Modified Puls Routing

For unsteady flow models, the HEC‑RAS Modified Puls Routing option can be used to define portions of a river reach that should be routed with the Modified Puls hydrologic routing method instead of the full St. Venant unsteady flow routing method. This option is very useful when encountering portions of the model that are very steep and the full unsteady flow routing method is either unstable or not feasible to use at all. This option only works as part of an unsteady flow analysis and is ignored when performing a steady flow analysis.

Modified Puls Routing Dialog Box

To display the Modified Puls Routing dialog box, select the Modified Puls Routing command from the Other Data dropdown menu of the Input ribbon menu.
Modified Puls Routing dialog box

To use the Modified Puls hydrologic routing option, the user must first create a steady flow model with the exact same geometry data. The purpose of the steady flow model is to compute a range of water surface profiles from very low to the highest expected flow rate. The results from the steady flow model are then used within the hydrologic routing reaches in order to provide the necessary discharge-volume data required by the Modified Puls hydrologic routing method.

Hydrologic routing reaches can be created almost anywhere in the model. A hydrologic routing reach must be at least two cross sections long. A hydrologic routing reach can be an upstream portion, downstream portion, or an intermediate portion of any existing HEC‑RAS unsteady flow river reach. The hydrologic routing reach can also encompass an entire HEC‑RAS river reach. Hydrologic routing reaches can contain roadway crossings (i.e., bridges and culverts) and lateral structures. However, it cannot contain an inline structure. If an inline structure is contained within a routing reach that is to be routed with the Modified Puls hydrologic routing method, then the hydrologic routing reach must stop at least two cross sections upstream of the inline structure. The hydrologic routing reach can then start immediately downstream of the inline structure.

The following data are defined in this dialog box.

Define Hydrologic Routing Regions

This data table is used to define the starting and ending cross sections where the Modified Puls hydrologic routing method should be applied. The following columns are used to define this data.

River and Reach
These two columns provide dropdown combo boxes that allow the user to select the river and the corresponding reach for defining the hydrologic routing reach segment. If the user has not selected a river from the dropdown combo box, the reach dropdown combo box does not list anything. Once the user selects a river from the dropdown combo box, the reach dropdown combo box automatically populates with the reaches that are associated with the selected river.
Upstream Cross Section
This column provides a dropdown combo box listing all cross section river stations contained within a river reach, except for the downstream most cross section. It does not list river stations corresponding to roadway crossings, inline structures, or lateral structures. Once a river and reach have been selected, this dropdown combo box shows by default the upstream most cross section river station.
Downstream Cross Section
This column provides a dropdown combo box listing all cross section river stations contained within a river reach, except for the upstream most cross section. It does not list river stations corresponding to roadway crossings, inline structures, or lateral structures. Once a river and reach have been selected, this dropdown combo box shows by default the second upstream most cross section river station.
Rating Curves Imported
This read-only column lists the number of entries imported from the selected HEC‑RAS steady flow scenario results. This column is blank until the user elects to import the HEC‑RAS steady flow scenario results.

Options

This section defines the options to be used in the Modified Puls routing.

Use Modified Puls routing in unsteady flow analysis
This checkbox is selected (i.e., checked) by default, and controls whether the Modified Puls routing method should be used in the defined hydrologic routing reaches. Unchecking this option will prevent the Modified Puls routing method from being used in the unsteady flow analysis.
Perform tailwater check
This checkbox is not selected (i.e., unchecked) by default, and controls whether the Modified Puls routing method should look for downstream tailwater elevation issues, creating backwater to upstream affected cross sections.

Import Rating Curves from Steady Flow Analysis Results

This section controls the importing of computed HEC‑RAS results (i.e., discharge vs. water surface elevation) for defining the hydrologic routing rating curve data.

Steady flow scenario (plan)
This dropdown combo box lists only steady flow scenarios (plans). The user can select from the combo box the HEC‑RAS steady flow model scenario (plan) to be used in the Modified Puls routing.
Number of profiles
This read-only field lists the number of profiles defined in the output file (or Steady Flow Data dialog box) for the selected HEC‑RAS steady flow model scenario (plan). This field is automatically updated once the user has selected the steady flow scenario.

Clicking the [Import] button causes the software to read in the computed discharge vs. water surface elevation data. This data is then stored as individual rating curve information at each cross section.

Note that the imported rating curve data for the Modified Puls routing is independent of the rating curve data defined in the Cross Section Data dialog box.