![](media/image1.png){width="3.7090277777777776in"
height="0.8409722222222222in"}

###### Version Date: April 19, 2002   

######## WinTR-55 User Manual

Table of Contents

Windows [iii](#windows)

Figures [iv](#figures)

Tables [iv](#tables)

Introduction [1](#introduction)

Historical Background [1](#historical-background)

Program Description [1](#program-description)

Model Overview [1](#model-overview)

Capabilities and Limitations [3](#capabilities-and-limitations)

Model Input [3](#model-input)

Minimum Data Requirements [3](#minimum-data-requirements)

User Responsibility [4](#user-responsibility)

Watershed Sub-areas and Reaches [4](#watershed-sub-areas-and-reaches)

Entry Window Features [5](#entry-window-features)

Welcome to TR-55 Window [6](#welcome-to-tr-55-window)

Purpose [7](#purpose)

Buttons [7](#buttons)

TR-55 Main Window [8](#tr-55-main-window)

Purpose [8](#purpose-1)

Menu [8](#menu)

Buttons [11](#buttons-1)

Identification Data Entry and Selection
[13](#identification-data-entry-and-selection)

Sub-area Entry and Selection [14](#sub-area-entry-and-selection)

Status Bar [14](#status-bar)

Land Use Details Window [15](#land-use-details-window)

Purpose [15](#purpose-2)

Data Entry and Selection [15](#data-entry-and-selection)

Summary Information [16](#summary-information)

Buttons [16](#buttons-2)

Land Use Summary Window [17](#land-use-summary-window)

Purpose [17](#purpose-3)

Data Selection [17](#data-selection)

Custom CN Window [18](#custom-cn-window)

Purpose [18](#purpose-4)

Data Entry and Selection [18](#data-entry-and-selection-1)

Buttons [19](#buttons-3)

Time of Concentration Details Window
[20](#time-of-concentration-details-window)

Purpose [20](#purpose-5)

Data Entry and Selection [21](#data-entry-and-selection-2)

Sheet Flow Length [21](#sheet-flow-length)

Buttons [21](#buttons-4)

Reach Window [22](#reach-window)

Purpose [22](#purpose-6)

Reach -- Routing Element Concept [23](#reach-routing-element-concept)

Data Entry and Selection [23](#data-entry-and-selection-3)

Selecting a Representative Cross Section
[23](#selecting-a-representative-cross-section)

Buttons [24](#buttons-5)

Reach Schematic Window [25](#reach-schematic-window)

Purpose [26](#purpose-7)

Buttons [26](#buttons-6)

Structure Data Window [27](#structure-data-window)

Purpose [27](#purpose-8)

Alternate Outlet Sizes for Multiple Structures
[27](#alternate-outlet-sizes-for-multiple-structures)

Data Entry and Selection [28](#data-entry-and-selection-4)

Pipe Outlet [28](#pipe-outlet)

Full Pipe Flow Assumption [29](#full-pipe-flow-assumption)

Weir Outlet [30](#weir-outlet)

Buttons [31](#buttons-7)

Storm Data Window [33](#storm-data-window)

Purpose [34](#purpose-9)

Data Entry and Selection [34](#data-entry-and-selection-5)

Buttons [37](#buttons-8)

Custom Rainfall Distributions Window
[37](#custom-rainfall-distributions-window)

Purpose [38](#purpose-10)

Data Entry and Selection [38](#data-entry-and-selection-6)

Menu [38](#menu-1)

Buttons [38](#buttons-9)

Dimensionless Unit Hydrographs Window
[40](#dimensionless-unit-hydrographs-window)

Purpose [40](#purpose-11)

Menu [40](#menu-2)

Data Entry and Selection [40](#data-entry-and-selection-7)

Buttons [41](#buttons-10)

Plot Windows [42](#plot-windows)

Purpose and Description [42](#purpose-and-description)

Buttons [42](#buttons-11)

Running WinTR-55 [43](#running-wintr-55)

Disclaimer [43](#disclaimer)

WinTR-55 Processes [43](#wintr-55-processes)

Time of Concentration (T~c~) [43](#time-of-concentration-tc)

Land Use Parameters [44](#land-use-parameters)

Channel Rating Table [44](#channel-rating-table)

Structure Rating Table [44](#structure-rating-table)

TR-20 Processes [44](#tr-20-processes)

Generate Hydrographs [44](#generate-hydrographs)

Combine Hydrographs [45](#combine-hydrographs)

Channel Route [45](#channel-route)

Structure Route [45](#structure-route)

Viewing Output [45](#viewing-output)

File Display Window [45](#file-display-window)

Menu [47](#menu-3)

Buttons [47](#buttons-12)

Output Definition Window [47](#output-definition-window)

Available Reports [48](#available-reports)

Buttons [50](#buttons-13)

Plotting and Viewing Hydrographs [50](#plotting-and-viewing-hydrographs)

Hydrographs or Output Graphics Window
[50](#hydrographs-or-output-graphics-window)

Graphics Window [51](#graphics-window)

Appendix A - Examples [52](#appendix-a---examples)

Example 1 -- Determining Runoff from a Single Sub-area for the Existing
and Developed Conditions and Sizing a Detention Basin
[52](#example-1-determining-runoff-from-a-single-sub-area-for-the-existing-and-developed-conditions-and-sizing-a-detention-basin)

Background [52](#background)

Solution [52](#solution)

Part A - Determine existing condition peak discharge and runoff volume
[52](#part-a---determine-existing-condition-peak-discharge-and-runoff-volume)

Part A - Results [57](#part-a---results)

Part B - Determine developed condition peak discharge and runoff volume
[58](#part-b---determine-developed-condition-peak-discharge-and-runoff-volume)

Part B - Results [62](#part-b---results)

Part C - Sizing the Detention Basin
[63](#part-c---sizing-the-detention-basin)

Part C - Results [68](#part-c---results)

Example 2 -- Evaluating Larger Watersheds and User Defined Storm Data
[69](#example-2-evaluating-larger-watersheds-and-user-defined-storm-data)

Background [69](#background-1)

Watershed Data [70](#watershed-data)

Rainfall Data [72](#rainfall-data)

Results [73](#results)

Discussion of Results [74](#discussion-of-results)

Example 3 -- Custom Dimensionless Unit Hydrograph
[76](#example-3-custom-dimensionless-unit-hydrograph)

Background [76](#background-2)

Part 1 - Enter custom dimensionless unit hydrograph
[76](#part-1---enter-custom-dimensionless-unit-hydrograph)

Part 2 - Determine peak discharge and runoff volume for the present
field tillage conditions.
[80](#part-2---determine-peak-discharge-and-runoff-volume-for-the-present-field-tillage-conditions.)

Results [86](#results-1)

Part 3 - Determine peak discharge and runoff volume \'with crop residue
management\' condition
[86](#part-3---determine-peak-discharge-and-runoff-volume-with-crop-residue-management-condition)

Results [89](#results-2)

Example 4 -- Custom Rainfall Distribution
[90](#example-4-custom-rainfall-distribution)

Background [90](#background-3)

Watershed and Basin Data [90](#watershed-and-basin-data)

Existing Conditions -- Type II Rainfall Distribution
[91](#existing-conditions-type-ii-rainfall-distribution)

Enter Historic Rainfall Distribution
[95](#enter-historic-rainfall-distribution)

Results [99](#results-3)

Appendix B - Equations [100](#appendix-b---equations)

Runoff Equation [100](#runoff-equation)

Composite CN (connected impervious area)
[100](#composite-cn-connected-impervious-area)

Composite CN (unconnected w/ \<30% impervious)
[100](#composite-cn-unconnected-w-30-impervious)

Sheet Flow [100](#sheet-flow)

Shallow Concentrated Flow [100](#shallow-concentrated-flow)

Channel Flow (Manning Equation) [101](#channel-flow-manning-equation)

Channel Rating Equations [101](#channel-rating-equations)

Storage Rating Equations [102](#storage-rating-equations)

Pipe Flow [102](#pipe-flow)

Weir Flow [103](#weir-flow)

Appendix C - References [104](#appendix-c---references)

## Windows

Window 1 - Welcome to TR-55 Window [6](#__RefHeading___Toc6972399)

Window 2. New User Help Window [7](#__RefHeading___Toc6972400)

Window 3 - TR-55 Main Window [8](#__RefHeading___Toc6972401)

Window 4 -- TR-55 Main Window (File) [9](#__RefHeading___Toc6972402)

Window 5 - TR-55 Main Window (Options) [9](#__RefHeading___Toc6972403)

Window 6 - TR-55 Main Window (Run) [11](#__RefHeading___Toc6972404)

Window 7 - TR-55 Main Window (Help) [11](#__RefHeading___Toc6972405)

Window 8 - Land Use Details [15](#__RefHeading___Toc6972406)

Window 9 - Land Use Summary [17](#__RefHeading___Toc6972407)

Window 10 - Custom Curve Number [18](#__RefHeading___Toc6972408)

Window 11 - Land Use Details Window with Custom Curve Number
[20](#__RefHeading___Toc6972409)

Window 12 - Time of Concentration Details
[20](#__RefHeading___Toc6972410)

Window 13 - Reach Data [22](#__RefHeading___Toc6972411)

Window 14 - Channel Rating Plot [25](#__RefHeading___Toc6972412)

Window 15 - Reach Flow Path Definition [25](#__RefHeading___Toc6972413)

Window 16 - Structure Data (Pipe Outlet)
[27](#__RefHeading___Toc6972414)

Window 17 - Structure Data (Weir Outlet)
[31](#__RefHeading___Toc6972415)

Window 18 - Structure Rating (Pipe Outlet)
[32](#__RefHeading___Toc6972416)

Window 19 - Structure Data Plot (Weir Outlet)
[33](#__RefHeading___Toc6972417)

Window 20 -- Storm Data [33](#__RefHeading___Toc6972418)

Window 21 - Watersheds Outside US [35](#__RefHeading___Toc6972419)

Window 22 - Storm Data Outside of US [35](#__RefHeading___Toc6972420)

Window 23 - Differing State/County and Storm Data Source Example
[36](#__RefHeading___Toc6972421)

Window 24 - Custom Rainfall Distributions
[37](#__RefHeading___Toc6972422)

Window 25 - Custom Rainfall Distributions (Edit)
[38](#__RefHeading___Toc6972423)

Window 26 - Custom Rainfall Distributions Plot
[39](#__RefHeading___Toc6972424)

Window 27 - Dimensionless Unit Hydrograph
[40](#__RefHeading___Toc6972425)

Window 28 - Dimensionless Unit Hydrograph Plot
[41](#__RefHeading___Toc6972426)

Window 29 - Typical Plot Window [42](#__RefHeading___Toc6972427)

Window 30 -- File Display [46](#__RefHeading___Toc6972428)

Window 31 - Output Definition [48](#__RefHeading___Toc6972429)

Window 32 - Output Graphics [51](#__RefHeading___Toc6972430)

Window 33 - Output Plot [51](#__RefHeading___Toc6972431)

## Figures

Figure 1. WinTR-55 System Schematic [2](#__RefHeading___Toc6972442)

Figure 2. Sample Watershed Schematic [4](#__RefHeading___Toc6972443)

Figure 3. Window Entry Terms [5](#__RefHeading___Toc6972444)

Figure 4. Additional Window Entry Terms [6](#__RefHeading___Toc6972445)

Figure 5. Pipe Outlet Schematics [29](#__RefHeading___Toc6972446)

Figure 6. Full-Pipe Flow Assumption Not Valid
[30](#__RefHeading___Toc6972447)

Figure 7. Weir Outlet Schematic [30](#__RefHeading___Toc6972448)

## Tables

Table 1. WinTR-55 Capabilities & Limitations
[3](#__RefHeading___Toc6972439)

Table 2. Sample Watershed Flows [4](#__RefHeading___Toc6972440)

Table 3. TR-55 Reports [49](#__RefHeading___Toc6972441)

# Introduction

## Historical Background

Technical Release 55 (TR-55) Urban Hydrology for Small Watersheds was
first issued in January 1975 as a simplified procedure to calculate the
storm runoff volume, peak rate of discharge, hydrographs and storage
volumes required for storm water management structures (SCS, 1975). The
first issue involved manual methods and assumed the NRCS Type II
rainfall distribution for all calculations.

In June 1986 major revisions were made in TR-55 by adding three rainfall
distributions (Type I, IA and III) and programming the computations.
Time of concentration was estimated by splitting the hydraulic flow path
into separate flow phases (SCS, 1986). The computer program became a
standard tool to analyze peak flow changes caused by urbanization in
many locations. Its wide acceptance by public and private users has also
indicated where improvements could be made in the procedures and the
computer program.

A WinTR-55 work group was formed in the spring of 1998 to modernize and
revise the Technical Release and the computer software. The current
changes include: upgrade the source code to Visual Basic, change the
philosophy of data input, develop a Windows interface and output
post-processor, enhance the hydrograph-generation capability of the
software and flood route hydrographs through stream reaches and
reservoirs.

The availability and technical capabilities of the personal computer
have significantly changed the philosophy of problem-solving for the
engineer. Computer availability eliminated the need for TR-55 manual
methods, thus the manual portions (graphs and tables) of the user
document have been eliminated.

This user manual covers the procedures used in and the operation of the
WinTR-55 computer program. Part 630 of the Natural Resources
Conservation Service (NRCS) National Engineering Handbook provides
detailed information on NRCS hydrology and is the technical reference
for this document. Appendix C, which lists all the references, contains
a list of the Part 630 chapters and their subjects. Users who are not
familiar with NRCS hydrologic procedures should refer to the appropriate
chapters for background information and the details of procedural
techniques.

## Program Description

WinTR-55 is a single-event rainfall-runoff small watershed hydrologic
model. The model generates hydrographs from both urban and agricultural
areas and at selected points along the stream system. Hydrographs are
routed downstream through channels and/or reservoirs. Multiple sub-areas
can be modeled within the watershed.

## Model Overview

A watershed is composed of sub-areas (land areas) and reaches (major
flow paths in the watershed). Each sub-area has a hydrograph generated
from the land area based on the land and climate characteristics
provided. Reaches can be designated as either channel reaches where
hydrographs are routed based on physical reach characteristics or as
storage reaches where hydrographs are routed through a reservoir based
on temporary storage and outlet characteristics. Hydrographs from
sub-areas and reaches are combined as needed to accumulate flow as water
moves from the upland areas down through the watershed reach network.
The accumulation of all runoff from the watershed is represented at the
watershed Outlet. Up to ten sub-areas and ten reaches may be included in
the watershed.

WinTR-55 uses the TR-20 (NRCS, 2002) model for all of the hydrograph
procedures: generation, channel routing, storage routing, and addition.

Figure 1 is a diagram showing the WinTR-55 model, its relationship to
TR-20, and the files associated with the model.

[]{#__RefHeading___Toc6972442 .anchor}Figure 1. WinTR-55 System
Schematic

![](media/image2.wmf)

## Capabilities and Limitations

WinTR-55 hydrology has the capacity to analyze watersheds that meet
these criteria:

[]{#__RefHeading___Toc6972439 .anchor}Table 1. WinTR-55 Capabilities &
Limitations

  ------------------------------------ ----------------------------------
  **Variable**                         **Limits**

  Minimum area                         No absolute minimum is included in
                                       the software. The user should
                                       carefully examine results from
                                       sub-areas less than 1 acre.

  Maximum area                         25 square miles (6,500 hectares)

  Number of Subwatersheds              1-10

  Time of concentration for any        0.1 hour [\<]{.underline} T~c~
  sub-area                             [\<]{.underline} 10 hour

  Number of reaches                    0-10

  Types of reaches                     Channel or Structure

  Reach Routing                        Muskingum-Cunge

  Structure Routing                    Storage-Indication

  Structure Types                      Pipe or Weir

  Structure Trial Sizes                1-3

  Rainfall Depth                       Default or user-defined\
                                       0 -- 50 inches (0-1,270 mm)

  Rainfall Distributions               NRCS Type I, IA, II, III, NM60,
                                       NM65, NM70, NM75, or user-defined

  Rainfall Duration                    24-hour

  Dimensionless Unit Hydrograph        Standard peak rate factor 484, ,
                                       or user-defined (e.g.
                                       Delmarva---see Example 3)

  Antecedent Moisture Condition        2 (average)
  ------------------------------------ ----------------------------------

# Model Input

The various data used in the WinTR-55 procedures are user entered via a
series of input windows in the model. A description of each of the input
windows follows the figure. Data entry is needed only on the windows
that are applicable to the watershed being evaluated.

## Minimum Data Requirements

While WinTR-55 can be used for watersheds with up to ten sub-areas and
up to ten reaches, the simplest run involves only a single sub-area.
Data required for a single sub-area run can be entered on the TR-55 Main
Window. These data include**: Identification** **Data**-User, -State,
‑County, -Project, and -Subtitle; **Dimensionless Unit Hydrograph**;
**Storm Data; Rainfall Distribution**; and **Sub-area Data.** The
sub-area data can be entered directly into the Sub-area Entry and
Summary table**: Sub-area name, sub-area description, sub-area flows to
reach/outlet**, **area**, **runoff curve number** (RCN), and **time of
concentration** (T~c~). Detailed information for the sub-area RCN and
T~c~ can be entered here or on other windows; if detailed information is
entered elsewhere the computational results are displayed in this
window.

