An Overview of Urban Stormwater- Management Practices in ...

An Overview of Urban StormwaterManagement Practices in Miami-Dade County, Florida

By David A. Chin

Prepared in cooperation with the SOUTH FLORIDA WATER MANAGEMENT DISTRICT

Open-File Report 2004-1346

U.S. Department of the Interior U.S. Geological Survey

U.S. Department of the Interior Gale A. Norton, Secretary

U.S. Geological Survey Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225

For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation: Chin, D.A., 2004, An Overview of Urban Stormwater-Management Practices in Miami-Dade County, Florida: U.S. Geological Survey Open-File Report 2004-1346, 17 p.

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Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Relevance and Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Urban Stormwater-Management Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Overview of Agency Stormwater-Management Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Miami-Dade Department of Environmental Resources Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Roadways. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Community Stormwater Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

South Florida Water Management District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Water-Quantity Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Water-Quality Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Florida Department of Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Open Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Storm Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Stormwater Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Design of Exfiltration Trenches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Agency Design Methodologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 South Florida Water Management District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Miami-Dade Department of Environmental Resources Management. . . . . . . . . . . 13 Florida Department of Transportation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Alternative Exfiltration Trench Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figures

1. Photograph showing exfiltration trench under construction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Map showing location of major roads and canals in Miami-Dade County,

Florida. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Hyetograph showing rainfall distribution for a hypothetical 3-day storm. . . . . . . . . . . . . . . 6 4. Map showing Florida Department of Transportation rainfall zones. . . . . . . . . . . . . . . . . . . . 9 5. Comparison of Miami-Dade Department of Environmental Resources

Management and Florida Department of Transportation intensity duration frequency curves for return periods of 5, 10, and 25 years . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Cross-sectional view of typical exfiltration trench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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Tables

1. Miami-Dade Department of Environmental Resources Management design storm frequenciesand flood limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Data points for a normalized South Florida Water Management District 3-day hyetograph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8

Conversion Factors and Vertical Datum

Multiply

inch (in.) inch per hour (in/hr)

inch per day (in/d) foot (ft)

square foot (ft2) foot per second (ft/s) foot per second squared (ft/s2) square foot per second (ft2/s) cubic foot per second per square foot per foot (ft3/s/ft2/ft)

acre

By

To Obtain

2.54 2.54 2.54 0.3048 0.09290 0.3048 0.3048 0.09290 1.000

0.004047

centimeter (cm)

centimeter per hour (cm/hr)

centimeter per day (cm/d)

meter (m) square meter (m2)

meter per second (m/s) meter per second squared (m/s2) square meter per second (m2/s)

cubic meter per second per square meter per meter (m3/s/m2/m)

square meter (m2)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88); horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27), unless otherwise noted.

Acronyms and Abbreviations

DERM

FDOT FEMA

HGL IDF mph NPDES ppm SFWMD USGS

Miami-Dade Department of Environmental Resources Management

Florida Department of Transportation Federal Emergency Management Agency Hydraulic grade line Intensity duration frequency mile per hour National Pollutant Discharge Elimination System part per million South Florida Water Management District U.S. Geological Survey

An Overview of Urban Stormwater-Management Practices in Miami-Dade County, Florida

By David A. Chin

Abstract

Agencies with jurisdiction over stormwater-management systems in Miami-Dade County, Florida, include the MiamiDade Department of Environmental Resources Management (DERM), South Florida Water Management District (SFWMD), and Florida Department of Transportation (FDOT). These agencies are primarily concerned with minor drainage systems that handle runoff from storms with return periods of 10 years or less (DERM), major drainage systems that handle runoff from storms with return periods of 25 years or more (SFWMD), and runoff from major roadways (FDOT). All drainage regulations require retention of at least a specified water-quality volume (defined volume of surface runoff), typically the first inch of runoff. The DERM and FDOT intensity duration frequency (IDF) curves used as a basis for design are similar but different, with differences particularly apparent for short-duration storms. The SFWMD 25-year 3-day storm incorporates an IDF curve that is substantially different from both the IDF curves of DERM and FDOT. A DERM methodology for designing closed exfiltration systems is applicable to storms of 1-hour duration, but is not applicable to all storms with a given T-year return period. A trench design that is applicable to all storms with a given T-year return period is presented as an alternative approach.

Stormwater-management systems include minor and major drainage systems. Minor drainage systems typically consist of stormwater inlets to subsurface systems that handle runoff from design storms with return periods of 10 years or less, whereas major drainage systems typically include the above-ground pathways that handle runoff from storms with greater return periods. A clear understanding of the role and function of stormwater-management systems and the regulatory environment in which these systems are designed provides for realistic expectations of their performance during periods of heavy rainfall.

The purposes of this report are to: (1) present an overview of the State and local regulations governing the design of stormwater management systems in Miami-Dade County, (2) describe the types of stormwater-management systems that are commonly used, and (3) present an approach for designing closed exfiltration trench systems to accept runoff from all storms with a given T-year return period. Agency documents should be consulted for detailed design guidance. This report is the result of a cooperative effort between the U.S. Geological Survey (USGS) and SFWMD.

Relevance and Benefits

Introduction

Stormwater management in Miami-Dade County, Florida, is regulated by several governmental agencies, primarily the Miami-Dade Department of Environmental Resources Management (DERM), the South Florida Water Management District (SFWMD), and the Florida Department of Transportation (FDOT). These agencies address the quantities of surface runoff that must be handled by drainage systems, and the amount of onsite treatment that must be provided.

This report is intended to assist engineers, scientists, regulators, and the general public in understanding the function and performance of stormwater-management systems in MiamiDade County, Florida. The Federal Government also has a stake in the effectiveness of stormwater management systems. The prevention of flooding and associated property losses are a concern of the Federal Emergency Management Agency (FEMA), and the quality of stormwater runoff discharged to surface waters in Miami-Dade County is covered by National Pollutant Discharge Elimination System (NPDES) permits.

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