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Highway Drainage Manual

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Highway Drainage Manual GHWAY Maryland Depapament of &nspo~at~on State Highway Adm~nfstmtlon GHWAV MANUAL MARY LAN D DEPARTMENT OF f RANSPORTATION STATE HIGHWAY ADMINISTRATION PREFACE In 1966 House Document 465 was published by the Task Force on Federal Flood Control Pol icy. Such act was later followed by the 1969 Environmental Protec- tion Act. After numerous intervening legal acts associ ated with envi ronmental matters, the U.S. Water Resources Council pub1 ished the following document "A Unified National Program for Flood Plain Management", dated September 1979. Such document sets forth the Federal requirements to meet Executive Order 11998. The State of Maryland, since the formation of the Department of Natural Resources, in 1972, has steadily pursued the task of developing plans for regulating and/or assisting in the regulation of activities within the 100 year flood plain. The Maryland General Assembly in an effort to more closely control State funded activities in the 100 year flood plain, passed the "Flood Hazard Management Act of 1976. As one of the means for exercising control over activities within the 100 year flood plain, the Water Resources Administration promulgated their "Rules and n-- ~-LL--- neyu I~Llor15 governing cvnstruttion on Non-Tidal ljaters and Fiooci Plains" dated August 11, 1978 and the "Maryland Interim Watershed Management Policy" of 1977. The Federal and State flood plain regulations were in a constant state of change and formation during the entire decade from 1970 to 1980. Such state of change naturally caused considerable confusion in the fields of hydrology and hydrau- lics especially in relation to highway construction within the 100 year flood plain. In an effort to eliminate much of the confusion and to set forth criteria State Highway Administration (S.H.A.) deems necessary to meet the Federal and State regulatory requirements, including those of the Federal Highway Administration, the S.H.A. has developed this present document. While special problems may require unique solutions, the design of most drainage faci 1ities can be accompl ished by routine procedures. This criteria will be used in conjunction with the current Standard Plates of the BOOK OF STANDARDS, HIGHWAY AND INCIDEKTAL STRUCTURES, Maryland State Highway Administrati~n. This document prior to its promulgation has been reviewed by the Maryland State Water Resources Administration and the Baltimore Office of the Federal Highway Administration. Since this document is a part of the S.H.A. 's effort to comply with Federal and State regu1ator.y requirements, the need for periodic updating is apparent; therefore, records of persons, firms, etc., uti1 izing the subject document must be accurately kept for updating purposes. Users cooperation in this matter is respectfully requested. CONTENTS PREFACE. ................................. i INTRODUCTION A. Organization of Document ...................... xv B. S.H.A. Objectives. ......................... xv C. Pub1 ic Involvement .........................xvii D. Location Hydraulic Studies ..................... xvii E. Only Practicable A1 ternative Findings. ...............xvii F. Design Storms. ...........................xvii G. Level of Environmental Studies by Project Planning ........ xviii LIST OF TABLES AND CHARTS. ......................xxi-xxii iii PART I . DIVISION OF HIGHWAY DEVELOPMENT CHAPTER 1 . DESIGN CRITERIA A. S.H.A. Computations .......................I-1-A-1 B. Private Development .......................I-1-B-1 CHAPTER 2 . BASIC CONCEPTS A. Hydrology ............................I-2-A-1 1. The Rational Method .....................I-2-A-1 a . Runoff Coefficient .................... I-2-A-1 b . Time of Concentration ..................I-2-A-10 c . Rainfall Intensity.................... I-2-A-27 d . Rainfall Intensity Coefficient.............. I-2-A-27 e . Drainage Area ......................I-2-A-27 2 . The Soil Conservation Service Methods ............I-2-A-49 a . Runoff Curve Numbers ................... I-2-A-49 b . Time of Concentration ..................I-2-A-52 c . Rainfaii Data ...................... I-2-A-52 d . Drainage on the Eastern Shore .............. I-2-A-52 e . TR-20 Input Data .....................I-2-A-68 B. Hydraul ics 1. Manning's Formula ...................... I-2-B-1 2 . The Continuity Equation ...................I-2-B-11 3 . Entrance Control Headwater ..................I-2-B-11 4 . Outlet Control Headwater ...................I-2-B-12 CHAPTER 3 . OPEN DRAINAGE A. Ditches. Gutters and Channels 1. Geiiera: Limitations . .................... i-3-A-i 2 . Design ........ ...................1.3. A.l 3 . Median Ditches.... .................... I-3-A-1 4 . Berm Ditches ..... ....................I-3-A-1 5 . Bench Ditches ...... ..................1.3. A.l 6 . Side Ditches..... ....................I-3-A-1 7 . Surface Drain Ditches ....................I-3-A-2 8 . Outlet Ditches. Inlet Ditches and Other Channel Improvements . ...................1.3. A.2 B . Inlets 1. General Limitations .....................I-3-B-1 2 . Median Inlets ........................ I-3-B-1 3 . Standard Curb Openings ....................I-3-B-1 CONTENTS C . Pipe Culverts 1. General Limitations .....................I-3-C-1 2. Pipe Culverts for Highways on New Locations ......... I-3-C-7 3 . Pipe Culverts for Rehabilitated and/or Relocated Highways ...................... I-3-C-7 4 . Design ............................I-3-C-7 D. Box Culverts ........................... I-3-D-1 CHAPTER 4 .STORM DRAIN SYSTEMS A. Structures 1. Inlets a . General Limitations ...................I-4-A-1 b . Inlets on Grade .....................I-4-A-1 c . Sump Inlets ....................... I-4-A-2 2 . Manholes ........................... I-4-A-2 3. Bend Structures .......................I-4-A-2 B. Pipes 1. General Limitations .....................I-4-B-1 2 . Design ............................I-4-B-1 C . Hydraul ic Gradient Calculations 1. Beginning Elevation .....................I-4-C-1 2 . Pipe and Structure Losses a . General ......................... I-4-C-1 b. Junctions ........................I-4-C-11 3 . General Limitations .....................I-4-C-12 CHAPTER 5 .STORM WATER MANAGEMENT A. Objective ............................I-5-A-1 5 . Projects Requiring Management .................. I-5-B-1 C . A1 1owable Discharge .......................I-5-C-1 D . Required Storage 1. Preliminary Design...................... I-5-D-1 2 . Final Design ..........................I-5-D-2 E. Detention Facility Types 1. Highway Projects ....................... I-5-E-1 2. Other Projects........................ I-5-E-1 CONTENTS F . Release Rates ..........................I-5-F-1 G . Control Structures ........................ I-5-G-1 CHAPTER 6 . KARST TOPOGRAPHY A . General .............................I-6-A-1 0 . Sinkholes as Outfalls ......................I-6-B-1 PART I1 .DIVISION OF BRIDGE DEVELOPMENT CHAPTER 1 . GENERAL A . Purpose ............................. 11-1-A-1 B . Applicability .......................... 11-1-B-1 C . Public Involvement ....................... 11-1-C-1 D. Location Hydraulic Studies ...................11-1-0-1 E. Only Practicable Alternative Findings.............. 11-1-E-1 CHAPTER 2 . DESIGN STANDARDS A . Commencement of Preparation of the Hydrologic/ Hydraulic Design ........................11-2-A-1 B . Basic Concepts 1. Hydro1ogy .......................... 2 . Hydraulics ......................... 3 . Freeboard .......................... 4 . Open Channel Flow...................... 5 . Storm Water Management ................... 6 . Karst Topography ...................... 7 . Private Development ..................... a . Basic Concept ...................... b . Openchannel ...................... c . Storm Water Management ................. Flood Plain Encroachments ....................11-2-C-1 Pre1iminar.y Cost Estimates ...................11-2-D-1 Conveyance ...........................11-2-E-1 Data to be Shown on Construction Plans .............11-2-F-1 Existing Facilities .......................11-2-G-1 Design Storms .......................... 11-2-H-1 Util ity Protection Against Flood Loss ..............11-2-1-1 Design Needs to Meet Permit Requirements ............ 11-2-J-1 i . Undefined F.I.A. Speciai Flood Hazard Areas ......... 11-2-4-2 a . Plan Development . Phase I1............... 11-2-J-2 b . Plan Development . Phase I11 ..............11-2-J-3 2 . F.I.A. Designated Special Flood Hazard Area Boundary Map Promulated ...................11-2-J-4 a . Plan Development .Phase I1............... 11-2-J-4 b . Plan Development .Phase 111 ..............11-2-J-4 3 . F.I.A. Has Provided Notice of Final Base Flood Elevations ...................... 11-2-J-4 a . Plan Development .Phase I1............... 11-2-J-5 b . Plan Development .Phase I11 .............. 11-2-J-5 CONTENTS CHAPTER 3 . CONTENTS OF DESIGN REPORT A. Hydrologic Portion 1. General .............. 2 . Maps and Map Details ....... 3 . Coefficients of Runoff ...... 4 . Recurrence Intervals of Storms to be Considered ........... 5 . Maximum Previous Known Discharge . 6 . High Water Elevation of Record . 7 . Pertinent Gage Station Data .... 8 . Pertinent Existing Highways .... 9 . Evaluation of HlJD Material .... B . Hydraulic Portion........................ 11-3-B-1 1. Map Depicting Limits of the 100 Year Flood .........11-3-B-1 2 . Utilization of Contour Maps ................. 11-3-B-1 a . Use with Multiple Water Surface Profiles ........11-3-B-1 b . Flow Distribution.................... 11-3-B-2 3 . Streamprofile .......................11-3-B-2 4 . StageIDischarge
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