use projections and previously made proposals for Commercial and Industrial developments, in combination with hydrologic and hydraulic modeling, were used to estimate current drainage facility capacities, and needed capacities both now and in the future to prevent significant flooding.
Drainage infrastructure improvement will be essential over the coming years if major drainage problems are to be avoided. A comprehensive program of runoff mitigation and improved channel conveyance is needed to prevent such problems. This Chambers County Master Drainage Plan provides that needed plan.
Data used to develop the Chambers County Master Drainage Plan for the Working Study Area include previous studies and plans completed by a variety of parties; information from local, regional, state and federal agencies and entities; and data from Chambers County, drainage entities, and cities in the county. Numerous reports have been previously prepared about various particular developments and drainage projects in the Working Study Area. A review of these earlier reports is provided in this Chambers County Master Drainage Plan. Inventories of bridges, siphons, crossing, watercourses, and critical facilities (e.g., hospitals), which are candidates for flood protection, are also provided. Significant ponding of waters in low lying areas, as identified by review of digital topographic data called Light Detection and Ranging (LiDAR) data, presents
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a potential drainage hazard as well. Major drainage swales or ditches within the Working Study Area are identified that could reduce flooding in such areas.
ES.1 Identified Projects
Proposals to address development-driven drainage improvement needs and provide for existing flooding problems are the following: In general, options for project implementation include 1) conveyance improvements by widening and deepening of channels and 2) use of flood control detention.
Horsepen Gully: This watercourse is under development upstream of SH 146 as part of the Kilgore Parkway Development. Conveyance improvements or mitigating detention options dealing with flooding downstream of the railroad and SH 146 were identified.
Sawpit Gully: Sawpit Gully will serve, among others, the Ameriport Development. Estimate of conveyance improvements needed to serve future development and reduce flooding west of FM 1405 are determined.
Sutton Gully: Sutton Gully will serve developing northern portions of the Cedar Crossing Development. The drainage plans for Sutton Gully are being developed by the Chambers County Improvement District #1 and are not included in this study.
Ijams and Water Oak Gullies: These two gullies, along the most downstream portion of Cedar Bayou, will serve the mid and southern portions of the Cedar Crossing Development. The drainage plans for these gullies to provide such service are being developed by Chambers County Improvement District #1 and are not included in this study.
Cotton Bayou and Hackberry Gully: These two waterways originate in Mont Belvieu north of IH-10, pass under IH-10, and join at a confluence in the vicinity of the eastern portions of Cove. The hydrologic analysis for these watercourses was combined in a single hydrologic model. Likewise, the hydraulic models for the two watercourses along their entire length were combined in a single hydrualic model. For the region north of IH-10, the combined model was taken from the Cotton Bayou and Hackberry Gully models developed for the City of Mont Belvieu Master Drainage Plan (selected portions of this plan are presented in an appendix to this Study). For the region south of IH-10, models developed for prior conveyance improvement analysis (done in 2011 [Klotz, 2011e; see References at
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conclusion of main text]) were combined with the models from upstream of IH-10 to create a single hydraulic model for the two watercourses.
Upstream of IH-10, channel and detention improvements by the City of Mont Belvieu are being developed in general accord with the Mont Belvieu Master Drainage Plan. South of IH-10, modeling has been used to evaluate conveyance improvement needs and detention alternatives to carry the 100-year flood flow down the channels without significant overbank flooding. The more cost effective solution will combine conveyance improvements (allow most overbank flow) with some detention.
Drainage Gullies Along Trinity Bay and Cotton Lake: Four watercourses which discharge to Cotton Lake or Trinity Bay were analyzed for improvement to address flooding along their existing lower reaches and potential future flooding from development in their upper reaches, such development occurring generally south and east of SH 99 and the anticipated Cedar Crossing development in Chambers County Improvement District #1. These four gullies are the following: Cedar Gully, Skylane Gully, Point Barrow Gully, and Tri-City Gully. Impacts to Fischer Road Gully are not included because the contributing drainage area is not hydrologically substantial enough to warrant costly improvements.
Spring Creek Gully: This short watercourse located north and south of IH-10 near the eastern boundary of the Study Area discharges to the northern boundary of Cotton Lake. Drainage along the Gully passes through parts of the eastern portions of Cove. Because of prior environmental limitations which prevented channel relocation in the close vicinity of Cove, a diversion is proposed from the Gully directly to Cotton Lake to reduce flows down the creek to residential areas in Cove.
Mont Belvieu Watercourses: Improvements for watercourses or watercourse segments in Mont Belvieu are not explicitly evaluated (but note the discussion above regarding Cotton Bayou and Hackberry Gully modeling); such improvements have been previously described in the Mont Belvieu Master Drainage Plan (pertinent portions of which are presented in Appendix K) and are planned to be implemented by Mont Belvieu.
Cotton Bayou and Spring Creek Diversion Channels: Two new diversion channels (one on Cotton Bayou and one on Spring Creek, the latter discussed above) in the eastern portion of the Work Study Area are proposed as possible improvements to address reported flooding issues in Cove and areas to the east.
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Channel Clearing: Smaller watercourses were also identified for which capacity needs might be satisfied with channel clearing only.
Sub-regional Detention: Sub-regional detention requirements for sub-watersheds across the Study Area were also estimated. Detention in these sub-watersheds reduces the potential for flooding along the watercourses in the sub-watersheds.
Basic dimensions, including approximate right-of-way needs for these various options, were calculated. Costs for construction and right-of-way acquisition were estimated. The various project locations and cost are shown in Exhibits ES-3 and ES-4. These costs include direct construction costs, engineering, environmental permitting, and contingency costs. Costs also include estimated right-of-way cost based upon representative land costs as determined by a sampling of county land assessor data.
Option 1 - Channel Option 2 – Detention Watershed Excavation ROW Cost Excavation ROW Cost (cy) (acre) (ac-ft) (acre) Cedar Gully 221,500 34.9 $ 4,100,000 829.1 110.5 $ 19,800,00 Skylane Gully 706,800 52.6 $ 11,500,000 322.2 43.0 $ 7,700,000 Point Barrow 95,900 18.6 $ 2,500,000 178.9 23.9 $ 4,300,000 Tri-City Gully 114,300 16.5 $ 3,300,000 241.3 32.2 $ 5,700,000 Spring Creek 148,900 31.9 $ 3,900,000 168.0 22.4 $ 4,000,000 Upper Cotton Bayou 39,600 58.0 $ 2,600,000 547.5 73.0 $ 13,100,000 Lower Cotton Bayou 85,700 75.9 $ 3,500,000 230.8 30.8 $ 5,500,000 Hackberry Gully 148,900 55.8 $ 4,500,000 310.6 41.4 $ 7,400,000 Horsepen Bayou 34,100 17.8 $ 1,900,000 73.1 9.7 $ 1,700,000 Sawpit Gully 34,900 21.3 $ 2,400,000 37.7 5.0 $ 900,000
Section 9.0 to this report includes conclusions and recommendations. The County may want to use this high level information to develop an initial prioritization of projects however Preliminary Engineering Reports (PER) are needed to provide sufficient details for use in prioritization ranking for inclusion into the County’s Capital Improvement Plan.
Several more conveyance improvement and regional detention solutions are currently being proposed throughout Chambers County. Improvement recommendations contained within this study are being considered for future implementation under GLO Contract Texas CDBG Disaster Recovery Grants, and various other tentative contracts and plans. While the surety and timeline associated with any of these and other future plans is beyond the scope of this MDP, current
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knowledge and documentation associated with those plans should be acknowledged. Documentation available at the time of this study can be found in Appendix M.
ES.2 Solving the Right Problem and the No Action Alternative
Essential to the engineering development of a particular project is the need to assure that the drainage problem being addressed is the right problem. Local flooding from inadequate secondary storm sewer drainage systems can be a source of what is reported or interpreted as riverine flooding along a major watercourse. It should be expected that as part of preliminary engineering studies, a clarifying investigation of the reasons for what is believed to be the source of flooding should be undertaken.
In some instances, the combination of project cost, environmental constraints, and anticipated project benefits does not reasonably justify the implementation of an infrastructure project. Alternatives to the infrastructure option must be used, including a no-action alternative.
ES.3 Recommendations for Programmatic Improvements
Supplementing the proposed projects are programmatic improvements. Programmatic improvements intended for drainage management and flood control in Chambers County should consider the following:
Regulation and Criteria: Modify standard drainage regulation and criteria to make criteria more consistent, effective, and encourage beneficial and responsible development, including rigorous standards for secondary drainage, effective management of sheet flow, and adequate local storm sewer design.
Coastal Flood Protection: Assure frequent inspection of residential coastal structures and rigorous review of residential construction activities (plans and on-site inspection) to maximize compliance with state and regional construction codes for construction in high hazard coastal zones.
Use of Regional Detention: Encourage the use of efficient regional or sub-regional detention though careful planning, coordination with developers, potential tax or fee incentives, and/or structuring drainage ordinances and criteria to encourage regional detention projects.
Tracking Growth and Drainage Issues: Institute a management system in the county, in coordination with the cities that 1) tracks growth so that anticipatory drainage mitigation actions can be undertaken; and 2) maintain a comprehensive record of citizen complaints
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about drainage related problems. These records could be used as a guide in drainage planning and priority setting for future project implementation.
Installation of a Rain and Depth Gauge Network: Currently there are several Trinity Bay Conservation District (TBCD) rain gages distributed throughout the County. Installation of a more extensive rain and depth gauge network will allow the County to calibrate and update the watershed models and perform detailed analysis to truly define the level of service within each system.
There are a variety of funding methods that can be considered for funding the proposed projects. Particularly promising are 1) grants from funding agencies, 2) partnerships with other public entities, 3) impact fees to be assessed against new developments and 4) cost sharing with public entities and private developers for projects that serve multiple uses. Joint arrangements involving cost sharing and cost reimbursement between the County, developers as well as other public entities appear particularly promising. See Section 8 of this report for more details on funding options.
Note that the projects and associated cost estimates, ROW requirements, Environmental Issues, permitting requirements and other issues identified in this Master Drainage Plan are high level information. More detailed evaluations are needed for each potential project. Escalation of project costs should also be considered. The unit prices used in the estimated costs are based on 2013 values.
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1. INTRODUCTION
1.1 Authorization
The preparation of this Chambers County Master Drainage Plan (CCMDP) was authorized by agreement between Chambers County and Klotz Associates dated January 29, 2013.
1.2 Background
Chambers County is an 872 square mile (sq-mi) coastal county of Texas lying between Harris County on the west, Jefferson County on the east, Liberty County on the north, and Galveston Bay and the Gulf of Mexico on the south. The open water of Galveston Bay occupies approximately 1/4 of the county. Interstate Highway 10 (IH-10) is the major east-west transportation corridor and splits the County into approximately northern and southern halves.
The eastern half of the county is predominately rural and is not included in the Work Study Area (WSA). In the western half of the county, north of IH-10, the area is dominated by the City of Mont Belvieu and various petrochemical industrial facilities. In the western half of the county south of IH-10, the county is undergoing significant C&I and residential growth, in part sparked by the 2008 opening of portions of State Highway 99 (SH 99), also known as the Grand Parkway. SH 99 will ultimately connect Mont Belvieu north of I-10 to Baytown south IH-10.
1.3 Objectives
The primary objective of this study was to prepare a master drainage plan to address current and future drainage and flood control needs. While a variety of focused or localized drainage studies have been prepared in the past (see References and Appendix B), the plan presented here is the first unabridged master drainage plan for Chambers County.
This plan identifies drainage and flooding conditions for existing and projected future conditions as well as develops a plan to address drainage problems and identify major infrastructure improvements.
1.4 Scope of Chambers County Master Drainage Plan
This CCMDP scope had 13 major tasks: 1) Agency Coordination, 2) Obtaining and Reviewing Available Data, 3) Public Involvement, 4) Develop Inventory and Assessment of the Facilities, 5) Direction of and Coordination of Field Surveys, 6) Field Verify Existing Watershed Conditions, 7) Prepare Base Maps and Existing Service Area Maps, 8) Anticipate Future Development Conditions, 9) Prepare Peak Runoff Rates, 10) Identify Level of Service and Design Frequencies,
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11) Perform Alternatives Analyses to Address Drainage, 12) Develop Recommendations For Improvements, and 13) Prepare Final Master Drainage Plan Report.
1.4.1 Coordination and Interaction: Tasks 1 and 3
Coordinate with Chambers County staff and other agencies in developing the plan. Coordination with the public was done under the direction of the County.
1.4.2 Data Collection and Review, Inventory, Field Survey: Tasks 2, 4, 5, 6, 7
Pertinent data on drainage, flooding, and infrastructure were collected from the County, selected public entities, previously prepared studies identified by the County and/or Klotz Associates, and discussions with the County. This information was reviewed and assessed as appropriate. Base maps were developed to provide key drainage information for the WSA. References at the end of the text of this document identify sources for cited material. In some cases, for the ease of understanding, information about a particular subject is only summarized in the main text, with additional detailed information being provided in appendices.
1.4.3 Existing Conditions, Future Growth, Levels of Service: Tasks 8, 9, 10, 11
Information on current land-use and development levels were evaluated. Estimates of future land-use and development were made with the assistance of the County. Hydrologic and hydraulic analyses were conducted to determine existing capacities of drainage facilities and estimate needed future capacities for various types of drainage infrastructure.
1.4.4 Proposed Remedies and Future Infrastructure: Tasks 12 and 13
Based upon the analysis of drainage needs, proposed improvements were recommended. Costs of improvements and potential funding sources were identified.
1.5 Study Focus
This study focused on the following criteria:
1.5.1 Study area
The WSA is limited to Chambers County west of the Trinity River. Information for conditions east of the Trinity River is provided for background purposes only.
1.5.2 Scale of Problems and Problem Resolution
Chambers County formally recognizes two broad classes of drainage facilities [Dodson, 2005]:
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Primary Drainage Facilities: Open channels, bridges, culverts, and enclosed drainage systems
Secondary Drainage Facilities: Storm sewers, roadside ditches, and associated structures; sheet flow swales; small culverts; and other structures for small drainage areas
This CCMDP focuses on publically owned primary drainage systems. Because of the planning nature of this Study, drainage issues within a residential subdivision or a C&I site, commonly served by secondary drainage facilities, are addressed only if of special significance to the primary drainage systems of this master plan. Scope and Describe Study 1.5.3 Non-Hurricane Conditions Purpose (Chap 1) Area (Chap 2)
Evaluation of drainage issues and identification of improvements assume non-tropical storm conditions.
1.5.4 Date of Information Identify & Describe Growth, Data Collection Land-use and Processes This CCMDP is developed using data generally Issues (Chap 4) (Chap 3) available through early 2013.
1.6 Structure of CCMDP Report
The overall Study process is shown in Figure 1-1. Describe Describe Framework for After preliminary work in obtaining information, Hydrologic and Remedy of Hydraulic development levels and conditions were defined. Drainage Needs Methods (Chap 5) (Chap 6) Hydrologic and hydraulic methods used in evaluating drainage needs are described. Individual critical drainage areas are identified and evaluated. Current channel capacities are Programmatic Identify and evaluated. Options for conveyance improvements Remedies and Descrbe Remedies Funding Sources and Projects are identified. Future peak discharge and (Chap 8) (Chap 7) necessary channel capacities for ultimate development levels were computed with Hydrologic Engineer Center Hydrologic Modeling Conclusions and Recommendations System (HEC-HMS) and Hydrologic Engineer (Chap 9) Center River Analysis System (HEC-RAS) Figure 1-1. Schematic of Work Flow
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software models. Results attained from these models were assessed and costs for improvements were estimated. The more practical and cost efficient improvements were selected and prioritized to define the CCMDP.
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2. DESCRIPTION OF STUDY AREA
2.1 Chambers County
Chambers County has approximately 599 sq-mi of land and 273 sq-mi of open water [SCS, 1976]. The southern and southwestern land areas of the county lie on the shores of Trinity Bay and East Bay (arms of Galveston Bay) and the Gulf of Mexico; see Exhibit 2-1.
2.2 Study Area Boundary
Per Study scope, this CCMDP was developed for those areas of Chambers County west of the Trinity River. The “Study Area” lands, delineated in Exhibit 2-1, cover approximately 133 sq-mi.
2.3 Working Study Area
A significant portion of the WSA is undevelopable because of wetlands, swamplands, marshes, and both formally and informally defined wildlife conservation areas. Drainage improvements recommended are therefore limited to the areas west of these undevelopable areas.
The western boundary of this undevelopable land was defined by Texas Natural Resources Inventory System (TNRIS); see Exhibit 2-1. This boundary generally lies along Old River and the western sides of Cotton and Dutton Lakes. Study Area lands west of these undevelopable lands, totaling approximately 94 sq-mi, define the WSA.
2.4 General Physiographic Characteristics
Chambers County has an average annual rainfall of 51.5 inches (in.) and average monthly rainfall minimum and maximum of 2.7 in. (in March) and 5.49 in. (in July) [SCS, 1976], respectively.
Study Area lands are dominated by coastal waters on the south, Cedar Bayou on the west, Trinity River and Trinity Bay on the east, and elevated lands near the northern boundary of the Study Area. For convenience in presentations, a line generally from Dutton Lake westward to the crossing of Cedar Bayou by State Highway 146 (SH 146) was used to divide the WSA into the northern and southern portions (e.g., see Exhibit 2-3 N&S).
2.4.1 Topography
Chambers County is part of the Texas Coastal Plain. The general topography of the Study Area is illustrated by the Light Detection and Ranging (LiDAR) map of Exhibit 2-2. Lands are relatively broad and flat with elevations ranging from sea level to elevations commonly on the order of 50 ft
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in the northern portion of the WSA. Thus, the potential for flooding from more intense rainfall or storm surge from coastal water bodies is significant [Trust for Public Land, 2009; FEMA, 2013a].
The highest elevation in the County is Barbers Hill in the City of Mont Belvieu with a maximum elevation of approximately 82 ft. This elevation is, however, not representative, of the entire WSA and is due to a massive subsurface salt dome.
Natural rivers generally flow from the northern part of the County to the bays along the south side of the County or Cedar Bayou on the west. Common ground surface slopes in the WSA are about 2 to 4 feet per mile (ft/mi) in the north-south direction and 8 ft/mi in the east-west direction.
2.4.2 Soils and Geology
Soils in Chambers County are primarily slowly draining coastal clay and sandy loam that provide ideal conditions for agriculture, grazing, migratory birds, and coastal marine life [SCS, 1976].
Two soil associations are found in the Study Area: The Beaumont-Morey-Lake Charles association and the Stowell-Clodine association. The former is a clayey and loamy soil while the latter is a sandy and loamy soil [SCS, 1976]. The Stowell-Clodine association is located predominately south of Old River between Lake Anahuac and Cotton Lake (and thus not generally in the WSA). West of the Stowell-Clodine association, all the way to Cedar Bayou, the soil is predominately of the Beaumont-Morey-Lake Charles association.
The soils of both the Beaumont-Morey-Lake Charles and the Stowell-Clodine associations are classified as a soil of Hydrologic Soil Group D [Halley et al., 2013].
2.4.3 Watersheds, Subwatersheds and Study Drainage Areas
River basins are defined as large, macro-scale delineations of areas draining to a major river. The WSA lies in two river basins defined by the United States Geologic Survey (USGS) [USEPA, 2013]: 1) Lower Trinity and 2) North Galveston Bay.
Watersheds are considered subdivisions of the river basins, while drainage areas (also called sub- watersheds) are subdivisions of watersheds. Subdivisions of drainage areas are loosely termed catchments or service areas. Service areas commonly drain particular areas of subdivisions or C&I sites. Individual drainage areas are shown in Exhibit 2-3 N&S.
Drainage areas were delineated for this Study to provide consistency with, not only LiDAR-based elevations, but also watershed and drainage area delineations developed in previous studies. These prior delineations included drainage area boundaries developed by the Harris County Flood
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Control District (HCFCD) along Cedar Bayou; boundaries developed in master drainage plans for Mont Belvieu [Klotz, 2009] and Baytown [Klotz, 2011]; and boundaries defined by the Texas Department of Transportation (TxDOT) in studies of Sawpit Gully (sometimes spelled as Saw Pit Gully), Horsepen Gully (sometimes spelled as Horse Pen Gully), and McAdams Ditch [PB, 2007; Klotz, 2010; HCFCD, 2013]. Watersheds and drainage areas not covered by these prior studies were delineated using Geographical Information System (GIS) ArcHydro software paired with professional judgment to provide realistic and consistent set of drainage areas derived from the various data sources. The various drainage areas are listed in Table 2-1.