### User Responsibility

Results from the model can be sensitive to the input data. It is the
user's responsibility to ensure that all input data (whether it is
actually entered or implied through default values for blank data
fields) is appropriate for the watershed and watershed conditions being
analyzed.

## Watershed Sub-areas and Reaches

To properly route stream flow to the watershed outlet, the user must
understand how WinTR-55 relates watershed sub-areas and stream reaches.
Figure 2 and Table 2 show a typical watershed with multiple sub-areas
and reaches.

![](media/image3.png){width="5.979861111111111in"
height="2.9854166666666666in"}

[]{#__RefHeading___Toc6972443 .anchor}Figure 2. Sample Watershed
Schematic

[]{#__RefHeading___Toc6972440 .anchor}Table 2. Sample Watershed Flows

+------------+-----------------+------------+------------+------------+
| **[Sub     | **[Flows        |            | **[        | **[Flows   |
| -area]{.un | into            |            | Reach]{.un | into]{.un  |
| derline}** | ]{.underline}** |            | derline}** | derline}** |
|            |                 |            |            |            |
|            | **[Upstream End |            |            |            |
|            | of              |            |            |            |
|            | ]{.underline}** |            |            |            |
+============+=================+============+============+============+
| Area I     | Reach A         |            | Reach A    | Reach C    |
+------------+-----------------+------------+------------+------------+
| Area II    | Reach C         |            | Reach B    | Reach C    |
+------------+-----------------+------------+------------+------------+
| Area III   | Reach C         |            | Reach C    | OUTLET     |
+------------+-----------------+------------+------------+------------+
| Area IV    | Reach B         |            | Reach D    | OUTLET     |
+------------+-----------------+------------+------------+------------+
| Area V     | Reach C         |            | Reach E    | OUTLET     |
+------------+-----------------+------------+------------+------------+
| Area VI    | Reach E         |            |            |            |
+------------+-----------------+------------+------------+------------+
| Area VII   | OUTLET          |            |            |            |
+------------+-----------------+------------+------------+------------+
| Area VIII  | OUTLET          |            |            |            |
+------------+-----------------+------------+------------+------------+
| Area IX    | Reach D         |            |            |            |
+------------+-----------------+------------+------------+------------+
| Area X     | OUTLET          |            |            |            |
+------------+-----------------+------------+------------+------------+

Reaches define flow paths through the watershed to its outlet. Each
sub-area and reach contribute flow to the upstream end of a receiving
reach or to the Outlet. Accumulated runoff from all sub-areas routed
through the watershed reach system, by definition, is flow at the
watershed outlet.

## Entry Window Features

Figures 2 and 3 show some of the features Windows uses, with the
features labeled.

[]{#__RefHeading___Toc6972444 .anchor}Figure 3. Window Entry Terms

![](media/image4.wmf){width="6.493055555555555in"
height="2.673611111111111in"}

  ----------------------------------- -----------------------------------
  **Feature**                         **Function**

  Window Title                        Displays title of the window

  Tool Buttons                        Quick access to functions or
                                      windows

  Combo Entry Box                     Select an entry or type in new data

  Option Button                       Select one option of several

  Entry Grid                          Enter data into cells

  Menu Bar with Pulldowns             Select menu options with further
                                      sub-options

  Entry Box                           Enter data into box

  Display Data                        Display only, cannot enter data
                                      into a display area

  Status Bar                          Displays status information:
                                      filename, date, time
  ----------------------------------- -----------------------------------

[]{#__RefHeading___Toc6972445 .anchor}Figure 4. Additional Window Entry
Terms

![](media/image5.png){width="4.1125in" height="2.61875in"}

  ----------------------------------- -----------------------------------
  **Feature**                         **Function**

  Check box                           Click on box to turn an option on
                                      or off

  Button                              Click to access named function
  ----------------------------------- -----------------------------------

## Welcome to TR-55 Window

[]{#__RefHeading___Toc6972399 .anchor}Window 1 - Welcome to TR-55 Window

![](media/image6.png){width="4.842361111111111in"
height="3.5118055555555556in"}

### Purpose

This windows displays introductory information to the user.

[]{#__RefHeading___Toc6972400 .anchor}Window 2. New User Help Window

![](media/image7.png){width="3.95in" height="2.0729166666666665in"}

To skip this introduction in the future, click on the entry box in the
lower left hand corner. The user may read additional help information or
go directly to WinTR-55.

### Buttons

#### [N]{.underline}ew User?

Click [N]{.underline}ew User to display introductory help text.

#### [R]{.underline}eturn to TR55

Click [R]{.underline}eturn to begin using WinTR-55 software.

## TR-55 Main Window

[]{#__RefHeading___Toc6972401 .anchor}Window 3 - TR-55 Main Window

![](media/image8.png){width="4.459027777777778in"
height="4.419444444444444in"}

### Purpose

The TR-55 Main Window allows the input of basic watershed data for a
WinTR-55 watershed hydrology analysis. Other data and settings are
accessible through the menus, buttons, and boxes on the window. WinTR-55
returns to this main window when other data input windows are closed.

### Menu

The menu bar is located at the top of the TR-55 Main Window, just below
the dark blue window title.

[]{#__RefHeading___Toc6972402 .anchor}Window 4 -- TR-55 Main Window
(File)

![](media/image9.png){width="2.9805555555555556in" height="2.1875in"}

+-------+-------------+-----------------------------------------------+
| ##### | ##          | ####### Explanation                           |
|  Menu | ##### Pull- |                                               |
|  Item | down Choice |                                               |
+-------+-------------+-----------------------------------------------+
| ####  | [N]{.u      | Create a new input file                       |
| # [F] | nderline}ew |                                               |
| {.und |             |                                               |
| erlin |             |                                               |
| e}ile |             |                                               |
+-------+-------------+-----------------------------------------------+
|       | [O]{.un     | Open an existing input file                   |
|       | derline}pen |                                               |
+-------+-------------+-----------------------------------------------+
|       | [S]{.un     | Save current input data using current file    |
|       | derline}ave | name                                          |
+-------+-------------+-----------------------------------------------+
|       | Save        | Save current input data with different        |
|       | [A]{.       | filename                                      |
|       | underline}s |                                               |
+-------+-------------+-----------------------------------------------+
|       | [P]{.un     | Setup printer for page output                 |
|       | derline}age |                                               |
|       | Setup       |                                               |
+-------+-------------+-----------------------------------------------+
|       | [E]{.un     | Exit software                                 |
|       | derline}xit |                                               |
+-------+-------------+-----------------------------------------------+
|       | List of     | List of recently accessed files tghat         |
|       | Recent      | provides a shortcut to any of them            |
|       | Files       |                                               |
+-------+-------------+-----------------------------------------------+

[]{#__RefHeading___Toc6972403 .anchor}Window 5 - TR-55 Main Window
(Options)

![](media/image10.png){width="1.2402777777777778in"
height="0.6590277777777778in"}

+-------+-------------+-----------------------------------------------+
| ##### | ##          | ####### Explanation                           |
|  Menu | ##### Pull- |                                               |
|  Item | down Choice |                                               |
+-------+-------------+-----------------------------------------------+
| **[O] | [U]{.und    | Declare measurement system: English or        |
| {.und | erline}nits | metric. Also choose watershed area display    |
| erlin |             | units: acres or square miles for English and  |
| e}pti |             | hectares or square kilometers for metric.     |
| ons** |             |                                               |
+-------+-------------+-----------------------------------------------+
|       | [C]{.und    | Clear the list of recently opened files at    |
|       | erline}lear | the bottom of the File menu                   |
|       | Recent      |                                               |
|       | Files       |                                               |
+-------+-------------+-----------------------------------------------+

Window 4 - TR-55 Main Window (Project Data)

![](media/image11.png){width="1.9055555555555554in" height="1.3in"}

+-------+-------------+-----------------------------------------------+
| ##### | ##          | ####### Explanation                           |
|  Menu | ##### Pull- |                                               |
|  Item | down Choice |                                               |
+-------+-------------+-----------------------------------------------+
| **[   | [L]{.un     | Open Land Use Details Window                  |
| P]{.u | derline}and |                                               |
| nderl | Use Details |                                               |
| ine}r |             |                                               |
| oject |             |                                               |
| D     |             |                                               |
| ata** |             |                                               |
+-------+-------------+-----------------------------------------------+
|       | [T]{.un     | Open Time of Concentration Details Window     |
|       | derline}ime |                                               |
|       | of          |                                               |
|       | Co          |                                               |
|       | ncentration |                                               |
|       | Details     |                                               |
+-------+-------------+-----------------------------------------------+
|       | [           | Open Structure Data Window                    |
|       | S]{.underli |                                               |
|       | ne}tructure |                                               |
|       | Data        |                                               |
+-------+-------------+-----------------------------------------------+
|       | [R]{.und    | Open Reach Data Window                        |
|       | erline}each |                                               |
|       | Data        |                                               |
+-------+-------------+-----------------------------------------------+
|       | Reach       | Display Reach Flow Path Schematic Window      |
|       | [F]{.un     |                                               |
|       | derline}low |                                               |
|       | Path        |                                               |
+-------+-------------+-----------------------------------------------+

Window 5 TR-55 Main Window (Global Data)

![](media/image12.png){width="1.9527777777777777in" height="0.8in"}

+-------+-------------+-----------------------------------------------+
| ##### | ##          | ####### Explanation                           |
|  Menu | ##### Pull- |                                               |
|  Item | down Choice |                                               |
+-------+-------------+-----------------------------------------------+
| **    | [S]{.und    | Open Storm Data Window                        |
| [G]{. | erline}torm |                                               |
| under | Data        |                                               |
| line} |             |                                               |
| lobal |             |                                               |
| D     |             |                                               |
| ata** |             |                                               |
+-------+-------------+-----------------------------------------------+
|       | [C]{.unde   | Open Custom Rainfall Distributions Window     |
|       | rline}ustom |                                               |
|       | Rainfall    |                                               |
|       | Di          |                                               |
|       | stributions |                                               |
+-------+-------------+-----------------------------------------------+
|       | [D]{.       | Open Dimensionless Unit Hydrograph Window     |
|       | underline}i |                                               |
|       | mensionless |                                               |
|       | Unit        |                                               |
|       | Hydrograph  |                                               |
+-------+-------------+-----------------------------------------------+

[]{#__RefHeading___Toc6972404 .anchor}Window 6 - TR-55 Main Window (Run)

![](media/image13.png){width="0.4305555555555556in"
height="0.2611111111111111in"}

+-------+-------------+-----------------------------------------------+
| ##### | ##          | ####### Explanation                           |
|  Menu | ##### Pull- |                                               |
|  Item | down Choice |                                               |
+-------+-------------+-----------------------------------------------+
| ####  | Run TR-55   | Analyze watershed using currently entered     |
| # Run |             | data                                          |
+-------+-------------+-----------------------------------------------+

[]{#__RefHeading___Toc6972405 .anchor}Window 7 - TR-55 Main Window
(Help)

![](media/image14.png){width="2.042361111111111in"
height="1.0729166666666667in"}

+-------+--------------+----------------------------------------------+
| ##### | ####### Pull | ####### Explanation                          |
|  Menu | -down Choice |                                              |
|  Item |              |                                              |
+-------+--------------+----------------------------------------------+
| ####  | [S]{.u       | Displays WinTR-55 Welcome Window             |
| # [H] | nderline}how |                                              |
| {.und | WinTR-55     |                                              |
| erlin | Welcome      |                                              |
| e}elp |              |                                              |
+-------+--------------+----------------------------------------------+
|       | [H]{.u       | Displays help                                |
|       | nderline}elp |                                              |
|       | for TR-55    |                                              |
|       | Main Window  |                                              |
|       | F1           |                                              |
+-------+--------------+----------------------------------------------+
|       | [A]{.un      | Display program version number and date      |
|       | derline}bout |                                              |
|       | WinTR-55     |                                              |
+-------+--------------+----------------------------------------------+
|       | System       | Display System information, such as          |
|       | Information  | operating system                             |
+-------+--------------+----------------------------------------------+

### Buttons

The the button bar near the top of the TR-55 Main Window provides a
graphical shortcut for some common functions described in the preceding
menu section.

#### Open ![](media/image15.png){width="0.5965277777777778in" height="0.5069444444444444in"}

Opens a previously created and saved WinTR-55 input data file.

#### Save ![](media/image15.png){width="0.5520833333333334in" height="0.44305555555555554in"}

Saves the current data in the file named on the status bar (bottom left
corner of window). This button is not available until some data has been
entered. If the current data does not have a filename associated with
it, a box allowing entry of a filename is displayed when "Save" is
clicked.

#### Input Data Printout ![](media/image15.png){width="0.5041666666666667in" height="0.4534722222222222in"}

Prints a brief report of data on the TR-55 Main Window.

#### Land Use Details ![](media/image16.png){width="0.3402777777777778in" height="0.3402777777777778in"}

Displays Land Use Description Window to enter or edit land use data by
hydrologic soil group for any sub-area.

#### Time of Concentration ![](media/image17.png){width="0.3402777777777778in" height="0.3402777777777778in"}

Displays Time of Concentration Window to enter or edit flow path
information used to compute time of concentration for any sub-area.

#### Structure Data ![](media/image18.png){width="0.3402777777777778in" height="0.3402777777777778in"}

Displays Structure Window to enter or edit data for storage ponds with
either a pipe or weir outlet.

#### Reach Data ![](media/image19.png){width="0.32916666666666666in" height="0.32916666666666666in"}

Displays Reach Window to enter or edit reach data for all reaches in the
watershed.

#### Reach Flow Path ![](media/image20.png){width="0.5097222222222222in" height="0.44027777777777777in"}

Displays Reach Flow Path Schematic

#### Storm Data ![](media/image21.png){width="0.3402777777777778in" height="0.3402777777777778in"}

Displays Storm Data Window to view or edit rainfall depths and
frequency. The associated rainfall distribution may be changed.

#### Custom Rainfall Distribution ![](media/image22.png){width="0.3909722222222222in" height="0.36944444444444446in"}

Displays Custom Rainfall Distribution Window to enter or edit custom
rainfall distributions.

#### Dimensionless Unit Hydrograph ![](media/image23.png){width="0.32916666666666666in" height="0.32916666666666666in"}

Displays Dimensionless Unit Hydrograph Window to enter or edit custom
dimensionless unit hydrographs.

#### Run TR-55 ![](media/image24.png){width="0.32916666666666666in" height="0.32916666666666666in"}

Uses currently entered WinTR-55 data reformatted into TR-20 input to run
the TR-20 model. Results from TR-20 are then available to the WinTR-55
program for output displays and/or reports. "Run TR-55 " is not
available until a minimum amount of data has been entered.

#### Summary Reports ![](media/image25.png)

Prints summary output reports. "Summary Reports" is not available until
data has been entered and run.

#### Output Hydrographs![](media/image26.png)

Views output hydrographs at various locations in the watershed. "Output
Reports" is not available until a run has been completed.

#### Help - Context Sensitive ![](media/image27.png){width="0.2902777777777778in" height="0.28888888888888886in"}

Once clicked, displays context-sensitive help for any data entry box on
the TR-55 Main Window that is subsequently clicked. The help data is
displayed below the data grid, at the bottom of the window. While in
help mode, a question mark (?) is displayed next to the cursor. Clicking
"**?**" a second time will return to the standard cursor.

Some help windows will not display completely with a 600x800 screen
resolution. For better viewing, change the monitor's screen resolution
to a higher setting, such as 1024x768.

### Identification Data Entry and Selection

Begin by entering the identification data: user, project name, and
subtitle. The appropriate state and county (for locations within the
U.S.) can be selected from the pull-down lists. For locations outside of
the U.S., entering a name for the new \'state\' causes the labels
\'state\' and \'county\' to change to \'region\' and \'locale\'. State
and county names supplied with the program cannot be edited, while
user-entered names may be edited. Entering a single letter jumps to the
first match in the list.

Next, click the sub-area units option button; English units of area are
acres or square miles, metric units are either hectares or square
kilometers. To change from English to metric or vice versa, select Units
from the Options pull-down menu.

The default dimensionless unit hydrograph is the \<standard\>
dimensionless NRCS unit hydrograph with a peak rate factor of 484 (NEH
Part 630, Chapter 16). If a different dimensionless unit hydrograph is
desired, select from the pull-down list or create a new one. To create a
new dimensionless unit hydrograph, open the Dimensionless Unit
Hydrograph Window.

Verify the Storm Data Source displayed. WinTR-55 supplies 24-hr rainfall
amounts for many counties in the U.S. with the appropriate NRCS rainfall
distribution. If needed, user may alter the storm data with different
24-hour rainfall amounts or a select a different rainfall distribution.
Whenever, user-supplied data is used, the "user-provided storm data
source" message is displayed on the TR-55 Main Window.

Note: changing the state and county locations on the TR-55 Main Window
does not automatically change the Storm Data source. The user must
verify that the storm data source is appropriate for the displayed
location.

Verify the current rainfall distribution displayed. If a different
rainfall distribution is desired, select a previously entered rainfall
distribution or open the Rainfall Distribution Window and create a new
distribution.

