Stormwater management for land development:methods and calculations for quantity control

STORMWATER MANAGEMENT

FOR LAND DEVELOPMENT

Stormwater Management for Land Development: Methods and Calculations for Quantity Control. Thomas A. Seybert © 2006 John Wiley & Sons, Inc. ISBN: 978-0-471-72177-2

STORMWATER

MANAGEMENT FOR

LAND DEVELOPMENT

Methods and Calculations for

Quantity Control

THOMAS A. SEYBERT

JOHN WILEY & SONS, INC.

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Copyright 2006 by John Wiley & Sons, Inc. All rights reserved.

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Library of Congress Cataloging-in-Publication Data:

Seybert, Thomas A.

Stormwater management for land development: methods and calculations for quantity

control / Thomas A. Seybert.

p. cm.

ISBN-13: 978-0-471-72177-2 (cloth)

ISBN-10: 0-471-72177-8 (cloth)

1. Urban runoff—Management. 2. Land use—Environmental aspects. 3. Water

quality management. I. Title.

TD657.S49 2006

628.2—dc22

2006000885

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

To my loving wife and best friend, Chris

vii

CONTENTS

PREFACE xi

ACKNOWLEDGMENTS xv

1 INTRODUCTION TO STORMWATER MANAGEMENT 1

1.1 Introduction / 1

1.2 Effect of Land Development / 1

1.3 Stormwater Design Criteria / 2

1.4 Comprehensive and Innovative Design / 4

1.5 Book Organization / 8

2 FLUID PROPERTIES AND BASIC STATICS 11

2.1 Introduction / 11

2.2 Units / 12

2.3 Fluid Properties / 15

2.4 Pressure / 20

2.5 Forces on Submerged Objects / 26

2.6 Buoyant Force / 31

3 FLUID FLOW 34

3.1 Introduction / 34

3.2 Flow Rate / 35

3.3 Conservation of Mass / 37

viii CONTENTS

3.4 Energy Methods / 40

3.5 Bernoulli Equation / 43

3.6 Energy Losses / 47

3.7 General Energy Equation / 56

3.8 The Orifice / 58

4 OPEN CHANNEL FLOW 66

4.1 Introduction / 66

4.2 Flow Classifications / 67

4.3 Hydraulic Radius and Depth / 69

4.4 Flow Behavior / 71

4.5 Steady Uniform Flow / 73

4.6 Specific Energy and Critical Depth / 82

4.7 Channel Sizing / 86

4.8 Circular Conduits Flowing Full or Partially Full / 88

4.9 The Weir / 90

5 HYDROLOGY, WATERSHEDS, AND SOILS 98

5.1 Introduction / 98

5.2 The Hydrologic Cycle and Water Budget / 99

5.3 Watersheds / 102

5.4 Soils and Infiltration / 111

5.5 Watershed versus Site Hydrology / 116

6 RAINFALL 120

6.1 Introduction / 120

6.2 Rainfall Characteristics / 121

6.3 VDF and IDF Charts / 126

6.4 Design Storms / 130

7 TRAVEL TIME 145

7.1 Introduction / 145

7.2 Time of Concentration / 145

7.3 Sheet Flow / 148

7.4 Concentrated Flow / 153

7.5 Mixed Sheet and Concentrated Flow / 157

7.6 Channel or Pipe Flow / 162

7.7 Segmental Flow Analysis / 164

CONTENTS ix

7.8 NRCS Segmental Method / 169

7.9 NRCS Lag Equation / 171

7.10 Comparison of Methods / 173

8 RUNOFF DEPTH AND PEAK FLOW 179

8.1 Introduction / 179

8.2 Runoff Curve Number Method / 180

8.3 NRCS Graphical Peak Discharge Method / 197

8.4 Rational Peak Flow / 204

9 HYDROGRAPHS 215

9.1 Introduction / 215

9.2 Unit Hydrograph Concepts / 217

9.3 NRCS Dimensionless Unit Hydrograph / 224

9.4 Delmarva Unit Hydrograph / 234

9.5 NRCS Tabular Hydrograph / 236

9.6 Rational Hydrograph / 247

10 ROUTING METHODS 257

10.1 Introduction / 257

10.2 Channel Routing / 258

10.3 Muskingum Channel Routing / 260

10.4 Muskingum-Cunge Channel Routing / 269

10.5 Modified Puls Basin Routing / 272

11 DRAINAGE CONVEYANCE AND CONTROL 284

11.1 Introduction / 284

11.2 Swales and Open Channels / 285

11.3 Storm Sewer Design / 296

11.4 Culverts / 312

12 MULTIPLE-EVENT DETENTION DESIGN 326

12.1 Introduction / 326

12.2 Detention Volume Estimates / 327

12.3 Multiple-Stage Outlet Flow Analysis / 332

12.4 Storage and Outlet Design Procedure / 337

12.5 Design Example / 339

x CONTENTS

APPENDIX A DEVELOPMENT OF THE MANNING EQUATION 358

APPENDIX B DEVELOPMENT OF THE MUSKINGUM ROUTING

EQUATIONS 361

APPENDIX C DETAILED CALCULATIONS FOR EXAMPLE 11.4 364

APPENDIX D MOODY DIAGRAM 367

INDEX 369

xi

PREFACE

Stormwater Management for Land Development: Methods and Calculations

for Quantity Control, was written in response to the need for a book that

covers the basic methods of hydraulics and hydrology used in land develop￾ment design. The structure of the book is placed in three segments: fluid

