MIDUSS Version 2

Evaluation of Drainage Management Software

The following sections outline the input requirements, computational methods, and output options available with this software. The theoretical basis of this software was compared with the MTO Drainage Management Manual (1997). A summary of model capabilities, and the requirements for using this software for MTO design, analysis, or approvals is provided

General Information

Model Capabilities:

Functionality:

Use in MTO Drainage Management Practices:

Information Sources:
MIDUSS Version2 Reference Manual
MIDUSS Version2 Appendices
MIDUSS Version2 Tutorial Manual
www.alanasmith.com/


General Information

Title of Software: MIDUSS Version 2
Purpose: Design of Urban Stormwater Systems
Publisher: Alan A. Smith Inc.
Version: 2
Year Published: 2004
Affiliate Software: N/A
Platform(s): MS Windows 98, NT4, Me, 2000, XP, Server 2003
Media: CD ROM, or internet download
System Requirements: Pentium III-400, 256MB memory, 600 MB hard disk space, CD ROM 1024x768 resolution video
Availability: Available from the ShopMIDUSS web site, http://www.shopmiduss.com

Model Capabilities

What does it do?

Miduss Version 2 is a hydrological and hydraulic analysis tool used to assist drainage engineers in the design of stormwater management systems.

A watershed model is developed by first defining the rainfall hyetograph for design. The drainage system is broken down into catchments and other elements such as culverts, channels, and detention ponds. As each element is added the user defines the necessary parameters before routing the flow through that element to obtain the intermediate outflow hydrograph. The program generates both tabular and graphical output; there is also the option to display the model on a layout screen. The significant model components are:

Hydrology: Calculates runoff from catchment areas based on one of 5 design storm options (Chicago, Huff, Canada AES, Historic, Mass Curve).

Hydraulic Design: Models the routing of runoff hydrographs through an assortment of drainage elements (pipe, channel, pond, diversion, trench, culvert, cascade).

Below is a general summary of the capabilities of the software. This is not an endorsement of the quality, or evaluation of the performance of the model. The information was taken from the MIDUSS Version2 Reference Manual, which contains a much more detailed discussion of all aspects of the model, including several chapters on background theory.

How does it do it?

The user defines the watershed and drainage network by entering various elements (e.g. catchments, pipes, channels, ponds, etc.). As they are entered the elements and connections are mapped on a layout screen. As the user moves through the model and enters various information intocommand boxes, that are initially disabled, boxes are activated, prompting the next step in the design process.

Set Up

To begin, the user selects the units and sets the time parameters in minutes (time step, maximum storm duration, longest hydrograph duration expected). Once this information has been entered the "Storms" input box becomes activated.

The user is also required to enter the orientation of the model layout by specifying the quadrant (e.g. NW) to work in. Flow through the model will then be away from the origin in whatever quadrant is specified (e.g. if NW is selected, the layout will be plotted to the northwest).


Hydrology

A rainfall hyetograph may be created by defining the parameters for one of four design storms or by inputting the observed data for a historic storm rainfall record. The design storm types available are:

  • Chicago Storm
  • Huff Storm Distribution
  • Mass Rainfall Distribution
  • Canada AES Storm (Any Duration can be specified. Tp data from the manual is based on the 1-hour storm and may not be reliable for longer durations.)

Input requirements are dependent on the storm selection. The results are displayed in both tabular and graphical form.

A previously created storm hyetograph file can be imported and used. Whatever storm is selected this will be applied by default until a new storm is specified.

Once the required storm information has been defined the catchments command is engaged, allowing the user to enter information to characterize the catchment and generate the runoff hydrograph. Information required includes a short description and ID number, area, % pervious vs impervious, slope, and flow lengths.

There are four overland flow routing methods available for this step:

  • Triangular SCS
  • Rectangular
  • SWMM Method
  • Linear Reservoir

Rainfall loss through infiltration may be determined through the use of one of 3 methods:

  • SCS Method
  • Horton Equation
  • Green Ampt Model

The same infiltration loss model is used for both pervious and impervious areas. Each area is modelled separately and the resulting hydrographs are summed to produce the runoff hydrograph for the catchment.