### Sub-area Entry and Selection

Enter or edit sub-area information in the Sub-area Entry and Summary
Table at the bottom of the TR-55 Main Window. Enter the Sub-area Name (1
to 10 characters) and if desired a Sub-area Description. Enter or select
from the choice list the Reach Name (1 to 10 characters) or OUTLET (for
the watershed outlet) into which the sub-area runoff flows in the
Sub-area Flows to Reach/Outlet column. The sub-area flow always enters
the reach at the upstream end. The network of sub-areas and reaches
defined here and on the Reach Data window must be configured such that
all flow eventually goes to the watershed Outlet. WinTR-55 will only run
if all the flow is directed to "Outlet".

The remaining columns in the table (Area, Weighted CN, and T~c~) may be
directly entered here or computed from more detailed information on
other input windows. Details for computing Area and Weighted CN can be
entered on the Land Use Description Window. Details for the T~c~ (time
of concentration) can be entered on the Time of Concentration Window.
Data entered directly in these columns is displayed in **blue**, and
data WinTR-55 computes from other windows is displayed in **green**.
Double-clicking on a column entry within the Sub-area Entry and Summary
Table automatically displays the appropriate input window---Land Use
Description, Time of Concentration, or Reach Window for additional data
entry or editing.

The total project area is displayed below the Area column in the
Sub-area Entry and Summary Table.

### Status Bar

The path and filename of the current data is displayed on the left side
of the status bar at the bottom of the window. If no file name has been
assigned to the current data, \<new file\> appears in this location. The
remainder of the status bar contains the current date and time. The same
status bar appears on all other large size data entry windows.

## Land Use Details Window

[]{#__RefHeading___Toc6972406 .anchor}Window 8 - Land Use Details

![](media/image28.png){width="5.202083333333333in"
height="4.215972222222222in"}

### Purpose

The Land Use Description window allows the user to edit and view the
land use description for sub-areas with detailed land use data.

### Data Entry and Selection

There are two ways to find and view a specific Cover Description: the
vertical scroll bar or Land Use category option buttons.

The vertical scroll bar on the right side of the window allows the user
to make any portion of the land use list visible. Drag the scroll bar up
or down to change the portion of the cover description list displayed.
Scrolling from top to bottom may be time consuming since the table is
long. Resizing the window to a larger window displays more lines of land
cover.

Clicking any Land Use Categories option button causes the displayed
portion of the Cover Description list to jump directly to the beginning
of that category\'s cover descriptions. The complete list of the Cover
Descriptions for the Land Use category may be too long to display at one
time. If that is the case, use the vertical scroll bar to scroll down
and view additional cover descriptions.

Once the desired cover description is in view in the table, enter the
areas in the appropriate Hydrologic Soil Group columns (A, B, C, or D).
Multiple hydrologic soil group entries can be made for a single cover
description.

The average percent impervious areas shown for the Urban and Residential
Districts were those used to develop the composite CN\'s given. Other
assumptions made for urban and residential districts are: impervious
areas are directly connected to the drainage system, impervious areas
have a CN of 98, and pervious areas CN\'s are equivalent to Open Space
in \"good\" hydrologic condition. Of these four assumptions, three may
be changed. The impervious CN of 98 is the only constant.

If any other assumptions need to be changed to fit a particular project
the user should go the Custom Curve Number Window and make the
appropriate adjustments. See the Custom Curve Number documentation for
more details.

Click on the sub-area name combo box in the upper left corner to select
a previously named sub-area and display its data. To enter a new
sub-area, click in the combo box and type in a new name.

### Summary Information

The total watershed area accumulated from the sub-area information is
displayed near the bottom left of the window. This total includes all
sub-areas whether the data for each was entered in the detailed land use
description above or as sub-area area on the TR-55 Main Window.

The Summary Screen buttons provide a toggle for display of the Land Use
Summary for Sub-area Window. Click "On" to display the summary window
and click "Off" to close the summary window. Information on the summary
window is discussed after this current window discussion ends.

The accumulated sub-area area and associated weighted CN for the current
sub-area are displayed in the two boxes at the bottom center of the
window. As additional areas are entered or deleted, the summary values
change. If both boxes are blank, no detailed land use description data
has been entered for this sub-area.

### Buttons

#### [R]{.underline}ename

[R]{.underline}ename allows the user to rename the sub-area.

#### [C]{.underline}lear

[C]{.underline}lear clears all the currently displayed sub-area land use
details.

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

#### [C]{.underline}ancel

Click "Cancel" to lose all data entered or edited since this window was
opened. The window is closed and the TR-55 Main Window redisplayed.

#### [A]{.underline}ccept

Click "Accept" to retain all data entered on the window, close the
window, and to redisplay the TR-55 Main Window. The data is retained
only in the computer memory and can be lost if the program is terminated
prior to saving the data to a user file. To save data, use either the
Save or Save As choices from the File menu or click the diskette icon on
the TR-55 Main Window.

## Land Use Summary Window

[]{#__RefHeading___Toc6972407 .anchor}Window 9 - Land Use Summary

![](media/image29.png){width="5.303472222222222in"
height="0.6604166666666667in"}

### Purpose

The Land Use Summary window is for display only and shows the detailed
land uses and associated areas by hydrologic soil group for a sub-area.
The displayed sub-area is the selected sub-area on the Land Use
description window. The window is activated or closed from the Land Use
Description window. To move the summary window around, right click on
the window and drag.

### Data Selection

Click anywhere on a displayed land use line to jump to that entry on the
Land Use Description window.

## Custom CN Window

[]{#__RefHeading___Toc6972408 .anchor}Window 10 - Custom Curve Number

![](media/image30.png){width="3.26875in" height="2.129861111111111in"}

### Purpose

The Custom CN window allows entry and editing of data to develop a
custom urban curve number when the standard Cover Description
assumptions on the Land Use Detail window do not apply. The pervious
land use assumption of pasture in good hydrologic condition may not
apply, so the user may change the pervious CN. The percent of impervious
area in a sub-area may also be changed.

Impervious areas are connected impervious areas if its runoff flows
directly into the drainage system or if its runoff flows as shallow
concentrated flow over a pervious area and then into the drainage
system. Shallow concentrated flow velocity is fast enough to allow
little or no infiltration into the pervious area. An example of a
connected impervious area is a residential rooftop where runoff flows
from a roof downspout across a paved driveway, into the street gutter,
and finally into to a storm sewer drainage system.

An impervious area is unconnected if runoff from it flows as sheet flow
over a pervious area before entering the drainage system. The sheet flow
is slow enough that some infiltration is presumed to occur in the
pervious area. If the water from a roof downspout flows across a lawn as
sheet flow, with opportunity to infiltrate the lawn, the rooftop is an
unconnected impervious area. The user can enter appropriate numbers into
the Custom Curve Number window to create a Custom CN to fit a specific
land cover.

### Data Entry and Selection

Scroll to the Custom CN line of the Cover Description and click "Custom
CN" to create a custom urban curve number. The Custom Curve Number
button is located at the bottom of the Urban Area land use section and
just above the Developing Urban land use section.

Land use for setting custom curve numbers is divided into pervious and
impervious areas. The impervious area is further identified as either
connected impervious and unconnected impervious. Runoff from [connected
impervious areas]{.underline} flows directly into the drainage system or
onto another impervious area and then into the drainage system. Runoff
from [unconnected impervious areas]{.underline} flows over some pervious
area as sheet flow before entering the drainage system. The percent of
impervious area that is unconnected is only available if the percent
impervious area is less than or equal to 30 percent. The default
Pervious Curve Number for each hydrologic soil group is for pasture in
good condition. The user may change this default value, if needed.

Enter data for "Pervious Curve Number", "% Impervious Area", and "%
Impervious that is unconnected" in the appropriate entry boxes. A
composite curve number will be calculated using equations in Appendix B
and displayed in the "Resulting Curve Number" box. The Hydrologic Soil
Group entry indicates which CN column (Hydrologic Soil Group A, B, C or
D) of the "User defined urban" Cover Description line (Land Use Details)
window the computed curve number will be placed if the entered data is
kept.

### Buttons

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

#### [A]{.underline}ccept

Click "[A]{.underline}ccept" to close the Custom CN Window and redisplay
the Land Use Details Window with the newly defined custom curve numbers.

The window below shows the Land Use Window looks after the user has set
a custom curve numbers for Hydrologic Soil Groups "B" then closed the
Custom Curve Number window. In this example, the resulting custom curve
number is 67, with 20% of the hydrologic soil group "B" area is
impervious, and 50% of the impervious area is unconnected. A value of 61
for the pervious area was used. The user entered 22 acres of this curve
number in the sub-area "Custom CN".

[]{#__RefHeading___Toc6972409 .anchor}Window 11 - Land Use Details
Window with Custom Curve Number

![](media/image31.png){width="5.811805555555556in"
height="3.5340277777777778in"}

#### [C]{.underline}ancel

Click "Cancel" to close the Custom CN Window and redisplay the Land Use
Details Window, without incorporating the recently defined custom curve
number data.

## Time of Concentration Details Window

[]{#__RefHeading___Toc6972410 .anchor}Window 12 - Time of Concentration
Details

![](media/image32.png){width="5.8902777777777775in"
height="2.3965277777777776in"}

### Purpose

The Time of Concentration Details window allows entry, editing, and/or
viewing of sub-area flow path segment data and the resulting segment
travel times and time of concentration for sub-areas in the watershed
that have detailed time of concentration data. The computed sub-area
time of concentration is displayed in the T~c~ column of the Sub-area
Entry and Summary portion on the TR-55 Main Window. The sub-area time of
concentration can also be entered directly on the TR-55 Main Window.
Data computed from the Time of Concentration Window will override any
prior time of concentration entries on the TR-55 Main Window. Blue boxes
on the Time of Concentration Details window contain computed data while
white boxes contain user-entered data.

### Data Entry and Selection

Time of concentration is computed as per NRCS NEH Part 630.15, Chapter
15 and WinTR-55 (10/86)*.*

After opening the Time of Concentration Details Window, select the
sub-area in the sub-area combo box. The current 2-year, 24-hour rainfall
depth is displayed. To change the 2-year, 24-hour rainfall depth, go to
the storm data window.

Up to five flow segments may be entered: one for sheet, two for shallow
concentrated, and two for channel flow. For sheet and shallow
concentrated flow enter the length, slope, and surface. For channel
flow, either enter length, slope, Manning *n*, flow area, and wetted
perimeter or enter length and velocity directly.

The equations used for computing each segment's travel time are in found
in Appendix B.

### Sheet Flow Length

Sheet flow length in the DOS version of WinTR-55 was limited to 300 feet
(100 m). Sheet flow for 300 feet is very unusual because the surface and
the corresponding flow would need to be extremely uniform. Generally,
beyond 100 feet the flow becomes concentrated flow. Therefore, sheet
flow length is limited to 100 feet (30 m) in this version of WinTR-55.
For additional information see: USDA-SCS, *Time of Concentration,*
Northeast Hydrology Technical Note No. N4, August 1986.

### Buttons

#### [R]{.underline}ename

[R]{.underline}ename allows the user to rename the sub-area.

#### [C]{.underline}lear

[C]{.underline}lear clears all the currently displayed time of
concentration details.

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

#### [C]{.underline}ancel (See Cancel comments on Land Use Details window)

Click "Cancel" to lose all data entry or revisions since this window was
opened and redisplay the TR-55 Main Window.

#### [A]{.underline}ccept (See Accept comments on Land Use Details window)

Click "Accept" to retain all data entered or edited on the window, close
the window, and redisplay the TR-55 Main Window. To save the data file,
go to the TR-55 Main Window and click the diskette icon or "Save As" on
the "File" menu.

## Reach Window

[]{#__RefHeading___Toc6972411 .anchor}Window 13 - Reach Data

![](media/image33.png){width="5.116666666666666in"
height="4.272916666666666in"}

### Purpose

The Reach window allows editing and viewing of the stream network, shows
whether each reach is a channel reach or a storage (structure) reach,
and provides information on creating a channel rating if the reach is a
channel reach. No data is required in this window if all sub-areas flow
directly to the watershed Outlet. Again, WinTR-55 will only run if all
the flow is directed to "Outlet".

If the watershed exceeds 10 reaches or the channel hydraulics require a
complex rating relationship (for example, a principal spillway and an
auxiliary spillway) another routing method should be used, such as TR-20
(NRCS, 2002) or SITES (NRCS, 2001).

### Reach -- Routing Element Concept

Reaches can be conceptualized as routing elements that exist in two
types. The first type of routing element is a channel routing element,
which is a stream reach. Data for a stream reach is entered on the Reach
Data Window.

The second type of routing element is a storage routing element, which
is a reservoir or structure. If the routing element is a structure, the
structure name is entered on the Reach Data Window. The corresponding
data for a structure, however, is entered on the Structure Data Window.

### Data Entry and Selection

Each reach must have a unique "Reach Name" and a "Receiving Reach".
Reach names are 1 to 10 characters in length and may be entered here or
previously entered as "Sub-area Flows to Reach/Outlet" on the TR-55 Main
Window.

A downstream "Receiving Reach" is required for each reach. A pull-down
choice list provides previously entered reach names to chose from along
with the watershed "Outlet". If a new name is entered into the Receiving
Reach box, it will also be added to the Reach Name list as long as the
current number of reaches is less than 10. If the current number of
reaches is 10, then no new names are accepted in the Receiving Reach
box.

When data is entered on the reach line for one type of routing, the
box(es) for the other routing type will be grayed out. Data may still be
entered in a gray box but will cause previously entered data on the line
of the other routing type to be lost. Data for only one type of routing
per line is retained.

To channel route, enter data for reach length, Manning *n*, friction
slope, bottom width, and side slope. The reach length would be either
the stream channel length or the floodplain length for the reach. Which
length is used depends on whether expected flows are within bank or out
of bank. The other parameters define a representative cross section for
the reach. Based on the channel cross section information entered, a
channel rating relationship for the reach is computed and displayed
below the grid. The equations used in development of the channel rating
are in Appendix B.

To storage route, enter a Structure Name or select from the choice list
(if the structure has been previously described). To edit or view
structure data, double-click the Structure Name to display the Structure
Data Window.

### Selecting a Representative Cross Section 

A WinTR-55 reach cross section is either a rectangular, triangular, or
trapezoidal channel. The cross section rating is based on the channel
bottom width, side slope, Manning *n*, and friction slope data. The
cross section rating includes Manning equation discharges for fixed
depths at the cross section (0.5, 1.0, 2.0, 5.0, 10.0, and 20.0 feet).

The Muskingum-Cunge flood routing method estimates how the hydrograph
changes as it flows through the reach utilizing this rating information.
Typically, reach storage reduces and delays the peak discharge. In
addition, the hydrograph peak becomes more rounded.

During a WinTR-55 run, all selected storms use one cross section rating
for a reach. For this reason, selecting a representative cross section
for the reach is extremely important. Generally, the channel has a
capacity of a 5-year discharge or less (if the channel has a large
capacity, the following discussion may not apply). If the peak discharge
stays in the channel banks and the channel dimensions and roughness are
entered, then the routing is reasonable. If the peak discharge flow
overtops the channel banks, the reach routing is still based on the
channel shape extending the side slopes up to 20 feet, which will not
give a good representative stage-discharge relationship.

The user must judge if this is a reasonable approximation of the shape
of the cross section above the channel banks. For example, the 2-year
channel could be a 10-foot bottom width stream with 2:1 side slopes and
0.04 Manning *n*. However, the 100-year flow area might be represented
by a 100-foot bottom width floodplain with 10:1 side slopes and 0.07
Manning *n*. However, WinTR-55 only accepts one set of data to represent
the channel reach for all storms.

If the channel-only (no floodplain) approximation is unreasonable, one
alternative is to enter a reach cross section representative of the
floodplain (width, side slope, and Manning *n*). This alternative
neglects the effect of the channel on the total cross section rating.

A second alternative is to use a hydraulic model, such as Corps of
Engineers HEC-RAS, to develop the total cross section rating to include
both the channel and floodplain. Then use NRCS TR-20 hydrologic model to
develop and route the storm hydrographs. Using channel cross section
data to represent the floodplain cross section will generally raise the
peak discharge at the downstream end of the reach and translate it
downstream sooner than if the floodplain and its storage are considered.
The impact will vary with the floodplain width and its associated
roughness.

### Buttons

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions. Close the help-text window to return to
data entry.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

#### [P]{.underline}lot

[]{#__RefHeading___Toc6972412 .anchor}Window 14 - Channel Rating Plot

![](media/image34.png){width="3.95in" height="3.582638888888889in"}

Click "Plot" to produce a graphical representation of the channel
discharge and end area ratings from the data entered.

#### [C]{.underline}ancel (See Cancel comments on Land Use Description window)

Click "Cancel" to lose all data entry or revisions since this window was
opened and redisplay the TR-55 Main Window.

#### [A]{.underline}ccept (See Accept comments on Land Use Description window)

This button saves all data, closes the window, and returns to the TR-55
Main Window. To save the data file, go to the TR-55 Main Window and
click on "Save" or select "File Save" from the menu.

#### [R]{.underline}each Flow Path

Click "Reach Flow Path" to display the Reach Flow Path window.

## Reach Schematic Window

[]{#__RefHeading___Toc6972413 .anchor}Window 15 - Reach Flow Path
Definition

![](media/image35.png){width="4.052083333333333in"
height="3.3243055555555556in"}

### Purpose

This window displays a reach schematic of the currently entered reach,
sub-area, and structure information.

### Buttons

#### [D]{.underline}etail

This button toggles between displaying detailed information with labels
or displaying labels only in the schematic.

