Direct rainfall or rain-on-grid modelling first appeared on the hydraulic modelling landscape in the mid-2000s using TUFLOW as an easier way to model rainfall-runoff in Sydney’s urban environments instead of the traditional, and somewhat tedious approach of delineating sub-catchments for a hydrologic model.
However, there has been very little demonstrating of fit-for-purpose through calibration to historic data with many modellers running blind as to whether their modelling is representative of the real-world. Whilst hydrologic models remain substantially faster, improvements to 2D solvers and GPU acceleration continue to make products like TUFLOW increasingly viable options for simulating the rainfall-runoff hydrologic process due to their faster model setup times and more visual result presentation formats for stakeholders.

Join this webinar to learn about the accuracy of direct rainfall modelling based on benchmarking and calibration to historic data sets, and how new features in TUFLOW’s 2020 release have substantially overcome previous shortcomings of 2D hydraulic solvers for rain-on-grid modelling.


Phil Ryan


Phil has over 15 years’ experience working on numerical hydraulic modelling tasks. These include flood studies, floodplain management studies, flood impact assessments, storm tide studies, Monte Car... Read more

Bill Syme


Bill has over 30 years’ experience working on riverine, estuarine and coastal studies, of which most have been in the flood hydraulics field.  During this time, he has successfully managed and led ... Read more

Key Messages:

  • Direct rainfall or rain-on-grid modelling to simulate the hydrologic rainfall-runoff process is increasingly viable due to advancements in GPU hardware, but benchmarking through calibration has been vitally needed to demonstrate proof-of-concept.
  • New features in TUFLOW’s 2020 release have overcome major shortcomings of 2D hydraulic solvers for direct rainfall modelling.
  • Direct rainfall modelling can be confidently carried out provided the modeller is aware of the pitfalls.

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