Introduction

Urban stormwater flood modelling can be carried out using a 1D/1D or a 1D/2D approach. The 1D/1D approach has a simplified representation of the overland surface hydraulics compared to the 1D/2D approach.

In recent years coupled 1D/2D modelling applications have been widely used in urban stormwater analysis. The advantage of the 1D/2D approach is that the model is faster to configure, and it provides a more realistic hydraulic description of the surface flow. Model simulation times are however generally long, which makes the design and testing of stormwater improvements and installations difficult and time-consuming.

The advantage of the 1D/1D approach is that the simulation time is considerably faster than the 1D/2D approach and is therefore more suitable for detailed design option runs. However, configuring the 1D/1D model is more time-consuming than the 1D/2D model.

A 1D/1D stormwater model typically comprises three main components: the sewer/stormwater system, the overland flow system, and rainfall-runoff hydrology.

The set of tools is developed to specifically address some normally time-consuming aspects of building a 1D/1D stormwater model.

For a catchment study a staged approach is usually needed, for example:

• The first stage involves catchment-wide modelling in a combined 1D/2D model to assess the performance of the system and identify potential improvement locations;
• For the second stage, a full 1D/1D model is built only for the improvement location including the 1D overland flow path network. The 1D/1D model runtimes are fast and allow for quicker assessment of stormwater improvements.

The stormwater tools focus on building the stormwater model within a 1D framework, which include:

• Cross section extraction from the DEM
• Lateral snapping of nodes according to the DEM
• Auto connection of overland network to stormwater network
• Sequential labelling of nodes

The tools can be activated from the menu under the CS network tab.