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions. Close the help-text window to return to
data entry.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

#### [C]{.underline}lose

This button closes the reach flow path window and returns the user to
the previously displayed window.

## Structure Data Window

[]{#__RefHeading___Toc6972414 .anchor}Window 16 - Structure Data (Pipe
Outlet)

![](media/image36.png){width="4.509027777777778in"
height="4.009722222222222in"}

### Purpose

The Structure Data window allows data editing for the pond's surface
area, structure outlet type and dimensions, and structure rating
relationship for a structure. Three different outlet sizes (trials) may
be defined for each structure. No data is required for this window if
there are no structures in the watershed.

If the temporary ponding storage or structure hydraulics require a
complex rating relationship another routing method should be used, such
as TR-20 (NRCS, 2002) or SITES (NRCS, 2001).

### Alternate Outlet Sizes for Multiple Structures

Three different outlet sizes may be entered for any structure. If the
watershed has multiple structures and multiple outlet sizes, WinTR-55
will only compute up to three trials. Alternative one will combine the
Trial #1 outlet sizes of each structure, alternative 2 will combine the
Trial #2 outlet sizes of each structure, and alternative 3 the Trial #3
outlet sizes. Otherwise, the statistically possible number of
alternatives with 10 structures and 3 outlet sizes is 3^10^ (greater
than 59,000)! Since WinTR-55 only computes three trials, computation
time is much faster and the user has only three alternatives to review
and evaluate.

### Data Entry and Selection

Enter the Structure Name (1 to 10 characters) or select from the choice
list in the combo box. If data has been previously entered for the
structure name, it will be displayed in the combo boxes in the window.
If no data had been previously entered, all other entries will be blank.
The first eight characters in structure names must be unique in each
file. For example, *Structure1* and *Structure2* are invalid names
because the first eight characters of the name are not unique. However,
*Struct1* and *Struct2* are valid structure names.

Enter the Pond Surface Area @ Spillway Crest and optionally a height
above the spillway crest and the pond surface area at that height. The
pond area and height data are used to calculate the temporary storage
for the ponded area. If only the surface area at the spillway crest is
specified, the pond has vertical sides and the storage area remains
constant as stage increases for the temporary storage calculation. If a
height above the spillway crest and the pond surface area at that height
are also provided, the pond cross section is trapezoidal and incremental
storage varies with stage for the temporary storage calculation. The
equations used to calculate the temporary storage are in Appendix B.

Select the Outlet Type (Pipe or Weir). The default is pipe.

### Pipe Outlet

If Pipe is selected, one to three pipe diameters may be specified along
with the Height (outlet to spillway). WinTR-55 will compute pipe head
from the entered data. The minimum pipe diameter is 6 inches or 150 mm.
The minimum Height (outlet to spillway) should be at least twice the
smallest pipe diameter. The discharge equations used in the structure
rating can be found in Appendix B. Once the first pipe diameter and the
Height is entered, a pipe rating table will be displayed below the
Outlet Description. The table is updated as additional information is
entered or is revised.

[]{#__RefHeading___Toc6972446 .anchor}Figure 5. Pipe Outlet Schematics

![](media/image37.wmf) ![](media/image38.wmf)

### Full Pipe Flow Assumption

At any given stage, WinTR-55 assumes full-pipe flow for the computed
pipe head. This is a reasonable assumption for the riser and pipe
configuration (Figure 4 bottom schematic). However, this full pipe flow
assumption may be unreasonable for large, straight pipes (Figure 4 top
schematic).

For example, if the structure outlet is a 36-inch (1-m) diameter pipe
culvert and the maximum computed stage is 1.5 feet (0.5 m), then the
pipe has never been more than half-full (Figure 5). In this case, the
full-pipe flow assumption has not been satisfied. Other routing
software, such as SITES (NRCS, 2001), is necessary to analyze these
cases.

[]{#__RefHeading___Toc6972447 .anchor}Figure 6. Full-Pipe Flow
Assumption Not Valid

![](media/image39.png){width="5.493055555555555in"
height="2.7041666666666666in"}

### Weir Outlet

If Weir is selected, one to three weir lengths may be specified. The
entry of a zero weir length indicates a V-notch weir while all other
lengths are for rectangular broad-crested weirs. The weir discharge
equations used in the structure rating are found in Appendix B. Once the
first weir length is entered, a weir rating table will be displayed
below the Outlet Description. The figure below shows the weir diagram.

[]{#__RefHeading___Toc6972448 .anchor}Figure 7. Weir Outlet Schematic

![](media/image40.wmf)

The table is updated as additional information is entered or is revised.
The window for weir entry follows.

[]{#__RefHeading___Toc6972415 .anchor}Window 17 - Structure Data (Weir
Outlet)

![](media/image41.png){width="4.53125in" height="3.9916666666666667in"}

Additional items to note about entry on the Structure Data window are:

1.  Toggling between the two different outlet types clears the outlet
    dimension values.

2.  Minimum data for a valid run is surface area at the spillway crest,
    outlet type, and one outlet size. If the outlet is a pipe, height
    must also be entered.

### Buttons

#### [C]{.underline}lear

Clears all data for existing structure.

#### [D]{.underline}elete

Deletes current structure data and name.

#### [R]{.underline}ename

Renames current structure

#### [A]{.underline}ccept

Accept current data, closes the window, and returns to TR-55 Main
Window.

#### [C]{.underline}ancel

Click "Cancel" to lose all data entry or revisions since this window was
opened and redisplay the TR-55 Main Window.

#### [P]{.underline}lot

Click "Plot" to produce a graphical representation of the structure
rating as shown in the following windows.

[]{#__RefHeading___Toc6972416 .anchor}Window 18 - Structure Rating (Pipe
Outlet)

![](media/image42.png){width="4.632638888888889in" height="4.375in"}

[]{#__RefHeading___Toc6972417 .anchor}Window 19 - Structure Data Plot
(Weir Outlet)

![](media/image43.png){width="4.632638888888889in" height="4.375in"}

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions. Close the help-text window to return to
data entry.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

## Storm Data Window

[]{#__RefHeading___Toc6972418 .anchor}Window 20 -- Storm Data

![](media/image44.png){width="3.8722222222222222in"
height="3.0972222222222223in"}

### Purpose

The Storm Data window allows the user to select the NRCS-supplied
rainfall data for the state and county or to enter custom rainfall
depths and select a different rainfall distribution. Storm data consist
of at least one rainfall amount / rainfall return period, and an
associated rainfall distribution. The user may request NRCS storm data
for the state and county specified. If such data exist, they will be
displayed in the window entry boxes when the NRCS Storm Data button is
clicked. The user can modify the NRCS storm data or may provide unique
storm data. If NRCS storm data is altered or unique data is entered, the
Storm Data Source on the TR-55 Main Window is listed as "User-provided
custom source data". NEH Part 630, Chapter 4 lists sources for rainfall
data.

### Data Entry and Selection

#### Watersheds Inside United States 

Some counties have easily-defined rainfall data and this data is loaded
into WinTR-55. However, other counties may vary in rainfall depths or
appropriate distributions. These data are not supplied in WinTR-55. To
select the NRCS-supplied storm data, click on the NRCS Storm Data
button. If no data is available for the current state and county
information entered on the TR-55 Main Window, this button is temporarily
disabled. If this is the case, the user must enter the rainfall depths
and select a rainfall distribution. The user must verify the
appropriateness of all rainfall inputs, even if it is NRCS-provided.
Local design requirements may supersede NRCS-provided storm data.

#### Watersheds Outside United States

No rainfall data is provided outside the United States. For example, if
the watershed is in Durango, Mexico, the TR-55 Main Window combo box
entry labels change from "State" and "County" to "Region" and "Locale"
as shown in Window 20.

[]{#__RefHeading___Toc6972419 .anchor}Window 21 - Watersheds Outside US

![](media/image45.png){width="4.501388888888889in" height="3.08125in"}

Therefore, all watersheds outside the United States require the user to
enter all the rainfall return period data and 24-hour rainfall amount
because the "[N]{.underline}RCS Storm Data" button on the Storm Data
Window is disabled. The user must also select a rainfall distribution
from the "Rainfall Distribution Type" combo entry box.

[]{#__RefHeading___Toc6972420 .anchor}Window 22 - Storm Data Outside of
US

![](media/image46.png){width="3.8722222222222222in"
height="3.0972222222222223in"}

#### Rainfall Distribution

To change the associated rainfall distribution type displayed on this
window, click on the pull-down list to select any previously entered
distribution. To enter a new rainfall distribution, click Cancel to
return to the TR-55 Main Window and select Custom Rainfall Distributions
from the Global Data pull-down menu.

#### Creating a New File

When "File-New" is selected from the TR-55 Main Window, all the project
data (Land Use, T~c~, Structure, and Reach) is cleared. However, the
global data (Storm Data, Rainfall Distribution, and Dimensionless Unit
Hydrograph) are not changed. Furthermore, the global data is not changed
even if the state and county are changed on the TR-55 Main Window.

[]{#__RefHeading___Toc6972421 .anchor}Window 23 - Differing State/County
and Storm Data Source Example

![](media/image47.png){width="4.459027777777778in"
height="4.419444444444444in"}

The window above shows that the Project Identification Data is Maui,
Hawaii. However, the storm data source lists Champaign County, Illinois.
Champaign Illinois storm data is not appropriate for Maui, Hawaii.
Therefore, the user must go to the Storm Data window for each project
and verify the accuracy of the storm data.

#### Template Files for Storm Data

Some users may use the same storm data set or sets repeatedly. If these
data sets are not NRCS storm data sets, it would become tedious to
re-enter the same rainfall data for each project. To create a template
file, click "File- New" on the TR-55 Main Window to clear all the
project data. Then enter the desired custom storm data. All the project
data (Land Use, T~c~, Structure, and Reach) has been cleared in the
file. Save this file with a filename descriptive of the storm data.

To utilize this storm data for future projects, open this template file
with the storm data first. Then proceed by entering project data (Land
Use, T~c~, Structure, and Reach). Make sure to save the project file as
a different name so the template file isn't overwritten.

### Buttons

#### [N]{.underline}RCS Storm Data

This button retrieves NRCS rainfall data, if it is available. If the
button is not available, the rainfall is not available in the data base.
Therefore, the user must supply all the rainfall data.

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions. Close the help-text window to return to
data entry.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

#### [C]{.underline}ancel

Click "Cancel" to lose all data entry or revisions since this window was
opened and redisplay the Main TR-55 Window.

#### [A]{.underline}ccept

"Accept" applies all new data, closes the window, and returns to the
Main TR-55 Window. To save the data file, go to the TR-55 Main Window
and click "Save" or select "File Save" from the menu.

## Custom Rainfall Distributions Window

[]{#__RefHeading___Toc6972422 .anchor}Window 24 - Custom Rainfall
Distributions

![](media/image48.png){width="2.7104166666666667in" height="2.90625in"}

### Purpose

This window allows the user to input and revise non-standard 24-hour
rainfall distributions. The standard rainfall distributions in WinTR-55
may not be edited or deleted.

The first point of each distribution is 0.00000 and the last point
should be 1.00000. No blank points are allowed. Each successive point
must be equal to or larger than the previous one. Data is read left to
right, starting at the top line and continuing to the bottom line.

For further information on rainfall distributions, see NRCS NEH Part
630, Chapter 4.

### Data Entry and Selection

To enter a new distribution, type the name into the Local
Distribution(s) entry box. To delete a distribution, select the
distribution name from the pull-down list and then click "Delete".

Once the distribution name is complete, begin entering distribution data
points in the table. WinTR-55 automatically displays the time increment
in hours and the number of data points as each point is entered.

### Menu

#### Edit 

[]{#__RefHeading___Toc6972423 .anchor}Window 25 - Custom Rainfall
Distributions (Edit)

![](media/image49.png){width="0.8631944444444445in"
height="0.41041666666666665in"}

The Edit menu is a mouse right-click menu. The Edit menu allows the user
to create and revise data points for the current rainfall distribution.
"Insert Point" inserts a blank data point before the current point.
"Delete Point" removes the current data point and moves successive
points up. Click within a cell to edit the data in that cell.

### Buttons

#### [R]{.underline}ename

This button allows the user to rename the currently displayed rainfall
distribution.

#### De[l]{.underline}ete

This button deletes the current distribution.

#### [P]{.underline}lot

Clicking on plot produces a graphical representation of the current
rainfall distribution. Only one distribution may be displayed at a time.

[]{#__RefHeading___Toc6972424 .anchor}Window 26 - Custom Rainfall
Distributions Plot

![](media/image50.png){width="5.71875in" height="4.395833333333333in"}

#### [D]{.underline}one

"Done" on the Dimensionless Unit Hydrograph Window prompts WinTR-55 to
save the distribution and return to the TR-55 Main Window. Note that
this process is different than saving project-specific data such as Land
Use Details, which only updates data in memory.

## Dimensionless Unit Hydrographs Window

[]{#__RefHeading___Toc6972425 .anchor}Window 27 - Dimensionless Unit
Hydrograph

![](media/image51.png){width="3.0701388888888888in"
height="2.8826388888888888in"}

### Purpose

This window allows the user to input and revise non-standard
dimensionless unit hydrographs. The standard dimensionless unit
hydrograph (peak rate factor = 484) in WinTR-55 may not be edited or
deleted.

No blank points are allowed in the dimensionless unit hydrograph data
table. Each point must increase from 0.00000 to 1.00000, then decrease
to 0.00000. Data is read left to right, starting at the top line and
continuing to the bottom.

For further information on dimensionless unit hydrographs, see NRCS NEH
Part 630, Chapter 16.

### Menu

#### Edit 

The Edit menu is a mouse right-click menu. The Edit menu allows the user
to create and revise data points for a user defined dimensionless unit
hydrograph. "Insert Point" inserts a blank data point before the current
point. "Delete Point" removes the current data point and moves
successive points up. The user may also click within a cell to edit the
data in that cell.

### Data Entry and Selection

To enter a new dimensionless unit hydrograph, type the name into the
local hydrograph(s) entry box.

Once the dimensionless unit hydrograph name is complete, begin entering
the dimensionless unit hydrograph data points into the table. WinTR-55
automatically displays the number of data points as each point is
entered. To delete a local dimensionless unit hydrograph, select the
dimensionless unit hydrograph name from the pull-down list and then
click "Delete".

### Buttons

#### [R]{.underline}ename

This button allows the user to rename the displayed dimensionless unit
hydrograph.

#### [D]{.underline}elete

This button deletes the current dimensionless unit hydrograph.

#### [P]{.underline}lot

Click "plot" to produce a graphical representation of the dimensionless
unit hydrograph.

[]{#__RefHeading___Toc6972426 .anchor}Window 28 - Dimensionless Unit
Hydrograph Plot

![](media/image52.png){width="4.632638888888889in" height="4.375in"}

#### [D]{.underline}one

Clicking "Done" prompts WinTR-55 to save the dimensionless unit
hydrograph and return to the TR-55 Main Window. Note that this process
is different than saving watershed-specific data such as Land Use
Details, which only updates data in memory.

## Plot Windows

### Purpose and Description

The plot windows for various functions (dimensionless unit hydrograph,
rainfall distribution, reach rating, output hydrograph, etc.) show
graphically how two or more variables relate to one another. For
example, the following plot shows how discharge and end area vary with
elevation.

[]{#__RefHeading___Toc6972427 .anchor}Window 29 - Typical Plot Window

![](media/image53.png){width="4.632638888888889in" height="4.375in"}

### Buttons

#### Save As

Saves the current plot to a bitmap file.

#### Print

Prints the current plot to the user-selected printer.

#### Copy to Clipboard

Copies the plot to the system clipboard for later insertion into other
software, such as word processors.

#### Zoom In

Allows the user to zoom into selected areas of the plot.

#### Zoom Out

Restores the view of the full plot.

#### Line Attributes

Allows the user to select various line widths, colors and types.

#### Grid Lines

Toggles between no grid lines, horizontal grid lines only, vertical grid
lines only, and both horizontal and vertical grid lines.

#### [C]{.underline}lose

Closes the plot window and returns to the previous window.

# Running WinTR-55

To run the WinTR-55 model, Click "Run" on the menu bar. The Run TR-55
window comes up, allowing the user to choose which frequencies to run.
Click Run again. A TR-20 input data file is prepared and the TR-20 model
is run producing hydrographs for all of the sub-areas, reaches (upstream
and downstream), as well as the watershed outlet. If the run is
successful, the Hydrograph Peak/ Peak Time Table will be displayed in
the File Display window. If the run is unsuccessful, the Error file from
TR-20 will be displayed in the File Display window. Any data errors
identified will need to be corrected before re-running the watershed
data.

## Disclaimer 

*Although all pieces of the WinTR-55 system have been tested by the
developers, NO warranty, expressed or implied, is made as to the
accuracy and functioning of the programs and related program materials
nor shall the fact of distribution constitute any such warranty, and NO
responsibility is assumed by the developers in connection therewith.*

## WinTR-55 Processes

WinTR-55 preprocesses data, during data entry, for TR-20 hydrograph
computations. The preprocessing computations are: Time of Concentration,
land use parameters, channel rating table, and structure rating table.

