Hydrological and (mathematical) hydraulic modelling in practice is the production of mathematical (or computer) models which more or less accurately, and in more or less detail, simulate processes in nature. By using state-of-the-art computer tools, it is now possible to model and simulate numerous flood-related and flood risk management processes. Two key processes are modelling the movement or transport of water within river basins or other completed areas (so-called hydrological modelling) and detailed modelling of water spillage and movement in the event of certain situations (hydraulic modelling) on shorter or limited sections of watercourses. Moreover, many other processes related to water management can also be simulated.

The result of hydrological modelling is a so-called hydrological model or computer tool that enables us to inspect quantities or water flows that change over time in the framework of an area or river basin or section of the watercourse. Hydrological models are used for calculating peaks or entire flood waves in individual profiles of the entire network of modelled watercourses upon the occurrence of various precipitation and other scenarios and for predicting floods.

The result of hydraulic modelling is a so-called hydraulic model of a particular section of a watercourse, with which it is possible to simulate and provide a detailed insight into the (hydraulic) state in individual smaller parts of the modelled area (usually a section of the watercourse), namely – specific depths, speeds and other characteristics.

The results of both hydrological and hydraulic modelling are used for different purposes; in particular, they are used for preparing and implementing various types of flood protection measures (predicting floods, mapping flood areas, flood event simulation, preparing and developing structural and other flood prevention measures, etc.).

It should be emphasised that all hydrological or hydraulic modelling results must pass a critical assessment by an experienced expert or group of experts, possibly an expert on the local situation. Even the most sophisticated software tool or model can only approximate the real situation, and it often happens that certain results must be corrected based on practical experience and data on historical events.