Which routing model to select

There are 3 available simulation types using the 1D urban solver. In each case the 1D shallow water equations are solved, however certain assumptions are made to simplify these for each routing model selected. There are advantages to each of these simulation types, but also certain limitations that must be taken into account.

Steady state - the time-invariant case and the simplest form of routing (i.e. no routing). Simplifications are made to the mass and momentum equations by assuming flow is constant at all times.

Steady state simulations have limited use, and cannot be used on certain network configurations. However, they are fastest to run and results can be useful to determine the initial flow within a network, for example.

Kinematic Wave routing - simplifications are made to the momentum equation by assuming the water level slope is approximately equal to the channel bottom.

Kinematic Wave routing also imposes certain restrictions on the network configuration, and cannot account for scenarios such as pressurised flow and back-water effects. This routing type can be good for very long simulations, however, as a much larger timestep can be used with still maintaining stability in comparison to Dynamic Wave routing.

Dynamic Wave routing - the most theoretically-accurate solution of the 1D shallow water equations. No assumptions are made and the equations are solved in full.

Dynamic Wave routing is the most the most sophisticated solution and accounts for pressurised flow and back-water effects. There are no restrictions imposed on the network configuration and so more complex pipe layouts are possible. A smaller timestep is necessary, however, and therefore simulation runtimes will be longer than the other routing options.