2.4.4 Water Bodies
Within the boundaries of the WSA are a variety of hydrographic features, e.g, lakes, large ponds, reservoirs, watercourses, raw water supply canals, wetlands, swamps, and wildlife refuge areas. The more significant of these various water bodies are identified in Table 2-2 and Exhibit 2-3. Appendix C.4 provides aerial photographs of the several significant drainage gullies in Beach City along Trinity Bay.
2.4.5 Undevelopable Swamplands, Wetlands, Refuge Areas
Dispersed swamplands and other wetlands are found widely distributed across much of Chambers County. Undevelopable lands are particularly concentrated in the far eastern portion of the WSA and adjacent lands to the east. Many of these lands are tidally influenced by the waters of East Bay or Trinity Bay. Swamplands are concentrated particularly along several major waterways and in several national wildlife refuges. Formally designated wildlife refuge areas lie to the north, east and southeast of the eastern portions of the WSA [USFWS, ca. 2012].
Important fish and wildlife conservation habitats in Chambers County include freshwater and saltwater marshes, flyway corridors for migratory birds, riparian corridors, oak mottes, cypress swamps, and upland coastal prairies [Trust for Public Land, 2009]. Widespread woodlands and mudflats provide significant habitat for migratory birds. Various threatened and endangered species are also found in these refuges [Trust for Public Land, 2009].
The areas along the Trinity River, the Old River, and the Lost River are dominated by wild and undeveloped swamps and wetlands. Anthropogenic development, except for roadways, is virtually absent. Proposed river modifications for flood control and other purposes in these areas have been controversial (e.g., the Wallisville Project along the Trinity River [Connell, 2008; USACE, 2013]).
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2.4.6 Well Known Chambers County Conservation Areas near Study Area
East and north of the Study Area are several well-known conservation areas:
Anahuac National Wildlife Refuge: This 35,000 acre wildlife refuge borders the East Bay behind Bolivar Peninsula in the central coastal areas of the county, some 20 miles southeast of the City of Anahuac [Wikipedia/Anahuac National Wildlife Refuge, 2013].
Candy Cain Abshier Wildlife Management Area: This wildlife management area is a 207 acre nongame preserve located some 25 miles south of the City of Anahuac and near Smith Point [TPWD, 2006].
Moody National Wildlife Area: Located west of the City of Anahuac and east of Upper Galveston Bay along the East Bay coast, this area is part of the Texas Chenier Plain National Wildlife Refuge Complex covering approximately 3516 acres [Texas Chenier Plan, NWR Complex, Site Partner Sourcebook, circa 2012].
Trinity River National Wildlife Refuge: This refuge covers some 25,000 acres along the Trinity River in Liberty County north of the WSA [USFWS, 2013]. The refugee has grown over the years through a patchwork of land acquisition. The Trinity River, the Old River, the Lost River, the Old River Lake, the Lost Lake, and the Trinity River Delta are primary hydrographic features of this refuge area.
2.4.7 Floodplains
One-hundred year floodplains for Chambers County as delineated on Flood Insurance Rate Maps (FIRMs) were first developed in the 1980s and 1990s. Preliminary (i.e., not yet officially recognized by FEMA) floodplain delineation data were published electronically by FEMA in January of 2013 [FEMA, 2013a, 2013b, 2013c]. Data for the FEMA 2013 preliminary floodplains were used to plot the current 100-year floodplains shown in Exhibit 2-4. Coastal flooding driven by surge tides, in addition to riverine flooding, is included in these delineations.
2.5 Significant Anthropogenic Features
Important administrative or political units and features, shown in Exhibit 2-5, are the following:
2.5.1 Political and Administrative Boundaries
Commissioner Precincts: Chambers County has four commissioner precincts. The Study Area and the WSA lie within Precincts 2, 3, and 4. Precinct 3 lies largely north of IH-10 while Precincts 2 and 4 lie to the south of IH-10. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 2 - 4
Trinity Bay Conservation District (TBCD): TBCD lies to the east of the Trinity River [TBCD, 2013] and is thus outside the Study Area. The Trinity Bay Conservation District has prime responsibility for drainage management east of the Trinity River.
Trinity River Authority (TRA): The TRA has water management responsibilities for the Trinity River (a “water of Texas”) on the eastern boundary of the Study Area.
Harris County Flood Control District (HCFCD): HCFCD manages Cedar Bayou on the western boundary of the Study Area.
Chambers County Improvement Districts (CCID)
CCID No. 1: Located on the northeast shore of Galveston Bay, CCID#1 was created in 1993. The district contains approximately 13,900 acres [Pate, 2005; Pate 2006] and includes the Cedar Crossing Industrial Park which occupies much of the WSA peninsula zone. This industrial park (currently in development) district is the Houston area’s largest master- planned industrial park. The district functions are related to economic diversification; economic development; promotion of the control, treatment, storage, and distribution of water and sanitary facilities; transportation of agricultural; C&I products; and promoting improvements district watercourses to permit or aid navigation and commerce. In 2012, the district sold bonds for development of a barge dock and laydown yards [RBC, 2012] along Cedar Bayou in the southern portion of the WSA.
CCID No. 2: This improvement district was created by the Texas Legislature in 2009 to promote (as in other improvement districts) economic development and provide public utility services to people, industries, and commerce within the district boundaries.
CCID No. 3: CCID No. 3 is located along the Grand Parkway near and southwest of the intersection of IH-10 and FM 3180. The CCID#3 was created in 2012 for the purpose of developing and managing infrastructure improvements arising from C&I development within the district.
2.5.2 Population and Communities in the Study Area
The primary communities lying in the WSA are Mont Belvieu, portions of Baytown, portions of Old River-Winfree, and Cove (see Exhibit 2-6). Table 2-3 provides information about these communities. Mont Belvieu and Baytown extraterritorial jurisdictions (ETJ) are shown in Exhibit 2-5.
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Year 2010 population distribution for the Study Area is shown in Exhibit 2-6. Relatively high population concentrations are found in Mont Belvieu and Baytown. These 2010 data, obtained from HGAC databases, show only limited change from year 2000 HGAC.
2.5.3 Major Transportation Arteries
Roadways are a common magnet for development. Existing State and Federal roadways in the WSA are shown in Exhibit 2-1 and listed in Table 2-4.
Union Pacific Railroad (UPRR) and Burlington Northern Santa Fe (BNSF) [Cushman & Wakefield, 2010] are major rail line operators in the Study Area. Rail lines extend south to north for areas east of Cedar Bayou with east-west lines extending to Baytown and Harris County.
2.5.4 Petrochemical Pipelines
Pipelines may be used for provision of municipal services such as water supply, sanitary sewage disposal, or drainage of storm waters. Removing or relocating such pipelines is not typically a major difficulty in the construction of storm water conveyances such as channels or ditches.
On the other hand, petrochemical pipelines, which can carry a variety of petrochemical gases and liquids, can present a major impediment to development of storm water conveyances, particularly new channels and ditches. Petrochemical pipelines, as shown in Exhibit 2-7 for data 2013 data from the Railroad Commission of Texas (RRC), are numerous in the WSA. The concentration of pipelines in the Mont Belvieu area is one of the highest concentrations in the nation. Projects proposing new crossings of such pipelines can be difficult and expensive to construct; for these reasons, projects proposing a pipeline crossing are not generally recommended for this Study.
2.5.5 Land-use
Within the WSA, historical, existing, and future land-use data from various sources were evaluated and compared to identify trends in both short-term and long-term development. Land- use is comprehensively examined in Section 4.
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3. DATA COLLECTION AND REVIEW
3.1 Purposes of Data Collection and Review
Data were collected and reviewed in order to:
Provide drainage and infrastructure descriptions
Identify existing drainage problems and concerns
Estimate anticipated future needs
3.2 Data Sources and Collection
Data sources included Chambers County databases throughout their various websites; documents provided by the County, the County Engineer and his staff; and various miscellaneous parties.
Information (in hard-copy and electronic formats) was obtained from public domain sources (including internet sources); cities in the WSA; prior studies done for the county or cities in the WSA; regional planning entities (e.g., HGAC); state agencies (e.g., TNRIS; TxDOT); federal agencies (e.g., U.S. Army Corps of Engineers [USACE]); and documents prepared by consulting engineers.
The following sections summarize the information from various sources.
3.2.1 Prior Studies and Reports
Information collected for review is identified in the References section at the end of this Study volume. Summary reviews of more pertinent information are provided in Appendix B.
3.2.2 Floodplain Data
Floodplain data were obtained from FEMA FIRM data or results of hydraulic modeling studies done for various projects in the County. Repetitive loss data were provided by Chambers County.
3.2.3 Databases
The County provided Klotz Associates with various electronic data in a GIS shapefile format, Excel spreadsheets, PDF files, and, in some cases, hard copy data tabulations. State, regional (e.g., TNRIS, HGAC), and county GIS databases as well as Environmental Systems Research Institute (ERSI) databases were accessed to obtain information for watershed delineation, water body location, stream and channel identification, and transportation corridors.
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Aerial photographs were obtained from HGAC or downloaded directly from Google Earth. The HGAC photographs represent conditions in the 2011-12 timeframe. Google Earth photographs represent early 2013 condition, unless specifically noted otherwise.
LiDAR data (dated 2013) were obtained from TNRIS (TNRIS obtained these data from the United States Geological Survey [USGS]).
3.2.4 Critical Facilities:
A critical facility is a public structure or collection of structures that house or support essential health or safety functions (e.g., fire stations and hospitals) or that is generally important to the wellbeing and safety of the public. Critical facilities are addressed in detail in Section 4.
3.2.5 Land-use
Historical and current land-use was determined by review of previous studies and detailed inspection of Google Earth photographs. Information identified on Google Earth photographs was transferred to GIS shape files for additional analyses.
3.2.6 Other Miscellaneous Technical Data
Other miscellaneous technical data were obtained from Chambers County, Coastal Water Authority (CWA), HCFCD, TxDOT; TNRIS, the Railroad Commission of Texas (RRC), and private firms and public agencies.
3.3 Hydraulic and Hydrologic Models
Both hydrologic models using HEC-HMS (USACE Hydrologic Engineering Center Hydrologic Modeling System software) and hydraulic models using HEC-RAS (Hydrologic Engineering Center River Analysis System software) were collected from available sources including Chambers County, HCFCD, and studies by engineering consultants (including Klotz Associates). Hydrologic and hydraulic models are detailed in Section 5.
3.4 Discussions with Chambers County and Others
Discussions with Chambers County staff and officials were used to assist in identifying current conditions and providing insight to future development. Access to county files (approved by the Chambers County Engineer) was used to identify and review plans and correspondence regarding prior and proposed development in the County. Discussion with other consultants and municipal representatives was also used to gather miscellaneous information.
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4. FACILITIES, LAND-USE AND DRAINAGE ISSUES
4.1 Introduction
Collected information was used to describe historical, existing or future drainage conditions on:
Land-use, which affects amounts and rates of runoff
Primary drainage facilities because they modify, control or impact runoff or stream flow
Drainage problems and issues recognized in the development of this CCMDP
The CCMDP addresses “existing” (or “current”) and “future” (or “proposed”, “projected”) land- use and drainage-influencing conditions.
4.2 Land-use
The existing condition land-use represents conditions at the approximate start of this Study based upon available data (generally drawn from information applicable to the approximate 2012 to 2013 timeframe). Current conditions were sometimes revised (based upon updated information) to more-recent yet still prior conditions. With that said; however, it must be stated that development in the WSA is rapid and in flux. Consequently, describing “existing” conditions is inherently imprecise.
Future conditions represent conditions and factors that are expected to affect drainage and flooding in the county in the coming years, both in the short-term and the long-term.
4.2.1 Land-use and Imperviousness
Using information from various sources [HCFCD, 2009; HGAC, 2013a; Klotz 2000a; Klotz, 2009a], land-use categories identified for this Study to describe land-use impacts on drainage are listed in Table 4-1. Different land-uses have different representative levels of imperviousness and consequently different volumes and velocities of runoff.
Residential and C&I land-uses were subdivided into high, medium and low intensity (i.e., relative development “intensity”) to represent changing land-use intensity over time. Data from different sources and professional judgment was used to span the various values of development and imperviousness for the listed uses.
Figure 4-1 compares original data from various sources [Maidment, 1992, Chap 28; Klotz Associates, 2003; HCFCD, 2004, 2009; Dodson, 2005; HGAC, 2013a, 2013b;] for
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imperviousness and level of development used in this Study. The equation of the empirical correlation between imperviousness (% IMP) and development (% DLU) is given in Figure 4-1.
Development In Relation to Imperviousness
100 90
80 Data Categories Selected for this Study 70
Data from Other Sources 60
50 Log. (Data Categories Selected for this Study)
40 %Developed Log. (Data Categories 30 Selected for this Study) 20 y = 29.439ln(x) - 34.259 10 R² = 0.8916 0 0 20 40 60 80 100 % Imperviousness
Figure 4-1. Correlation of % Development with % Imperviousness
Also listed in Table 4-1, for reference, is the estimated SCS Curve Number (CN) for the various imperviousness levels. Note that Soil Group D exists virtually throughout the WSA and has little variation in curve number (CN) values.
4.2.2 Existing Land-use
Existing land-use estimates, shown in Exhibit 4-1, are based upon review of 2012 and 2013 aerial photographs (from Google Earth), data from miscellaneous reports [Brown & Gay, 2008; Bury & Partners, 2006; Cobb Fendley, 2012; Cushman & Wakefield, 2010; HGAC, 2013a, 2013b; Jones & Carter, 2010; Klotz, 2000, 2009a; Pate Engineers, 2005, 2006; PB, 2007], and information from Chambers County. These estimates show concentrated development in the western portions of the WSA, particularly in Mont Belvieu and along Cedar Bayou.
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4.2.3 Ultimate Land-Use
To provide a reasonable projection of future ultimate development land-use conditions over the planning horizon, a review of existing land-use was made to identify areas that might be likely to be developed. Land-use projections were made in view of available open areas; the general nature and location of undeveloped areas; nearby and existing developed land-use; proposed C&I developments; location of roadways and railways; previously made projections; and major infrastructure improvements already being planned or under construction (based upon data provided by Chambers County, TxDOT, municipalities, and various reports). Depending upon location, already developed land was also sometimes increased in its level of development.
Projected land-use determined after analysis and refinement is that shown in Exhibit 4-2. Review of the regional forecasts for projected land-use for 2035 as well as 2005 created by HGAC [HGAC, 2013a, 2013b] showed negligible change in land-use between 2005 and 2035 in the WSA. Significantly, the HGAC projections indicate no change for areas along SH 99 or in Mont Belvieu. As such, lack of impacts is considered unrealistic. Consequently, the HGAC land-use projections were not used for this Study. Land-use projections from master drainage planning for Mont Belvieu and Baytown [Klotz, 2009a; Klotz, 2000], on the other hand, were incorporated into land-use projections for the CCMDP.
4.2.4 Historical Development and Land-use
To provide a reasonable estimate of the timeframe for which land-use changes could manifest, a database of historical photographs was assembled. Historical photographs spanning the period from December of 1970 to April of 2013 and shown in Appendix C were downloaded from Google Earth and reviewed. Based upon the review, the following observations were made:
In the northern portion of the WSA:
Industrial land-use in western Mont Belvieu appeared to undergo significant growth in intensity and extent over the period 1/1995 to 1/2006 (11 years.)
Commercial development along the IH-10 corridor appeared to significantly intensify during the period of 1/1995 to 1/2006 (11 years.)
Residential development to the east of and outside the confines of Mont Belvieu appear to begin to significantly increase between 1/1995 and 4/2002 (7 years.) Development appears to have grown at a moderate pace until recently.
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Significant expansion of the industrial areas along Cedar Bayou between SH 146 and SH 99 occurred between 1/1995 and 4/2002, a period of approximately 7 years. Only limited intensification of the industrial land-use occurred in the subsequent years through 2012.
Residential development on the west side of Dutton Lake and in the northern areas of Beach City became significant in the period of 1/1995 to 12/2002. The development intensity grew in the following years until it began to stabilize in about 1/2008. Thus, the residential development grew at a low intensity to a moderately high intensity in about 14 years.
In the southern portion of the WSA:
Expansion of existing industrial land-use became apparent in the period of 1/1995 to 4/2002 (7 years).
Limited intensification of industrial land-use occurred over the period of 4/2002 to 2012 (10 years).
The following information was also drawn from various reports:
Grand Parkway Impact Evaluation: Impact assessment of the construction of SH 99 [PB, 2007] concluded that the eight counties (including Chambers County) will grow in population from about 5.3 million to 8.9 million between 2005 and 2035(i.e., about 66.7%), equivalent to an average annual growth rate of 2.6% for the county.
During the period of 1970 to 1980, Mont Belvieu grew nearly 34%, but between 1980 and 1990 the population dropped by nearly 31% [Knudson & Associates, 1999], likely reflecting the adverse Houston economic conditions in the 1980s. However, Mont Belvieu is projected to grow from a 2005 population of 2726 to a 2035 population of 5324 (i.e., about 95.3%) [PB, 2007]. This latter increase corresponds to an annual growth rate of 3.4% for Mont Belvieu growth.
Baytown: Master drainage planning for Baytown [Klotz, 2000] includes estimates of existing and future development in the city’s ETJ east of Cedar Bayou extending to Beach City. The projections of future land-use of this area are of limited validity in light of the rapid development of this area in the last decade.
Mont Belvieu: Master drainage planning for Mont Belvieu [Klotz, 2009a] includes projections for existing and ultimate development for the portions of the Cherry Point Gully, Cotton Bayou, Hackberry Gully, Old Ditch, and Smith Gully watersheds lying within Mont Belvieu city limits.
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4.2.5 Estimation of Planning Time Horizon
The time horizon is defined as the duration of time from the current condition to some future condition by which the drainage needs for ultimate development are expected to be generally achieved across the WSA.
Using the historical data described in the preceding section, an analysis was done to estimate annual growth rates during periods of both rapid and moderate growth. Both the time for both rapid growth and moderate growth gave an estimate of the timeframe for approximate ultimate development beyond the current time. Appendix F details the analysis.
It is estimated that, historically, it has taken about 25 years for development levels to change from low to ultimate. This period of 25 years corresponds to a planning time horizon extending to approximately 2040. The annual growth rate (consisting of both moderate and rapid growth periods) over this time horizon is estimate to range from a low of 1.5% to a high of 2%.
4.3 C&I and Roadway Development Planned or Underway
In developing land-use descriptions, alterations to projected land-use delineations were made to recognize known major C&I development projects currently in planning phase, in early phases of development, or currently under construction. Depending upon the status of the development, representation and estimation of features of a particular development may or may not be well defined. Identified larger C&I developments are, in alphabetical order, the following:
C&I-1. Ameriport: This is a 685 acre master planned light industrial and commercial development [Jones and Carter, 2009; Jones and Carter, 2008; Berg-Oliver, 2009] lying south of IH-10, east of SH 146, and west of SH 99 located along FM 565 near the intersection of FM 565 and FM 1405. Sawpit Gully is situated within the northern portions of the proposed Ameriport development and is the primary drainage watercourse for the development.
C&I-2. BayTen Business Park: This business park, currently under development, is located along the Kilgore Parkway between SH 99 and Hackberry Gully near FM 3180. The ultimate design for the business park has approximately 250 acres set aside for development and some 100 acres for regional detention [Jones and Carter, 2012].
C&I-3. Brine Company, Hatcherville Road: This is a proposed brine storage facility adjacent to a Coastal Water Authority (CWA) canal in the Mont Belvieu area about 5 miles north of
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the intersection of SH 146 and FM 1492. The industrial site covers some 114 acres, of which approximately 47 acres will be brine storage ponds [Carnes, 2011].
C&I-4. Cedar Crossing: This is a master-planned industrial park partially developed in the southern portions of WSA. The Cedar Crossing Industrial Park is the Houston area’s largest master-planned industrial park, covering approximately 15,000 acres. 120 acres of the area is proposed to be a business park [Bury and Partners, 2006].
C&I-5. GreenTransport Facility: The GreenTransport facility (also sometimes spelled as Green Transport) is a proposed 74 acre transport facility to be located on the northeast corner of the intersection of Cedar Bayou and SH 99 (after replacement of Spur 55). The site will be a terminal for the offload of containers. Approximately 16 acres of the total site lies in both the Cedar Bayou floodplain and the coastal flooding zone of Galveston Bay [Brown & Gay, 2008].
C&I-6. Kilgore Parkway Development: This is an approximately 2051 acre development both north and south of Horsepen Gully, west of SH 99, and spanning Kilgore Parkway [Lippke, 2013]. The development has planned an extensive interior network of channels for drainage to a proposed regional detention pond. The pond will discharge to Horsepen Gully.
C&I-7. Kilgore Business Park: This site lies between the Kilgore Parkway Development and the BayTen Business Park [Combs, 2013]. The park is in the planning stages and has not yet undergone actual on-site development. Predicted uses will be similar to the BayTen Business Park.