Other options in the catchments menu include a lag and route procedure for large catchments, the option to add baseflow, and the new IUH command, allowing users to generate a runoff hydrograph with a specific peak flow and either duration or time to peak.

Hydrograph

Once the user accepts the results of the catchment modelling the hydrograph command box is activated. The hydrograph menu contains all of the options for manipulating hydrographs. Some of the frequently used commands are: start new tributary (clears inflow hydrograph), add runoff (adds catchment runoff to inflow hydrograph), combine (adds hydrographs at a junction), and next link (copies outflow hydrograph to inflow hydrograph for downstream element).

Design

The next step is for the user to define a conduit for flow from the catchment, which is done through the design menu. The options available are as follows:

  • Pipe
    Pipes may be designed to carry the peak flow of the inflow hydrograph, or for a specified peak flow value if a hydrograph has not been calculated. After specifying a value for Manning's n the desired pipe diameter and gradient may be entered directly, or a pipe may be selected from a list of suggested designs and corresponding average velocities.

  • Channel
    Two channel shapes can be designed using MIDUSS: a trapezoid, or an arbitrary shape defined by up to 50 pairs of co-ordinates. Similar to the pipe command, entering a Manning's n value the program will propose a number of suitable channel designs corresponding to the flow rate and shape, and will determine the corresponding flow depth, and velocities. Alternatively, the user may specify a channel design. In either case when a channel design is selected or specified the program will calculate the depth of flow, channel capacity, velocity, and critical depth.

  • Pond
    The total volume and peak flow of the inflow hydrograph are used to estimate the storage requirements of a pond to achieve a specified peak outflow. First the user must enter a desired peak outflow from the pond. The program calculates depth-discharge and depth-storage information based on pond geometry entered by the user. Outflow control can be through pipes, weirs, or orifices. After routing the inflow hydrograph through the pond the design can be modified until the desired characteristics are achieved. Using the pond command means that many different types of storage facilities such as multi-stage ponds, over-sized pipes, parking lot and, rooftop storage, can be modelled.

  • Trench
    Allows for the design of an exfiltration trench. The inflow hydrograph is split into infiltration and transmitted portions of flow. Information that is required includes the size and shape of the trench (rectangular or trapezoidal), number and size of perforated pipes, soil characteristics, and outflow control device specifications (orifice, weir, or pipe).

  • Diversion
    An inflow hydrograph may be split into two components by a diversion structure. The flows are separated based on a specified threshold value, below which all inflow is transmitted to the outflow hydrograph, and above which a user specified proportion is diverted. The diverted flow hydrograph is saved for later use in the design process.

  • Culvert
    Culvert design options are circular pipe, box, horizontal or vertical ellipse, and pipe arch. Required data includes: length, Manning's n, invert elevations, inlet coefficient, and energy loss. The model assumes that the culvert is located under a highway embankment and calculates weir flow over the embankment when the culvert is surcharged. When the culvert is surcharged the effects of upstream storage in the channel are considered, and adjustments to the channel grade, length and embankment slopes can be made to fine tune the design. Up to 10 barrels can be specified, but all barrels must be identical. The culvert design tool can also be used as a stand alone tool to design for a specified steady flow. The culvert cross section and profile are displayed automatically. Output includes: headwater elevation, normal depth, critical depth, weir flow/culvert flow, and exit velocity.

  • Cascade
    The cascade design features allow an inflow hydrograph to be routed through a series of up to two storage cells. Cross sections available are the same as for culvert design. Input required includes the geometry, invert levels, orifice diameter, and outflow coefficient of contraction for each cell.

When the design is complete the Design/Route command must be used to complete the process of routing the hydrograph through the element.

Once the outflow hydrograph for each design element has been calculated it can be copied to the inflow hydrograph for the downstream catchment or for the next hydrologic object, or it can be saved at a junction node to be combined with another hydrograph from a neighbouring area of the watershed.

Tools

The Tools menu contains several design tools external to the model. The Add Comment command allows the user to enter notes into a comments section at the end of the output file. Microsoft Notepad and Wordpad can be accessed through the MIDUSS Tools menu to allow review of the various data files that are created during a design session.

The IDF curve tool can be used to either approximate values for a, b, and c constants for a Chicago storm to mimic a recorded event, or to generate an IDF curve with user specified a, b, and c constants.

