Why use 2D modelling?
• 13 Sep 2022
• Dark
Light

# Why use 2D modelling?

• Dark
Light

If flow pathways and full flood animations are desired, the floodplain may be better modelled in 2D; spatial datasets specify the underlying ground elevation, topographic features such as areas of high ground or pathways between buildings and any variations in land use (defined by changes in roughness coefficient). Certain 1D structures such as culverts and weirs can also be embedded directly into 2D domains. 2D models are used less often for modelling of in-channel flows, usually because raster ground survey data for these areas are a lot less available.

To run a 2D only simulation (for example, if modelling a floodplain in 2D) the user provides details such as the flow entering the floodplain (e.g. overtopped from a river) and a timestep. Based on this information and the specified calculation area (active area), the software calculates water levels and flows at each grid cell within the active area, at each requested timestep.

#### What is needed to run a 2D simulation?

A 2D simulation requires details about the 2D domain (the area to be modelled).

A ground elevation grid provides the underlying elevation data of the area; most commonly a Digital Terrain Model (DTM) or Digital Elevation Model (DEM) is used. The roughness of the area, alongside other topographic features such as areas of high ground, can be specified in additional datasets.

An active area must be defined, within which the calculations are performed.

A 2D simulation also requires boundary information to detail the flow entering / leaving the system. The location of the boundary line(s) and the flow data itself are both necessary.

When setting up a 2D simulation, the timing and simulation type must be provided, alongside the domain and boundary details. By default, depth, elevation, flow and velocity data are all calculated and additional outputs are also available.

#### What can I visualise from a 2D simulation?

In 2D, the map view is crucial for viewing all model components, including topography, domains, and boundary lines. These, together with any lines linking 1D and 2D modelling components, are drawn and edited directly on the map.

Alongside the map view, a variety of panels allow for further opportunities to visualise modelling components - for example, the '1D Urban Network' panel shows the currently active urban network in tabular form; the 'Layers' panel shows all loaded GIS data and shapefiles; and the 'Project' panel lists all other model files associated to the current project.

Tip:
You can hit the F1 key at any location in the interface to access further guidance on any function or tool!

A selection of tabs enables users to quickly switch between ribbons showing a multitude of commonly used functionality, categorised to assist through the model build, simulation run, and results viewing processes. Unique, clear icons are provided along each ribbon, together with user-friendly pop-up “tool tips” further clarifying the function of each button.

To further enhance the modeller’s experience, these aspects are all fully customisable. On the map view, labels, icons and layers can be hidden from view simply by checking boxes provided, and menus allow for changes to all line styles and colours. Panels can be moved around, resized, or hidden from view altogether to give an interface that suits your modelling needs.

For visualising 2D and integrated modelling results, Flood Modeller’s map view again provides the ideal solution. Depth, velocity, flow and water level are all calculated by default for any 2D or 1D-2D linked simulation. Once loaded, flood data maps for each of these outputs can be viewed on the map. These also can be visualised as animations, with controls provided to select the exact timestep of interest.