The approximate locations of these developments are shown in Exhibit 4-3.
Significant development also includes major roadway projects, as follows (see Exhibit 4-3):
RW-1. Extension of FM 1409: Exhibit 4-3 shows the approximate alignment for the proposed extension. Development of the extension is underway [Old River-Winfree Community News, 2011; De Leon, 2013; Dannenbaum, 2013].
RW-2. Eagle Drive in Mont Belvieu. Eagle Drive (also identified as FM 3180) is undergoing improvement including drainage, along much of its length in Mont Belvieu [KSA, 2012; R.G. Miller, 2011]. It is becoming a primary thoroughfare in the eastern portion of Mont Belvieu.
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RW-3. Grand Parkway North of IH-10: Planning documents indicate the extension of the Grand Parkway north of IH-10 in the western portions of Mont Belvieu. At this time, however, the route identified is only conceptual. Because of the uncertainty of the route alignment and the timing for its construction, the impact of this Grand Parkway segment on corridor development is uncertain.
RW-4. Kilgore Parkway: This proposed parkway is located south of IH-10 approximately 3 miles south of Old Needlepoint Road. It will extend from FM 3180 westward to SH 146 [Lippke, 2013]. Currently only conceptually designed, the project includes approximately 1300 acres of roadway and off-site drainage areas with mitigation to be provided by a regional detention basin of approximately 65 acres.
RW-5. Langston Road Extension: Located near IH-10 in Mont Belvieu, this is a proposed extension of Langston Road from McLeod Park eastward across the Cedar Point Lateral (a canal), the future Grand Parkway alignment, and Hackberry Gully to a location north of IH-10 near the intersection of Eagle Drive (FM 3360) and Lakes of Champions Boulevard [Klotz, 2011b].
4.4 Facilities
Data pertaining to facilities significant to drainage planning were gathered as follows.
4.4.1 Inventory of Bridges, Major Culverts and Siphons
Primary drainage infrastructure other than conveyances (e.g., channels, ditches) themselves, important to primary drainage planning were bridges, major culverts (bridge class, which are culverts usually spanning approximately more than 21 ft), and siphons. Modifications to bridges required for increased conveyance exhibit major construction complications and increase project costs. Siphons (for raw water transport) limit the design of crossing waterways and potentially significantly increase conveyance project costs.
Bridges that cross state and federal roadways are identified in TxDOT and federal databases [TxDOT, 2013; List of Highways, 2013]; these facilities are located in Exhibit 4-4. Appendix A provides an inventory of these bridges and key information about them.
Other bridges that cross county or municipal roadways discovered by review of aerial photographs, engineering drawings and reports, and miscellaneous data sources are also listed in Appendix A.
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Many stormwater conveyance systems in the WSA cross elevated raw-water canals that are operated by CWS. Siphons are commonly used to convey the canal water under the storm water conveyance. Locations of siphons in the WSA [CSA, 2013] are shown Exhibit 4-4.
4.4.2 Inventory of Critical Facilities
Critical structures are defined as facilities (often government-owned) that serve the public (e.g., courthouses), provide for the safety of citizens (e.g., fire and police stations), and promote the health and welfare of the community (e.g., hospitals). Flood damage to critical facilities can result in physical damage (possible injury or loss of life) and/or disruption in the facilities intended function. Table 4-2 is a general listing of types of such facilities based upon guidelines of the Association of State Floodplain Managers [ASFPM, 2011]. Exhibit 4-5 shows the locations of critical facilities located in the WSA.
4.5 Sources of Drainage and Flooding Problems
Existing problems are defined as drainage or flood-related conditions (or evidence of such conditions) that present significant adverse drainage conditions or significant potential for adverse drainage conditions on a regional or sub-regional (i.e., drainage area or larger) basis.
4.5.1 Repetitive Losses
Information on repetitive losses to residential structures experiencing flooding damages were reported to FEMA and were provided by Chambers County. The data cover only the last 10 years. Losses are classified as either repetitive losses (RL) or severe repetitive losses (SRL) to residential structures. As defined by FEMA [FEMA, 2008], a RL is a flood-induced loss to a National Flood Insurance Program (NFIP)-insured residential structure that has had at least two claim payments of more than $1,000 each in any 10-year period since 1978. A SRL is a flood- induced loss to a NFIP-insured structure and property which, in a 10-year period since 1978, has had 4 or more separate claim payments of more than $5,000 each or 2 or more separate claim payments where the total of the payments exceeds the current value of the structure and property.
In essence, incurring more than one flood loss to a residential structure creates a repetitive loss while incurring 4 or more moderate (or 2 or more major) repetitive losses in the last 10-years creates a severe repetitive loss.
The repetitive loss data were used to develop a repetitive loss density map that provides a general overview of where repetitive losses are concentrated; see Exhibit 4-6. This map, developed using GIS methods, depicts the density of losses by summing the number of losses per unit of area
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within a circle defined by a particular radius. As the number of losses within the defined radius increase, the loss density increases; as the radius of density computation increases, the density decreases. The radius corresponding to an area of 0.75 sq-mi was used in developing Exhibit 4-6.
The density map of Exhibit 4-6 shows the following relatively high but isolated loss density areas; improved drainage should be considered for these high loss density areas.
Along Smith Gully in Mont Belvieu
Along Cedar Bayou in Baytown
In the vicinity of the City of Cove
In some coastal areas in Beach City
Repetitive losses in these areas result from two possible sources: 1) Tidal surge and associated wave effects; and 2) riverine flooding.
4.5.2 Excessive Ponding
Naturally occurring (i.e., not constructed by man) and topographically low areas without natural drainage create ponding conditions. If this ponding is located near structures (residences, critical facilities or roadways etc.), localized flooding during more severe storm events has the potential for damaging structures or causing other flooding impacts.
Potential areas of significant natural ponding can be approximately identified by creating a ponding map using LiDAR-based elevations. The raw LiDAR map shows ponding for very shallow to very deep ponding areas; ponding was also identified for both natural ponding areas (areas of unaltered land conditions) and intentional anthropogenic ponds (e.g. detention ponds). Only natural areas of ponding were of interest for drainage. Visual review of the ponding areas was used to separate natural ponding areas from anthropogenic ponding areas. Man-made ponds attribute relative straight line boundaries.
Areas of potentially significant natural ponding were considered if ponding depths exceeded more than 0.5 ft.; these are identified in Exhibit 4-7. Areas of natural ponding with maximum depths greater than 0.5 ft are labeled in the exhibit.
Natural ponding areas do not necessarily pose significant concern if no structures exist near a ponding area. Future development, on the other hand, would typically address ponding concerns as part of development design. Ponding areas of significant concern may be filled, provided drainage relief, or preserved for environmental purposes; all of which reduces the flooding
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concern. Other ponding areas are, or have the potential to be, a source of significant localized flooding.
4.5.3 Local Street and Property Flooding
Stormwater accumulations in streets and at shallow depths on adjacent properties cause inconveniences and pose the possibility for damage to structures and structure contents. Citizen complaints about local street and property flooding often translate into a need for drainage infrastructure projects. This could involve the upgrade of secondary drainage systems, upgrade of a watercourse for capacity, construction of a detention facility, or upgrade of bridge and culvert system capacity.
On the other hand, local street flooding may not actually pose significant drainage hazards because streets and roadside ditches are often used as intended pathways for drainage of storm waters. Only when the ponding depth typically exceeds a roadway crown or curb level does ponding pose a significant flooding problem.
Common causes of significant depths of street ponding include the following:
Inadequate capacity of roadside ditches and small drainage ditches in developed areas
Inadequate capacity of subsurface storm sewers and storm sewer systems
Inadequate capacity of storm water inlets to subsurface storm water conveyances
Temporary blockage of inlet and conveyances due to trash or debris accumulations
Drainage system maintenance insufficient to prevent trash, debris or sediment accumulations
High tailwaters at drainage system outfalls that inhibit drainage from getting to receiving waters.
4.5.4 Coastal Flooding
Near-coastal areas may be subject to flooding during storm conditions. Severe storms can result from a combined effect of tidal surge and associated wave action and on-shore rainfall events. Flooding along shores near more downstream portions of Cedar Bayou and all of Beach City are areas subject to tidal surge [FEMA, 2013a, 2013b, 2013c]. Some of the repetitive losses in Beach City and the more downstream reaches of Cedar Bayou are likely the result of tidal surge.
FEMA FIRMs for coastal flooding represent the combined effects of tidal surge and riverine flooding that together have a 100-yr frequency [FEMA, 2013a, 2013b, 2013c]. Flood level
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predictions for such coastal storms are not specifically addressed in the CCMDP since the 100-yr modeled storm duration accounts for both on-shore and offshore storm events.
Depending upon floor slab elevations in affected areas, such flooding may or may not pose a problem for coastal structures. Flood protection in coastal areas using flood proofing is often the major protection method [FEMA, 2013a], such as 1) waterproofing of walls, 2) use of watertight walls and doors; 3) temporary berms, dikes, and levees to isolate and protect structures; 4) construction of the habitable (upper) levels of structures above flood levels; and 5) improving drainage structures to speed post-storm runoff for flood protection.
Hurricane surge levels have also been estimated by the USACE [2009] using the Sea, Land, and Overland Surge from Hurricane (SLOSH) computer model. Exhibit 4-8 shows computed surge levels estimated from this model. Note that even Category 1 hurricanes can cause significant inundation in southern portions of the WSA.
4.5.5 Riverine Flooding
Riverine flooding occurs when water levels rise above the top of banks in a watercourse and move into adjacent floodplains.
Structures located in or near floodplains are at risk of flooding, the risk becoming greater the closer a structure is to the flooding watercourse. Structures not actually in a FEMA delineated floodplain (e.g., not in a 100-yr floodplain) but merely close to a floodplain or along a watercourse with identified floodplains are also at risk because:
The tributary may have significant riverine flooding even though floodplains have not been delineated. Some streams have never been studied by FEMA, and FEMA floodplain delineation stops at upstream points where the tributary drainage area is less than 1 sq-mi.
Backwater effects from a downstream watercourse can inhibit drainage in an upstream watercourse and cause upstream flooding.
4.5.5.1 Common Causes of Riverine Flooding
Because increases to residential development-produced imperviousness are often addressed by on-site mitigation, the flooding arising from residential development is commonly associated with secondary drainage deficiencies (often including inadequate sheet flow areas) or the location of the development (or some structures in the development) in or near ponding areas or floodplains. Local street flooding (Section 4.5.3 above) is often mistaken for riverine flooding. Local street flooding arises because of inadequate (in some form) storm sewer system drainage. Riverine Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 4 - 11
flooding arises essentially because of insufficient capacity of drainage conveyances (channels, ditches, etc.). Such insufficiency occurs because of one or more of the following:
Heavy rainfall with consequent heavy runoff
Insufficient size of a drainage channel to handle the heavy runoff
Channel blockage or impediments to flow because of low capacity hydraulic structures (e.g., undersized culverts, debris, etc.)
High tailwaters (e.g., coastal tide levels) which prevent, slow or impede drainage along a watercourse
Riverine flooding concerns in C&I development arises because of several factors:
Increased imperviousness and consequent increases in runoff: Such increases are usually deleterious unless mitigated.
Modification of drainage paths and outfall locations: Such modification may or may not be beneficial to drainage conditions beyond the development boundaries; modifications can either reduce the flow in a channel or speed high flows to downstream points of concern.
Fill of low-lying areas, including floodplain and habitat areas: Loss of natural storage by fill can increase flood levels unless carefully mitigated. Loss of ponding along watercourses results in larger flows downstream.
C&I development is among the greatest drainage concerns for the county because:
Size: Because of the common size of such development; large areas are affected
Diversity of Impacts: Impacts are diverse and potentially severe
Extensive Mitigation: Necessary mitigation is often extensive
Need for Public Response: To avoid significant adverse drainage impacts beyond the development site, adequate drainage capacity is often required in public right-of-way (ROW).
Rapidity: C&I development is occurring at a very rapid pace in the WSA.
Importance to Economic Development: C&I development is fast becoming a backbone of county prosperity. A variety of C&I development sites as well as major roadway improvements are undergoing construction or being considered for development in the WSA.
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4.5.5.2 Flooding Problem Areas
Flooding is evidenced by reports, including report repetitive loss reports, citizen reports and reports and observations from prior studies. Conditions conducive to riverine flooding problems and local ponding are discussed above. Based upon review of collected information for the WSA, potential flooding problem areas are identified in Exhibit 4-7.
4.5.5.3 Types of Infrastructure Remedies for Riverine Flooding
Infrastructure-based measures to reduce riverine flooding or its impact include the following:
Reduction of runoff by modification of overland flow behavior before it enters a watercourse. Creation of intentional overland flow areas (by removal of flow blocking structures) and use of swales to direct runoff to low impact areas is a common technique for management of overland flow.
Use of localized onsite detention to capture, reduce, or slow the rate of storm water runoff
Use of regional detention to reduce runoff rates to points downstream of the detention facility
Increase in capacity of riverine watercourses
Reduction in riverine tailwater levels to increase the capacity of the riverine watercourse
Diversion of a portion of flood flows to another existing or new waterway
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5. MODELING METHODOLOGY
5.1 Purpose of This Section
Hydrologic and hydraulic modeling is the primary tool for quantifying drainage conditions and needs. In this Study, “modeling” means simulation of hydrologic and/or hydraulic behavior using digital software. The primary software modeling tools used for CCMDP development were 1) the HEC-HMS, version 3.5, hydrologic model; and 2) the HEC-RAS, version 4.1.0, hydraulic model.
Previously developed HMS and RAS models and model information were used when possible and appropriate. Modifications to previous models or model data were made to remove identified errors; update model conditions; expand model extent and coverage; or provide consistency with other models, updated stream geometry, drainage area delineation or other applicable information. If necessary, new models were constructed.
HMS hydrologic models were used to predict existing and future discharges for all drainage areas for various storm frequencies. On the other hand, RAS hydraulic models were used only for drainage areas for which drainage improvements were considered necessary. Table 5-1 summarizes the models used while Exhibit 5-1 shows where HMS and RAS models were applied. Compact disks (CD) attached to this report provides electronic copies of the models used.
This Section summarizes procedures, parameters, calculations and related information using HMS and RAS models. Reference to Appendix D should be made for additional details.
5.2 Modeling Timeframes
The procedures for describing the hydrology and hydraulics for different points in time (i.e., current or future) were the same for all conditions; only input parameters (discussed below) and the resulting outputs from the models changed.
5.2.1 Existing and Revised Existing Condition Models
Existing models describe existing or revised existing conditions. When a new existing condition model was constructed (because no previous model existed), data were developed from existing information. For hydraulic models requiring new model geometry, elevation data were commonly LiDAR-based.
If a previously developed model was modified to more accurately represent conditions at the current time, the revised model, after revision, was for convenience termed the existing condition
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(referenced in tables as the “ext” condition) model for this Study. The original model which may have been revised to create the “existing condition” model was termed the “source model”.
5.2.2 Future Condition Models
A future condition (referenced as “fut” in tables) model incorporates conditions anticipated to occur in the future when conditions reach their ultimate level of development. A future condition model was created from the existing condition model by the following types of changes:
Imperviousness Change: Change in imperviousness in the drainage area or areas to which the future condition model applied.
Minor Drainage Improvements: Changes arising from anticipated 1) minor channel modifications involving minor realignment and smoothing, 2) inclusion of specific developments affecting runoff amounts (when available information indicated the development runoff would differ in major effect from that estimated for the future level of imperviousness of the drainage area in question; and 3) changes in general miscellaneous detention development throughout a drainage area.
Changes were incorporated by modification of the various parameters used in the hydrologic modeling of a drainage channel.
In addition to the future condition model incorporating the above two types of changes, the future condition models were modified to account for proposed major channel conveyance improvements.
Major conveyance improvements are changes arising from deepening and widening of a channel reach along much of its length in order to significantly increase channel capacity. These conveyance improvements formed an option (“Standard Option 1”; see Section 7) for significant channel capacity improvement. The hydrologic conditions (i.e., the future peak flows) determined for “minor drainage improvement” along a channel for the major conveyance remained the same while the hydraulic parameters (e.g., channel size, roughness, and slope) were modified to reflect channel modifications for the improvement.
5.3 Input Parameters for HMS Models
Previously developed information was used if possible to construct an HMS model for a particular watershed. If discharge information or reliable parameters were not available from prior studies, calculation of discharge and parameters needed to execute the RAS and HMS were determined as follows: Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 5 - 2
5.3.1 General Drainage Topology and Drainage Areas
The topology (i.e., connectivity of drainage areas and streams) of the HMS models was based on prior hydrologic studies and the delineation of drainage areas done for this Study. The general topology defines the drainage areas used for modeling. Drainage areas are shown in Exhibit 2-3 N&S. Drainage areas were organized according to five general watersheds: Cedar Bayou, Cotton Bayou and Hackberry Gully, Cherry Point Gully, Old River Ditch, and Beach City and Nearby Environs (the last referred to simply as Beach City).
5.3.2 Drainage Topology with Development Projects
Numerous C&I and residential developments are expected to be developed in the WSA. New residential developments will commonly have internal secondary drainage systems that will feed into primary drainage systems. The residential developments will often have on-site mitigation and the consequent impact of residential drainage on primary drainage will be absent or limited. Some residential developments may make use of regional detention; and in some instances, potential regional detention sites for residential development may be identified.
C&I developments, while certainly having some internal secondary drainage systems, have a major impact on primary drainage because of their location and the volume of runoff they can produce. Some C&I developments have developed to the point that their major drainage features can be broadly described and, in particular, 1) their future outfall points to the existing drainage system can be approximately located, and 2) their impact on future drainage can be estimated. In some instances, the impacts may be mitigated within the development boundaries so that the future runoff conditions are no greater (at least approximately) than the existing runoff.
5.3.3 Rainfall for Hydrologic Modeling
Total rainfall for 10-and 100-yr storm events were used to construct a frequency-based 24-hour rainfall event with the peak rainfall occurring at 67% of the total 24-hour rainfall event for all areas in the WSA (see Appendix D).
5.3.4 Soil Moisture and Rainfall Excess
Rainfall losses (i.e., the rainfall that does not runoff) during a storm event are due to depression storage, interception, and infiltration, factors that depend upon soil type, vegetation, topography and imperviousness. Values [HCFCD, 2009] for interception and depression storage in the HCFCD HMS model for Cedar Bayou were used for all CCMDP models because topography, soil, and vegetative conditions in the WSA are similar to those of the Cedar Bayou watershed. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 5 - 3
These values included parameters for the Green-Ampt (abbreviated as Gr-Amp tables) equation for describing infiltration and soil type for estimating initial losses, wetting front suction, and hydraulic conductivity. Soil moisture parameters are discussed in Appendix D. Table 5-2 summarizes the soil infiltration parameters used for all HMS modeling.
5.4 Runoff Discharge for Hydrologic Modeling
Two types of discharge were recognized in the HMS modeling: Runoff from a drainage area and flow down a channel that has received runoff from one or more individual drainage areas.
5.4.1 Drainage Area Runoff
Rainfall excess was transformed into runoff by HEC-HMS software using the Clark unit hydrograph method in conjunction with the Tc & R method. Clark’s method uses the time distribution and amount of excess rainfall to determine the runoff from a drainage area using unit hydrograph concepts. The Tc & R method is an HCFCD recommended method [HCFCD, 2004] that provides an empirical estimate of the time of concentration Tc and the storage factor R to define the shape and magnitude of the unit hydrograph [HCFCD, 2009; Brazoria County, 2003].
Tc and R were computed in the same manner as they are in the method prescribed by HCFCD [2009] with the exception that the percent development is expressed in terms of percent impervious using the relationship defined by Figure 4-1. This computation of R is different than prescribed in the CCDCM [Dodson and Associates, 2005]. Based upon discussion with the authors of the CCDCM [Dodson and Associates, 2005], the CCDCM uses an approximate method that assumes the ratio of R to Tc is a constant (i.e., 3). For consistency with prior studies and more accuracy, the CCMDP uses the HCFCD method for estimation of R [HCFCD, 2009]. Details of the Tc & R method are provided in Appendix D.
New values of Tc&R were calculated when no prior estimates (from previously developed models) of Tc or R were available or the previously developed values were considered unreliable. Table 7-4 summarizes the calculation of Tc and R for the various drainage areas in the WSA.
5.4.2 Flood Routing Down a Channel
Flood routing along a channel used in a source model was retained for the existing and proposed models, with possible modifications to reflect change in channel length (with storage assumed to be proportional to channel length). Routing models in the source HMS model generally existed for main stem channel in various watersheds. These existing routing models used either the
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Modified Puls Method or the Muskingum-Cunge model (the majority used the Modified Puls Method).