mechanics and hydraulics, watershed analysis and basic hydrologic methods,

and stormwater design for conveyance and detention. The book is intended

as a text for engineering and engineering technology students at the bacca￾laureate level. It is specifically written for academic programs where a single

fluid mechanics and hydrology course is used to present stormwater manage￾ment methods. In addition to academic use, the text is intended as a desktop

reference for professionals engaged in stormwater runoff calculations, con￾veyance design, and detention design. It is recognized that in professional

practice, the majority of stormwater calculations are done with specialized

commercial software. However, the practitioner must understand the methods

behind the software, and this book explains the origin and application of many

of these computerized methods.

The need for a texbook like this became apparent to me while teaching

portions of the Penn State University continuing education short course titled

Computational Methods in Stormwater Management. The short course, which

was first started in 1978 by hydrology faculty in the Department of Civil

Engineering at Penn State, is intended for consulting engineers, municipal

engineers, landscape architects, surveyors, and other professionals engaged in

the design or review of stormwater management plans. I joined the short

course teaching staff in 1984, and many attendees would ask me to recom￾mend a single reference that includes basic coverage of hydraulic and hydro￾logic methods in stormwater design. I was not aware of any single book that

xii PREFACE

would fill the need. For the short course, notes in a three-ring binder were

prepared and distributed to the attendees as their stormwater reference. These

notes were developed by various graduate students and faculty at Penn State,

and I developed four or five of the sections over the years. In time, accu￾mulation of the sections that I wrote created the foundation for part of this

book, mainly the hydrology chapters.

In Pennsylvania, Maryland, and a few other states, surveyors and surveying

engineers are allowed, by law, to practice stormwater management design,

mainly in connection with subdivision of land for housing or commercial

development. In these states, there is a need for continuing education of sur￾veyors to gain the skills necessary to complete reasonable stormwater design

with accepted hydraulic and hydrologic methods. To fill this need, I, and my

mentor and colleague Gert Aron, developed a set of workshops to cover basic

hydraulics and hydrology for surveyors engaged in land development design.

The workshops also serve as an exam review for surveyors-in-training who

are getting ready to sit for their registration exam. The workshops have been

offered over the past 15 years at the Pennsylvania Society of Land Surveyors

State Conference, held annually in Hershey, PA. Notes developed for use in

this workshop have served as the framework for several parts of this book,

mainly the fluid mechanics and hydraulics chapters.

In 1996, I became a faculty member in the Surveying Program, College of

Engineering, at Penn State University, Wilkes-Barre campus. One of my im￾mediate duties was to create a course in stormwater management that would

be appropriate for baccalaureate surveying graduates who intended to practice

surveying in Pennsylvania. A three credit elective course was developed in

1997, and after two modifications, it evolved into a three credit course that

contains fifteen weeks of instruction, with the first five weeks focusing on

fluid mechanics and hydraulics, the next seven weeks focusing on hydrologic

methods, and the last three weeks focusing on stormwater design. I knew that

a good textbook for this course was not available, so I began to write a

textbook in the Fall of 1998. During each course offering I would try to write

a new chapter, and use the draft chapters as a class reference. After a few

years of this approach, I had five chapters written, with about seven to go.

The following year I was awarded a sabbatical, and during the sabbatical

year, I finished the manuscript.