The time of concentration tool calculates the Tc for up to three travel time components, these are overland flow, gutters, and conduit flow in a circular pipe or trapezoidal channel. At the time of review the overland flow time of concentration can be calculated using either the Friend's equation or the Kinematic Wave equation. Friend's equation is a method recommended by the Malaysian government. Use of this method is not endorsed by the MTO. The time of concentration calculation methods endorsed by the MTO for use in Ontario are the Airport and Bransby Williams equations. The software developer will be adding the Airport and Bransby Williams methods to the time of concentration calculation options in a future update.

The Roughness Height tool converts from roughness height to Mannings n. The Edit Storm tool is the mechanism for creating or editing a mass rainfall distribution curve to be used in a model.

File Management

MIDUSS Version 2 contains several new options for saving and re-loading designs. The save session command saves all data in a single binary file. The file is given the same name as the output file with the extension '.bin'. The file contains a copy of the output file, the Q peaks summary table, and all layout diagram data. Any information entered in the Tools menu items (IDF curve fit, time of concentration, roughness height, edit storm) will not be saved in the session file. Once the save session command has been used the MIDUSS design session must be terminated. By using the load session command '.bin' files can be opened to continue with the design.

The save file command is used to save a hyetograph or hydrograph. These can then be retrieved for future use through the load file command.

The "Repeat from Start" is another new command in MIDUSS Version 2.0, allowing the design to be repeated with a new storm. The purpose of this is to allow the design of portions of the drainage system based on a shorter more intense storm, and then to change the storm for the design of the lower portion of the system using a longer duration storm.

MIDUSS also has a feature called automatic mode. Using this feature a '.bin' output file is converted to a '.mdb' database file. The database file contains all the information from the output file required to recreate the design session. This may be used to complete a design in several design sessions, test a design under a different design rainfall event, or refine a previous design.

Output Options

A wide variety of print options are available. The output file and any of the hydrographs or hyetographs can be printed. The Design Log can be saved or printed at anytime during a session. A text file (Qpeaks.txt) can be generated to show peak flows in a summary table. A composite graph can be created with one or more hydrographs and hyetographs. Graphs may be customized with annotations, and the fonts, lines, and patterns may be modified. The MIDUSS Window or entire screen can be printed at any time to illustrate the model process.

Top of page   Top of page


Functionality

Experience Required

Navigation, and use of the program requires basic knowledge of Windows based programs.

A solid understanding of hydrology and hydraulics is necessary to comprehend the different aspects of the program. The program is user friendly however, as with all models, previous stormwater system design experience is required to properly define input parameters and interpret results.

Using the program

Installing

Installation of the program is very straightforward. Once the CD is loaded installation begins automatically complete with appropriate prompts. A license serial number is required to fully activate the program.

Prospective purchasers can download a demonstration version from the MIDUSS website, once activated in demo mode this version provides limited functionality for the purposes of trying out the model.

Learning

A complete set of 21 audio-visual tutorials are available that demonstrate the various features of the program. Tutorials 1-14 work through a simple design example that utilizes some of the commonly used attributes of the program, and describes the applicable procedures. In these 14 tutorials two design sessions are illustrated, the first is the design of a basic system for a 5 year storm, while the second is the analysis, in automatic mode, of the first system subjected to a more severe storm. The same examples are described in the program's Tutorial Manual. Tutorials 15-21 illustrate some of the upgrades that are new to MIDUSS Version 2, including items such as culvert and cascade design, and features of the layout screen.

The Help System and Reference Manual are well written and describe in detail all of the commands, and procedures of the program. The theory behind each component is also explained in the manual.

Using

The program provides a number of features to assist the user. For example, procedures are only made available when the proper prerequisite information/data has been calculated or entered. The option also exists to have the program show prompt messages after each step. The brief messages describe the action taken, and suggest one or two logical subsequent actions. Another option available is to have the next logical step displayed with the mouse pointer positioned over the appropriate command. These features may be disabled once a user has become familiar with the operation of the program.

