How to model 2D infiltration in XPSWMM?

source: Innovyze Support Portal

XPSWMM 2D can simulate infiltration at the cell level when water is flowing through the cells. Although in XPSWMM you can define both the manning’s n and the infiltration in a single landuse entry. For simplicity and flexibility, usually it is a good idea to treat manning’s n and infiltration as two different type of landuse entries.

For example, you have 5 different type of landuse, and 3 type of soils for infiltration. In you define both landuse and soil in the same landuse, then for each combination you’ll have to create a new landuse, e.g. road with soil A, road with soil B, etc. As you can see, it can get complicated very quickly. A simpler way is to treat landuse and soil as two different type of input without mixing them up. And that is the approach we will show in this article.

Define landuse

As shown below, we first need to define manning’s and infiltration as separate landuse entries in the global database.

5: For manning’s n entries, we only check the “landuse” checkbox

6, 7, 8: For infiltration entries, we only check the “Infiltration” checkbox, then define the soil infiltration parameters.

Draw the polygons

There are 3 ways to get the manning’s n, and soil type polygons into XPSWMM.

• draw the polygon directly inside XPSWMM

• import from a shapefile

• using the external references (another blog will cover the steps)

Default landuse

We’ll need to define a default landuse for the model. When soil infiltration is used, we should provide the default landuse with an infiltration type defined.

An easy way to define a soil that doesn’t infiltrate at all is setting the IL/CL (initial/continuous infiltration to 0)