Other routing channels used a lag method, with the lag time approximated by the time of concentration for the drainage area in which the channel occurred. Note that some sources (specifically for the SCS method) recommend a lag time of 60% of the time of concentration as measured from the centroid of the rainfall excess [Maidment, 1992, Sec. 9.4.2]. Since the time of the centroid of rainfall excess (as measured from the beginning of a storm) is more than the lag time identified for the SCS method and, as well, flow velocities in Chamber County watercourses are quite slow (due to flat slopes), the lag time is merely set equal to the time of concentration for the drainage area in which the channel of interest occurs.
5.5 Types of Mitigation and Flood Control Storage
Detention storage is used for two purposes: 1) the capture of flood runoff to reduce flows to downstream reaches, and 2) the capture of flow to avoid downstream flow increases resulting from channel improvements at upstream points.
Detention storage can be accomplished by different means, including
Offline detention diverts a portion of the flow in a stream to a storage facility (usually a pond) for temporary storage and then subsequent return to the stream. Offline storage works well for large storage volumes along larger watercourses where complete diversion of watercourse flow is impractical and often unnecessary.
In-line detention captures all the flow in a stream and passes it through a storage pond with temporary storage before discharge to downstream waters. In-line storage is commonly used for mitigation of increases in runoff from new or upgraded smaller developments for which increases in runoff are limited, and for which the storage volume is not large. In-line storage can be used where significant amounts of land are available for construction of a storage pond.
Conveyance storage over-sizes a channel or underground conduit so that extra volume in the conveyance not needed for actual conveyance can (at least conceptually) serve as a storage device. Conveyance storage usually requires more volume than in-line or offline storage with a pond to achieve the same mitigating effect as a detention pond. The advantage of conveyance storage is the smaller land area needed to provide the storage.
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For the CCMDP, availability of land is not expected to generally be a limiting factor in development of mitigation storage since the WSA has considerable open area. Consequently, only detention storage is evaluated as a potential mitigation option. Use of a conveyance storage option can be assessed in engineering studies for particular projects.
5.6 Hydrologic Determination of Storage for Mitigation and Flood Control
Two options are available for storage sizing: Offline storage and online storage.
5.6.1 Off-line Detention
In an offline storage system, some of the flow in a watercourse is greater than desired, so some of the flow is diverted to an offline storage system to prevent the maximum discharge downstream of the diversion point from exceeding a design discharge Qd. Qd is also the flow at which diversion from the watercourse to the storage device approximately begins. If the hydrographs are approximated as triangular in shape (as illustrated in Figure 5-1 below), then, as shown in detail in Appendix D, the design storage volume for offline storage is given by
2 Soffline storage = V1 [1-(Qd/Qp1)] (5-1)
in which V1 is the volume of runoff, Qd is the design (peak) discharge after mitigation, and Qp1 is the peak discharge before mitigation.
Experience shows that inefficiencies in diversion structures require that an approximately 20% increase in theoretical storage capacity is needed to achieve the target flow Qd. In addition, if a 10% safety factor is incorporated in the design (because of the planning nature of the estimate as
used in the CCMDP), the design storage Sd is given by
Sd = 1.3 Soffline storage (5-2)
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This additional 30% storage is shown schematically in Figure 5-1 below.
Off-line Storage (practical) Off-line Storage (theoretical)
Discharge q QP1
On-line Storage
QP2
Time T
Tp1
Tp2
Ti Tb1 Tb2
Figure 5-1. Definition Sketch for Off-line and On-line Storage
5.6.2 On-line Detention
Two options for planning purposes are available for estimating on-line detention.
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5.6.2.1 Calculation of On-line Storage
In this method the reduction of peak discharge has a target discharge Qd = Qp2 and an existing discharge before mitigation, Qp1, just as in offline storage determination. The storage volume is given by (see Appendix D):
Sin-line = V1 [1 –(Qd/Qp1)] (5-3)
Including a 10% safety factor yields
Sd = 1.1 Sin-line (5-4)
5.6.2.2 Detention Rate Method
If the details of the detention are not needed, a detention rate method can be used. This method could be used for estimating volumes for on-site detention for individual development sites (particularly for smaller sites, about 200 ac or less) when the peak discharge from the development site is not of particular interest because it is assumed that sufficient on-site detention will be provided to mitigate runoff impacts from the development. In this situation, the peak discharge from the developed site could be approximated as the peak discharge before the development (assuming no mitigation in excess of that actually needed is used).
5.6.2.3 Detention Mitigation Rates
This method can be used for small drainage areas characteristic of residential subdivisions. To apply the detention rate method, a typical detention rate (in ac-ft of storage/ac of site) is used. Information about actual mitigation rates used for C&I development in the Study Area was taken from commercial and industrial developments previously described and a limited number of residential developments [Carnes Engineering, 2005; 2011; Carroll & Blackman, 2005; Pate, 2006, 2007; GC Engineering, 2008; Jones and Carter, 2008; Dodson, 2009]. While there is considerable variability in the data, an average rate of 0.40 ac-ft/ac for C&I development and 0.46 ac-ft/ft for residential development reasonably represent recommended HCFCD detention rates [HCFCD, 2009] (see Appendix H for details). A conservative level of 0.50 ac-ft/ac is used when applying this method. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 5 - 8
5.7 Applying Storage Sizing Equations
Equations for in-line and offline storage sizing were used in the following ways. The storage computation is applied individually to each drainage area or conveyance channel.
5.7.1 Mitigation to Reduce Increased Runoff Due to Development
This mitigation reduces increased runoff from increased imperviousness or similar effects associated with development: This mitigation assumes the design flow (Qd in equations 5.2 and 5.4) and runoff volume are based upon the conditions prior to the development while Qp1 is the discharge after the development (and the discharge which is to be reduced). Flows of the same frequency are used. The detention rate method can be also used to size the mitigation storage for this type of mitigation evaluation. The resulting mitigation storage will be that necessary to prevent downstream increases in future peak flows; the calculated storage will not reduce downstream flooding if the downstream areas are flooding before the increase in development.
5.7.2 Reduction of Large Flood Flows
Capture of large flood flow due to high runoff conditions occurring for existing conditions or future conditions and resulting from a variety of conditions (such as large areas or steep slopes) causing high runoff amounts from drainage areas. Flows are mitigated to reduce downstream flow delivery to an area or watercourse of concern. Captured flows may be temporarily stored or diverted to another location.
Qp1 in equations 5.2 and 5.4 is the discharge that is currently occurring and causing the flooding. The runoff for this flood level is V1. The discharge Qd is the peak discharge to which discharge is to be reduced because of the storage. The peak discharge Qd is determined by the maximum flood discharge to be allowed in the channel; the frequency Qd will typically be different than the frequency of Qp1.
5.7.3 Mitigation of Increased Conveyance
Mitigation of increased conveyance (created by future condition drainage modifications) along a watercourse can cause increases to flood levels upstream of the conveyance-improved section of the watercourse. Increased conveyance can result from channel modification (e.g., channel widening) or changes in channel energy losses (e.g., widening bridge openings).
This mitigation assumes the design flow (Qd in equations 5.2 and 5.4) and runoff volume are based upon the conditions prior to the conveyance improvement while Qp1 is the discharge after the improvement. Flows of the same frequency are used to size the mitigation storage. The Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 5 - 9
resulting mitigation storage will be that necessary to prevent downstream increases in flow levels but will not lower levels to less than those existing prior to conveyance improvement.
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6. FRAMEWORK FOR DEVELOPING DRAINAGE REMEDIES
6.1 Purpose
The constraints of individual projects are dictated by the nature of the drainage problem to be remedied and requirements on potential remedies. This Section addresses the application of previously described methods to particular problems.
6.2 Design Criteria
Drainage problem remedies are based upon several key criteria:
6.2.1 Capacity-Based Design
The capacity of a channel is determined by the peak discharge that will not cause floodwaters to rise above the top-of-bank (or top of bank minus some specified freeboard) of the watercourse.
6.2.2 Design Frequencies
Capacity can be defined in terms of peak discharge or in terms of the storm event frequency (e.g., 100-yr capacity) corresponding to the peak discharge magnitude. Design storm frequencies used for modeling in the CCMDP are the 10-yr and 100-yr storm frequencies. For preliminary design, more refined frequencies would require evaluation using the criteria of Table 6-1.
6.2.3 Design Criteria and Requirements for Modeling
Both the CCPID Standards and the CCDCM specify various design characteristics or criteria for drainage facilities that are particularly pertinent to the development of this CCMDP:
6.2.3.1 Chambers County Public Infrastructure Design (CCPID) Standards
General Procedures: The CCPID standards apply to all facilities that are to be dedicated to the county or maintained by the county.
Definition of Public Storm Sewers: Public storm sewers are sewers that provide drainage for a public ROW or more than one private tract, and which are located in public ROW or easement.
Overland Flow: Overland flow paths to drainage ways should be sized for the 100-year flow.
6.2.3.2 Chambers County Drainage Criteria Manual (CCDCM) Impact Criteria
CCDCM criteria of interest are the following:
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Zero Impact: Drainage changes should have no impact, i.e., no rise in upstream water levels and no increase in peak discharges to downstream watercourses. Any adverse impacts must be mitigated.
Level of Service (Flood Protection Level): “Neither increases in upstream flood levels nor in downstream flow rates are allowed in areas where there is the potential for flooding damages from storms with recurrence intervals of 100 years of less” [CCDCM, pg. 1-1].
Floodplain Storage: Decreases in 100-yr flood storage are prohibited.
6.2.3.3 Chambers County Drainage Criteria Manual Physical Criteria
Channel Slope Protection: Grass is recommended for earthen side slope protection.
Concrete: Reinforced concrete may be used for small areas of channel slope protection. The steepest concrete side slope is 1.5 to 1:0 (H:V).
Maximum Allowable Velocities in Open Channels: For the soils of WSA, maximum channel velocities are listed in Table 6-3.
6.2.3.4 Chambers County Drainage Criteria Manual Hydraulic Criteria
For hydraulic evaluation and modeling, the information of Table 6-3 (based upon information in the CCMDP) was used to estimate channel roughness. However, when a roughness developed in prior studies had a reasonable value, even if it did not match the information in Table 6-5, the prior-model value was not changed for the modeling of this Study.
Coincident flooding conditions were neglected. Tailwater levels were based upon previously developed conditions (as given in RAS model data) or hydraulically normal depth conditions.
6.3 Environmental and Preservation Issues
The presence of environmentally sensitive areas will usually mandate that environmental evaluation of a potential project be done as part of preliminary engineering design to assess potential environmental impacts and identify ways to avoid or minimize such impacts. Addressing environmental concerns are typically driven by 1) permitting of a specific project, 2) mitigation of project impacts, and 3) compliance to permit conditions and associated regulations.
6.3.1 Site Specific Permitting
Potential environmental issues to be addressed in project development may include:
1. Wetland classification and delineation
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2. Section 404 permitting
3. Section 10 permitting
4. Historic property and archeological review
5. Threatened and endangered species and critical habitat
6. Essential fish habitat coordination
7. Adjacency to other regulated areas
8. Texas General Land Office lease review
9. Assessment for compensatory stream mitigation
10. Water Quality Certification by the TCEQ
The first four of the above list are commonly of concern in infrastructure development for flood control; these are briefly described below.
6.3.2 Wetland Determination and Impact Mitigation
Under a 1990 Memorandum of Agreement between the USACE and the EPA, USACE has primary responsibility for administering wetland classification and impact mitigation arising from the Clean Water Act (CWA) Section 404. Mitigation, when necessary, consists of a three step prioritized process accomplished in the following order [CFR, 2011a]:
Avoidance: Adverse impacts to aquatic resources are to be avoided and no discharge to such sources shall be permitted if there is a practicable alternative with less adverse impact.
Minimization: When impacts are unavoidable, steps to minimize these impacts must be taken.
Compensation: Compensatory mitigation is required for any unavoidable adverse impacts that remain after application of avoidance and minimization options are maximized [CFR 2011b]. Methods of compensatory mitigation include 1) restoration of a previously existing wetland or other aquatic site, 2) establishment of a new aquatic site, 3) enhancement of an existing aquatic site’s function and 4) protection of an existing aquatic site.
6.3.3 Section 404 Permit for Fill or Excavation
An environmental review is required for projects involving excavation or fills occurring in wetland boundaries or other “waters of the US”; therefore, becoming subject to the federal jurisdiction. If a proposed project is subject to federal jurisdiction or will result in a net loss of waters of the US, USACE permit is required [Horizon, 2011]. There are three types of permits: Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 6 - 3
General Permit: Which are used to permit activities causing only minimal individual and cumulative environmental impacts. These activities may qualify for either a nationwide or a regional General Permits (GPs). There are currently 47 Nationwide General Permits (NWP) with 28 general conditions addressing Section 404 and Section 10 activities [USACE, 2011].
Individual Permit Which involve the evaluation of project specific applications involving: pre-application consultation, public notice and comment period on the permit application, and agency evaluation of the permit applications. If the proposed project is found to be in the public interest and meets the requirements of the Section 404(b)(1) Guidelines and other legal requirements [USACE, 2010], a permit can be issued
Letters of Permission (LOP): Which is an alternative procedure for evaluating individual permit applications through an abbreviated process that includes coordination with governmental fish and wildlife agencies and a public interest evaluation [CFR, 2011c].
6.3.4 Section 10 of the Rivers and Harbors Act of 1899
Section 10 permits cover any activity that would place a structure below, within, or over navigable waters of the United States, including activities that would involve the excavation, dredging or deposition of material into navigable waters of the U.S. or any work altering the course, location or condition or obstructing these waters [TxDOT, 2004].
6.3.5 Threatened or Endangered Species
Section 7 of the Endangered Species Act (ESA) of 1973 requires federal agencies to ensure any action authorized, funded, or carried out by them is not likely to jeopardize the continued existence of listed species or modify their critical habitat.
6.3.6 Historical Preservation
Proposed projects must be reviewed by the State (of Texas) Historical Preservation Office (SHPO) to determine if the State has any objections to the project because of known historical sites in the project area. Notice must be given to the SHPO prior to project construction.
6.3.7 Archeological Review
Proposed projects must be reviewed by the Archeology Division of the Texas Historical Commission for the purpose of protecting and preserving Texas archeological sites and artifacts. Notice must be given to the Archeology Division prior to project construction.
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6.3.8 Other Environmental Regulation Constraints
Each project has potentially unique features that may require certain regulatory review and/or approval beyond those commonly required and described above. A qualified environmental specialist should be consulted to address potentially unusually environmental concerns.
6.3.9 Cost of Environmental Review and Permitting
Typical project costs for environmental review and permitting are discussed in Section 7.
6.4 Hydrologic (HMS) Models
Hydrologic models were used to determine flows at various points along a watercourse for the following:
Providing flow inputs for RAS modeling, which in turn was used to estimate channel capacities and size channels to achieve design capacities.
Provide information for sizing a detention pond to 1) mitigate increased runoff due to development, 2) reduce flood flows to downstream points, or mitigate impacts of increased channel conveyance (see discussion of Section 5.7).
Evaluate the potential benefits of possible diversion options.
The following summarizes the various HMS models used for the above purposes. Models are organized under major watershed groups. All models used the rainfall, infiltration and runoff parameters discussed in Section 5. Only features unique to individual models are discussed below.
6.4.1 Cedar Bayou Watershed
The source for the Cedar Bayou existing condition HMS model was the latest regulatory-accepted (January 2013) watershed model for Cedar Bayou available from HCFCD (The source model was downloaded from the HCFCD website). This watershed model addresses runoff from the upper reaches of Cedar Bayou lying in Liberty County, tributaries on the west side of Cedar Bayou (these lie in Harris County), and tributaries on the east side of Cedar Bayou (some of which originate in Liberty County). The tributaries provide inputs to Cedar Bayou and flows only along the Cedar Bayou main stem and at the downstream confluence of the tributaries with Cedar Bayou.
Most of the hydrologic parameters for the Cedar Bayou HMS model were retained from the source model to construct the existing condition HMS model. Flow along the main stem of Cedar Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 6 - 5
Bayou was not of interest for potential changes; only key tributaries from the east side of Cedar Bayou were of interest for the CCMDP. Of special concern are the following key tributaries:
6.4.1.1 Hickory Island Gully
This tributary lies along the northern county line boundary between Chambers County and Liberty County; the majority of the drainage area lies in Chambers County. In evaluating impervious cover in this drainage area, only those portions of the drainage area in Chambers County were modified to reflect anticipated growth. Growth within Chambers County was assumed to be described by the land-use estimates made for future conditions in the county.
6.4.1.2 Smith Gully
The source model for the Smith Gully tributary did not account for the full drainage area discharging to Cedar Bayou. The HMS model for Smith Gully used for development of the Mont Belvieu Master Drainage Plan was put into the Cedar Creek model, replacing the Smith Gully model in the Cedar Bayou source model.
6.4.1.3 Horsepen Gully
For future conditions, it is anticipated that the Kilgore Parkway Development and areas east of the development but west of SH 99 will be fully constructed. Based upon current available information [Combs, 2013; Lippke, 2013a, 2013b], extensive regional detention is to be used to avoid runoff impacts from the Kilgore Parkway Development and areas draining directly to the development. The western boundary for these developments is approximately the UPRR railroad and SH 146 about 1 mile upstream of the Cedar Bayou and Horsepen Gully confluence. Consequently, for future conditions, the Horsepen drainage area was subdivided into two zones: the area upstream of the UPRR tracks and downstream of the UPRR tracks. Different options were considered that recognized this division; the options are described in Section 7.
6.4.1.4 Sawpit Gully
The source model for the Sawpit Gully was the HCFCD Cedar Bayou model. The existing and future conditions models were based upon information in the source model with estimated existing and projected land-use. The drainage areas were revised to account for the hydraulic boundary imposed by SH 99.
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6.4.1.5 Sutton Gully
The source model for Sutton Gully was the HCFCD Cedar Bayou model. The existing and future conditions models incorporated estimated existing and projected land-use. The drainage area was revised to account for the hydraulic boundary imposed by SH 99.
6.4.1.6 Ijams Gully and Water Oak Gully
The source model for these two drainage areas was the HCFCD Cedar Bayou model. The source model has a single drainage area lying on both the east and west side of Cedar Bayou describing flow from these two gullies. To better describe potential development impacts, this total area was subdivided into three individual drainage areas: Ijams Gully east of Cedar Bayou, Water Oak Gully east of Cedar Bayou, and the remaining residual area west of Cedar Bayou. The confluence of the residual area on the west, Ijams Gully, and Water Oak Gully were approximated as occurring at the same point as that in the source model.
Drainage area delineations were revised and new hydrologic parameters were computed. The existing and future condition models incorporated estimated existing and projected land-use.
6.4.2 Cotton Bayou and Hackberry Gully
North of IH-10, Cotton Bayou and Hackberry Gully are two separate watercourses. South of IH- 10, the two watercourses combine to form Cotton Bayou before discharging to Cotton Lake. Because of the Cotton Bayou and the Hackberry Gully confluence (particularly in the area where flooding problems are a recognized concern), Cotton Bayou and Hackberry Gully source models were combined into a single HMS model extending from the northern reaches of Mont Belvieu to the outfall at Cotton Lake.
The source models for the combined Cotton Bayou and Hackberry Gully came from the Mont Belvieu Master Drainage Plan and associated follow-on studies [Klotz, 2009a, 2010a, 2010b].
New residential development west of Hackberry Gully and Cotton Bayou (for Bayou Lexington Patio Homes and Townhomes, Section One and Future Sections Two & Three [Carroll & Blackman, Inc., 2005]) were incorporated in the Hackberry Gully and Cotton Bayou HMS watershed model to reflect the impact on drainage area configuration.
6.4.3 Beach City and Environs
The Beach City and Environs model evaluated flow along various tributaries discharging to Trinity Bay, Cotton Lake, and Dutton Lake. There was no source model for the existing condition model. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 6 - 7
Land-use projections for existing and future land-use were used to construct the model; drainage areas were determined as part of the drainage area delineation for CCMDP development.
The final HMS model is a collection of independent models combined for convenience. The existing and proposed condition models include sub-models for the following:
Direct Tributaries to Trinity Bay, including drainage gullies in Beach City draining to Trinity Bay or Dutton Lake. The location and the conditions of these tributaries are shown in Appendix C.
Tributaries to Cotton Lake, including not only Cotton Bayou but flow from tributaries to Hackberry Gully that receive drainage from the McAdams Ditch and portions of SH 99.
Spring Creek: A small watercourse discharging directly to the northwest portion of Cotton Lake and along which flooding problems have been reported.
Buck Gully: Only a small reach of the more upstream reaches of Buck Gully (in northeastern Chambers County) actually lies in Chambers County before discharge to Old River. Buck Gully was not modeled or evaluated for the CCMDP.