### Time of Concentration (T~c~)

The user may enter a sub-area T~c~ directly on the sub-area summary
portion of the TR-55 Main Window or compute it from detailed flow path
data entered on the TR-55 Time of Concentration Details window. Data
entry and computations are sub-divided into three types of flow (sheet,
shallow concentrated, and channel flow). While data for only one sheet
flow segment can be entered, one or two segments of data can be entered
for both the shallow concentrated and channel flows. The total computed
travel times for each flow path segment are indicated on the entry
window as is the T~c~ (sum of the travel times). The equations used to
compute the various travel times for each segment type can be found in
Appendix B. **Green** T~c~ values in the sub-area summary table indicate
computed values, **blue** values indicate data entered directly.

### Land Use Parameters

The user may enter a sub-area drainage area and weighted runoff curve
number directly on the sub-area summary portion of the TR-55 Main Window
or compute them from detailed land use data entered on the TR-55 Land
Use Details window. Land use area amounts are entered on the Land Use
Details window for each land use with the corresponding hydrologic soil
group. The land use areas entered are summed to determine the sub-area
drainage area. The land use areas are also used to weight the applicable
runoff curve numbers for the land use hydrologic soil group combination
to produce a sub--area weighted curve number. The equation used in the
curve number weighting is in Appendix B. **Green** areas and weighted CN
values in the sub-area summary table indicate computed values, **blue**
values indicate data entered directly.

The optional custom CN in the Land Use Details table is under user
control and is a weighted CN depending on an imperious area CN, the
percent of the area that is impervious (CN = 98) and the amount of the
impervious area not directly connected to the flow path.

### Channel Rating Table

For each reach with channel information entered, a channel rating table
is generated. The rating table consists of discharge, cross-section end
area, and top width for depths from 0 to 20 feet (6.1 meters). This
range should cover all WinTR-55 applications. The rating table data is
displayed below the entry portion of the Reach data window when
sufficient data is entered to perform the calculations. The equations
used for each of the rating parameters are in Appendix B.

### Structure Rating Table

For each reach that has structure information entered, a structure
rating table is generated. The information contained in the rating table
depends on the structure outlet type (pipe or weir). The pipe outlet
rating table consists of stage, head on pipe, pipe flow, and temporary
storage. The weir table consists of stage, weir flow and temporary
storage. One to three pipe diameters or weir lengths can be entered. A
set of 7 stages, based on either multiples of the smallest pipe diameter
or 0 to 20 feet (6.1 meters), is computed for weirs. The rating table
data is displayed below the entry portion of the Structure data window
when sufficient data is entered to perform the calculations. The
equations used for each of the rating parameters are in Appendix B.

## TR-20 Processes

WinTR-55 relies on the TR-20 model for all hydrograph processes. These
include: hydrograph generation, combining hydrographs, channel routing,
and structure routing. A brief description of each of these processes
follows.

### Generate Hydrographs

Hydrographs are generated from sub-areas using the appropriate rainfall
depth (for a specific frequency), rainfall distribution, sub-area
drainage area, time of concentration (T~c~), and curve number using the
NRCS hydrograph generation technique. The sub-area T~c~ is used to
establish the time interval for the spacing of points in the
dimensionless unit hydrograph. This time interval defines the hydrograph
time increment. The rainfall distribution is linearly interpolated to
develop mass rainfall values to use at the time increment needed.

### Combine Hydrographs

Two hydrographs are combined using the first hydrograph time increment
and linearly interpolating the second hydrograph. Next, the two
hydrographs are combined again using the time increment from the second
and linearly interpolating the first. The combined hydrograph with the
highest peak is the one retained along with the appropriate time
increment.

### Channel Route

The program uses a Muskingum-Cunge method of channel routing (Chow,
Maidment, and Mays, 1988; Maidment, ed., 1993; or Ponce, 1989). The
rating table generated by WinTR-55 for each reach is used to represent
flow in that reach. The unique feature of the Muskingum-Cunge routing is
the calculation of the length of a routing reach step based on inflow
peak discharge and cross section information. If the routing reach step
length is shorter than the reach length, the reach is sub-stepped. For
example, if there are two steps, the routing is accomplished by solving
the routing equation twice: the outflow hydrograph for the upper half of
the reach becomes the inflow hydrograph for the lower half of the reach.
If there are less than ten points from the beginning of the hydrograph
to the peak of the inflow hydrograph, the inflow hydrograph is
interpolated at a time interval to allow ten points, the routing
computed, and the outflow hydrograph interpolated to return it to the
original time increment.

### Structure Route

The storage-indication method (NRCS NEH Part 630, Chapter 17) is used to
route structure hydrographs. While the routed hydrograph time increment
(downstream end of reach) is the same as the increment at the upstream
end, the actual routing may sub-step the increment during the routing.
The routing time step is based on the smallest time to empty the
reservoir at each of the structure rating points. (The time to empty the
reservoir is computed as the structure rating storage volume divided by
the average outflow (rating outflow/2)). The hydrograph time increment
is compared to a percentage (currently 50%) of the smallest emptying
time to determine the number of time steps to use between hydrograph
points.

# Viewing Output

## File Display Window

This window, also referred to as the Report Viewer, displays various
TR-55 Reports.

This window opens after a WinTR-55 run. If there are any errors in the
WinTR-55 run, this window opens with the title "Error File". Carefully
examine the error messages, and modify the input data to correct the
errors.

If no errors are discovered in the data set, the WinTR-55 run is
executed and the window opens with the reports selected from "Output
Definition" window. If no reports were selected using the "Output
Definition" window, the report viewer window opens with "Hydrograph Peak
/ Peak Time Table."

[]{#__RefHeading___Toc6972428 .anchor}Window 30 -- File Display

![](media/image54.png){width="5.076388888888889in"
height="3.415277777777778in"}

Click "Close" to close this window.

Scroll through the reports using the viewer or select individual reports
on the File Display Window Menu. The following table contains a brief
description of the File Display Window Menu.

### Menu

  --------------------- ---------------------------- ----------------------------
  **Menu Item**         **Pull-down Choice**         **Explanation**

  [P]{.underline}rint   [P]{.underline}rint          Prints the displayed
                                                     report(s)

                        Page Setup                   Define target printer, page
                                                     size and orientation,
                                                     margins.

  [E]{.underline}dit    [C]{.underline}opy to        Copies the displayed
                        Clipboard                    report(s) to the Windows
                                                     system clipboard.

                        [F]{.underline}ind           Find a specific text or
                                                     number. Helpful for
                                                     navigating large output
                                                     reports.

                        Find [N]{.underline}ext      Repeats a previously defined
                                                     search.

  [V]{.underline}iew    [I]{.underline}nput File     View the TR-20 input file
                                                     created from WinTR-55 input
                                                     data.

                        [T]{.underline}R-20 Printed  View raw TR-20 output file.
                        Page File                    

                        [E]{.underline}rror File     View TR-20 error file. These
                                                     error messages are found in
                                                     the TR-20 user manual.

                        [D]{.underline}ebug File     View TR-20 debug file.

  [T]{.underline}R-55   See Table 3 for available    
  Reports               reports.                     

  [H]{.underline}elp    None                         Displays File Display window
                                                     help text.
  --------------------- ---------------------------- ----------------------------

### Buttons

#### Close

Click "Close" to close the File Display window and return to the Output
Definition window.

## Output Definition Window

Once rainfall data is entered, the "Output Definition" button on the
TR-55 Main Window is enabled. The user may select reports for viewing
prior to executing a WinTR-55 run. However, some report options may be
grayed-out, indicating that reports are not available for viewing until
an error-free WinTR-55 run is executed.

Click the Output Definition icon to open the "Output Definition" window.
Specify output by clicking the box to the left of the desired report.
Output may be sent to a file or to the report viewer, depending on which
option is selected.

[]{#__RefHeading___Toc6972429 .anchor}Window 31 - Output Definition

![](media/image55.png){width="3.1993055555555556in"
height="3.4965277777777777in"}

## Available Reports

Available reports shown in the Output Definition window are summarized
in the following table.

[]{#__RefHeading___Toc6972441 .anchor}Table 3. TR-55 Reports

  -------------------------- ----------------------------------------------------
  **Report Name**            **Description**

  [C]{.underline}urrent data Lists the current user-input data.
  description                

  [S]{.underline}torm Data   A listing of the Rainfall Depth by Rainfall Return
                             Period information. Also shows Storm Data source,
                             Rainfall Distribution and the Dimensionless Unit
                             Hydrograph.

  [W]{.underline}atershed    Watershed peak table is not available to the User
  Peak Table                 until an error-free WinTR-55 run is executed. Upon
                             completion of an error free WinTR-55 run, this
                             option will give a listing of peak discharges, by
                             reach, for each storm evaluated.

  [H]{.underline}ydrograph   Hydrograph peak /peak time table is not available to
  Peak / Peak Time Table     the User until an error-free WinTR-55 run is
                             executed. Upon completion of an error free WinTR-55
                             run, this option will give a listing of peak
                             discharge and time of peak, by sub-area or reach
                             identifier, for each storm evaluated.

  Structure                  Structure output table is not available to the User
  [O]{.underline}utput Table until an error-free WinTR-55 run is executed. Upon
                             completion of an error-free WinTR-55 run, this
                             option will give a list peak flow (PF), storage
                             volume (SV), and maximum stage (STG) for structures
                             included in the WinTR-55 run. If there are no
                             structures in the run, this table will be blank,
                             however, the headings will be shown.

  Sub-area Summary           A listing, by sub-area of Drainage Area, Time of
  [T]{.underline}able        Concentration, Runoff Curve Number, Receiving Reach
                             and Sub-area.

  [R]{.underline}each        Identifies, by reach, the receiving reach, reach
  Summary Table              length and routing method used.

  Sub-area Time of           A listing, by sub-area, of flow length, slope,
  Concentration              Manning "n" value, end area, wetted perimeter,
  [D]{.underline}etails      velocity and travel time for time of concentration
                             flow path segments along with the total time of
                             concentration.

  Sub-area                   A listing, by sub-area, of Land Use, Hydrologic Soil
  [L]{.underline}and Use and Group and area for each particular land use in a
  Curve Number Details       sub-area. Also lists the total area and weighted
                             curve number for each sub-area.

  R[e]{.underline}ach        Identifies, by reach, the reach length, Manning "n"
  Channel Rating Details     value used for that reach, friction slope, bottom
                             width, and side slope. Also includes the computed
                             channel rating for each reach. Channel ratings are
                             the WinTR-55 input data format: Stage -- Flow -- End
                             Area. Rating tables also include Top Width and
                             Friction Slope.

  Str[u]{.underline}cture    Provides a summary of the user entered structure
  Description                data by reach.

  Structure                  Provides a summary of the computed structure rating:
  Ratin[g]{.underline}       stage, storage, and flow.
  Tables                     
  -------------------------- ----------------------------------------------------

### Buttons

#### Help (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions. Close the help-text window to return to
data entry.

#### [A]{.underline}ll/Reset

If no report boxes are checked, the button label is "All". Click "All"
to check all the reports. If all the report boxes are checked, the label
toggles to "Reset", which will clear all the check boxes.

#### [V]{.underline}iew/Print

This button label toggles between View and Print, depending on which
option button is selected, either Printer/File or Report Viewer.

#### [C]{.underline}lose

Click "Close" to close the Output Definition window and return to the
TR-55 Main Window.

## Plotting and Viewing Hydrographs

### Hydrographs or Output Graphics Window

Click "Hydrographs" to open the Output Graphics Window and specify
hydrographs to plot or view. Select either Sub-areas or Reaches and then
check the box next to the name of the sub-area or reach for the desired
hydrographs. For Reach hydrographs, the hydrograph may be viewed at the
upstream or downstream or both ends of the reach. Select storm event
hydrographs by checking the appropriate box.

It is possible to plot all the hydrographs for all the sub-areas or
reaches for all of the available storm events on one plot. However, the
User should be aware that selecting several hydrographs to view at once
makes the hydrographs that much more difficult to read.

#### [P]{.underline}lot

Once the desired hydrographs have been specified, click
"[P]{.underline}lot" and a Graphics Window opens showing the desired
plot.

#### [C]{.underline}lose

Click "[C]{.underline}lose" to close this window and redisplay the Main
Window.

#### [H]{.underline}elp (See help comments on TR-55 Main Window)

Opens a new help-text window with an overview of window purpose and
general data entry instructions. Close the help-text window to return to
data entry.

#### Quick Help (?)

Click "?" to provide context-sensitive help for any data that is clicked
on next. To replace the help question mark cursor with the standard
cursor, click "?" again. Help is displayed at the bottom of the window.

[]{#__RefHeading___Toc6972430 .anchor}Window 32 - Output Graphics

![](media/image56.png){width="3.2694444444444444in" height="2.83125in"}

### Graphics Window

Click "Plot" on the Output Graphics Window to plot selected hydrographs.
Either save the plot to a file or print directly to a printer.

[]{#__RefHeading___Toc6972431 .anchor}Window 33 - Output Plot

![](media/image57.png){width="4.601388888888889in" height="4.375in"}

Click "[C]{.underline}lose" to close this window.

# Appendix A - Examples

## Example 1 -- Determining Runoff from a Single Sub-area for the Existing and Developed Conditions and Sizing a Detention Basin

### Background

An Industrial Development is planned on a 12.5 acre site in Franklin
County, Missouri. The land is presently being used for corn production
and is planted in straight rows. There are no special conservation
practices being used and the vegetative cover is typically in good
condition. The soils on this property are hydrologic soil group "B."

There is no defined channel running through the property, but there is
evidence of sheet flows and shallow concentrated flows. The sheet flow
path has been determined to be 25 feet long at a slope of 0.8%. The
shallow concentrated flow path has been determined to be 825 feet long
at a slope of 0.8%.

It is desirable to limit peak discharge from a 25-year storm for the
developed condition so that it does not exceed the peak discharge from a
50-year storm for the undeveloped condition. Therefore, it is necessary
to design some type of stormwater detention structure to control the
runoff.

### Solution

The design of the stormwater detention structure will be handled in
three parts. Part A will be to determine the peak discharge and runoff
volume for the existing condition. Part B will be to determine the peak
discharge and runoff volume for the developed condition. Part C will
focus on sizing the stormwater detention structure and analyzing its
effects.

### Part A - Determine existing condition peak discharge and runoff volume

STEP 1: Start the WinTR-55 program and enter User I.D., Project Name,
Subtitle, State and County. Specify sub-area units (default is acres).
Use the Storm Data Source default values based on the State and County
specified. To make certain the correct Storm Data Source and Rainfall
Distribution Identifier are selected, the User MUST complete STEP 2.

![](media/image58.png){width="4.470833333333333in"
height="4.425694444444445in"}

STEP 2: From the Main Window Menu, select "Global Data." From that
drop-down menu, select "Storm Data." On the Storm Data Window, the User
clicks the "NRCS Storm Data" Button and then the "Accept" Button to use
the default database values for the county-state combination being
modeled. Clicking the "Accept" Button accepts the data and returns the
User to the Main Window.

![](media/image59.png){width="3.8722222222222222in"
height="3.0972222222222223in"}

STEP 3: Enter Sub-area Name, Sub-area Description, and where the water
leaving this sub-area flows in the "Sub-area Flows to Reach/Outlet" box.

![](media/image60.png){width="3.597916666666667in"
height="3.560416666666667in"}

STEP 4: Click "Land Use Details" button to open the "Land Use Details"
window. In the "Land Use Details" window, enter the area of the sub-area
in the appropriate location. Click "Accept" to accept the data and
return to "TR-55 Main Window."

![](media/image61.png){width="4.907638888888889in"
height="3.6909722222222223in"}

> The sub-area area and runoff curve number now appear in the Sub-area
> Entry and Summary portion of the TR-55 Main Window.

![](media/image62.png){width="4.440972222222222in"
height="4.407638888888889in"}

STEP 5: Click "Time of Concentration Details" button to open the "Time
of Concentration Details" window. In the "Time of Concentration Details"
window, enter the appropriate information to compute the sub-area time
of concentration. Click "Accept" to accept the data and return to the
"TR-55 Main Window."

> ![](media/image63.png){width="5.9215277777777775in"
> height="2.4090277777777778in"}
>
> The sub-area time of concentration now appears in the Sub-area Entry
> and Summary portion of the TR-55 Main Window.
>
> ![](media/image64.png){width="4.459027777777778in"
> height="4.419444444444444in"}

STEP 6: Click the "Run" button to open the "Run TR-55" window. Select
the storm events for which output is desired. Once the storm events have
been selected, click "Run" to execute the run.

![](media/image65.png){width="2.1590277777777778in"
height="1.8902777777777777in"}

STEP 7: When the run is complete, the "File Display" window opens
showing the "Hydrograph Peak / Peak Time Table." To review other output,
click "View" or "TR-55 Reports" and select the reports to view. When
complete, click "Close" to close the "File Display" window and return to
the TR-55 Main Window.

![](media/image66.png){width="5.16875in" height="3.859027777777778in"}

STEP 8: To save the data, click "File" and "SaveAs." In the "Save a TR55
data file" popup window, specify a location and file name and click
"Save." The data is now saved, the popup window closes and TR-55 Main
Window is redisplayed.

![](media/image67.png){width="3.327777777777778in"
height="2.064583333333333in"}

### Part A - Results

50-year Pre-Development Discharge = 66.8 cfs

50-year Pre-Development Runoff Volume = 3.984 inches (watershed-inches)
= 4.150 ac-ft

The Runoff Volume can be found from the "File Display Window" by
selecting "View" and "TR-20 Printed Page File."

