The runoff model used is Flow2D.
Overview of the components of a runoff model
Note
that flow2d only solves the Overland Flow routing
equations mentioned on this page.
Flow2D was originally part of a more complete runoff model called CASC2D which in turn is part of the GIS known as GRASS. EH team member John Conery has done some work on the computational properties of flow2d. The version we currently use started out as his "Array" version.
Flow2d is very flexible program. The precip rate, time step, grid size, grid distance and test surface can all be chosen at runtime. A uniform precip rate over the entire domain is assumed.
There is also a parallel version of flow2d written with PETSC by Mark Ruesink who worked for EH team member Doug Johnston. Timings for pflow2d are available
Flow2d was first tested under domain sizes, timesteps and precip rates we felt would be typical for an EH application. Several modifications were made during this testing/development period. The model was converted from C++ to C for more portability. A DEL4 diffusion was added to handle instability seen when rain falls only in the middle of the domain. The ability to write a Vis5D file was added and finally the interface to the field transfer library was added. EH Team members Leigh Orf and Robert Jacob did the testing and modifications.