3Di is a process-based, hydrodynamic model for flooding, drainage and other water management studies. It can be used for the computation of water flow in 1D and 2D. The software is developed by a consortium of Stelling Hydraulics, Deltares, TU Delft and Nelen & Schuurmans. With 3Di it is possible to make fast simulations while using a high level of detail. 3Di allows the user to interact with the model during a simulation. One can interactively influence the simulation by changing the rainfall, wind force and model components like cross-sections, breaches and pump capacities.


The 3Di engine is based on state-of-the-art numerical schemes. The engine makes use of a so-called subgrid method. This technique includes high resolution information in coarse resolution computations. This guarantees both accuracy and efficiency. The 3Di engine includes a whole range of processes, including surface run-off, 1D and 2D surface water and groundwater flow. Moreover, it can deal with 1D sewer flow and structures like pumps, weirs and culverts. 3Di deals with numerous external forcings, like precipitation from radar images and wind. These unique characteristics makes 3Di suitable for climate impact studies, flood studies and hydraulic design of open channel and sewer networks.

The 3Di engine is developed by Prof. dr. ir. G. S. Stelling, who worked on the subgrid technique in close collaboration with Prof. dr. ir. V. Casulli. Most of the techniques used within the 3Di engine are published in scientific papers.

Where to start?

This document presents a description of the methods used in 3Di and tutorials how it is used. This document will help the novice as well as the experienced 3Di-user. For the novice it contains background information and key points for creating a first model, while for the experienced user it will serve as a reference work. The manual contains the following sections:

  • Starting from The grid the concepts behind the 3Di engine are explained in detail. Read these sections to learn how 3Di calculations work.
  • Then, Numerics starts of a series of more technical sections you may need when modelling or getting some specific results.
  • Finally, Before You Begin is the place to start if you want to get stuck in using existing models or changing them.

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