### Part B - Determine developed condition peak discharge and runoff volume

![](media/image68.png){width="3.327777777777778in"
height="2.222916666666667in"}

Rather than beginning with a new file to determine the peak discharge
and runoff volume for the developed condition, it is possible to edit
the existing condition file previously created.

STEP 1: Start the WinTR-55 Program and open the "Existing Conditions"
file by selecting "Open" from the "File" menu and locating the file
using the "Open a TR-55 data file" window.

STEP 2: Edit the User I.D., Project Name, and Subtitle as appropriate.
Edit Sub-area Name, Sub-area Description, and where the water leaving
this sub-are flows in the "Sub-area Flows to Reach/Outlet" box as
appropriate. Since this example uses the same county-state combination
established previously, there is no need to work through the "Global
Data" selection process to change the Dimensionless Unit Hydrograph,
Storm Data Source and Rainfall Distribution Identifier information.

![](media/image69.png){width="4.459027777777778in"
height="4.419444444444444in"}

STEP 3: Click "Land Use Details" button to open the "Land Use Details"
window. In the "Land Use Details" window, edit the land use as
appropriate, and click "Accept" to accept the changes and return to
"TR-55 Main Window."

> ![](media/image70.png){width="4.522222222222222in" height="3.40625in"}
>
> The sub-area area and runoff curve number now appear in the Sub-area
> Entry and Summary portion of the TR-55 Main Window.

![](media/image71.png){width="4.459027777777778in"
height="4.419444444444444in"}

STEP 4: Click "Time of Concentration Details" button to open the "Time
of Concentration Details" window. In the "Time of Concentration Details"
window, edit the appropriate information to compute the developed
condition sub-area time of concentration. Click "Accept" to accept the
changes and return to the "TR-55 Main Window."

> ![](media/image72.png){width="6.031944444444444in"
> height="2.422222222222222in"}
>
> The sub-area time of concentration now appears in the Sub-area Entry
> and Summary portion of the TR-55 Main Window.
>
> ![](media/image73.png){width="4.459027777777778in"
> height="4.419444444444444in"}

STEP 5: Click on the "Run" button to open the "Run TR-55" window. Select
the storm events for which output is desired. Once the storm events have
been selected, click "Run" to execute the run.

![](media/image74.png){width="2.1590277777777778in" height="1.8875in"}

STEP 6: When the run is complete, the "File Display" window opens
showing the "Hydrograph Peak / Peak Time Table." To review other output,
click "View" or "TR-55 Reports" and select the reports to view. When
complete, click "Close" to close the "File Display" window and return to
the TR-55 Main Window.

![](media/image75.png){width="5.127777777777778in"
height="3.827777777777778in"}

STEP 7: To save the data, click "File" and "SaveAs." In the "Save a TR55
data file" popup window, specify a location and a NEW FILE NAME and
click "Save." The data is now saved, the popup window closes and the
TR-55 Main Window is redisplayed.

![](media/image76.png){width="3.327777777777778in"
height="2.0597222222222222in"}

### Part B - Results

25-year Post-Development Discharge = 77.5 cfs

25-year Post-Development Runoff Volume = 4.373 inches (watershed-inches)
= 4.555 ac-ft

The Runoff Volume can be found from the "File Display Window" by
selecting "View" and "TR-20 Printed Page File."

### Part C - Sizing the Detention Basin

There are two approaches to sizing the detention basin. The first
approach is to maximize the storage volume while minimizing the pipe
size. Using this approach, the entire runoff volume from the 25-year
post-development storm would be stored and released at a slow rate over
a long period of time using a small diameter pipe. The second approach
is to minimize the storage volume while maximizing the pipe size. Using
the second approach, water is released at the maximum rate possible (in
this case the 50-year pre-development peak discharge) thereby minimizing
the volume of water that must be stored.

The following table offers a summary of some of the advantages and
disadvantages of each approach.

+--------------+------------------------+------------------------------+
| Method       | Advantages             | Disadvantages                |
+--------------+------------------------+------------------------------+
| Maximize     | Smaller diameter pipe  | Size of area required for    |
| Storage      | is less expensive      | detention basin is large     |
| Volume       |                        |                              |
|              |                        |                              |
| Minimize     |                        |                              |
| Pipe Size    |                        |                              |
+--------------+------------------------+------------------------------+
|              | Storage benefits for   | Cost of constructing a large |
|              | more frequent storm    | storage basin can be         |
|              | events are realized    | expensive.                   |
|              | because increased      |                              |
|              | runoff for the smaller |                              |
|              | events is also stored. |                              |
+--------------+------------------------+------------------------------+
| Minimize     | Size of area required  | Larger Diameter pipe is more |
| Storage      | for detention basin is | expensive                    |
| Volume       | not as large           |                              |
|              |                        |                              |
| Maximize     |                        |                              |
| Pipe Size    |                        |                              |
+--------------+------------------------+------------------------------+
|              | Lower construction     | Because pipe diameter is so  |
|              | costs for smaller      | large, there may not be a    |
|              | storage basin          | reduction in peak discharge  |
|              |                        | for more frequent storm      |
|              |                        | events. Increased runoff     |
|              |                        | volume from those more       |
|              |                        | frequent events may pass     |
|              |                        | through the basin without    |
|              |                        | any portion of the increased |
|              |                        | runoff for those storms      |
|              |                        | being stored.                |
+--------------+------------------------+------------------------------+

Note that many stormwater management ordinances require a combination of
storage volume and reduction in peak discharge. If that is the case,
both requirements must be met. However, for this example, a minimum
storage volume requirement does not apply. Therefore, in order to size
the basin, one must look only at ways of reducing the peak discharge.

There was not a tremendous amount of increase in peak discharge, or
storage volume for the developed condition. Peak discharge increased 16%
from Q~50pre~ = 66.8 cfs to Q~25post~ = 77.5 cfs. Runoff volume
increased 9.8% from Q~50pre~ = 3.984 in (4.150 ac-ft) to Q~25post~ =
4.375 in (4.555 ac-ft).

The chosen approach is to store only the increase in storage volume
between the pre- and post-developed condition or:

Δ Storage Volume = 4.555 -- 4.150 = 0.405 acre-feet

The detention basin will have a base area at the spillway crest
elevation of 150' on a side with side slopes of 3' horizontal : 1'
vertical. This results in a base area of approximately 0.517 acres at
the basin bottom. The depth required to store only the increase in
runoff volume is approximately 0.77 feet. At 0.77' above the spillway
crest elevation, the surface area is approximately 0.549 acres.

*Note: The WinTR-55 Structure Data Window uses only a standard riser /
conduit configuration for evaluating detention basins with pipes. The
only other option is a weir configuration. If either of these
configurations is unacceptable, use another method to size the detention
basin.*

A standard riser configuration is chosen for the outlet device. Based
upon the amount of control desired in the initial problem statement, it
is necessary only to use a pipe of sufficient diameter to reduce the
peak discharge from 77.5 cfs for the post-developed condition to 66.8
cfs for the pre-developed condition.

Again, rather than beginning with a new file, it is possible to edit the
existing developed condition data file created in determining the future
(or developed) condition discharge and volume.

STEP 1: Start the WinTR-55 Program and open the "Existing Conditions"
file by selecting "Open" from the file menu and locating the file using
the "Open a TR-55 data file" window.

![](media/image77.png){width="3.327777777777778in"
height="2.064583333333333in"}

STEP 2: Edit the User I.D., Project Name, and Subtitle as appropriate.
Edit Sub-area Name, Sub-area Description, and where the water leaving
this sub-are flows in the "Sub-area Flows to Reach/Outlet" box as
appropriate. In the situation where water flows into a detention basin,
the name of the basin is entered in the "Sub-area Flows to Reach/Outlet"
box. A reach name is entered here. The reach contains the structure.

![](media/image78.png){width="4.450694444444444in"
height="3.214583333333333in"}

STEP 3: Click on the "Structure Data" button to open the "Structure
Data" window. Enter the Structure Name, the surface area at the spillway
crest elevation, and the surface area at an elevation above the spillway
to define the storage characteristics of the basin. Note: If no surface
area above the spillway is entered, the program assumes the basin has
vertical sides. Enter the desired pipe sizes for initial evaluation of
the structure ratings, and the Height in feet from the centerline of the
outlet pipe to the spillway crest elevation. Note: For the standard
riser configuration this height should be approximately ½ of the largest
pipe diameter evaluated. As pipe diameters are entered, the structure
ratings are computed and shown at the bottom of the "Structure Data"
Window. Upon completion of this data, click "Accept" to accept the data
and return to the TR-55 Main Window.

![](media/image79.png){width="4.538888888888889in"
height="3.6166666666666667in"}

STEP 4: Click the "Reach Data" button to open the "Reach Data" window.
The name of the "Sub-area Flows to Reach/Outlet" name as entered on the
TR-55 Main Window is shown in the Reach Name column. In this case, the
sub-area was defined to flow to "Structure." Since the Structure is
located at the outlet of the watershed, the receiving reach is Outlet.
Also, since the sub-area flows through the structure, the Structure Name
is entered instead of reach data. This tells the program that the water
from the sub-area flows through the structure to the outlet. Click
"Accept" to accept the data and return to the TR-55 Main Window.

![](media/image80.png){width="5.407638888888889in"
height="3.1979166666666665in"}

STEP 5: Click the "Run" button and select the storm to evaluate. Click
"Run" to execute the run.

![](media/image81.png){width="2.1590277777777778in"
height="1.8902777777777777in"}

STEP 6: Upon successful execution of the run, the "File Display" window
opens showing the "Hydrograph Peak / Peak Time Table" report. By
scrolling down through the window, results of the runs for the different
pipe sizes selected can be viewed. To review other output, click "View"
or "TR-55 Reports" and select the reports to view. When complete, click
"Close" to close the "File Display" window and return to the TR-55 Main
Window.

![](media/image82.png){width="5.127777777777778in"
height="3.827777777777778in"}

STEP 7: To save the data, click "File" and "SaveAs." In the "Save a TR55
data file" window, specify a location and a NEW FILE NAME and click
"Save." The data is now saved and the user is returned to the "TR-55
Main Window."

![](media/image83.png){width="3.327777777777778in"
height="2.064583333333333in"}

### Part C - Results

Peak Discharges for the 3 different pipes evaluated are as follows:\
36" diameter 52 cfs\
42" diameter 58 cfs\
48" diameter 61 cfs

Since the limiting discharge value is 66.8 cfs, the 48" diameter pipe
may be used since the pipe discharge does not exceed the limiting value.
*(Note: It is possible, a larger pipe size may still meet the discharge
criteria, but larger pipes were not evaluated for this example
problem.)*

## Example 2 -- Evaluating Larger Watersheds and User Defined Storm Data

### Background

A small community in Any County, Some State has flooded multiple times
in the last several years. The community wants to reduce flood damages
and has requested assistance in evaluating peak discharges in the upper
reaches of the watershed. A schematic of the watershed appears below.

###   {#section .unnumbered}

### Watershed Data

#### Land Use Details

  ------------ -------------------------- ------------ -------- -------- --------
  **\          **\                        **Area by                      
  Sub-area**   Land Use**                 Hydrologic                     
                                          Soil Group**                   
                                          *(acres)*                      

                                          **A**        **B**    **C**    **D**

  Upper Main   Residential Districts: 2                         40       
  Creek        ac lots                                                   

               Pasture; fair condition                          80       

               Woods; fair condition                            55       

  County Road  Residential Districts: 2                         30       
  Branch       ac lots                                                   

               Meadow                                           60       

               Woods; fair condition                            110      

  Middle Main  Farmsteads                              10                
  Creek                                                                  

               Pasture; good condition                 30       10       

               Woods-Grass; fair                       20                
               condition                                                 

  Upper East   Residential Districts: 2                         60       
  Tributary    ac lots                                                   

               Woods-Grass; fair                                40       10
               condition                                                 

               Woods; fair condition                            10       10

  Lower East   Farmsteads                              10                
  Tributary                                                              

               Pasture; fair condition                 25       5        

               Woods-Grass; fair                       45       25       
               condition                                                 

  Upper West   Industrial                              15                
  Branch                                                                 

               Pasture; fair condition                 10                20

               Woods; fair condition                   15                5

  Lower West   Impervious; paved parking                        5        
  Branch       lots                                                      

               Industrial                                       15       

               Residential Districts: 1                         10       
               ac lots                                                   

               Pasture                                          20       

               Woods; fair condition                            25       

  Lower Main   Open Space, Lawns (fair                 15                
  Creek        cond.)                                                    

               Impervious; paved parking               15                
               lots                                                      

               Commercial & Business                   15                

               Residential Districts; ¼                85                
               ac lots                                                   
  ------------ -------------------------- ------------ -------- -------- --------

#### Where do the "Land Use Details" data come from?

The land use data for the watershed may be derived using GIS, if GIS
coverages exist for the watershed area, developed from current aerial
photographs, or determined from a watershed site visit. The hydrologic
soil group data may be obtained from the current soil survey for the
county or counties in which the watershed is located.

#### Time of Concentration Details

  ------------ --------- ---------- -------------- -------------- ---------- -------------- --------- ------------
  **\          **Sheet                             **Shallow                                **Open    
  Sub-area**   Flow**                              Concentrated                             Channel   
                                                   Flow**                                   Flow**    

               *Length   *Slope     *Surface       *Length        *Slope     *Surface       *Length   *Velocity
               (feet)*   (ft/ft)*   Description*   (feet)*        (ft/ft)*   Description*   (feet)*   (ft/sec):*

  Upper Main   75        0.047      Dense Grass    425            0.047      Unpaved        2500      2.66
  Creek                                                                                               

  County Road  75        0.067      Light Woods    425            0.067      Unpaved        2100      2.30
  Branch                                                                                              

  Middle Main  65        0.052      Short Grass    385            0.052      Unpaved        925       2.40
  Creek                                                                                               

  Upper East   50        0.110      Smooth Surface 285            0.110      Unpaved        1465      1.53
  Tributary                                                                                           

  Lower East   100       0.051      Light Woods    825            0.051      Unpaved        740       2.73
  Tributary                                                                                           

  Upper West   60        0.092      Smooth Surface 340            0.092      Unpaved        1705      1.50
  Branch                                                                                              

  Lower West   100       0.045      Smooth Surface 1000           0.045      Unpaved        510       1.51
  Branch                                                                                              

  Lower Main   100       0.036      Smooth Surface 1465           0.036      Unpaved        1100      1.10
  Creek                                                                                               
  ------------ --------- ---------- -------------- -------------- ---------- -------------- --------- ------------

#### Where do the "Time of Concentration Details" data come from?

Time of concentration data should be carefully estimated for each
sub-area. Length and slope for individual flow types (sheet, shallow
concentrated and open channel) can be obtained from USGS topographical
maps, aerial photographs, and field observation.

Sheet flow and shallow concentrated flow lengths may be difficult to
develop. The best way to estimate these values is to visit the site and
determine the actual flow paths. However, these values are generally
estimated from topographical maps and aerial photos.

Open channel flow paths typically appear as a blue line on USGS
topographical maps or as an obvious ditch or stream channel on aerial
photographs and therefore are much easier to determine.

Surface codes for sheet flow are best determined by making a site visit.
Carefully examine the land use along watershed divides.

Surface codes for shallow concentrated flow are simply paved or unpaved.
This is the simplest to determine.

For open channel flows, it is necessary to determine a flow velocity.
Either take bankfull velocity information from a previously developed
water surface profile model or entering the Manning *n* value, use
survey data to develop cross-sectional flow area, wetted perimeter, and
slope for the stream length in question. Experienced users may simply
estimate the flow velocity in the channel. Make certain that selected
values are representative of the entire open channel flow length, and
not just one segment of the open channel flow path.

#### Reach Data

  ----------- ----------- ----------- ----------- ----------- -----------
  **Reach     **Reach     **Manning   **Slope     **Bottom    **Side
  Name**      Length**    "*n*"**     (ft/ft)**   Width**     Slope**
              (feet)                              (feet)      (Z:1)

  Main Stem 1 540         0.065       0.003       20          55

  East Reach  685         0.065       0.006       30          33

  West Reach  810         0.065       0.011       35          40

  Main Stem 2 640         0.065       0.007       45          86
  ----------- ----------- ----------- ----------- ----------- -----------

#### Where do the "Reach Data" come from?

Reach data must be derived for each stream segment that receives water
from an upstream sub-area or another reach.

Rating curves are developed for the reaches which describe the flow
characteristics of the reaches. A particular cross-section surveyed
within the reach in question is picked to be representative of the
entire reach and the data for that cross-section is used. That
cross-section may be located anywhere within the reach, but will
represent the entire length of that reach.

Ratings for the reach are developed using the Manning "n" values, slope,
bottom width of the cross-section and side slopes. It is important to
estimate these values for the overall valley cross-section and not just
the channel section. These values may differ drastically between the
channel and the valley. The goal is to estimate a rating curve that
represents both.

### Rainfall Data

Rainfall Data for the watershed in "Any County, Some State" is shown in
the following table:

  --------------- ---------- ---------- ---------- ---------- ---------- ----------
  24-hour                                                                
  Precipitation                                                          
  Amount (inches)                                                        
  by Return                                                              
  Period                                                                 

  1-year          2-year     5-year     10-year    25-year    50-year    100-year

  3.0             3.5        4.5        5.1        5.8        6.5        7.2
  --------------- ---------- ---------- ---------- ---------- ---------- ----------

#### Entering Storm Data

Step 1: Select "Global Data" from the TR-55 Main Window Menu.

