Western Washington Hydrology Model 2012 User Manual

187 Pages·2016·14.25 MB·English

Western Washington Hydrology Model
2012

User Manual

February 2016
Western Washington Hydrology Model
2012

User Manual

Prepared by
Clear Creek Solutions, Inc.

February 2016
To download the Western Washington Hydrology Model
and the electronic version of this user’s manual,
please visit our website at:
http://www.ecy.wa.gov/programs/wq/stormwater/wwhm_training/wwhm/wwhm2012/index.html
.

If you have questions about the WWHM, please contact:
Foroozan Labib, Environmental Engineer
Department of Ecology
Water Quality Program
[phone]
[email protected]
If you require this document in an alternative format, please call the secretary at (360)
407-6401. The TTY number is 711 or 1-800-833-6388.
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Table of Contents

Introduction ......................................................................................................................... 1
Quick Start ......................................................................................................................... 3
Main Screens .................................................................................................................... 27

Map Information Screen .................................................................................................. 28

General Project Information Screen ................................................................................. 30
Schematic Editor .............................................................................................................. 31
Land Use Basin ................................................................................................................ 32
Pervious Lateral Basin ..................................................................................................... 35
Impervious Lateral Basin ................................................................................................. 36
Trapezoidal Pond ............................................................................................................. 37
Vault ................................................................................................................................. 39
Tank ................................................................................................................................. 40
Irregular Pond .................................................................................................................. 41
Gravel Trench Bed ........................................................................................................... 44
Sand Filter ........................................................................................................................ 45
Bioretention...................................................................................................................... 47
Green Roof ....................................................................................................................... 51
Permeable Pavement ........................................................................................................ 52
CAVFS ............................................................................................................................. 54
Riser/Weir ........................................................................................................................ 57
Infiltration ........................................................................................................................ 59
Auto Pond, Auto Vault, Auto Tank ................................................................................. 60
Stage-Storage-Discharge Table ....................................................................................... 63
High Groundwater/Wetland ............................................................................................. 64
Channel ............................................................................................................................ 66
Flow Splitter..................................................................................................................... 68
Time Series ...................................................................................................................... 70
SSD Table ........................................................................................................................ 71
Point of Compliance ........................................................................................................ 76
Connecting Elements ....................................................................................................... 79

Analysis Screen ................................................................................................................ 83
Stream Protection Duration.............................................................................................. 85
LID Duration .................................................................................................................... 87
Flow Frequency ............................................................................................................... 89
Water Quality ................................................................................................................... 90
Hydrographs ..................................................................................................................... 91
Wetland Fluctuations ....................................................................................................... 95
LID Analysis .................................................................................................................... 97
Recharge ........................................................................................................................ 100
Reports Screen ............................................................................................................... 105

Tools Screen................................................................................................................... 111
Import Parameters .......................................................................................................... 112
Predeveloped .................................................................................................................. 113
View/Edit PERLNDs ..................................................................................................... 114
View/Edit IMPLNDs ..................................................................................................... 115
Alternate Precip ............................................................................................................. 116
Export Dataset ................................................................................................................ 117
Import Dataset ................................................................................................................ 118
WDM Maintenance ........................................................................................................ 119

LID Analysis Screen ...................................................................................................... 121
LID Scenario Generator ................................................................................................. 122
LID Report .................................................................................................................... 127

Options ........................................................................................................................... 131
Duration Criteria ............................................................................................................ 132
Scaling Factors ............................................................................................................... 134
Time Step ....................................................................................................................... 135
Recharge ........................................................................................................................ 136

Appendix A: Bioretention Modeling Methodology ....................................................... 137
Appendix B: Default WWHM2012 HSPF Pervious Parameter Values
(except Clark2012SG) ................................................................................................... 143
Appendix C: Default WWHM2012 HSPF Impervious Parameter Values
(except Clark2012SG) ................................................................................................... 153
Appendix D: Default WWHM2012 HSPF Pervious Parameter Values for
Clark2012SG.................................................................................................................. 157
Appendix E: Default WWHM2012 HSPF Impervious Parameter Values
for Clark2012SG ............................................................................................................ 177

Western Washington Hydrology Model 2012 User Manual
INTRODUCTION

The WWHM2012 is the updated edition of the Western Washington Hydrology Model,
replacing WWHM3. It was designed by the Washington State Department of Ecology,
AQUA TERRA Consultants, and Clear Creek Solutions, Inc. (the successor to the
Washington offices of AQUA TERRA Consultants). This version has more options than
WWHM3. The user can model almost any hydrologic condition related to stormwater
control and design.

This user manual and development of WWHM2012 was funded by the Washington State
Department of Ecology Contract No. C1200124 with Clear Creek Solutions, Inc. Clear
Creek Solutions staff responsible for the WWHM2012 and this user manual are Joe
Brascher, Gary Maxfield, and Doug Beyerlein.

Purpose

The purpose of the WWHM2012 is to size stormwater control facilities to mitigate the
effects of increased runoff (peak discharge, duration, and volume) from proposed land
use changes that impact natural streams, wetlands, and other water courses.

The WWHM2012 provides:
 A uniform methodology for the 19 counties of Western Washington
 A more accurate methodology than single event design storms
 An easy-to-use software package

The WWHM2012 is based on:
 Continuous simulation hydrology (HSPF)
 Actual long-term recorded precipitation data
 Measured pan evaporation data
 Historic vegetation (for Predeveloped conditions)
 Regional HSPF parameters

Parameter values can be modified for local conditions.

What’s New in WWHM2012

WWHM2012 gives the user greater modeling flexibility, options, and accuracy. Version
3 included some simplified approaches to modeling stormwater LID (low impact
development) facilities. WWHM2012 includes modeling elements that more accurately
represent these stormwater facilities.

Specific changes and additions in Version 2012 include:
 Ability to run on Microsoft Windows 7, 8, and 10 operating systems either on a
workstation (single computer) or network.
 Updated precipitation data through water year 2009 (September 2009).
 Model simulations using a 15-minute time step in place of an hourly time step.
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Western Washington Hydrology Model 2012 User Manual

 15-minute precipitation data in place of hourly data.
 Updated water quality design flow calculations.
 Improved Auto Pond capabilities to optimize sizing of stormwater ponds and
vaults.
 New bioretention swale element that accurately represents bioretention and rain
gardens with or without underdrains and/or infiltration to the native soil.
 New CAVFS (compost amended vegetated filter strips) element to accurately
represent roadside bioretention-based water quality facilities.
 New green roof element to accurately model storage, evapotranspiration, and
runoff from vegetated roofs.
 New permeable pavement element to accurately model the movement of water
through the pavement and subgrade.
 Added SSD Table element options.
 Automated sizing options for infiltration facilities.
 Revised flow duration analysis with two duration standards: (1) Stream Protection
Duration, and (2) LID Duration.
 Revised wetland hydroperiod criteria calculations.
 New LID reporting features.

Computer Requirements
 Windows 2000/XP/Vista/7/8/8.1/10 with 200 MB uncompressed hard drive space
 Internet access (only required for downloading WWHM2012, not required for
executing WWHM2012)
 Pentium 3 or faster processor (desirable)
 Color monitor (desirable)

Before Starting the Program
 Knowledge of the site location and/or street address.
 Knowledge of the actual distribution of existing site soil by category (A/B, C, or
saturated).
 Knowledge of the planned distribution of the proposed development (buildings,
streets, sidewalks, parking, lawn areas) overlying the soil categories.
 An idea of a first approximation of the top surface area for a trapezoidal or
irregular-shape pond (if used).

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