6.4.4 Cherry Point Bayou
The Cherry Point Bayou discharges to the Old River Ditch. The source model was the model developed for the Mont Belvieu Master Drainage Plan [Klotz, 2009a]. The existing condition model was the same as the source model except that estimated existing land-use was recognized in parameter development (estimated land-use in the source model was largely used) . The future condition model recognized projected future land.
6.4.5 Old River Ditch
The Old River Ditch HMS model incorporated the watercourse draining to Old River and the Trinity River. They serve the receiving water for Cherry Point Gully. The source model for the existing condition Old River Ditch model was developed by Klotz Associates for the Old River Ditch as part of the Mont Belvieu Master Drainage Plan [Klotz, 2009a].
Old River Ditch discharges to the Trinity River and Trinity Bay. Hydrologic parameters for watercourses discharging directly to the Old River, Lost River, Trinity Bay, or the Trinity River in the source model for the Old River Ditch. They were not modified or reevaluated for modification; existing information about such watercourses in the source model was used.
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Existing watercourses in the source model discharging to the Old River, the Lost River, and the Trinity River were not modified for the existing conditions.
6.4.6 Areas Outside Chambers County
The Cedar Bayou watershed extends northward, far into Liberty and Waller Counties. The Old River watershed likewise extends northward into Liberty County. Modifications to the drainage areas as described in the source model for these out-of-study area lands were not altered for use in the existing and future condition models for the WSA.
6.5 Hydraulic (RAS) Modeling
RAS models were used to determine channel capacities and size channels to achieve required capacities.
6.5.1 Channel Capacity
Within a particular river reach, the largest flow that does not rise above the top-of-bank defines the channel capacity. For the CCMDP, channel capacity was defined as 1) less than a 10-yr storm frequency, 2) greater than a 10-yr frequency but less than a 100-yr frequency, or 3) 100-yr or more frequency.
6.5.2 Channel Conveyance Improvement
Channel geometry modification was the primary means used to achieve channel capacity requirements. Channel modifications to improve conveyance was accomplished by widening and deepening the channel under consideration. Channel conveyance improvements maintained or increased existing channel width and maintained or increased existing channel slopes. The minimum flowline was constrained by the flow line to which the channel discharges. The minimum channel depth (including freeboard) was set at 3 ft.
If a maintenance berm of width “B” on each side of a modified channel with top width “W2” was to be provided, the necessary minimum ROW for the modified channel at each channel section location became:
ROW = 2*B +W2 (6-1)
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6.6 RAS Models
RAS modeling was applied to existing channels to identify channel improvements needed to provide drainage for existing and future conditions. New RAS modeling was not done for those watercourse reaches in Mont Belvieu. Mont Belvieu is generally following its previously developed master plan [Klotz, 2009a] and is currently performing preliminary engineering for design of improvements to Smith Gully, Cotton Bayou (north of IH-10) and Hackberry Gully (north of IH-10). Appendix K provides selected portions of the Mont Belvieu Master Drainage Plan for information on recommendations for improved drainage in Mont Belvieu.
6.6.1 Source Models for RAS Modeling
Previously conducted hydraulic modeling studies were collected and reviewed. Review of FEMA data on the FEMA website indicated that models for various streams in the WSA were originally developed in the 1980s and the 1990s, but often addressed only tidal-surge flooding. For much of the county, riverine models have not been developed.
More recent updated RAS models collected for this Study overtopped all the early riverine (i.e., non-coastal) HEC-2 models initially developed by FEMA. These are described below.
For watercourses for which RAS models had not been previous developed, new RAS models were created for watercourses for which design modifications were to be made. Modifications use an approximated trapezoidal channel shape for the new models.
The following describes key features of these RAS models. For convenience, models were organized by watersheds.
6.6.2 Cedar Bayou Watershed
HCFCD has models for Cedar Bayou and its tributaries on both the east and west sides of Cedar Bayou. Tributaries on the west side of Cedar Bayou (i.e., in Harris County) were not of concern to the development of this CCMDP.
As implemented for this CCMDP, the RAS models for the Cedar Bayou Watershed consist of a model for the Cedar Bayou main stem and major tributaries to the main stem. Only certain tributaries were of interest. Except for defining tailwater conditions, flows along the Cedar Bayou main stem were not of interest for developing the CCMDP. Tributary models were developed from various tributary model sources. The following sections describe significant features of the tributary models of interest.
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6.6.2.1 Smith Gully
Smith Gully lies in Mont Belvieu but discharges directly to Cedar Bayou. Models constructed for Mont Belvieu drainage planning [Klotz, 2009a, 2010b] were used to hydraulically describe Smith Gully. A 1995 HEC-2 model was converted to a HEC-RAS model for the Mont Belvieu MDP in 2008. The RAS model was revised in 2012 for evaluation of the impacts of proposed culvert improvements along the Gully north of IH-10. Appendix K presents pertinent information on Smith Gully contained in the Mont Belvieu MDP.
6.6.2.2 Horsepen Bayou
Horsepen Bayou has its downstream portions in Baytown. The bayou is crossed by Hwy 146 in Chambers County. A 2005 update of the model was identified for use in this Study.
6.6.2.3 Sawpit Gully
Sawpit Gully drains to Cedar Bayou. The original floodplain delineation for Sawpit Gully with a HEC-2 model was done by FEMA in 1983. Revisions to the model in 2008 [Jones & Carter, 2009] produced a HEC-RAS model for Sawpit Gully that involved the existing culverts under FM 1505 and the existing natural channel cross section. Jones and Carter prepared a CLOMR with required detention to reduce discharges to Sawpit Gully for undeveloped conditions. Jones and Carter proposed to improve the culverts under FM 1505 by using 3-10 ft x 9 ft box culverts to provide a conveyance capacity of 1615 cfs.
6.6.3 Cotton Bayou and Hackberry Gully Watershed
Several gullies and bayous drain the general area of Mont Belvieu, which lies north of IH-10; major portions of these watercourses had HEC-RAS models developed by Klotz Associates for the Mont Belvieu Master Drainage Plan and related studies [Klotz 2006; Klotz 2009]. With the exception of Cotton Bayou and Hackberry Gully (see Section 6.6.3.1 discussion below), RAS models for watercourses lying within the city limits of Mont Belvieu were not constructed since conveyance improvements for watercourses in Mont Belvieu have been and are currently being evaluated as part of the City of Mont Belvieu planning and preliminary engineering studies.
6.6.3.1 Hackberry Gully and Cotton Bayou: Combined Model
These two watercourses drain southward from the crossing of IH-10 to their confluence several miles south of IH-10. The combined streams downstream of the confluence drain to the tidally affected Cotton Lake. HEC-RAS models were developed in 2010 for the streams using the
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Hackberry Gully and Cotton Bayou models north of IH-10 and field survey and LiDAR data for the streams south of IH-10.
Hackberry Gully: Hackberry Gully north of IH-10 was also studied in the Mont Belvieu MDP. It drains under IH-10 to a confluence with Cotton Bayou. Appendix K presents pertinent information on Hackberry Gully north of IH-10 contained in the Mont Belvieu MDP.
Cotton Bayou: Cotton Bayou was studied in the Mont Belvieu MDP. It drains under I-10 to a confluence with Hackberry Gully south of IH-10. Modifications to Cotton Bayou have recently been proposed [Klotz, 2012a, 2012b]; proposed modifications use an altered Mont Belvieu MDP model. Appendix K presents pertinent information on Cotton Bayou north of IH-10 contained in the Mont Belvieu MDP.
Combined Model: These available models for Hackberry Gully and Cotton Bayou upstream and downstream of IH-10 were combined into a single hydraulically connected model for the combined Hackberry Gully and Cotton Bayou watershed from Cotton Lake into the origins of the two watercourses in northern portions of Mont Belvieu. The combined model was used to estimate necessary conveyance improvements south of IH-10; changes north of IH-10 are defined by the MDP for Mont Belvieu (or subsequent follow-on studies by Mont Belvieu).
Because of the different times and methods (in detail) used to construct these models, there is a flow discontinuity immediately downstream of IH-10 (and the culverts which pass under IH-10) in the model. The flow discontinuity would require rectification in future preliminary engineering studies, possibly involving improvement or mitigation of flow at the IH-10 culvert system for either of the two watercourses.
6.6.3.2 Cotton Bayou-Cove Tributary
The eastern portions of Cove Tributary are located approximately at the confluence of Hackberry Gully and Cotton Bayou approximately one mile upstream of Cotton Lake to which Cotton Bayou outfalls. The original HEC-2 model for this tributary was done by FEMA in 1992. The FEMA models for Hackberry Gully and Cotton Bayou were combined into a single RAS model extending from IH-10 downstream to Cotton Lake. Studies done by Klotz in 2010-2011 evaluated increasing the conveyance of Cotton Bayou and Hackberry Gully upstream of their confluence to reduce flooding along these two streams. The improvements determined with the combined model have not been implemented at this time.
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6.6.3.3 Langston Road
Langston Road was proposed for extension westward from Eagle Drive to Hackberry Gully. No model was available or constructed for this area since Langston Road lies completely within Mont Belvieu.
6.6.3.4 Unnamed (McAdams) Stream Crossed by SH 565 and SH 99
A HEC-RAS model for TxDOT was developed in 2007 for an unnamed stream (referred to for the purpose of this report as McAdams Ditch) crossed by SH 99 and SH 565 in eastern Baytown to evaluate impacts from the SH 99 construction and its crossing of McAdams Ditch. The ditch is 0.6 miles southwest of the intersection of FM 565 and FM 3180 in the ETJ of Baytown. Based upon a prior mitigation study [PB, 2007], the ditch has enough capacity to convey the 100-yr flows; however, the mitigation study raised questions about the impact of poor channel maintenance and potential overtopping of FM 3180 and FM 565.
6.7 Cherry Point Gully Watershed
Cherry Point Gully lies generally south of the Chambers-Liberty county line, draining to a confluence with the Old Ditch.
6.8 Old River Ditch Watershed
The Old River Ditch watershed is a small watershed immediately east of the Cherry Point Watershed that drains to the Old River and Cherry Point Gully watersheds. It was also studied in the Mont Belvieu MDP.
6.9 Beach City and Environs Watershed
Beach City is an incorporated area located along the western side of Trinity Bay. Lying along the coast, the city is narrow in the east-west direction and long in the north-south direction. Only coastal, non-riverine models (i.e., models based upon off-shore storm conditions) developed by FEMA in the early 1980s were discovered.
Because of anticipated future development as well as reported flooding in some of the gullies passing through Beach City, new discrete RAS models were developed for the following: Cedar Gully, Skylane Gully, Point Barrow Gully, Tri-City Cutoff Gully.
In addition, because of reported flooding in the eastern portions of Cove along Spring Creek, a new RAS model was constructed for Spring Creek. While not actually in Beach City, it is conveniently identified as in the environs of Beach City.
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6.10 Tailwater Conditions for RAS Modeling
Tailwater levels used in the RAS models were one of the following types:
1. Tailwater at normal depth
2. Tailwater set at downstream water level determined by another downstream model (such as levels defined by Cedar Bayou for tributaries to Cedar Bayou)
3. Tailwater set at level used in prior modeling with the RAS model being currently used
4. Tailwater set at coastal water levels for watercourses discharging directly to a coastal water body such as Trinity Bay (for coastal watercourses, #4 and #3 are the same). Coastal waters levels were in the 1 to 4 ft range. Prior studies for Cotton Bayou and Hackberry Gully for south of IH-10 had established a range by review of coastal tide gauge information.
Conditions used in prior models were used to the maximum extent possible. 10-yr and 100-yr tailwater levels were considered to be the same for 10-yr and 100-yr flood modeling.
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7. REMEDIES AND PROJECTS
7.1 Introduction
In this section, specific infrastructure projects for primary storm drainage improvement in the WSA are described. Projects identified are considered significant to addressing existing or anticipated future drainage and flooding problems. In general, conveyance improvement and detention storage are proposed as two basic options. Other options are sometimes evaluated because of special conditions or opportunities. Estimated project implementation costs are also presented. Projects are organized by major watersheds defined for HMS modeling purposes.
7.2 Types of Projects
Drainage infrastructure improvements and flood control projects considered in this Study include projects of the general types listed in the following. The potential design goals for the projects are summarized in Table 7-1.
7.2.1 Channel Conveyance Improvements: Standard Option 1
Channel conveyance improvements can include: 1) channel widening and deepening, which can include channel reconfiguration by straightening, realignment, localized restriction removal, bend removal, or cross sectional shape modification; 2) channel lining with erosion resistant and smoother surfaces, such as concrete; 3) bridge or culvert modification, such as bridge widening; and 4) channel clearing to remove flow-impeding vegetation.
Channel widening and deepening may be limited or extensive. Costs are based upon channel widening and deepening necessary to meet design goals. Channel lining is not specifically considered since lining will typically be limited in extent, but channel roughness is sometimes reduced to reflect removal of significantly flow-impeding vegetation. Bridge and culvert modification is included in cost estimates for conveyance improvements by incorporating the occurrence of roadway and pipeline crossings (as discussed below in developing cost estimates).
Limited conveyance improvements may be achieved with channel clearing rather than channel widening and deepening. The feasibility of conveyance improvement can be approximately examined by assessing the likely change in flow capacity due to hydraulic roughness. An existing channel will likely have a roughness on the order of n (i.e., Manning n value) equal to about 0.040 while extensive clearing, without other channel modification, could reduce the n value to perhaps 0.035, thereby achieving a conveyance increase of approximately, at best, 0.040/0.035≈ 15% (all other factors being unchanged). Whether such a change could actually be Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 7 - 1
obtained would require a preliminary engineering study, including an assessment as to whether the clearing would be maintained over long periods of time at a level consistent with the results of the initial cleaning. Failure to maintain the cleared channel would allow the channel conveyance to fall back to its original condition.
Channel widening and deepening can represent a reliable solution (assuming environmental constraints do not prevent its implementation) for conveyance improvement over a long period. Conveyance improvement by widening and deepening defines potential maximum ROW requirements; such requirements are essential to developing future conveyance improvements. Channel conveyance improvement is a standard option to consider for flood prevention and is referred to as “Standard Option 1.” Unless noted otherwise, it is assumed that a conveyance improvement is achieved by deepening and widening of the channel.
Practical Considerations in Channel Widening: Deepening of a channel is limited by downstream flow line elevations while widening is often limited by structures near the bank of the watercourse. To define a feasible solution with a reasonable cost, it may be necessary to allow limited flooding (i.e., flow rise above the top of bank) instead of trying to carry the design flow totally within banks over the full reach of the channel in question. When this situation arises, the following options, which could be examined in detail in preliminary engineering studies, could be considered (individually or in combination):
Fill: Fill in low bank areas to raise the top of bank for selected channel lengths
Detention: Use small scale detention to reduce flow in selected areas
Allow Limited Flooding: In regions with no current or anticipated nearby development, overbank flooding could be allowed (in effect, providing local detention)
Conveyance Improvement Mitigation: As a supplement to conveyance improvements, detention could be considered in order to limit the downstream impact of flow increases due to upstream conveyance improvements. If an unimproved channel lies downstream of the conveyance improved reaches of a channel, mitigation storage will likely be needed. When needed, conveyance improvement mitigation is part of the conveyance improvement cost. If the improved channel reach discharges directly to a large receiving water, such as Cotton Lake, for which no unimproved downstream reaches are proposed, no mitigation would be necessary.
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7.2.2 Detention Ponds for Flood Mitigation: Standard Option 2
Detention ponds can be a valuable component to conveyance improvement and/or flood control. Ponds for flood mitigation can be used as an independent control method or in conjunction with channel conveyance improvement. Generally, for the planning purposes of this Study, detention ponds for flood mitigation are considered an alternative to channel conveyance improvement.
Ponds can be used in a variety of roles, but for planning purposes the following is considered:
Flood Mitigation Pond: Detention is used to prevent increased runoff to downstream points due to upstream development. Future 100-year discharges are retained with storage to prevent downstream increases above existing 100-year discharges. This option is a no-impact solution; flooding would be no worse than it currently is. Potential channel improvements should be evaluated to contain current flows within the channel banks.
When used, detention ponds are presumed to be generally located in the same drainage area upon which their sizing is based. The exact location would require preliminary engineering evaluation in light of 1) available lands and land ownership; and 2) drainage facilities needed to carry unmitigated flows upstream of the pond location to the pond location for mitigation.
Detention ponds are identified for the various channels for which channel modification is evaluated. The actual pond might be one pond or a collection of ponds providing the total computed storage. Generally, appropriate selection of one or several ponds would require additional preliminary engineering evaluation to determine the optimal pond volume and reach in which to locate the pond.
Computation of storage volumes for Standard Option 2 is summarized in Table 7-4b. For flood mitigation ponds within this study, offline storage is evaluated.
7.2.3 Diversions
Diversions may be used to route flow around obstructions or away from areas where flow concentrates and consequent flooding occurs. Diversions are generally evaluated similarly to a channel improvement except with no existing channel; the diversion channel is new.
Impediments to using diversions include ROW acquisition, additional excavation, environmental impact, and potential petrochemical pipeline crossings. Diversion alternatives are considered only where available RRC information (see Section 2.5.4) indicates that crossing of petrochemical pipeline would not be necessary to implement the diversion.
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For planning purposes, diversions are designed to reduce the original 100-yr peak flow in a channel to a 10-yr peak flow in the downstream channel; this assumption provides a conservative estimate of costs. Detailed design could change the flow division. The diversion channel itself would be designed to handle the entire diverted flow or, if constructed in conjunction with a pond, the 10-year peak flow in the channel downstream of the diversion pond.
7.2.4 Channel Hydraulic Structure Modification
To lessen channel obstructions, bridge, culvert or siphon upgrade or replacement may be desirable or necessary. For planning purposes, it is assumed that hydraulic structure obstructions are addressed as part of conveyance improvement projects involving channel widening and deepening. Hydraulic structure improvements are recognized by the inclusion of their improvement cost in overall conveyance improvement project cost.
7.3 Methods for Estimating Project Costs
Project costs include estimated construction cost, environmental permitting costs, engineering cost, ROW costs, and contingency costs. Construction costs are decomposed into four categories as described below. Costs are assumed the same irrespective of ownership. The same methodology and unit costs are applied to both channels and ponds.
7.3.1 Direct Construction Costs
Direct construction costs items and their unit-costs are listed in Table 7-2.
Excavation and Fill: Both on-site and off-site import and disposal unit costs are given. Because details of construction are not known for planning, the unit costs for excavation and fill (if any) are the average of on-site and off-site values.
Site Preparation and Demobilization: This accounts for move general site cleaning, pollution control plans, and general site restoration after construction.
Inlet/Outlet Structures: For ponds, this cost represents the inflow structure (likely a weir) and the outflow devises and outfalls (such as pipes with headwalls). For channels, this cost represents construction of inflow pipes or a drop structure and outflow pipes or a structure.
Conduit Replacement: This cost represents the cost for crossings of a road (or similar barrier) using pipes where the channel being crossed is expected to be less than approximately 20 ft.
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Bridge Replacement: Bridges are used to make crossings over wide channels. Their cost is estimated from the approximate square footage of bridge deck; deck area is taken as the width of the channel being crossed and the number of traffic lanes (each lane is assumed 12 ft wide).
Crossing of Petrochemical Pipelines: Projects requiring crossing of petrochemical pipelines are avoided; if a pipeline is crossed, a lump sum estimate of $200,000 is assumed, but costs could be higher and these areas should be specifically evaluated for alternatives and actual costs.
Utility Crossings: Information on potential costs of utility lines is limited at the planning stage. Consequently, costs for crossing of water, sewer, storm sewer, etc. pipelines are approximated as a flat percentage of excavation costs.
7.3.2 Other Construction Related Costs
Engineering Costs: These costs, priced at a percentage of total direct construction cost (exclusive of petrochemical pipeline crossings) account for preliminary and detailed engineering, and supporting work such as survey, geotechnical investigation, and construction management.
Contingency: Construction contingency is set at a conservative level because of the planning level character of this CCMDP.
7.3.3 ROW
Estimation of ROW acreage needed for a project is based on the approximate dimensions of the project. For channels, the acreage is estimated as the length of the channel and an estimated top width plus two 30-ft berms (one on each side of the channel). For ponds, the surface acreage is estimate from the required surface (plus 10% for berms) and a nominal storage depth of 8 ft (plus 1 ft of freeboard) and the required storage volume.
The unit cost of land for ROW acquisition is based upon an estimated cost per acre. A review of Chambers County Assessment District for (unimproved) property yielded a correlation (see Table 7-2) for the unit cost of land acquisition. Because of the volatility of land costs when a project is proposed, ROW costs are only approximate.