Step 2: Under "Global Data," select "Storm Data."

Step 3: When the "Storm Data" window opens, enter the rainfall amount by
return frequency for the desired storms and select the appropriate
rainfall distribution from the drop-down menu.

Step 4: Once the rainfall distribution type is selected and the rainfall
amounts have been entered, click "Accept" to accept the data and return
to the main window.

NOTE: The user should enter the state and county name on the Main
Window, BEFORE going to the Storm Data window to enter the custom
rainfall amount.

For this example problem, the Storm Data Window appears as follows upon
completion of data entry. Press the "Accept" button to return to the
main window.

![](media/image84.png){width="3.7381944444444444in"
height="2.9944444444444445in"}

### Results

Upon completion of data entry, the TR-55 Main Window should appear as
follows:

![](media/image85.png){width="4.459027777777778in"
height="4.419444444444444in"}

The 5-, 10-, 50-, and 100-year storm events were analyzed and peak
discharges obtained for each sub-area and reach. The Watershed Peak
Table contains a listing of peak discharges for each of the sub-areas
and reaches.

WinTR-55 provides the following output data by sub-area and reach:

![](media/image86.png){width="5.1819444444444445in"
height="5.648611111111111in"}

### Discussion of Results

In order to evaluate the output results and make a judgement as to
whether or not results are reasonable, an understanding of how WinTR-55
processes the data, and in particular, how the hydrographs are added in
WinTR-55, is beneficial.

In the Watershed Peak Table, peak discharges are listed both by sub-area
and by reach. The Sub-area Peak Discharges represent the peak discharge
values obtained in determining the runoff contributed solely by a
particular sub-area. So, for this example, the peak discharge for the
UpperMain sub-area for the 5-year storm event is listed at 375 cfs. This
peak is that obtained for the UpperMain sub-area SOLELY. Likewise, for
the MiddleMain sub-area, the 5-year storm event peak discharge is 124
cfs. And again, this represents only the peak discharge produced by the
rainfall falling on the MiddleMain sub-area. Obviously, the MiddleMain
sub-area also receives water from the UpperMain and CountyBranch
sub-areas; but the sub-area peak discharge, as listed in the Watershed
Peak Table, is that produced by rainfall on the MiddleMain sub-area and
to this point does not include waters coming from outside of that
sub-area. In short, the sub-area peak discharges are independent peaks
and have not been routed or added to produce any composite hydrographs.

The peak discharges by Reach are added and routed and represent
composite hydrographs. However, it is necessary to take a close look at
these peaks to understand how the WinTR-55 routing procedure works. As
stated previously, the peak discharge for the UpperMain sub-area for the
5-year storm event is 375 cfs. The peak discharge for the CountyRoad
sub-area for the same storm event is 350 cfs. Runoff from both of these
hydrographs flow through the MiddleMain sub-area via MainStem1 reach. If
we look at the peak for MainStem1reach in the Watershed Peak Table, we
notice a value of 723 cfs. This peak represents the peak of the added
hydrographs for the UpperMain and CountyRoad sub-areas. That is, the
hydrographs for UpperMain and CountyRoad sub-areas added together
produce a peak of 723 cfs for the 5-year storm event. Notice also that
there is a Peak Discharge of 695 cfs listed on the Watershed Peak Table
for the Downstream end of MainStem1 reach. This value represents the
peak discharge for the routed hydrograph resulting from the runoff from
the UpperMain and CountyRoad sub-areas. In summary, the runoff from
UpperMain and CountyRoad produced hydrographs which when added together
produced a peak of 723 cfs at the upper end of the MainStem1reach. When
this hydrograph was routed through the MainStem1 reach, a hydrograph
with a peak discharge of 695 cfs resulted. At this point, the runoff
from the MiddleMain sub-area is not yet included.

For this example, the peaks listed for MainStem2 reach become somewhat
more complicated because two tributaries enter the system. However,
applying the concepts of adding the hydrographs and developing peaks as
explained in the previous paragraph, it should be obvious to the user
that the peak discharge at the upper end of the MainStem2 reach
represents the combination of the following:

1.  Resultant hydrograph obtained from the runoff produced by the
    UpperMain and CountyBranch sub-areas routed through MainStem1 reach.

2.  Runoff hydrograph produced by MiddleMain sub-area.

3.  Runoff hydrograph produced by UpperWest sub-area routed through
    WestReach reach.

4.  Runoff hydrograph produced by LowerWest sub-area.

5.  Runoff hydrograph produced by UpperEast sub-area routed through
    EastReach.

6.  Runoff hydrograph produced by LowerEast sub-area.

From the Watershed Peak Table, the peak at this point for the 5-year
storm event is 1,527 cfs. Notice at the downstream end of this reach
that the peak is reduced to 1,516 cfs. The 1,516 cfs represents the peak
of the hydrograph as it is routed downstream through MainStem2 reach.
The only thing left at this point is to add the runoff produced by the
LowerMain sub-area. The hydrograph for the LowerMain sub-area produces a
peak discharge of 296 cfs. When these final two hydrographs are added,
the resultant peak at the watershed outlet is 1,802 cfs.

## Example 3 -- Custom Dimensionless Unit Hydrograph

This example demonstrates the use of a Custom Dimensionless Unit
Hydrograph (DUH) instead of the standard one preloaded in the program.
In certain areas of the country different DUH\'s are applicable due to
variations between geomorphic regions and differences in urbanization,
channelization, and available storage (in wetlands, floodplains, and/or
reservoirs) in watersheds. Users should contact the NRCS State
Conservation Engineer if they have questions on whether or not to use
the standard DUH in a location. This example uses the coastal Delmarva
Dimensionless Unit Hydrograph named for Delaware, Maryland, and
Virginia.

### Background

Owen Davies owns a 12.5 acre site in Talbot County on Maryland\'s
Eastern shore. Forest covers 1.5 acres of the property, and the
remaining 11 acres are presently in Silver Queen sweet corn production,
planted in straight rows. He uses conventional tillage with no special
conservation practices and the vegetative cover is typically in good
condition. The soils on the cropland portion of the property are
hydrologic soil group C. Hydrologic soil group D soils underlie the
wooded part.

His plot is almost rectangular, with the cropland located on higher
ground and the wooded part in a forested stream corridor, although the
stream itself lies outside of his property. There is no defined channel
running through his property, but there is evidence of sheet flows and
shallow concentrated flows. The sheet flow path is 100 feet long with a
slope of 0.1%. The shallow concentrated flow path through the cornfield
is 858 feet long, also at a slope of 0.1%. The path of the flow through
the woods is 131 feet long at a slope of 0.095%.

Owen has considered leaving crop residues on his field to reduce erosion
and pollutant discharge into the stream. His daughter Branwen wants to
show him what a difference crop residues can make. She will use WinTR-55
to calculate the peak discharge from a range of storms for his land.
She\'ll also use the Delmarva Unit Hydrograph (Welle, et al., 1980)
which applies to the eastern shore of Maryland instead of the standard
NRCS one. The Delmarva Unit Hydrograph was developed specifically for
this area and reflects the discharge measured by USGS stream gages over
years of monitoring.

Solution:

This analysis has three parts. First, enter the Delmarva dimensionless
unit hydrograph into the data file. Second, determine the peak discharge
and runoff volume for the present field tillage condition. Third,
determine the peak discharge and runoff volume for the future condition
with crop residue. Since the pollutants are carried by the runoff from
the fields, a reducing runoff indicates a reduction in soluble pollutant
load, if other factors are constant.

### Part 1 - Enter custom dimensionless unit hydrograph 

STEP 1: Branwen starts the WinTR-55 program and selects \"new\" from the
pull down choice list for \"File\". She enters User ID, Project Name,
Subtitle, State and County and specifies sub-area units as acres. The
Dimensionless Unit Hydrograph, the Storm Data Source and the Rainfall
Distribution identifier have default values given when the program
starts up, based on the last file used. The default Dimensionless Unit
hydrograph is the standard NRCS one, with a peak factor of 484.

![](media/image87.png){width="2.9583333333333335in"
height="2.8958333333333335in"}

> Branwen can click on Global Data in the TR-55 Main Window Menu Bar,
> and then on the Storm Data in the pull down choice list
> (![](media/image88.png){width="1.2222222222222223in"
> height="0.4048611111111111in"}), or on the storm data icon
> (![](media/image21.png){width="0.3402777777777778in"
> height="0.3402777777777778in"}) on the button bar to bring up the
> Storm Data Window:

![](media/image89.png){width="2.571527777777778in"
height="2.0368055555555555in"}

Clicking the NRCS Storm data button will fill in the data for Talbot
County, Maryland:

![](media/image90.png){width="2.55in" height="2.033333333333333in"}

By clicking the Accept button, Branwen selects this as her Storm Data
Source, which reflects on the TR-55 Main Window. She is ready to
concentrate on the dimensionless unit hydrograph.

![](media/image91.png){width="2.9305555555555554in"
height="2.901388888888889in"}

***STEP 2:*** Branwen visited the Talbot County Agricultural Service
Center and has a table with the values for the Delmarva DUH. She can
click on Global Data in the TR-55 Main Window Menu Bar and then on
Dimensionless Unit Hydrograph in the pull down choice
list(![](media/image88.png){width="1.2222222222222223in"
height="0.3819444444444444in"}) or click on the icon for the
dimensionless unit hydrograph
(![](media/image23.png){width="0.32916666666666666in"
height="0.32916666666666666in"}) on the button bar to bring up the
Dimensionless Unit Hydrograph Window:

![](media/image92.png){width="1.8in" height="1.8916666666666666in"}

STEP 3: The Dimensionless Unit Hydrograph (DUH) Window allows entry of a
custom DUH. Branwen enters Delmarva for the DUH in the Local Hydrograph
combo entry box. She then enters the points that define the DUH in the
Dimensionless Hydrograph Points Grid. The points should begin and end at
0.0 and should be no greater than 1.0. The program will calculate and
show the number of points automatically.

![](media/image93.png){width="1.8in" height="2.175in"}

STEP 4: If she wants, she can click on the Plot button and plot the DUH.
The second line of the Title gives the path where her work is located.

![](media/image94.png){width="3.0909722222222222in"
height="2.8986111111111112in"}

STEP 5: She must return to the Main Window and select the Delmarva
Dimensionless Unit Hydrograph from the choices displayed by the DUH
pulldown for the program to actually use the Delmarva hydrograph in its
calculations. After highlighting Delmarva in the pull-down choice list,
she double-clicks on it to enter it as her choice for use. If she wants
to use this dimensionless unit hydrograph in another job, all she needs
to do is click on its name in the hydrograph list.

![](media/image95.png){width="2.9305555555555554in"
height="2.901388888888889in"}

STEP 6: Branwen now enters the Sub-area Name, Sub-area Description, and
where the water leaving this sub-area flows in the "Sub-area Flows to
Reach/Outlet" box to set up her watershed, ready to do her land use and
time of concentration calculations.

![](media/image96.png){width="2.9305555555555554in"
height="2.901388888888889in"}

### Part 2 - Determine peak discharge and runoff volume for the present field tillage conditions. 

STEP 1: Branwen can double click on the \'Area (ac)\' label, the
\'Weighted CN\' label, or on either of the two blank cells in the entry
grid below them to open the "Land Use Details" window. In the "Land Use
Details" window, for each land use she enters the area involved under
the appropriate hydrologic soil group. She can click the Summary Screen
"On" to see all her land use categories. Clicking "Accept" returns the
program to the "TR-55 Main Window."

![](media/image97.png){width="5.65625in" height="4.254166666666666in"}

![](media/image98.png){width="4.459027777777778in"
height="4.419444444444444in"}

> The sub-area area and runoff curve number now appear in the Sub-area
> Entry and Summary portion of the TR-55 Main Window.

STEP 2: Branwen opens the "Time of Concentration Details" window the
same way as the \"Land Use Details\" window. She enters the appropriate
information to compute the sub-area time of concentration and clicks
"Accept" to return to the "TR-55 Main Window."

![](media/image99.png){width="3.9590277777777776in"
height="1.5652777777777778in"}

> The sub-area time of concentration now appears in the Sub-area Entry
> and Summary portion of the TR- 55 Main window.
>
> ![](media/image100.png){width="4.490277777777778in"
> height="3.191666666666667in"}

STEP 3: Branwen clicks the "Run TR-55 " button or the \'Run\' icon
(![](media/image24.png){width="0.32916666666666666in"
height="0.32916666666666666in"}) to open the "Run TR-55 " window and
selects the storm events for which she would like output. Then she
clicks the Run button to execute the run. While the program is running,
a processing bar appears and displays the program\'s progress as a
series of little blue rectangles that march from left to right over and
over again. This reassures Branwen that something is happening, even if
she\'s not sure what. The appearance of this processing bar excludes
user entry of new data.

![](media/image101.png){width="1.5805555555555555in"
height="1.363888888888889in"}

![](media/image102.png)

STEP 4: When the run is complete, the "File Display" window opens
showing the "Hydrograph Peak / Peak Time Table." Branwen can review
other output by clicking "View" or "TR-55 Reports" and selecting the
reports to view. She clicks "Close" to close the "File Display" window
and return to the TR-55 Main Window.

![](media/image103.png){width="3.4180555555555556in"
height="2.5069444444444446in"}

![](media/image104.png){width="1.2326388888888888in"
height="0.7888888888888889in"}

![](media/image105.png){width="2.0069444444444446in"
height="1.9444444444444444in"}

![](media/image100.png){width="4.490277777777778in"
height="3.191666666666667in"}

STEP 5: From the Main Window Branwen can click on the Output Definition
icon (![](media/image106.png){width="0.32916666666666666in"
height="0.32916666666666666in"}) to get a list of output summary reports
available for printing or viewing. She selects the Watershed Peak Table
to show her Dad.

![](media/image107.png){width="2.120833333333333in" height="2.3in"}

![](media/image108.png){width="3.4180555555555556in"
height="2.5069444444444446in"}

STEP 6: To save the data, she returns to the Main Window by clicking
"Close" on the File Display Window and "Close" on the Output Definitions
Summary Window. She then clicks "File" on the Menu Bar and "SaveAs." In
the "Save a TR-55 data file" popup window, she specifies a file name (Ex
3-till for corn, conventional tillage) and clicks "Save." The data is
now saved, the popup window closes and the "TR-55 Main Window" is
redisplayed.

![](media/image109.png){width="3.327777777777778in"
height="2.064583333333333in"}

### Results

Conventional Tillage Discharge

  --------------- ------------ ------------ ------------ ------------- ------------- ------------- --------------
  **Frequency**   **1-year**   **2-year**   **5-year**   **10-year**   **25-year**   **50-year**   **100-year**

  **Discharge**   21.2 cfs     28.8 cfs     43.4 cfs     54.2 cfs      63.7 cfs      74.7 cfs      85.7 cfs

  **Volume\***    1.1"         1.7"         2.8"         3.5"          4.1"          4.9"          5.7"
  --------------- ------------ ------------ ------------ ------------- ------------- ------------- --------------

\*The Runoff Volume can be found from the "File Display Window" by
selecting "View" and "TR-20 Printed Page File."

### Part 3 - Determine peak discharge and runoff volume \'with crop residue management\' condition 

Rather than beginning with a completely new file to determine the peak
discharge and runoff volume for the crop residue condition, Branwen
decides to edit the existing condition data file previously created and
save it under a different name.

STEP 1: She starts the WinTR-55 Program and opens the "Existing
Conditions" file by selecting "Open" from the "File" menu and locating
the file using the "Open a WinTR-55 data file" popup window.

![](media/image110.png){width="3.327777777777778in"
height="2.064583333333333in"}

![](media/image111.png){width="2.1013888888888888in"
height="2.0479166666666666in"}

She may also go into the pull down choice list under File and select Ex
3-till.w55 from the last files used displayed in the history list.

STEP 2: Branwen edits the Subtitle, and the Sub-area Name, to reflect
crop residue conditions. She will need to also edit the CN and Tc to
account for the new practice. Clicking "Land Use Details" button opens
the "Land Use Details" window in which she edits the land use and clicks
"Accept" to return to "TR-55 Main Window."

![](media/image112.png){width="4.509027777777778in"
height="3.261111111111111in"}

![](media/image113.png){width="5.727083333333334in"
height="3.3722222222222222in"}

> The sub-area area and the new runoff curve number now appear in the
> Sub-area Entry and Summary portion of the TR-55 Main Window.

***STEP 3:*** Branwen opens the "Time of Concentration Details" window
and edits the data (assuming her Dad will have greater than 20% residue)
to compute the new sub-area time of concentration. Clicking "Accept"
returns her to the "TR-55 Main Window."

![](media/image114.png){width="6.102083333333334in"
height="2.415277777777778in"}

> The sub-area time of concentration now appears in the Sub-area Entry
> and Summary portion of the TR-55 Main Window.

