Not all solvers are the same | How to choose the right 2D solver

Flood Modeller provides three 2D solvers as standard, allowing you to select the most appropriate solution method for each project. However, it can be difficult to know how to choose the right 2D solver. In this article, we provide some useful information to help you decide which one to use – in some cases you may wish to use more than one!


What 2D solvers are available?

2D ADI solver

The 2D ADI (Alternating Direct Implicit) solver can be applied to fluvial, overland, estuarine and coastal modelling problems, and in many cases, is the ‘go to’ solver for 2D modelling. It is the preferred solution for various flood modelling packages due to it being an accurate, robust and fast method which can be applied to a wide range of flood risk management studies, including surface water modelling, local and catchment scale assessments, and flood and hazard mapping.


The 2D ADI solver represents the 2D model domain as a grid of square cells. Water levels are calculated at each cell centre, and the two components of velocity at cell edges. This allows the model to use the velocity components to calculate flow across cell edges and between cells.


Multiple 2D domains, with different cell sizes and time-steps, can be incorporated into your model to represent different areas of a floodplain. This allows you to model areas of interest in greater detail, without compromising simulation run times.


The solver can be linked dynamically to Flood Modeller's 1D river and 1D urban solvers to enable integrated catchment modelling of surface and sub-surface flows. Models can be linked by water level or by flow and can represent lateral floodplains, a 1D channel running into a 2D estuary, spill over defences, and other river, coastal or floodplain systems.