ROW is assumed to be purchased by fee simple title. ROW may be acquired using easements at a likely lower cost; however, purchase of ROW is assumed for planning purposes.
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7.3.4 Environmental Protection Costs
Projects may requires federal permit because of potential environmental or historical impacts as discussed in Section 6. Drainage and flood control projects typically require excavation or fill. A permit for infrastructure projects with excavation or fill is a key project cost.
Estimated potential permit costs (including studies to prepare a permit application) are summarized in Table 7-3 for representative projects based upon experience with previous studies in which Klotz Associates personnel have been involved. As projects become larger, environmental permitting costs typically become larger. Based upon professional experience, minimum permitting costs are the maximum of either those listed in Table 7-3 or 8% of the direct construction costs. These costs are based upon overall project site area classes of less than 0.5 acres, between 0.5 and 10 acres, and greater than 10 acres.
7.4 Conveyance Improvement and Flood Mitigation Pond Projects
The following discusses proposed projects in various watersheds. Table 7-4a describes projects using conveyance improvement (Standard Option 1). Table 7-4b describes projects using storage for drainage improvement (Standard Option 2). Tables 7-4a and 7-4b summarize estimated costs for these options. Projects and conveyance improvement options are shown in Exhibits 7-1a through 7-1o.
In developing potential conveyance improvement and flood control projects, projects identified in the Mont Belvieu MDP [Klotz, 2009a] are not presented; only projects not within the Mont Belvieu city limits are identified. For projects within Mont Belvieu, the City’s MDP should be consulted; see Appendix K.
In these projects, mitigation will be required to prevent downstream impacts from increased channel conveyance. In other projects, the improved channel is at the downstream end of an existing channel, where it discharges to a receiving water body, such as Trinity Bay or Cotton Lake. In these latter cases, mitigation of channel improvements is not necessary. Whether-or-not mitigation is anticipated to be required should be evaluated during Preliminary Engineering Studies.
When mitigation is required, the amount of conveyance mitigation needed is evaluated in a manner similar to that described in Section 7.2.2, in which the goal of the mitigation is reduce the peak 100-yr future discharge to the existing condition 100-yr peak discharge. This design goal
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corresponds to (at least in approximate numerical amounts) Standard Option 2 in Section 7.2. The computations for various detention options are used to determine the necessary storage.
The following discusses the various projects (as well as providing supplementary information).
7.4.1 Smith Gully
Smith Gully lies almost entirely in Mont Belvieu. No RAS modeling was done as part of this MDP. Channel improvements are under active development along the channel in accord with the City’s MDP or studies undertaken by Mont Belvieu after the plan development.
7.4.2 Horsepen Gully Improvements
This project is intended to eliminate or significantly reduce existing flooding in the Horsepen Gully upstream of its confluence with Cedar Bayou. Approximately 1,900 ft of the channel above the confluence lies to the west of SH 146 and approximately 5,800 ft, from the confluence, lies the north-south UPRR railroad tracks. Residential areas lie both north and south of the gully along much of the reach between Cedar Bayou and SH 146.
Upstream of SH 146 and the railroad tracks, the gully lies within the proposed Kilgore Parkway C&I development; the gully serves as the development’s receiving waters.
For future conditions, it is anticipated that the Kilgore Parkway development and areas east of the development but west of SH 99 have been constructed. Based upon current available information [Lippke, 2013a, 2013b], extensive regional detention is to be used to avoid runoff impacts to the Kilgore Parkway Development and areas draining directly to the development. Consequently, for future conditions, the Horsepen drainage area was subdivided into two zones: the area upstream of the UPRR tracks and downstream of the UPRR tracks and the following options were evaluated.
Standard Option 1- Conveyance Improvement: The conveyance solution for Horsepen Gully from the railroad crossing (near HEC-RAS river station 5050) to the outfall at Cedar Bayou includes channel modifications and selected culvert replacements. The channel modifications for Horsepen Gully include enlarging the channel from its beginning downstream of the railroad tracks to its outfall into Cedar Bayou. Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with bottom widths ranging from 10 to 25 ft.
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Further channel improvements include constructing a 3 ft high berm downstream of SH 146 to ensure 1 foot of freeboard in the channel as it nears residential properties along the left bank. An additional 0.5 foot berm is recommended on the right bank from just upstream of SH146 to approximately river station 2987 to ensure 1 foot of freeboard in the channel.
As a consequence of the aforementioned channel modifications, the existing culvert under the UPRR will need to be replaced with an adequately sized culvert system whose dimensions depend on the final design of the channel.
Standard Option 2-Mitigation of Future Development: Ponds are used to prevent the future 100- yr peak discharge downstream of the SH 146 tracks from exceeding the 100-yr existing condition peak discharge. Assuming off-line storage is needed, an estimated 73.1 ac-ft of storage would be required (see Table 7-4b). A location upstream of the UPRR has been identified.
7.4.3 Sawpit Gully
This project would address potential flooding west of the Ameriport C&I development from SH 146 downstream to the confluence with Cedar Bayou. Riverine flooding currently occurs along much of this reach of the gully. The project is intended to reduce flooding along the project reach and possibly mitigate a portion of the runoff from the Ameriport development.
Standard Option 1- Conveyance Improvement: The conveyance solution for the main channel of Sawpit Gully from FM 1405 (near HEC-RAS river station 5878) to river station 875 near Old West Bay and Shell Dock Road includes channel modifications. Channel improvements upstream of FM 1405 were derived from an existing Baytown 2009 CLOMR produced by Jones and Carter (in response to planned development nearby [Jones and Carter, 2008]). The channel modifications downstream of FM 1409 for Sawpit Bayou included enlarging the channel from river station 5878 to river station 875 near the outfall into Cedar Bayou. Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass- lined channel was used for the channel modifications with a bottom width of 15 ft. Details regarding channel improvements and culvert additions upstream of FM 1405 can be found in the 2009 CLOMR.
Further channel improvements include constructing an 8’ high berm just US of RS 1794 down to RS 865/Old West Bay Exit (Shell Dock Road) to contain the channel within the banks for future development; however the proposed 100 year water surface elevation without a berm remains safely beneath the driving lanes of South FM-565 along the right bank of Saw Pit Gully. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 7 - 8
Standard Option 2- Mitigation of Future Development: Detention along the channel somewhere upstream of FM 1405 sufficient to reduce the future 100-year peak discharge to the 100-year existing condition discharge. If an offline pond is used for storage, an estimated 37.7 ac-ft of storage would be required.
7.4.4 Ijams and Water Oak Gullies
Ijams and Water Oak Gullies are part of the Cedar Crossing, Phase 1 Development [Pate, 2005]. The development lies in CCID#1. The details of the improvements are being planned as part of the CCID#1 planning for Cedar Crossing.
7.4.5 Sutton Gully
Sutton Gully is part of the Cedar Crossing, Phase 2 Development [Pate, 2006]. The development is part of CCID#1. Upstream within Cedar Crossing, Sutton Gully has a confluence with a major tributary; this confluence breaks Sutton Gully into upstream and downstream reaches.
The upstream reach of Sutton Gully was studied in 2000 by Pate Engineers as part of the Master Drainage Study- Phase II: Chambers County Improvement District No. 1. The study addressed potential improvements for Sutton Gully where land is developable, while father downstream near the confluence with Cedar Bayou no future development was projected due to the presence of a FEMA 100-year floodplain. This lower reach was therefore not studied for the CCMDP with anticipation that a very detailed study would improve the reach as needed for that particular development.
7.4.6 Cotton Bayou and Hackberry Gully Upstream of IH-10
This watershed includes the two separate Cotton Bayou and Hackberry Gully watercourses upstream of IH-10, with the watercourses continuing downstream of IH-10 with Cotton Bayou merging into Hackberry Gully before its discharge to Cotton Lake. The culvert system which carries the two watercourses under IH-10 serves as significant flow constraints.
North of IH-10, Cotton Bayou and Hackberry Gully lie in Mont Belvieu. Implementation of the recommendations of the Mont Belvieu MDP is underway. Appendix K provides pertinent portions of the Mont Belvieu MDP. Modifications to the plan have been made as part of preliminary engineering studies, in part necessary because of recently developed plans for proposed FM 1409 highway from Old River-Winfree to Cove [Dannenbaum, 2010]. Options for regional detention are also being considered. Options being considered as part of the Mont Belvieu preliminary engineering evaluations include the following:
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Detention for upstream runoff from the Cotton Bayou watershed, thereby reducing flood flow magnitudes to downstream reaches of Cotton Bayou north of IH-10.
Detention for mitigation (in part or totally) increased runoff from the proposed Cottonwood Estates Phase 2 residential development.
Detention for the increased volume of runoff from the proposed FM 1409; portions of the runoff from the new roadway are proposed to discharge to Cotton Bayou. While FM 1409 runoff is to be mitigated by in-line detention in the drainage channels from the roadway to reduce peak discharge, it is possible that portions of this runoff will increase the net volume of runoff draining to Cotton Bayou from the FM 1409 ROW.
7.4.7 Cotton Bayou and Hackberry Gully Downstream of IH-10
Flooding occurs in the vicinity of the confluence of Cotton Bayou and Hackberry Gully in and around the City of Cove as well as along the tributary to Cotton Bayou that extends northward to the Plantation Subdivision.
For convenience, portions of Cotton Bayou south of IH-10 but upstream of the confluence of Cotton Bayou and Hackberry Gully are referred to as Upper Cotton Bayou. Downstream of the confluence, the bayou is sometimes referred to as Lower Cotton Bayou.
Standard Option 1: RAS modeling was used to identify potential improvements along Cotton Bayou and Hackberry Gully to reduce flooding along the two watercourses by increasing conveyance. These improvements following the concepts of Standard Option 1 for channel conveyance improvement.
Cotton Bayou: The conveyance solution for Cotton Bayou-Lower from just downstream of IH-10 (near HEC-RAS river station 22301) to the confluence with Hackberry Gully and from the confluence to the outfall into Cotton Lake (i.e., Upper Cotton Bayou and Lower Cotton Bayou, respectively) includes channel modifications. Modifications are recommended only from IH-10 down to river station 19350 and from river station 12367 to river station 9598 at the Hackberry Gully Confluence. Along Cotton Bayou-Lower, channel modifications from river stations 6543 to 4531 are recommended. Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with bottom widths of 30-100 ft.
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It should be noted that there are known flooding issues at the Cotton Bayou – Hackberry Gully confluence. The recommended channel modifications address out of bank flooding for both Upper and Lower Cotton Bayou however; due to substantial differences in bank elevations beginning at the confluence and continuing to the Cotton Lake outfall, the construction of a 6’ berm is recommended along the left bank. An alternative solution is to not construct the berm and instead purchase additional right-of-way from the affected residents.
Hackberry Gully: The conveyance solution for Hackberry Gully from just downstream of IH- 10 (near HEC-RAS river station 25321) to the confluence with Cotton Bayou includes channel modifications. Modifications are recommended only from IH-10 down to river station 17851. Upstream of IH-10, modifications are specified in the Mont Belvieu Master Drainage Plan (see Appendix K), side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with a bottom width of 65 ft.
It should be noted that there are known flooding issues at the Cotton Bayou – Hackberry Gully confluence. The recommended channel modifications address out of bank flooding for Hackberry Gully upstream of FM 3180 however due to substantial differences in bank elevations beginning near river station 15213 and continuing to the Cotton Bayou confluence, the construction of a 1-4’ berm is recommended. Upon further analysis the variation of the height and placement of the berm can be more accurately estimated.
Standard Option 2: Detention was evaluated for possible mitigation ponds along the watercourses. These are summarized in Table 7-4b.
Additional Option- Cotton Bayou Diversion: A diversion of significant portions of the Cotton Bayou flood flows is proposed as a third option. This is intended to reduce flooding in the community of Cove downstream of the confluence of Hackberry Gully and Cotton Bayou west of Cotton Lake and, as well, reduce backwater flooding along the tributary to the Plantation Subdivision.
The proposed (approximate) alignment of the diversion is shown in the figure of Table 7-7c. Summary computations of the diversion characteristics are provided in Table 7-7a. This option is quite expensive because of the length of the diversion. However, in view of environmental issues
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and constraints encountered in previous proposals involving Cotton Bayou and Hackberry Gully modifications south of IH-10, it may be a viable option to consider.
7.4.8 McAdams Ditch Improvements
The McAdams Ditch carries drainage from already completed sections of SH 99 north of SH 565 eastward for discharge to Hackberry Gully south of IH-10. Channel improvements and a dual 5’ x 7’culvert crossing are proposed for McAdams Ditch to reduce flooding. These proposed improvements are part of the GLO contract and implementation of the recommended improvements is dependent on future approvals.
7.4.9 SH 99 Segment Completion South of IH-10
The former SPUR 5 between the already completed sections of SH 99 lying west of FM 1405 and north of SH 565 is anticipated to be completed in the near future. While drainage to and from the roadway will be provided as part of the roadway construction, this drainage will require integration into the drainage systems maintained by Chambers County in the area in which the SH 99 section will lie. Anticipated drainage flows from the completed SH 99 were integrated into future runoff estimates for the areas east and west of the highway.
There should be close coordination between TxDOT and the County in the final drainage design of this SH 99 section, but because the drainage of SH 99 is not finalized and TxDOT has not defined for Chambers County how it proposes to potentially discharge roadway drainage to county drainage systems, only preliminary concepts and costs are considered. This conceptual information is intended only to serve as a guide as to what might be expected to occur in regard to this project and its impact on county drainage conditions.
7.5 Cherry Point Watershed
No channel improvements are recommended for the Cherry Point Watershed for this CCMDP; portions of the watershed within Mont Belvieu for which improvements are recommended are contained in the Mont Belvieu MDP. See Appendix K for additional information.
7.6 Old River Ditch Watershed
No channel improvements are recommended for the Old River Ditch Watershed for this CCMDP; portions of the watershed within Mont Belvieu for which improvements are recommended are contained in the Mont Belvieu MDP. See Appendix K for additional information.
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7.7 Beach City Area
The Beach City HMS watershed captures drainage from the coastal areas of Beach City, inland areas to the north and west of the city limits, and (as defined for describing the Beach City HMS watershed) Spring Creek sub-watershed that lies on the northern side of Cotton Lake.
7.7.1 Watercourses within Beach City
Because of inland development (including Cedar Crossing) and reported flooding problems in some areas, the watercourses in the Beach City Area were evaluated for conveyance improvements. For RAS-based evaluations, new RAS models were developed.
Standard Options 1 and 2 are presented for these new models in Tables 7-4a and 7-4b. The watercourses evaluated in Beach City are described in the following:
7.7.1.1 Cedar Gully
The conveyance solution for Cedar Gully from just downstream of Fisher Road (near HEC-RAS river station 9247) to the outfall into Trinity Bay at river station 183 includes channel modifications (see Exhibit 7-1n). Modifications are recommended only upstream of FM 2354 (Tri-City Beach Road). Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with a bottom width of 100 ft.
As a consequence of the aforementioned channel modifications, existing culverts under FM 2354 (Tri-City Beach Road) will need to be replaced with an adequately sized structure whose dimensions depend on the final design of the channel.
Conveyance improvements and detention options are summarized in Tables 7-4a and 7-4b.
7.7.1.2 Skylane Gully
The conveyance improvement solution for Skylane Gully from just upstream of FM 2354 (near HEC-RAS river station 8946) to the outfall into Dutton Lake at river station 57 includes channel modifications (see Exhibit 7-1i). Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with bottom widths ranging from 115 to 140 ft.
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As a consequence of the aforementioned channel modifications, existing culverts under South Cotton Lake Road, Skylane Road, Lake View Road, and an unnamed access road near the outfall at Dutton Lake will need to be replaced with an adequately sized structure whose dimensions depend on the final design of the channel.
Conveyance improvements and detention options are summarized in Tables 7-4a and 7-4b.
7.7.1.3 Point Barrow Gully
The conveyance improvement solution for Point Barrow Gully from just downstream of McCollum Park Road (near HEC-RAS river station 5420) to the outfall into Trinity Bay at river station 61 includes channel modifications (see Exhibit 7-1j). Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with bottom widths ranging from 40 to 50 ft.
As a consequence of the aforementioned channel modifications, the existing culvert under Point Barrow Road will need to be replaced with an adequately sized structure whose dimensions depend on the final design of the channel.
Conveyance improvements and detention options are summarized in Tables 7-4a and 7-4b.
7.7.1.4 Tri-City Cutoff Gully
The conveyance improvement solution for Tri-City Cutoff Gully from just upstream of FM 2354 (near HEC-RAS river station 3133) to the outfall into Trinity Bay at river station 31 includes channel modifications (see Exhibit 7-1o). Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with bottom widths ranging from 30 to 85 ft.
As a consequence of the aforementioned channel modifications, existing culverts under Tri City Beach Road and Cedar Gully Road will need to be replaced with an adequately sized structure whose dimensions depend on the final design of the channel.
Conveyance improvements and detention options are summarized in Tables 7-4a and 7-4b.
7.7.2 Spring Creek
Standard Option 1- Conveyance Improvement:
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The conveyance improvement solution for Spring Creek from just upstream of South FM 565 (near HEC-RAS river station 8458) to the outfall into Cotton Lake at river station 69 includes channel modifications (see Exhibit 7-1e). Channel side slopes of 4:1 were used for these channels. The main channel is assumed to have an improved roughness value of 0.03 as a consequence of improvement and general maintenance. A trapezoidal grass-lined channel was used for the channel modifications with bottom widths ranging from 30 to 35 ft.
Further channel improvements include constructing a 1.5’ high berm downstream of Gou Hole Road to ensure 1 foot of freeboard in the channel as it nears residential properties along the left bank. As a consequence of the aforementioned channel modifications, existing culverts under South FM 565 and Gou Hole Road will need to be replaced with an adequately sized structure whose dimensions depend on the final design of the channel.
Standard Option 2- Detention: Detention was evaluated on the watercourse south of IH-10 but north of the residential areas along the watercourse south of FM 565. Detention options are summarized in Table 7-4b.
Additional Option- Spring Creek Diversion: This would use a diversion south of IH-10 as shown in Table 7-7c. The diversion would be located south of a known pipeline corridor near IH-10 (as reported by the RRC). Preliminary characteristics of the diversion are summarized in Table 7-7b.
This option would reduce residential flooding along Spring Creek north of the eastern portions of Cove. Flooding problems in residential areas of Cove along Spring Creek have been reported. Flow originates both upstream and downstream of IH-10 for this watercourse.
The costs for these options are summarized in Table 7-7b.
7.8 Future Projects
Several more conveyance improvement and regional detention solutions are currently being proposed throughout Chambers County. Improvement recommendations contained within this study are being considered for future implementation under GLO Contract Texas CDBG Disaster Recovery Grants, and various other tentative contracts and plans. While the surety and timeline associated with any of these and other future plans is beyond the scope of this MDP, current knowledge and documentation associated with those plans should be acknowledged. (See appendix M). Cost Estimates are based on 2013 prices. PER’s are needed for each project. Escalation of unit prices and costs should be considered.
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8. PROGRAMMATIC IMPROVEMENTS AND FUNDING
8.1 Complementary Roles
Funding of projects is the critical element in project development. Discussion of potential funding strategies and sources are discussed below. To guide and encourage successful project development, an effective legal and management environment is needed. Features of a programmatic management structure by Chambers County can benefit such a desirable environment.
8.2 Programmatic Improvements for Chambers County
Problem remedies that do not rely on infrastructure construction but rather upon how projects are designed, constructed, managed or funded are programmatic remedies. For the CCMDP, programmatic improvements identified are the following:
8.2.1 Regulation and Criteria
Modify drainage regulation and criteria to make criteria more consistent, effective, and encourage beneficial and responsible development, including standards for secondary drainage, sheet flow management, avoidance of or elimination of ponding areas in developments, and minimum detention requirements.
In particular, drainage plans for residential development should be required to include quantitative demonstration of the adequacy of storm water inlet size and spacing, adequacy of inlet drain lines and leads to storm sewer collection lines, and estimated maximum depths of street flooding for design storm conditions. If predicted street flooding depths exceed allowable depths then inlets, inlet leads, and other necessary components should be required to be upsized, even if such upsizing requires more than minimum (as specified by the CCDCM) sizing of inlets and inlet leads.
8.2.2 Coastal Flood Protection
Frequent inspection (by the county or responsible municipality) of residential coastal structures and rigorous review of residential construction activities (plans and on-site inspection) to maximize compliance with state and regional construction codes for construction in high hazard coastal zones should be conducted.
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In particular, as flooding impacts prevention measures, county review should require or confirm that new residential development be set at levels that meet coastal flooding protection minimums for first floor elevation.