This book covers common methods used in stormwater design for quantity

control. The book does not cover design for other stormwater topics such as

water quality, groundwater recharge, and stream bank erosion. The original

outline of topics for this book did include chapters on innovative methods in

stormwater management and stormwater design with best management prac￾tices. Unfortunately, these chapters were dropped as the deadline for the man￾uscript approached. This kept the entire focus of the book on stormwater

quantity claculations, which is probably for the better. If inspiration and time

come my way, a companion text may be written dealing with these other

issues. For now, I plan to concentrate on maintaining and improving this text.

PREFACE xiii

As with any first publication of a technical book, it has been my experience

that, even with the closest checking and double checking, some errors will

most likely exist in the printed manuscript. As the author, I am responsible

for these errors. Questions about the text and possible errata should be di￾rected to me. Example problems have been checked for numerical accuracy,

yet it is difficult to discover all errors. Hopefully, the context of a concept

will be clear enough such that errors will not impede the understanding of a

concept, but simply cause the reader to examine the topic a bit closer.

THOMAS A. SEYBERT

Wilkes-Barre, Pennsylvania

xv

ACKNOWLEDGMENTS

During the time it took me to complete this book, several people were very

helpful and encouraging through the process. First and foremost, I am blessed

with a very supportive and loving wife, and two wonderful children Beth and

Ben. There were many long hours during evenings, weekends, and early

mornings during the writing, when I was not able to be with my three favorite

people. For their patience, understanding and encouragement, I am very grate￾ful. I also wish to acknowledge my father and mother. They taught me how

to embrace work and persevere through a task.

Encouragement for pursuing the book came from several engineering fac￾ulty at Penn State Wilkes-Barre. However, the most helpful faculty encour￾agement came from Chuck Ghilani, Professor of Engineering in the Surveying

Program, who, at the time, was in the process of writing his second book for

surveying students and professionals. We had many discussions about the

book writing process, and these discussions made me realize that I could

write a textbook if I put my mind to it. Early draft versions of the manuscript

were used and reviewed by baccalaureate students in surveying. Many of the

practice problems and example problems were solved by these students. Irene

Stubb, staff assistant, read several chapters for grammatical errors and also

prepared, in part, some of the tables in the text. Several other chapters were

reviewed for format and grammar by my wife, Chris. All through the writing

process, she was always willing to help, even at times when she had a dozen

other things to do to keep our household running smoothly.

Much of the research for writing this book was performed through the

Penn State Library System. Marcia Nelson and Matthew O’Conner, library

staff at Penn State Wilkes-Barre, were very helpful in finding reference ma-

xvi ACKNOWLEDGMENTS

terial, particularly some of the very old documents dating back to the late

nineteenth and early twentieth centuries.

The manuscript was reviewed in its entirety by Gert Aron, Professor Emer￾itus of Civil Engineering, Penn State University. He provided several very

good suggestions on content and organization. Jim Harper, book editor, and

Elizabeth Cepeda, production editor of the Wiley Publishers staff, were very

helpful and pleasant during the writing and production process.

Last and not least, I would like to thank my faithful writing companion,

Ramsey, our Australian cattle dog. Through all those long hours of writing,

he stayed with me—usually sleeping on the floor near my feet—keeping me

company while I typed.

1

CHAPTER 1

INTRODUCTION TO

STORMWATER MANAGEMENT

1.1 Introduction 1

1.2 Effect of Land Development 1

1.3 Stormwater Design Criteria 2

1.4 Comprehensive and Innovative

Design 4

1.5 Book Organization 8

1.1 INTRODUCTION

Whenever rainfall hits the surface of the Earth, one of several things will

happen. The rainfall may wet a dry surface, cling to that surface, and evap￾orate after the rainfall event ends. It may collect and be held in a surface

depression where it will infiltrate slowly into the Earth’s subsurface. It may

infiltrate directly into the soil, wetting and saturating the soil and subsurface,

eventually adding to the local groundwater supply. It also may be repelled by

a saturated soil or impervious surface and gathered to form surface runoff.

This last possibility of rainfall transforming into surface runoff is a critical

issue in land development. When land is developed, the site will respond

differently to rainfall. The change is usually dramatic, with increases in runoff

rates and runoff volumes. Stormwater management is that specialized field of

science and engineering that is applied to minimize, control, and remediate

the effects of land-use change on a watershed or land development site.

1.2 EFFECT OF LAND DEVELOPMENT

The development of land to construct industrial facilities, businesses, and

homes involves land-use change that transforms pervious surfaces of woods,

Stormwater Management for Land Development: Methods and Calculations for Quantity Control. Thomas A. Seybert © 2006 John Wiley & Sons, Inc. ISBN: 978-0-471-72177-2