XPRafts is a non-linear runoff routing model used extensively throughout Australasia and South East Asia. The software works well on catchments ranging in size from a few square metres to thousands of square kilometres urban or rural. XPRafts can model up to 2000 different nodes and each node can have a sub-catchment attached, as well as a storage basin.

XPRafts uses the Laurenson non-linear runoff routing procedure to develop a stormwater runoff hydrograph from either an actual event (a recorded rainfall time series) or a design storm utilising Intensity-Frequency-Duration data together with dimensionless storm temporal patterns, as well as standard AR&R 1987 data (Institution of Engineers, Australia, 1987).

Three loss models may be employed to generate excess rainfall:

• Initial and Continuing Loss Model
• Initial/proportional loss model
• ARBM Losses water balance model. 

A reservoir (pond) routing model allows routing of inflow hydrographs through a user-defined storage using the level pool routing procedure. Modelling of hydraulically interconnected basins and on-site detention facilities can also be performed.

Three levels of hydraulic routing are possible:

• Simple Manning’s-based lagging in pipes and channels
• The Muskingum-Cunge procedure to route hydrographs through channel or river reaches
• The transfer of hydrographs to the XP-EXTRAN HydroDynamic simulation model.