8.2.3 Sheet Flow Management
Review of site and drainage plans (by the county or responsible municipality) for a proposed development to determine need for and provision of sheet flow areas as an integral part of the drainage management for the development. Developers of new residential or C&I development should be required to include a well-documented sheet flow management plan as part of the drainage plan for a new development.
8.2.4 Use of Regional Detention
Encourage the use of efficient regional or sub-regional detention through careful planning, coordination with developers, potential tax or fee incentives, and/or structuring drainage ordinances and criteria to encourage regional detention projects. Ordinances considered should be those that generally outline options for use and implementation of regional detention as a viable and desirable option for mitigation of runoff from developing areas.
8.2.5 Tracking Growth and Drainage Issues
Institute a management system in the county (in coordination with cities and villages) that 1) tracks growth so that anticipated drainage mitigation actions can be undertaken; and 2) maintain a comprehensive record of citizen complaints about drainage problems to use as guide in future drainage planning and setting priorities for project implementation.
8.3 Funding Strategies
Different sources of project funding are available. Which source is potentially accessible for a particular project will depend upon the purpose of the project, the anticipated benefits of the project, estimated overall cost of the project, contributors and the amount of participation by various contributors in providing project funding. Source funding also depends on who will benefit from a particular project.
Potential strategies to most effectively use available funds include the following:
Phasing of construction to spread funding needs over time
Expanding internal funding options to use funds from sources under the control of the County
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Joint development of projects with developers of the project
Impact fees
Establishing utility or special districts
Accessing external funding to generate funds from non-County sources
These options are discussed in the following sections.
8.3.1 Project Phasing and Project Decomposition
Large-scale expensive projects can be considered for phased construction if the project operation does not lend itself to phased development because of operational issues. Diversions, for example, can typically be excluded from possible phasing because of the impracticality of constructing a diversion in phases. Detention projects and channel improvements, on the other hand, are well suited to phased construction if funding is limited.
For projects to be phased, the first phase typically includes ROW acquisition and environmental permitting, because inability to obtain ROW or permits would render a project infeasible. For projects that could be phased, the project can be separated into sub-projects such that each phase is within feasible funding limits. Thus, e.g., channel improvement can be separated into individual reach sub-projects, with each sub-project reach completed separately over time.
8.3.2 Developing Additional Internal Funding
Internal funding is defined as project funding provided by the County. This funding may be combined with money from other sources to generate the necessary money for a particular project. Internal funding may come from existing or new county sources, the latter developed to supplement existing traditional sources.
Traditional sources of funding support the County’s general fund which can be utilized for a variety of purposes. Some traditional sources are following:
General sales tax
Property tax
General license and permit fees
Fines and forfeitures
Special district fees, such as industrial improvement district fees, collected from operators of industrial or commercial enterprises in specified areas in lieu of property taxes. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 8 - 3
Engineering/civil permits
Consideration can also be given to funds limited to specific purposes, such as the following:
Service Improvement Fees (e.g., drainage improvement fees): These are fees that are collected for the specific purpose of generating revenue for funding of improvements for certain types of facilities (e.g., drainage systems). These fees are typically the same for each household and/or business and independent of any use levels. The authority to collect such fees can be established by ordinance.
Drainage District Fee Assignment: These are funds collected by a drainage district for the purpose of management and operation of the drainage district system. These funds typically go directly to the drainage district, but modifications could be made so that the County receives (is “assigned”) some portion of the fee because the drainage district is responsible to the County.
Special Assessments: These are fees charged to a particular set of individuals or business enterprises that are favorably impacted by a drainage project. Assessments can be one-time charges or charges of short duration for the particular benefits received because of the project.
Department Transfers: Funds from other operations in the County can be transferred to particular drainage projects if benefits to other operations can be identified.
8.3.3 Joint and Cooperative Funding of Projects
By combining county funds with other public agency funds, specific projects can be built using fund leveraging. Partnering with TxDOT, HGAC, TPWD, drainage districts, and cities is an option to use funds available through joint efforts.
Using cooperative arrangements, external sources can be combined with county funds for projects which benefit both the county and partners in the project. Examples are the following:
Intergovernmental transfers, e.g., fund transfers from a city or governmental source for services provided by the county to the other city or governmental entity.
Joint project development, e.g., joint development of a regional project in conjunction with drainage districts or TxDOT. Bridge improvements, for example, done as part of roadway improvement might be the basis of joint project development.
8.3.4. Joint Funding of Projects in Coordination with Private Developers
Working in coordination with private developers is accomplished by having certain portions or features of a development funded by the county while the remaining portions are funded by Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 8 - 4
private parties benefitting from a particular project. When the public good can be demonstrated by such coordination, there is justification for county funds being used to construct certain portions of such private development. The development of regional detention systems are one example. The regional detention serves many private parties as well as the public at large for reducing impacts for anticipated development, not just the current portion of the development. Arrangements for county coordination with private developments are specific to the situation, but will commonly identify portions of a project, e.g., regional detention, that benefits many parties, including the population at large, as those features in which county support may be provided.
8.3.5 Impact Fees
Impact fees are fees assessed to property developers that are used to recover anticipated costs to be incurred in the future by a county or municipal entity because of the additional municipal services (including utility) that will arise from development. The impact fees can also be used to recover costs already incurred by the county or municipality in project development, such as coordination with private developers in the development of project (as discussed in Section 8.5.4 above). Impact fees are commonly assessed at the time of county or municipal permit application and based upon amount of area to be permitted. One benefit of impact fees are that they are established by ordinance and can be administered in an unbiased fashion.
8.3.6 Utility or Special Districts
Legally defined special entities with well-defined powers, i.e., state or county created districts, can be a means to generate additional revenue through taxation of various types of projects.
Drainage districts or storm water utilities can be established by ordinance for the purpose of providing drainage and/or flood control services. Drainage districts typically have a broader range of responsibilities (e.g., provision of irrigation waters) than storm water utilities, which usually restrict their services to drainage or storm water drainage related issues. The district or utility is established with authority to levy various fees. The authority is commonly based upon a surrogate defining the amount of drainage service being provided (e.g., the amount of impervious area in a land parcel because the level of imperviousness affects the amount of runoff generated). Collected revenues are dedicated to provision of drainage and flood control in the service area of the district or utility.
8.3.7 External Funding
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External funding sources should always be investigated as part of a particular project. If investigation of funding sources is undertaken as part of preliminary engineering, the design of the project could potentially be modified to meet requirements of funding sources.
Opportunities for funding different projects depend upon where the project is located, where the benefits of the project will be realized, who the project will benefit, and the type of project.
External funding sources for flood control projects can encompass flood control ponds and channel improvements to reduced flooding. Water quality and recreational components of a project expand options for funding from additional sources with water quality responsibilities. External funding is typically accompanied by requirements for financial participation by the entity (often termed the “local sponsor”) seeking the external funding. The participation party may be a single entity, such as the county, or a group of cooperating parties, such as the county, a drainage district, and a city. The following sections identify particular external drainage or flood control project funding sources.
8.4 External Funding for Drainage and Flood Control Projects
The following funding sources are potentially available for drainage improvement or flood control projects.
8.4.1 FEMA Grants
These are grants typically administered by the Texas Water Development Board (TWDB) or the Department of Emergency Management (DEM) that are directed to the direct prevention or response to floods. Specific types of grants include:
Pre-Disaster Mitigation Grants (PDM): This program provides grants and technical assistance to local communities for cost-effective hazard mitigation activities that complement a comprehensive hazard mitigation program to reduce injuries, loss of life, and damage and destruction of property.
Flood Mitigation Assistance Grant (FMA): The FMA grant program provides federal funding to assist states and communities to fund cost-effective measures to reduce or eliminate the long-term risk of flood damage to structures insurable under the National Flood Insurance Program (NFIP).
Repetitive Loss (RL) Grant Program: This program provides grants for projects which can be shown by a benefit-cost analysis to reduce repetitive losses to residential structures
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8.4.2 Texas Water Development Board Loans
The TWDB operates several loan programs for financing the planning, design, construction, improvement or expansion of water and wastewater facilities. Wastewater facilities can be interpreted as to include systems that improve storm water quality. Particular loan programs though which such leverage might be achieved include the following:
Clean Water State Revolving Fund (CWSRF): Using federal capitalization grants, the TWDB offers low interest loans through the Clean Water State Revolving Fund (CWSRF). CWSRF loans may be made to any political subdivision with the authority to own or operate a wastewater system to finance wastewater projects or to political subdivisions to finance nonpoint source pollution control or estuary management projects.
Texas Water Development Fund (DFund): The TWDB offers loans through DFund with interest rates at approximately 0.35 percent above the TWDB's cost of funds through the state general obligation bond-funded program. DFund loans are available for planning, design and construction of various projects, including flood control project. Detention ponds built for flood mitigation and storm water quality improvement may qualify for loans under this program.
State Participation Program: This program enables the TWDB to assume temporary ownership interest in a regional project when the local sponsors are unable to assume the debt for an optimally sized project.
8.4.3 Amenity Funding by Texas Department of Parks and Wildlife
Another external funding source to consider is the Texas Department of Parks and Wildlife (TDPW). Outdoor Recreation Grants are made available from the TDPW Account and the Land and Water Conservation Fund (LWCF) to local governments for the acquisition and/or development of outdoor recreation sites. These funds are available for acquisition and development of State and local park and recreation areas adjacent to storm water detention facilities. Of the various grant programs administered by the TPWD, the following have the potential to provide money for detention pond amenity development:
Outdoor Recreation Grants: This program provides matching grant funds to municipalities, counties and other local units of government with a population less than 500,000 to acquire and develop parkland or renovate existing public recreation areas.
Indoor Recreation Facility Grants: This program provides matching funds to municipalities, counties, and other local units of government with a population less than 500,000 for constructing
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recreation centers, community centers, nature centers and other facilities (buildings). Such facilities might be included as part of the amenity features for some projects.
Regional Grants: This grant program provides assistance to local governments with the acquisition and development of multi-jurisdictional public recreation areas in the metropolitan areas of the state. It allows cities, counties, water districts, and other units of local government to acquire and develop parkland for both active recreation and conservation opportunities.
Recreational Trail Grants: TPWD also administers the National Recreational Trails Fund in Texas for the Federal Highway Administration (FHWA). This program receives its funding from a portion of federal gas taxes paid on fuel used in non-highway recreational vehicles.
8.4.4. State Administered Grant Programs
Different agencies in the State are involved in administering various grant and loan funds made available from federal sources.
8.4.4.1 Texas Coastal and Estuarine Land Conservation Program (TCELCP)
Texas General Land Office (GLO) administers the TCELCP program authorized by federal Public Law 107-00 for the purpose of protecting important coastal and estuarine areas that have significant conservation, recreation, ecological, historical, or aesthetic values, or that are threatened by conversion from their natural or recreational state to other uses [GLO, 2009]. Projects are prioritized for funding by the GLO and focus upon land acquisition for conservation purposes.
8.4.4.2 Texas Department of Rural Affairs
The Texas Department of Rural Affairs (TDRA) provides grants for a variety of rural development purposes. Among the grant programs, TDRA sponsors grants for disaster relief (such as hurricane recovery) and rural planning activities. Some of these grant programs, could provide funding for drainage improvements and flood control projects:
Disaster Relief and Urgent Need Fund: The assistance available through this fund can be used for eligible relief activities in situations where the Governor of Texas has declared a state disaster or requested a federal disaster declaration.
Small Towns Environmental Program: Funds in this program are used for water and sewer infrastructure improvements utilizing self-help methods such as local volunteer labor resources.
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Disaster Recovery: These are funds allocated to local and county entities for recovery from natural disasters, such as hurricanes, for areas designated by the Governor as a disaster area.
Community Development Funds: These are funds available on a biennial basis for public facilities’ development, including water and wastewater infrastructure, street and drainage improvements, housing activities, and some other limited purposes.
8.4.5 U.S. Army Corps of Engineers Project Monies
Executive Order No. 11888 (May 24, 1977) provides funds for floodplain management pursuant to the National Environmental Policy Act of 1969, the National Flood Insurance Act of 1968, and the Flood Disaster Protection Act of 1973. It directs the USACE to undertake projects to minimize the impacts of floods on human safety, health, and welfare, and to restore and preserve the natural and beneficial values served by floodplains. These efforts are accomplished by acquiring, managing, and disposing of Federal lands and facilities; providing federally undertaken, financed, or assisted construction and improvement projects; and conducting Federal activities and programs affecting land-use.
USACE has joint participation programs in which local governments can financially participate. This participation is by a local sponsor, which might be the county. The USACE is usually responsible for the design and construction of the projects but the local participant assumes responsibility for the subsequent operation and maintenance of the constructed facilitates.
8.4.6 Multi-Purpose Detention Systems to Access Other Program Funds
While the primary purpose of the sub-regional detention ponds is provision of storage to mitigate increased runoff from land development, sub-regional detention ponds are also considered as opportunities for multi-use activities that provide community amenities and can become a community asset. Inclusion of community amenities as part of a regional detention pond system may also increase the likelihood of obtaining external grant or loan monies for the pond development.
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9. CONCLUSIONS AND RECOMMENDATIONS
9.1 Conclusions
A comprehensive plan to address primary drainage problems and riverine flooding has been developed. Projects have been identified to address problems and concerns.
9.2 Major Projects
Potential major projects are conveyance improvement or detention ponds. Conveyance improvements and detention make-up the majority of the recommended drainage improvements. A limited number of special features have been defined for some projects when conditions or opportunities arise to define additional future project options such as flow diversions to a new point of discharge.
9.2.1 Conveyance Improvements
The primary focus of this CCMDP is on infrastructure improvements by improving channel conveyance using channel depth and/or width modifications or by reducing channel flows by partial capture of runoff in detention ponds. Table 9-1 lists the various conveyance improvement projects evaluated along with the use of ponds as an option to the conveyance improvements. The primary conveyance improvements characteristics are summarized and costs for the improvements are estimated for 10 different major channel segments. Also included in the conveyance improvements are estimated detention pond requirements, with costs, for mitigation of increased flow to downstream points due to the enhanced conveyance. Exhibit 9-1 shows where conveyance improvements have been identified and evaluated.
9.2.2 Diversions
Two diversions have been identified as options to conveyance improvements: The Cotton Bayou Diversion (see Table 7-7a and 7-7c) diverts flood flow around the eastern portions of Cove lying near the confluence of Cotton Bayou and Hackberry Creek. The Spring Creek diversion diverts flow from the eastern portion of Cove (see Table 7-7b and 7-7c).
9.2.3 Flood Mitigation Ponds
Flood mitigation ponds, detention for mitigation of increased runoff due to development, is considered as the alternative to conveyance improvements, as listed in Table 9-1. Data for pond sizes are taken from computations in Section 7 and assume ponds are offline. Costs for the ponds are estimated and listed in the table.
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For potential selection of a pond as an alternative to conveyance improvement, only flood mitigation ponds are considered. Conveyance improvements were evaluated to generally lower the 100-yr water surface sufficiently to keep flood waters within banks. The comparable pond option is elimination of downstream flooding using a flood control pond.
9.2.4 Optimal Combinations of Conveyance Improvement and Flood Mitigation Storage
Project costs evaluated considered conveyance improvement and flood mitigation ponds as two distinct and separate options. In reality, it is likely that a combination of conveyance improvements and ponds will be the most cost effective. Finding optimal (and practical) combinations of conveyance improvements and ponds will require detailed engineering evaluation.
9.2.5 Costs for Major Projects
Estimated costs for major project options are given in Table 9-1. Exhibit 9-1 shows project locations and categories of costs in which various projects lie: small project costs are assumed to be less than $5 million in total; large projects have costs over $5 million.
Option 1 - Channel Option 2 – Detention Watershed Excavation ROW Cost Excavation ROW Cost (cy) (acre) (ac-ft) (acre) Cedar Gully 221,500 34.9 $ 4,100,000 829.1 110.5 $ 19,800,000 $ Skylane Gully 706,800 52.6 322.2 43.0 $ 7,700,000 11,500,000 Point Barrow 95,900 18.6 $ 2,500,000 178.9 23.9 $ 4,300,000 Tri-City Gully 114,300 16.5 $ 3,300,000 241.3 32.2 $ 5,700,000 Spring Creek 148,900 31.9 $ 3,900,000 168.0 22.4 $ 4,000,000 Upper Cotton 39,600 58.0 $ 2,600,000 547.5 73.0 $ 13,100,000 Bayou Lower Cotton 85,700 75.9 $ 3,500,000 230.8 30.8 $ 5,500,000 Bayou Hackberry Gully 148,900 55.8 $ 4,500,000 310.6 41.4 $ 7,400,000 Horsepen Bayou 34,100 17.8 $ 1,900,000 73.1 9.7 $ 1,700,000 Sawpit Gully 34,900 21.3 $ 2,400,000 37.7 5.0 $ 900,000
Costs for the two diversions are given in Table 7-7a and in Table 7-7b.
9.3 Issues in Project Options and Their Selection
Selection of projects and options should be based on estimated cost and sources of funding, anticipated project effectiveness and urgency. Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 9 - 2
9.3.1 Issues in Costs
Options range from relatively inexpensive channel clearing to major and quite costly major flood control detention or channel conveyance improvements. In examining options in regard to cost, several important cost mitigating factors should be recognized:
Conservative Cost Estimates: Because this Study is a planning study, estimated costs are conservative (i.e., “on the high side”) and include a 30% construction contingency.
Staging of Project Implementation: Some projects can be readily accomplished in stages with each stage having a potential to be more affordable. Conveyance improvements, e.g., can address short length reaches that compose the entire conveyance improvement reach. In such projects, benefits are obtained from each stage and allow for continuing participation in project costs as additional stages are added.
Excavation Cost Uncertainty: The total cost for most identified projects are dominated by excavation costs. Excavation costs can vary widely from project to project due to the issues of hauling and disposal and other uses of the excavated material (a flat rate of $8.00/CY was used). How much and how far excavated material must be taken for disposal is uncertain at the planning level.
Optimal Design Frequency: In general accord with the CCDCM, conveyance improvements were sized to control the 100-yr flood condition. For some project locations, there could be a significant benefit in reducing the design flood (say, 50-yr or 25-yr). This could result in significant cost reduction with substantial but not full flood reduction. When a project is under consideration, preliminary engineering should investigate the cost savings and change in benefits that could result from reduction of the design flood level.
Optimal Combinations of Conveyance Improvement and Detention: While options presented involving conveyance improvement and detention are generally presented as two opposing options, the optimal solution could be a mixture of conveyance improvement and flood mitigation detention. Preliminary engineering studies would be required to identify such an optimal solution because of the numerous trials that would have to be evaluated.
9.3.2 Other Alternatives
While this Study has focused on infrastructure alternatives, two important alternatives should not be forgotten: Klotz Associates Proj. No. 1057.002.000 Master Drainage Plan November 2014 Chambers County, Texas 9 - 3
Solving the Right Problem: Different types of flooding might be rooted in different causes, including ponding because of low topography (e.g., homes built in a topographic low); inadequate or deficient storm sewer systems (e.g., storm water inlets spaced at too great a distance); surge levels in coastal areas; and true drainage channel deficiencies. Before committing to construction of a particular project, review and clarify with appropriate engineering investigation and study the true source of the apparent flooding problem. The true source of the problem should guide the selection of an appropriate solution.
Is No Action the Best Solution? The combination of cost, available funding, environmental limitations, and the limited impact of the problem may warrant the need for a no-action response to the problem. The benefits (both tangible and intangible) to be achieved with a particular infrastructure improvement may not be sufficient to warrant the necessary expenditure of funds for a project. Available funds may best be spent on other projects.
9.4 Infrastructure Improvement Recommendations
A multi-project program of drainage improvement and flood control projects has been identified. These projects are listed in Table 9-1 and include new or modified drainage channels, and ponds of varying sizes and purposes. Exhibits 7-1a-p locates the recommended conveyance projects while Exhibit ES-3 details and estimates the cost for both the conveyance and detention project.
Projects can be approximately ranked in order to set priorities for implementation. Two methods for ranking are considered:
9.4.1 Project Rank by Cost
One of the most common ways to prioritize projects is by costs. When sources of funding would likely be different because of the magnitude of project cost, cost rankings can be broken into two categories: 1) small projects (which might be funded wholly by county funds), with estimated costs less than some critical level, such as $500,000; and 2) large projects (which might be funded by multi-sources in addition to the county), with estimated costs greater than the critical value.
For each project, the least expensive option is identified and ranked by cost in Table 9-2.
