The coastal software packages are typically used to simulate flow phenomena and related processes in coastal areas and seas. The two main products are MIKE 21 and MIKE 3 for two- and three-dimensional water modelling. As the modelling systems are generalised packages, the usage also finds its way to inland modelling, for instance in flood applications of overland flow modelling or urban flooding with dynamic coupling of MIKE 21 with DHI’s river and urban drainage model technology MIKE 11 and MIKE URBAN, respectively, and MIKE 3 when you need to look at stratification effects in rivers or study full 3D dynamics in lakes.
The choice between a 2D and a 3D model depends on a number of factors. For example, in shallow waters, wind and tidal current are often sufficient to keep the water column well-mixed, i.e. homogeneous in salinity and temperature. In such cases a 2D model can be used.
In water bodies with stratification, either by density or by species (ecology), a 3D model should be used. This is also the case for enclosed or semi-enclosed waters where wind-driven circulation occurs.