WMS:HY-12

The US Federal Highway Administration's HY-12 is a DOS-based storm drain analysis program that can be used for designing inlets, pipes, and the general layout of a storm drain network. An HY-12 model can be generated by drawing the proposed pipe and inlet locations in a storm drain coverage. Then the map module locations are converted to a 1D schematic where the HY-12 model parameters are defined. Many of the HY-12 computations, such as channel calculations, curb and gutter calculations, and rational method computations, are based on computations in FHWA's Hydraulic Toolbox software. You can refer to the documentation in both the Hydraulic Toolbox and in HY-12 to learn about the specific computation methods used in HY-12.

This tutorial shows you how to model and design a storm drain network in a small suburban sub-basin. You learn how to assign pipe invert, access hole, ground, and inlet elevations to your model. You also learn how to associate computed hydrologic model data with rational method data so it can be used in HY-12. It is recommended that you be familiar with some of the more advanced watershed modeling techniques in WMS by following the advanced watershed modeling tutorial before attempting this one.

HY-12 Menu

The HY-12 menu has the following commands:

• Import HY-12 File
• Export HY-12 Export
• Run HY-12 – opens the Run HY-12 Simulation dialog.
• Edit Project Parameters – Opens an Edit Properties dialog where parameters for the project can be specified.
• Edit Parameters – Opens an Edit Properties dialog where parameters for nodes and links can be specified.
• View Detailed Link/Node Output
• View Hydrographic Plots
• View EGL and HGL Plots – Brings up the EGL and HGL Profiles dialog.
• Link Outlets and Inlets – brings up the Link Storm Drain and Drainage Nodes dialog.

HY-12 Select Elevation Source dialog

• Assign Elevations – this group of commands will assign elevation data from a TIN to each node and link. Each command brings up a corresponding Select Elevation Source dialog where the elevation source data can be selected.
  • To Ground
  • To Access Hole
  • To Inlets
  • To Outlets
  • To Channels
  • To Gutters
  • Pipes
  • Pipe Storage
• Assign Lengths and Orientations
• Assign Hydrology Data
  • Area – This command assigns the computed basin areas upstream from the outlet points you have linked to the rational method computations at each node.
  • Runoff Coefficient – This command areaweights the runoff coefficients for the sub-basins assigned to each outlet and assigns the area-weighted runoff coefficient to the rational method computations at each node.
  • Time of Concentration – This command computes the average time of concentration for the sub-basins assigned to each outlet and assigns this time of concentration to the rational method computations at each node.

HY-12 Parameters

The HY-12 Model has several HY-12 Properties dialog where parameters can be defined.

HY-12 Project Properties

The HY-12 Properties is reached by using the Edit Project Parameters command in the HY-12 menu.

File:WMS HY12 Properties.jpg

Project HY-12 Properties dialog

HY-12 Nodes and Links Properties

HY-12 Properties dialog for Nodes and Links

Select either a node or a link using the Select Hydraulic Node Tool or the Select Hydraulic Link Tool then right-click. In the right-click menu select the Edit Parameters command. This will bring up the HY-12 Properties dialog for Nodes and Links. This dialog can also be reached by using the Edit Parameters command in the HY-12 dialog.

• Attribute Type – lets the user choose between viewing nodes or links.
• Show – this option lets you search between all or selected nodes or links.
• Filter using: Type – this combo box allows the user to view nodes or links based on the structure type.
• Group Name
• Value/HY-12 ID – this column shows the node or link value and the corresponding HY-12 ID.
• Structure Type – The structure type for the node or link is assigned in this field. Selecting the New button will assign the structure type. The following structure types are available:

Node Structure	Link Structure
Access Hole	Channel
Gutter Inlet	Gutter
Junction	Pipe
Minor Loss	Pipe Storage
Outfall
Rational Method Basin
Reservoir
Transition

• Structure Name
  • New – clicking on this button will assign the structure type to the selected nodes or links.
• Define Structure
  • Define – selecting this button will bring up a HY-12 Properties dialog where definitions for the structure type can be entered.

  File:WMS HY-12 Define Node Properties.jpg

  Example of the HY-12 Properties dialog as reached through the Define button in the Nodes and Links HY-12 Properties dialog. This dialog is for defining Access Hole structures.

• Structure Downstream – shows structures assigned as downstream structures.
• Delete Structure
  • Delete – removes the assigned structure type.

Once parameters have been assigned for nodes and links, double-clicking on a node or link will bring up a HY-12 Properties dialog showing the attributes for that node or link.

HGL and EGl Profiles

The HGL and EGL Profiles plot is created by using the View HGL and EGL Plots command in the HY-12 menu.

HGL and EGL Profiles plot

Link Storm Drain and Drainage Nodes

HY-12 Link Storm Drain and Drainage Nodes dialog

• Storm Drain Nodes
• Drainage Nodes
• Linked Nodes
• Link Nodes
• Auto Link
• Tolerance
• Unlink Nodes

Run HY-12

The Run HY-12 command will bring up the Run HY-12 Simulation dialog where specifications can be reviewed. Clicking OK on this dialog will run the model.

Run HY-12 Simulation dialog

Related Topics

• Hydraulic Modeling Introduction
• Models