XPSWMM XP2DExtreme Support

Overcoming instability issues in XP2D Extreme

Problem:

We are having difficulty stabilizing our XPSWMM models using the XP2D Extreme solution.

Solution:

Sure.

XPSWMM will generate the SX connections for inlets, but it does not when the pipe is selected as Link Invert to 2D. This image from the TUFLOW manual illustrates the connection and the requirements well. Nodes connected to the 2D domain need a 2D boundary connection. XPSWMM automatically generates points for the pits, but for culverts and end sections, this is up to you.

In the image from the TUFLOW Manual, the culvert boundary connection can be a point, line, or region. Despite TUFLOW's support, XPSWMM doesn’t allow a polygon here.

TUFLOW Manual - Section 10.2.2 SX 2D Flow Boundary

I don’t think this issue was covered in the XP training, or in the getting started guide.

SX connections are typically used to transfer flow between 1D and 2D for 1D structures and at pits/drains/gully traps that capture water into the pipe network. Unique to SWMM, when using it as the 1D solver, an SX connection is only required at the downstream end of a 1D culvert (it uses a HX link at the upstream end due to limitations of the SWMM software).

One nice element is the QGIS TUFLOW plugin's ability to generate those required elements. As a user, you must create the layers and import the SHP files for each layer (1D/2D Interface line and 1D/2D Connection line). I hope XP recognizes how they connect. Otherwise, you will need to draw both or ensure they snap correctly manually.

This should help you overcome the XPSWMM model’s instability.