![](media/image115.png){width="4.529166666666667in"
height="3.347916666666667in"}

STEP 4: Branwen saves her data now using "SaveAs" to give it a new name
(Ex3-residue), and then clicks "Run TR-55 " button to open the "Run
TR-55 " window. The program saves the storm events for which the last
run was made, so she can "Run" to execute the run. When the run is
complete, the "File Display" window opens showing the "Hydrograph Peak /
Peak Time Table." She can click "View" or "TR-55 Reports" and select the
reports to view. When complete, she clicks "Close" to close the "File
Display" window and return to the TR-55 Main Window.

![](media/image116.png){width="3.4180555555555556in"
height="2.5069444444444446in"}

### Results

Crop Residue Tillage Discharge

  --------------- ------------ ------------ ------------ ------------- ------------- ------------- --------------
  **Frequency**   **1-year**   **2-year**   **5-year**   **10-year**   **25-year**   **50-year**   **100-year**

  **Discharge**   15.8 cfs     22.4 cfs     35.0 cfs     44.6 cfs      53.1 cfs      62.7 cfs      72.4 cfs

  **Volume\***    1.0"         1.4"         2.5"         3.2"          3.8"          4.6"          5.3"
  --------------- ------------ ------------ ------------ ------------- ------------- ------------- --------------

\*The Runoff Volume can be found from the "File Display Window" by
selecting "View" and "TR-20 Printed Page File."

STEP 5: Summary of Results

Crop Residue vs Conventional Tillage Discharge

  --------------- ------------ ------------ ------------ ------------- ------------- ------------- --------------
  **Frequency**   **1-year**   **2-year**   **5-year**   **10-year**   **25-year**   **50-year**   **100-year**

  Discharge       21.2 cfs     28.8 cfs     43.4 cfs     54.2 cfs      63.7 cfs      74.7 cfs      85.7 cfs
  (conv. tillage)                                                                                  

  Volume (conv.   1.1"         1.7"         2.8"         3.5"          4.1"          4.9"          5.7"
  tillage)                                                                                         

                                                                                                   

  Discharge       15.8 cfs     22.4 cfs     35.0 cfs     44.6 cfs      53.1 cfs      62.7 cfs      72.4 cfs
  (residue)                                                                                        

  Volume          1.0"         1.4"         2.5"         3.2"          3.8"          4.6"          5.3"
  (residue)                                                                                        

                                                                                                   

  **Discharge     **5.4 cfs**  **6.4 cfs**  **8.4 cfs**  **9.6 cfs**   **10.6 cfs**  **12.0 cfs**  **13.3 cfs**
  decrease                                                                                         
  (w/residue)**                                                                                    

  **Volume        **0.1"**     **0.3"**     **0.3"**     **0.3"**      **0.3"**      **0.3"**      **0.4"**
  decrease                                                                                         
  (w/residue)**                                                                                    
  --------------- ------------ ------------ ------------ ------------- ------------- ------------- --------------

Branwen can now carry these results to her Dad and demonstrate the
advantages of residue in reducing flows from his corn field.

## Example 4 -- Custom Rainfall Distribution

### Background

Minor Lake Subdivision in Champaign County, Illinois has an existing
stormwater detention basin designed with 100-year Type II rainfall
distribution. A nearby watershed recently experienced a 7-inch 24-hour
storm for which hourly precipitation data is available. A local
hydraulic engineer estimated the recurrence interval of this event to be
110 years.

The local homeowners want to know how their existing detention basin
would perform during such an event. For comparison purposes, the
engineer completed a 100-year Type II distribution design analysis
first. The historical event was analyzed second.

### Watershed and Basin Data

The existing hydrologic design listed the drainage area as 25 acres of
¼-acre residential lots on hydrologic soil group "B" soils -- curve
number 75. The time of concentration had been computed at 0.45 hours.
The 100-year rainfall depth is 6.61".

The existing detention basin has a surface area of 2.0 acres at the
spillway crest. Three feet above the spillway crest the surface area is
2.4 acres. The inlet crest of the 15-inch diameter pipe is 3.5 feet
above the outlet.

### Existing Conditions -- Type II Rainfall Distribution

Enter the existing data on the TR-55 Main Window, Structure window, and
Reach window.

![](media/image117.png){width="4.459027777777778in"
height="4.419444444444444in"}

![](media/image118.png){width="4.509027777777778in"
height="4.009722222222222in"}

![](media/image119.png){width="5.086805555555555in"
height="3.198611111111111in"}

The resulting flow path schematic is shown below.

![](media/image120.png){width="3.890277777777778in"
height="2.3979166666666667in"}

Go to the Global Data menu on the TR-55 Main Window and select
[S]{.underline}torm Data. On the Storm Data window, click
[N]{.underline}RCS Storm Data to choose the NRCS Champaign County
rainfall data. Note that Type II rainfall distribution is the default
distribution.

![](media/image121.png){width="3.8722222222222222in"
height="3.0972222222222223in"}

Click [A]{.underline}ccept to accept the data and return to the TR-55
Main Window. Save this data as "Ex 4 Type 2". Run the 100-year design
storm.

![](media/image122.png){width="5.128472222222222in"
height="3.713888888888889in"}

Using the Type II rainfall distribution, the peak flow from the Minor
Lake watershed area is nearly 90 cfs into the basin. The flow out of the
basin is approximately 14 cfs. To look at the respective 100-year design
hydrographs, click the hydrographs button on the TR-55 Main Window.

![](media/image123.png){width="3.2694444444444444in" height="2.83125in"}

![](media/image124.png){width="4.601388888888889in" height="4.375in"}

The short-duration highly-peaked line hydrograph is from subdivision
houses and the long low line represents outflow from the basin.

### Enter Historic Rainfall Distribution

From the TR-55 Main Window save the existing data file as "Ex
4-historical". Click the custom rainfall distributions button on the
TR-55 Main Window and enter the recorded hourly rainfall distribution as
shown below. The values are a ratio of the total rainfall. For example,
0.21"of rain fell during the first hour, so the first data point after 0
is 0.03000 (0.21"/7" = 0.03).

![](media/image125.png){width="2.7104166666666667in" height="2.90625in"}

The plot below shows how the rainfall was distributed during the 24-hour
storm.

![](media/image50.png){width="5.71875in" height="4.395833333333333in"}

Now that the custom rainfall distribution has been entered and saved,
click on the Storm Data button on the TR-55 Main Window. Select the
previously defined distribution, Historical Storm, from the pull-down
list for distribution types. Make sure the 2-year rainfall is still
3.01" for time of concentration computations. Enter 7.00" for the
110-year rainfall on the right side of the window. Click "Accept" to
return to the TR-55 Main Window.

![](media/image126.png){width="3.8722222222222222in"
height="3.0972222222222223in"}

Click "Accept" to close the Storm Data window and return to the TR-55
Main Window.

![](media/image127.png){width="4.459027777777778in"
height="4.419444444444444in"}

The storm data source now reads "User-provided custom storm data". Click
the run button to compute the hydrographs using the historical rainfall
distribution and depth.

![](media/image128.png){width="5.120833333333334in"
height="3.7840277777777778in"}

The historical peak is estimated at 18 cfs from Minor Lake sub-area. The
detention basin lowers the peak to approximately 12 cfs. The hydrographs
are plotted below.

![](media/image129.png){width="5.71875in" height="4.395833333333333in"}

The thin, jagged line represents the flow from the subdivision and into
the basin. The thicker line represents the estimated outflow from the
detention basin during the historical rainfall event.

If detailed information is needed, such as a table of hydrograph points,
go the the output definition window and view any report to open the file
display window. Select View-TR-20 Printed Page File to see the following
hydrograph.

![](media/image130.png){width="5.1819444444444445in"
height="5.345138888888889in"}

This TR-20 printed page report is a text file in the WinTR-55
subdirectory labeled "tr20.out".

### Results

The peak [inflow]{.underline} to the existing stormwater detention basin
was reduced from the 90 cfs (Type II) design value down to 12 cfs
(historical storm). This dramatic peak flow reduction is due to the
less-intense historical rainfall distribution. The peak discharge
decreased even though the rainfall depth increased slightly from 6.61"
design depth to 7" historical depth.

However, the peak [outflow]{.underline} from the detention basin is
reduced only slightly, from 13 cfs to 12 cfs. Therefore, this analysis
demonstrates that the existing stormwater detention basin would
performed adequately during the historical storm event that occurred in
the nearby watershed.

# Appendix B - Equations

## Runoff Equation 

  ----------------------------------------------------------------------------------------
  Q =        **\[**   P -- 0.2         **(**   [1000]{.underline}\   -10    **)\]**    2
                                               CN                                      
  ---------- -------- ---------------- ------- --------------------- ------ ---------- ---
                      P + 0.8          **(**   [1000]{.underline}\   -10    **)**      
                                               CN                                      

  ----------------------------------------------------------------------------------------

Where\
Q = runoff (in)\
P = rainfall (in), and\
CN = runoff curve number

## Composite CN (connected impervious area) 

  ----------------------------- ----- ---------------------- ----- -------------------
  CN~c~ = CN~p~ +               (     [P~im~]{.underline}\   )     (98-CN~p~)
                                      100                          

  ----------------------------- ----- ---------------------- ----- -------------------

Where\
CN~c~ = composite runoff curve number\
CN~p~ = pervious runoff curve number, and\
P~im~ = percent imperviousness

## Composite CN (unconnected w/ \<30% impervious)

  ---------------------- ---- ----------------------- ---- -------------------------------
  CN~c~ = CN~p~ +        (    [P~imp~]{.underline}\   )    (98-CN~p~) (1 --0.5 R)
                              100                          

  ---------------------- ---- ----------------------- ---- -------------------------------

Where\
R = ratio of unconnected impervious area to total impervious area

## Sheet Flow 

  ----------------- -----------------------------------------------------
  T~t~ =            0.007 (nL) ^0.8^

                    (P~2~) ^0.5^ S ^0.4^
  ----------------- -----------------------------------------------------

Where\
T~t~ = travel time (hr)\
*n* = Manning roughness coefficient (for sheet flow)\
L = flow length (ft)\
P~2~ = 2-year, 24-hour rainfall (in), and\
s = slope of hydraulic grade line (land slope, ft/ft)

## Shallow Concentrated Flow 

$V = \text{16}\text{.}\text{1345}\sqrt{s}$ (Unpaved)

$V = \text{20}\text{.}\text{3282 }\sqrt{s}$ (Paved)

Where\
V = average velocity (ft/s), and\
s = slope of hydraulic grade line (watercourse slope, ft/ft)

These two equations are based on a solution of the Manning equation with
different assumptions for *n* (Manning roughness coefficient) and r
(hydraulic radius, ft). For unpaved areas, *n* is 0.05 and r is 0.4; for
paved areas, *n* is 0.025 and r is 0.2.

## Channel Flow (Manning Equation) 

$$V = \frac{1\text{.}\text{49}r^{23}\sqrt{s}}{n}$$

Where\
\
V = average velocity (ft/s), and\
r = hydraulic radius (ft) and is equal to a/p~w~\
a = cross sectional flow area (ft^2^)\
p~w~ = wetted perimeter (ft)\
s = slope of hydraulic grade line (channel slope, ft/ft)\
*n* = Manning roughness coefficient (for open channel flow)

## Channel Rating Equations

$$\text{TW} = \text{BW} + (2 \ast \text{Stage} \ast Z)$$

$$\text{EA} = \frac{(\text{BW} + \text{TW})}{2} \ast \text{Stage}$$

$$\text{WP} = \text{BW} + 2 \ast \sqrt{(\frac{\text{TW} - \text{BW}}{2})^{2} + (\text{Stage})^{2}}$$

$$\text{Flow}_{\text{channel}} = \frac{1\text{.}\text{486}}{\text{Manning}\ n} \ast \text{EA}^{53} \ast \frac{\sqrt{\text{Friction}\ \text{Slope}}}{\text{WP}^{23}}$$

Where:

EA = End Area, square feet

Flow~channel~ = cfs

TW =Top Width, ft

> BW = Bottom Width, ft
>
> Stage = ft
>
> WP = Wetted Perimeter, feet

Z = Side slope, dimensionless

Friction Slope = no units

## Storage Rating Equations

Temporary storage

> $$\text{Storage}_{\text{temporary}} = \text{Stage} \ast (\frac{A_{\text{crest}} + \text{Stage} \ast \Delta}{2})$$

$\Delta = \frac{(A_{\text{above}\ \text{crest}}) - (A_{\text{crest}})}{(\text{Ht}_{\text{above}\ \text{crest}})}$

Where

> ∆ = delta, ft
>
> Height~above\ crest~ = feet
>
> Stage = feet
>
> Area @ crest = acre
>
> Area @ height above crest = acre
>
> Storage~temporary~ = acre-feet

## Pipe Flow

$$\text{Head}_{\text{pipe}} = \text{Height} + \text{Stage} - \frac{D_{\text{pipe}}}{\text{24}}$$

$$A_{\text{pipe}} = \pi(\frac{D_{\text{pipe}}}{\text{24}})^{2}$$

$$\text{Flow}_{\text{pipe}} = A_{\text{pipe}}c_{d}\sqrt{2\text{gHead}_{\text{pipe}}}$$

For g = gravity and C = 0.6

$\text{Flow}_{\text{pipe}} = 4\text{.}8 \ast A_{\text{pipe}}\sqrt{\text{Head}_{\text{pipe}}}$

Where

> Height = feet
>
> Head~pipe~ = feet
>
> Stage = feet
>
> D~pipe~ = inches
>
> A~pipe~ = square feet
>
> Flow~pipe~ = cfs

## Weir Flow 

$\text{Flow}_{\text{broad} - \text{crested}\ \text{weir}} = 2\text{.}8 \ast L_{\text{weir}} \ast \text{Stage}^{1\text{.}5}$

For L~Weir~ = 0

$$\text{Flow}_{\text{90}^{o}V - \text{notch}\ \text{weir}} = 2\text{.}5 \ast L_{\text{weir}}\text{Stage}^{2\text{.}5}$$

Where

> L~weir~ = Weir Length, ft
>
> Stage = feet
>
> Flow~weir~ = cfs

# Appendix C - References

United States Department of Agriculture, Soil Conservation Service.
1975. *Urban Hydrology for Small Watersheds*, Technical Release 55, 91
pp.

United States Department of Agriculture, Soil Conservation Service.
1986. *Urban hydrology for Small Watersheds*, Technical Release 55, 156
pp.

United States Department of Agriculture, Soil Conservation Service,
Northeast National Technical Center. 1986*. Time of Concentration,*
Hydrology Technical Note No. N4, 12 pp.

National Engineering Handbook, Part 630 HYDROLOGY
(http://www.wcc.nrcs.usda.gov/water/quality/frame/hydrolog.html)

Preface: Preface (PDF 5kb) 2001

Chapter 1: Introduction (PDF 53kb) 1997

Chapter 2: Procedures (PDF 220kb) 1999

Chapter 3: Preliminary Investigations (PDF 77kb) 1999

Chapter 4: Storm Rainfall Data (PDF 159kb) 1993

Chapter 5: Streamflow Data (PDF 123kb) 1997

Chapter 6: Stream Reaches and Hydrologic Units (PDF 86kb) 1998

Chapter 7: Hydrologic Soils Groups

Chapter 8: Land Use and Treatment Classes (PDF 110kb) ?

Chapter 9: Hydrologic Soil-Cover Complexes (original) (PDF 557kb) 1969

Chapter 10: Estimation of Direct Runoff from Storm Rainfall (original)
(PDF 1164kb) 1972

Chapter 11: Estimation of Direct Runoff from Snowmelt (original) (PDF
279kb) 1971

Chapter 12: Hydrologic Effects of Land Use and Treatment (PDF 247kb)
2002

Chapter 13: Stage-Inundation Relationships (original) (PDF 408kb) 1971

Chapter 14: Stage-Discharge Relationships (original) (PDF 3502kb) 1972

Chapter 15: Travel Time, Time of Concentration, and Lag (original) (PDF
882kb) 1972

Chapter 16: Hydrographs (original) (PDF 1040kb) 1972

Chapter 17: Flood Routing (original) (PDF 5661kb) 1972

Chapter 18: Selected Statistical Methods (PDF 359kb) ?

Chapter 19: Transmission Losses (original) (PDF 2304kb) 1983

Chapter 20: Watershed Yield (original) (PDF 862kb) 1971

Chapter 21: Design Hydrographs (original) (PDF 7668kb) 1972

Chapter 22: Glossary (original) (PDF 550kb) 1971

(The above documents requires a PDF reader, generally available free of
charge.)

United States Department of Agriculture, Natural Resources Conservation
Service. 2001 (draft). *TR-20 System: User Documentation*, 105 pp.

United States Department of Agriculture, Natural Resources Conservation
Service. 2001 *SITES Water Resource Site Analysis Computer Program
User\'s Guide*. 469 pp.

Maidment, D. R. (ed.), *Handbook of Hydrology*, McGraw-Hill, 1993, 1422
pages.

Chow, V. T., Maidment, D. R, and Mays, L. W., *Applied Hydrology*,
McGraw-Hill, 1988, 586 pages.

U. S. Army Corps of Engineers, Hydrologic Engineering Center, *HEC-RAS
User\'s Manual*, Version 2.0, April 1997,

Ponce, V.M., *Engineering Hydrology*, Prentice Hall, 1989, 640 pages.

Welle, P.I., Woodward, D. E., Fox Moody, H*., A Dimensionless Unit
Hydrograph for the Delmarva Peninsula*, 1980. Paper No. 80-2013, ASAE
1980 Summer Meeting, 18 pp.