9.4.2 Factors for Project Ranking
A set of factors can be selected to establish approximate rankings for prioritizing projects for implementation. Complex weighting schemes [Collins, 2008; Komogorova and O’Neil, 2006; Lal, 2011] can be applied, but a more direct and applicable method is used here. Important
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factors are identified and reviewed to assess the qualitative extent to which a project addresses the factor. Factors to consider include:
Degree and extent to which project can be expected to lessen flood damage
The severity of flooding and flood damage that the project addresses
Protection provided to critical facilities
Location relative to floodplains locations
Ability to promote growth and serve communities existing and future needs
Cost and alternative opportunities for funding
Based upon the above factors and estimated utility of the project addressing these factors and discussions and input from the Chambers County Commissioners, the proposed projects will be prioritized into two broad groups:
High priority projects- projects that should be given rapid attention for implementation
Low priority- projects that address needed improvements but for which lack of rapid implementation would not be of major concern
9.5 Recommendations for Programmatic Improvements
Programmatic improvements for drainage management and flood control in Chambers County should consider the following:
Regulation and Criteria: Modify drainage regulation and criteria to make criteria more consistent, effective, and encourage beneficial and responsible development, including standards for secondary drainage, sheet flow areas, minimum detention requirements, and adequate storm sewer design.
Coastal Flood Protection: Conduct (by the county or responsible municipality) frequent inspection of residential coastal structures and rigorous review of residential construction activities (plans and on-site inspection) to maximize compliance with state and regional construction codes for construction in high hazard coastal zones.
Sheet Flow Management: Review of site and drainage plans (by the county or responsible municipality) for a proposed development to determine the need for and provision of sheet flow areas as an integral part of the drainage management for the development.
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Use of Regional Detention: Encourage the use of efficient regional or sub-regional detention through careful planning, coordination with developers, potential tax or fee incentives, and/or structuring drainage ordinances and criteria to encourage regional detention projects.
Tracking Growth and Drainage Issues: Institute a management system in the county (in coordination with cities) that 1) tracks growth so that anticipatory drainage mitigation actions can be undertaken; and 2) maintain a comprehensive record of citizen complaints about drainage problems to use as guide in future drainage planning and setting priorities for project implementation.
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REFERENCES
Note: References marked with * indicate data source obtained directly from Chambers County Engineer’s Office
Anahuac National Wildlife Refuge, 2013. Anahuac National Wildlife Refuge, (http://en.wikipedia.org/wiki/Anahuac_National_Wildlife_Refuge) Feb 18 2013 ASFPM, 2011. Critical Facilities and Flood Risk, Association of State Floodplain Managers, Paper on Critical Facilities, Feb. 2011 *Berg Oliver, 2008. Wetland Assessment, Jurisdictional Waters of the United States, 723 Acres, More or Less, FM 565 & FM 1405 (Ameriport LLC), Report 7254WD08, Apr 2009 Berg Oliver, 2010a. Phase One Environmental Site Assessment, 218.014 Acres, More or Less, Northwest of U.S. IH-10 and FM 3180, Chambers County, Texas, Report No. 7638XP110, Report to Chambers County, Berg Oliver Associates Inc., Jul 2010 Berg Oliver, 2010b. Evaluation Letter, City of Mont Belvieu, 208.97 Acres More or Less West of FM 3180 and North of Interstate 10, Chambers County, Texas, Report No. 7743E, Berg Oliver Associates Inc., Nov 2010 Berg Oliver, 2011a. Wetland Assessment, Jurisdictional Waters of the United States, 40.56 Acres North of I-10 East and West of FM 3180, Chambers County, Texas, Report No. 7743WD11, Sep 2011 Berg Oliver, 2011b. Land Management Scoping for City of Mont Belvieu, 75.49 Acre Tract (Section B) and 92.92 Acre Tract (Section C), Chambers County, Texas, proposal letter to N. Sullins, Klotz Associates, Sep 28 2011b *BHA, 1994. Cherry Point Side Lot Ditches, Mont Belvieu, Cherrypoint Ranchets, Busch, Hutchison and Associates (Includes drainage easement information), Nov. 1994 *Brown & Gay, 2008. 74.25-Acre GreenTransport Facility, Drainage Impact Study, Cedar Bayou, Chambers County, Texas, Brown & Gay Engineers, Aug 2008 *Bury and Partners, 2006. Cedar Crossing Phase II Replating, Bury and Partners, Inc., Aug 2006 *Carnes, 2005. Drainage Report, I-10 Feeder Road, prepared for Chambers County and Texas Dept. of Transportation, Carnes Engineering Co., May 2005 Carnes, 2011. Engineering Plans, Brine Co., 14663 Hatcherville Road, Carnes Engineering Co., Sep. 2011 *Carroll & Blackman, Inc., 2005. Supplemental Storm Drainage and Detention Design Report for Storm Sewer, Storm Detention, Water and Sanitary Sewer Improvements, to Serve Lexington Patio Homes and Townhomes, Section One and Future Sections Two & Three, Carroll & Blackman, Inc., Aug 2005
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CFR, 2011a. 40 CFR Part 230 COMPENSATORY MITIGATION FOR LOSSES OF AQUATIC RESOURCES, Subpart J and 33 CFR §332 CFR, 2011b. 40 CFR Part 230 COMPENSATORY MITIGATION FOR LOSSES OF AQUATIC RESOURCES, Background CFR, 2011c. 33 CFR Part 325 Processing Of Department Of Army Permits §325.2, Alternative Procedures *Chambers County, 2003. Flooding Pictures, Southern Plantation Subdivision, correspondence and pictures of flooding, Chambers County Files, Mar 2003 *Chambers County, 2006. Chambers County Texas Public Infrastructure Design Standards, Apr 11, 2006, pg. 47-50 Chambers County, 2013a. Chambers County, Texas, (http://en.wikipedia.org/wiki/ Chambers County_Texas) Feb 18 2013 *Chambers County, 2013b. Email regarding and Plat of Subdivision of Bayridge Subdivision, (Beach City), circa 2013 *Chandler, 2003. Survey plot, Tiffany Acres Subdivision Section 2, Chambers Survey and Mapping, Michael W. Chandler, Survey, June 2003 Claunch & Miller, 2000. Feasibility Study – Improvements to Old River Country Ditch (Pin Oak – Oak Ridge Ditch) for Mont Belvieu, Claunch & Miller, Feb 2000 Claunch & Miller, 2004. Eagle Drive Drainage Study (FM 565-I10), City of Mont Belvieu, Claugh & Miller, Inc., Houston, TX, Jun 2004 *Cobb Fendly, 2012. Cedar Crossing Logistics Terminal, Topography and Watershed Map, CobbFendly, Jul 2012 Collins, 2008. Ranking Procedure for Capital Improvement Projects in Sugar Land, M.A. Collins, C. Stueving, and S. Kumar, Texas Section ASCE Spring Convention, Corpus Christi, TX, Apr 2008 Combs, 2013. Kilgore Business Park, Combs Commercial Investment Properties, Investment description PDF report, downloaded from Google, Aug 30, 2013 Connell, 2008. Wallisville Lake Project: Tranquility along the Trinity, T. L. Connell, Texas Highway Magazine, 2008 (http://www.texashighways.com) Feb 21, 2013 Crout, 1976. Soil Survey of Chambers County, Texas, by J.D. Crout, U.S. Soil Conservation Service Soil Survey, May 1976 Cushman & Wakefield, 209. Cedar Crossing Industrial Park, Cushman & Wakefield of Texas, Inc., Houston, TX, 2010 CWA, 2013. Map of Coastal Water Authority Facilities, provided by CWA, Septermber 2013.
Klotz Associates Proj. No. 1058.002.000 Master Drainage Plan November 2014 Chambers County, Texas R - 2
Dannenbaum, 2012. (Draft) Farm-to-Market Road 1409 Extension Drainage Analysis and Mitigation Design, prepared for Chambers County and TxDOT, Dannenbaum Corporation, Feb 2012 De Leon, 2013. Preliminary FM 1409 Route, Email Communication, O. DeLeon, Beaumont District, TxDOT, Jul 19, 2013 Dodson, 2005. Drainage Criteria Manual for Chambers County Texas, prepared by Dodson & Associates for Chambers County, Aug 9 2005 *Dodson, 2008. Champion Lakes Detention Analysis, Dodson and Associates, Inc. and Champion Lakes Detention Analysis, Amendments, pgs. 4 to 12, Jan 2009 *ESOR, 2005a. Borrow Ranch – Ultimate Drainage Conditions – Drainage Calculations, ESOR Consulting Engineers Inc., Transmittal Fax, Sep 2005 *ESOR, 2005b. Borrow Ranch, Section III – Drainage Piping and Culvert Piping Replacement, Ultimate Drainage Conditions –Drainage Calculations, ESOR Consulting Engineers Inc., Transmittal Fax, Sep 2005 Fugro, 209. Preliminary Geotechnical Study, Hackberry Detention Basin, City of Mont Belvieu, Mont Belvieu, Texas. Fugro Consultants, Nov 5 2010 Fugro, 2012. Proposal for Geotechnical Study, Old River Ditch Slope Improvements, Mont Belvieu, Letter Proposal to Klotz Associates, Fugro Consultants, Jan 30 2012 FEMA, 2013a. Flood Insurance Rate Study, Chambers County, Texas, Preliminary, Volume 1 of 3, FEMA, January 31, 2013. FEMA, 2013b. Flood Insurance Rate Study, Chambers County, Texas, Preliminary, Volume 2 of 3, FEMA, January 31, 2013. FEMA, 2013c. Flood Insurance Rate Study, Chambers County, Texas, Preliminary, Volume 3 of 3, FEMA, January 31, 2013. *GE Engineering, 2008. ICET Lake Subdivision, Master Drainage Plan, Chambers County, GE Engineering, Inc., Proj. No. 0648, Jul 2008 GLO, 209. Texas Coastal and Estuarine Land Conservation Program Plan, Texas General Land Office, Coastal Coordinating Division/Council, Jul 2010 Halley, 2013. M.C. Halley, S. O. White, and E.W. Watkins, ArcView GIS Extension for Estimating Curve Numbers, Proc. ESRI.com, Professional Paper 657, (http://proceedings.esri.com/ library/userconf/proc00/professional/papers/pap657/p658.htm) Feb 2013 HCFCD, 1988. Hydrology for Harris County, Seminar, jointly sponsored by HCFCD and Texas Section, Houston Branch, American Society of Civil Engineers, Mar 1988 HCFCD, 2008. Hydrology and Hydraulics Guidance Manual, Harris County Flood Control District, December 2009 Klotz Associates Proj. No. 1058.002.000 Master Drainage Plan November 2014 Chambers County, Texas R - 3
HGAC, 2013a: HGAC Land-use 2005 Regional Forecast, downloaded from HGAC website, July 2013 HGAC, 2013b: HGAC Land-use 2035 Regional Forecast, downloaded from HGAC website, July 2013 HHM, Inc. 2006 Intensive-Level Historic Resources Survey Report, Dayton Canal Along SH 146, Liberty County, Texas. On file at TxDOT ENV, Austin, Texas. Horizon, 2011. Horizon Environmental Services, Letter to N. Nikolov, Klotz Associates, Mar 7 2011 *Jones and Carter, 2008. Ameriport (Proposed 701-Acre) Rozelle Tract Development, Drainage and Detention Analysis, Jones and Carter, Inc., October 2008, revised October 2011 *Jones and Carter, 2008. Request for Conditional Letter of Map Revision (CLOMR) for Sawpit Gully – Ameriport CLOMR in Chambers County, Texas, Jones and Carter Inc., Apr 2009 *Jones and Carter, 209. Proposed 701 Acre Rozelle Tract Development, Drainage and Detention Analysis (Ameriport), Jones and Carter, Inc., Oct 2008, revised Apr 2010 (with H&H HMS models) Jones and Carter, 2012. Overall Layout (Map), Bay 10 Phase IB, Jones and Carter, 2012. Klotz, 2000. City of Baytown, Master Drainage Plan 2010, Vols 1 & 2, Klotz Associates and Wayne Smith & Associates, Inc., Feb 2000 Klotz, 2003. Brazoria County Drainage Criteria Manual, Klotz Associates, Nov 2003 Klotz, 2009a. City of Mont Belvieu, Master Drainage Plan (with Appendices), prepared by Klotz Associates, March, 2009 Klotz, 2009b. Project Proposal for Drainage Evaluations for McAdams Ditch, Sawpit Gully, and Plantation and Maley Woods Subdivision in Cove, Chambers County, Letter, Klotz Associates, to Chambers County Engineer, May 22, 2009 Klotz, 2010a. City of Mont Belvieu, Hackberry Gully Regional Detention Pond System, Preliminary Engr. Rept., Klotz Associates, Inc., Nov 2010 Klotz, 2010b. 190 Acre Detention Basin Site on Hackberry Creek, Letter Report, to Mont Belvieu, Klotz Associates, Feb 18, 2010 Klotz, 2010c. Performance Statement, Contract DRS010024 with Chambers County, Apr 2010 Klotz, 2011a. City of Baytown, Master Drainage Plan 2010, Vols 1 & 2, Klotz Associates, Sep 2010 Klotz, 2011b. Alignment Study for Extension of Langston Road to Eagle Drive, Mont Belvieu, Letter report to Mont Belvieu, Klotz Associates, Nov 2011 Klotz, 2011c. Presentation entitled “Old River Ditch Survey Investigation,” prepared by Klotz Associates for Mont Belvieu, Jan. 24, 2011. Klotz, 2011d. Hackberry Gully and Cotton Bayou Chambers County Ditch Improvements, prepared for TxDOT, 60% Preliminary Plans, Klotz Associates, May 2011
Klotz Associates Proj. No. 1058.002.000 Master Drainage Plan November 2014 Chambers County, Texas R - 4
Klotz, 2011e. Drainage Analysis and Construction Plan Preparation for Cotton Bayou South if IH-10 and Hackberry Gully South of IH-10 to Cotton Bayou, proposal to Carroll & Blackman, Inc, Klotz Associates. Apr 2011. Klotz, 2012a. BCA Analysis (HMGP/DR 1791-293) and FEMA Application, Cotton Bayou Diversion and Relief Channel, Phase 1, Mont Belvieu, Klotz Associates, June 2012 Klotz, 2012b. Draft Environmental Assessment, City of Mont Belvieu, Cotton Bayou Diversion and Relief Channel, Phase 1 Conditional Approval, HMGP / DR 1791-293, Mont Belvieu, Chambers County, Texas, Klotz Associates, February 2012 Klotz, 2012c. Response to FEMA RFI, Cotton Bayou Diversion and Relief Channel, Phase 1 Conditional Approval, HMGP/ DR 1791-293, Mont Belvieu, Chambers County, Klotz Associates, Jun 2012. Klotz, 2012d. Master Drainage Plan, Galveston County, prepared by Klotz Associates, April 2012 Klotz, 2013. City of Mont Belvieu, Cotton Bayou Diversion and Relief Channel Project, Phase I Conditional Approval DR1791-293,30% Drawings, Klotz Associates, Jan 2013 Knudson & Associates, 1998. Comprehensive Plan, City of Mont Belvieu, Texas, Knudson & Associates, in association with Traffic Engineers, Inc., CivilTech, Inc., and Brooks and Sparks, Inc., 1998. Komogorova and O’Neil, 2006. Integrating GIS and Capital Improvement Program: Quantifiable Prioritization Process, T. Komogorova and O’Neil, ISRI, 2006 KSA, 2012. East Eagle Drive Infrastructure Master Plan (Drainage), City of Mont Belvieu, Chambers County, Texas, KSA Engineers, Dec 2012 Lal, 2011. The Introduction to the Water Quality Index, H. Lal, Jo. of Water Efficiency, Sep./Oct. 2011, pg. 44. Lippke, 2013a. y, Segment Exhibit entitled “Offsite Drainage System with Conceptual Regional Drainage Easements, for Kilgore Parkway, Segments 4& 5,” Lippke Cartwright & Roberts, Inc., Jan 16 2013 Lippke, 2013b. Kilgore Regional Drainage Plan (Preliminary), report to Chambers County,” Lippke Cartwright & Roberts, Inc., Jul 16, 2013 List of Highways, 2013. List of Highways in Chambers County, Texas, (http://www.texashighways.com/?option=com_content&catid=39&id=5804&view=article) Feb 18 2013) Maidment, 1992. Handbook of Hydrology, David R. Maidment, Editor, McGraw Hill Book Co., New York, NY, 1992 Mont Belvieu, 2013. Miscellaneous drawing, Cottonwood Estates, Phase 2, provided by City of Mont Belvieu, Sep 2013 Klotz Associates Proj. No. 1058.002.000 Master Drainage Plan November 2014 Chambers County, Texas R - 5
NOAA, 2013. Booklet Chart, Galveston Bay, US National Oceanic and Atmospheric Administration (NOAA) Chart 326 (http://ocsdata.ncd.noaa.gov/BookletChart/11326_BookletChart.pdf), Feb22 2013 Old River-Winfree Community News, 2011. FM 1409 Extension News from Chambers County Commissioner’s Court, Old River-Winfree Community New and Information, March, 2011 *Pate Engineers, 2005. Master Drainage Study – Phase I, Chambers County Improvement District No. 1, Pate Engineers, Inc., Jun 2005 *Pate Engineers, 2006. Master Drainage Study – Phase II, Chambers County Improvement District No. 1, Pate Engineers, Inc., Jan 2006 PB, 2008. State Highway 99, Drainage Impact Study, Chambers County, prepared for the Texas Department of Transportation Bridge Division and the Beaumont District, by PB Inc., Dec 2007 PBS&J, 2001a. State Highway 99 Drainage Study, Chambers County, Texas Department of Transportation, PBS&J, 2001 PBS&J, 2001b. Final Drainage and Impact Analysis, S.H. 99, Chambers County, Texas (CSJ 3510-10- 002), PBS&J, May, 2001 R.G. Miller, 2011a. Drainage Analysis for Proposed Eagle Drive Roadway Improvements, City of Mont Belvieu, Chambers County, Texas R.G. Miller, 2011b. Engineering Drawings, Eagle Drive, Mont Belvieu, R.G. Miller, Nov-Dec 2011RBC 2012. Official Notice of Sale and Preliminary Official Statement, Chambers County Improvement District No.1, RBC Capital Markets, RBC Capital Markets, 2012 TCB/AECOM, 2006. Final Drainage Impact Analysis for SH 99 (CSJ 318.7-010005 and 318.7-02-006), Turner Collie & Braden, TCB/AECOM,May 2006. Texas State Historical Association, 2013. Wildlife Areas, Handbook of Texas Online, (http://www.tshaonline.org/handbook/online/articles/gbw02) Feb 18 2013 Trust for Public Land, 2008. Chambers County Greenprint for Growth and Conservation, The Trust for Public Land, June 2009 TPWD, 2006. Candy Cain Abshier WMA, Texas Parks and Wildlife Department, (http://www.tpwd.state.tx.us/huntwild/hunt/wma/find_a_wma/list/?id=36) February 21, 2013 TBCD, 2013. Trinity Bay Conservation District webpage, July 2013 TxDOT, 2001. Hydraulic Design Manual, TxDOT, Oct 2001 TxDOT, 2004. Environmental Manual: Texas Department of Transportation Manual System; Environmental Affairs Division (ENV), Texas Department of Transportation, 2004 TxDOT, 2013. TxDOT webpage: Project Tracker; Project Detail, June 12, 2013
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USACE, 2013. Wallisville Lake Project Office, U.S. Army Corp of Engineers, Galveston District, (http://www.swg.usace.army.mil/Locations/WallisvilleLakeProjectOffice.aspx) Feb 21 2013 USACE, 2011. U.S. Army Corps of Engineers Galveston, PE-R Permit Information, accessed April, 2011 USACE, 2010c. U.S. Army Corps of Engineers Regulatory Program Overview; USACE Fort Worth District, 2010 USACE, 2008. National Hurricane Program Storm Surge Mapping, Sabine Study Area, National Planning Center of Expertise for Coastal Storm Drainage Reduction, USACE, and FEMA, Nov 2009 USEPA, 2013. Chambers County, TX, “Surf Your Watershed,” (http://cfpub.epa.gov/surf/locate/index.cfm) Feb 18 2013 USFWS, ca. 2012. Texas Chenier Plain National Wildlife Refuge Complex, Site Partner Network Sourcebook, U.S. Fish and Wildlife Service, pg. 17 USFWS, 2013. Refuge Map – Anahuac - U.S. Fish and Wildlife Service, USFWS and National Wildlife Refuge System, (http://www.fws.gov/refuges/profiles/index.cfm?id=21521) Feb 18 2013 USGS, 2013. Geographic Names Information System – GNIS, United Stated Geologic Survey, (http://nhd.usgs.gov/gnis.html), Feb 21 2013 *Wilson Survey, 2008. Robert Barrow Plat (with subdivision flooding photos), Preliminary Plat of Perry Barrow Tract (42.381 ac), Wilson Survey Group, Jun 2007
Klotz Associates Proj. No. 1058.002.000 Master Drainage Plan November 2014 Chambers County, Texas R - 7 F
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