Comparison to Previous Version

Previous releases of MIDUSS software were the original DOS version and MIDUSS 98. There have been no fundamental changes to the function, or to the theoretical basis of model. New design features include:

  • IUH Hydrograph - Allows the user to generate an input runoff hydrograph with a desired peak flow and time to peak or duration.
  • Culvert - A variety of culvert barrel shapes can be designed. This tool can be used as part of a larger system or independently. The culvert tool includes a graphical plot of the culvert profile and/or cross section.
  • Cascade - Allows the design of a two celled storage device.
  • Channel Cross Section - Channel cross section information can be saved and imported, also different roughness coefficients can be used for different segments of a channel.
  • Pond Outflow - Horizontal orifice and pipe outflow control options have been added.
  • Trench Outflow - A pipe outflow control device has been added.

To improve the ease of use a number of new commands have been added and some existing commands have been improved. A few examples are:

  • File and Edit commands - A variety of increased options for saving files and loading previous design sessions for modification and the addition of the common Windows cut, copy and paste commands.
  • Layout - A visual representation of the drainage network is created on a layout screen, the layout is updated as elements are added. The objects can be moved around the screen to better represent the field conditions that the model is intended to represent. Visual cues on the layout screen assist in the modelling process. There are several options and tools available for the layout screen.
  • IDF Curve Fit Tool - Can be used to calculate the parameters for a Chicago Storm to match a recorded storm. Also can be used to generate an IDF curve based on specified parameters for comparison with an observed event.
  • Time of Concentration Tool - Calculates the time of concentration.
  • Check for Update/Get Update - Connects to MIDUSS website to check for or download updates.

A complete list of upgrades is available on the MIDUSS website, or in Appendix D of the program's reference manual.

Top of page   Top of page


Use in MTO Drainage Management Practice

Minimum Requirements for Inclusion in Report

This section provides some guidance to designers and reviewers on the type of information and minimum requirements for reporting the results of a MIDUSS analysis. This should not be considered a comprehensive list of all information required for a Drainage Report.

Summary of input parameters

A summary of input parameters in a tabular, or other easy to read format is required. Other information provided in a report should include:

  • Watershed discritization.
  • Details of the watershed characteristics of the study area to support parameter selection.
  • Rationale behind selection of storm type/settings, routing and infiltration methods.
  • The model layout screen.

Summary of Output

The report should include:

  • The MIDUSS output file. This includes:
    • Time parameter input
    • Storm input data (e.g., storm type, duration, coefficients/constants, depth, Tp, etc.)
    • Catchment data (% pervious/impervious, area, slope, routing method, manning's n, C, IA, etc.)
    • Runoff data generated by the model (time of concentration, runoff depth, peak flow, etc.)
    • Results of all combined hydrograph operations.
    • Channel design information (e.g., basewidth, bank slope, depth, etc.)
    • Results of channel analysis (e.g., flow depth, velocity, critical depth, etc.)
    • Pipe design information (e.g., Manning's n, diameter, gradient, etc.)
    • Pipe design analysis (e.g., flow depth, velocity, pipe capacity, etc.)
    • Pond design information (e.g., # stages, target outflow, max water level, geometry, outlet device specifications, etc.)
    • Pond design analysis (e.g., Level/Discharge/Volume table, max water level, peak outflow, maximum storage, etc.)
    • Diversion design information (e.g., threshold, diverted fraction, required outflow peak)
    • Diversion design analysis (e.g., peak diverted flow, volume of diverted flow)
    • Trench design information (e.g., trench geometry, water table level, outflow specifications, target outflow, inverts, etc.)
    • Trench design analysis (e.g., level/discharge/volume table, peak outflow, infiltrated volume, max storage, etc.)
    • Culvert design information (e.g., geometry, material, invert elevations, weir information, inlet coefficients, etc.)
    • Culvert design analysis (e.g., peak outflow, normal depth, weir flow, etc.)
    • Cascade design information (e.g., geometry, invert elevation, coefficient of contraction, etc.)
    • Cascade design analysis (e.g., volume, peak flow, etc.)
  • Hydrograph plots at locations throughout the drainage system for pre and post development conditions.
  • A summary table of peak flow rates at all key locations for pre and post development conditions.
  • Any other output pertinent to the model should also be included, for example: the results of any calibration studies and intermediate results as required to justify/support conclusions.

Top of page   Top of page

 

Back to Top