Numerical modelling

numerieke modellering

We use a variety of commercial software, open source solutions and proprietary programmes and tools for our numerical modelling. Flanders Hydraulics Research has the proper in-house expertise to select the most appropriate tool from the existing portfolio of models for every application. We continuously maintain and extend the portfolio. We are familiar with numerous software packages for a wide variety of applications. The most important are listed below.

Hydrological models

Hydrodynamic models

Water balance models

Wave models

Sediment transport and morphological models

Shipping traffic analysis

Computational fluid dynamics

Hydrostatics of vessels

Hydrodynamics of vessels

Filling & emptying locks

Impact of floods

Hydrological models

Flanders Hydraulics Research uses hydrological models to calculate the runoff from a river basin to the waterway. We use these to define the boundary conditions to be used in hydraulic models and water balance models. Most hydrological models, especially operational models, from Flanders Hydraulics Research are conceptual reservoir models. For research assignments, we make comparisons between conceptual models (NAM, PDM, etc.), mixed conceptual physics-based models (e.g. WetSpa) and highly detailed, physics-based and fully distributed models (e.g. MIKE SHE).naar boven

Hydrodynamic models

Flanders Hydraulics Research mainly uses 1D hydrodynamic models to calculate water levels and discharges in rivers and their floodplains as a function of time. We use models such as MIKE11 which we maintain and update to reflect the actual situation as closely as possible.

In terms of 2D and 3D hydrodynamic models, a range of applications is possible. Flanders Hydraulics Research uses these models for the coastal zone, the river deltas and for specific issues such as saltwater intrusion in ports. These software packages also include modules to simulate sediment transport.

Depending on the functionalities required for the job and the partners, we apply programmes such as TELEMAC, Delft3D and MIKE21. We work on new developments for several of these software packages by writing new code for specific applications or modules, or by extensively testing new functionalities.

We use hydrodynamic models in both studies, advice and research as well as for our operational forecast models. Typical study topics are scenario analyses to support water management, planning and policy development. In addition to water movement, these software packages also contain morphology modules.

For the operational forecast models, Flanders Hydraulics Research connects its hydrological and hydrodynamic models to the WISKI database via web services. This database continuously stores information on rainfall, discharges, water levels and sediment quantities based on field naar bovenmeasurements. This allows us to make forecasts at least 4 times per day for the next 48 hours for all navigable waterways in Flanders.

NEVLA model

The NEVLA model, short for ‘NEderlands-VLAams’ [Dutch-Flemish], is a hydrodynamic model developed in the SIMONA software. It encompasses the Belgian coastal zone,NEVLA schematisatie the Western Scheldt, the Sea Scheldt and the Durme, Rupel, Nete, Dijle and Zenne tributaries. All these rivers are included in the model up to their tidal boundary. SIMONA stands for ‘SImulatie MOdellen voor de NAtte waterstaat’ [Simulation models for wet water management] and the instruments which the Dutch government (Rijkswaterstaat) uses for its water management tasks. By creating and maintaining the NEVLA schematisation in this software, the model can easily be used in an international (Flemish-Dutch) context.

The model is maintained by Flanders Hydraulics Research in 3D and 2D versions. The 3D version is mainly used for salinity and sediment (sand and silt) transport calculations. The 2D version performs computations more quickly and provides operational predictions.

Water balance models

We rely on water balance models (such as MIKE Basin) for studies on water availability and water allocation. We utilise them, for example, in scenario analyses of changing climatic conditions or changing water demand.

Wave models

Numerical modelling of waves is a way to study the behaviour of coastal defences. Flanders Hydraulics Research mainly uses SWAN, Mike21BW, SWASH, DualSPHysics and XBeach. SWAN, Mike21BW and SWASH are mainly used for wave transformation, DualSPHysics for wave-structure interaction (see also CFD section below) and XBeach for coastal morphological studies.

Sediment transport and morphological models

One of the major concerns of waterway-, estuarine- and coastal managers is the changing bathymetry and turbidity introduced by natural or anthropogenic changes in fine sediment and sand transport. The turbidity and morphology of the Belgian coast and Scheldt estuary is strongly influenced by fresh water discharges, seasonal effects, storms, climate change, but also by human interventions like channel deepening and maintenance, infrastructural works and coastal defence.
The sediment is brought into suspension and transported by the water forced by currents and waves. At sheltered sites and during slack water, the sediment settles back to the bed. Coupling the hydrodynamic models and/or wave models with a sediment transport model allows for simulating the transport of sediments and bottom evolution. However, the processes of suspending and settling sediment, but also other processes like flocculation of fine sediments in the water column and consolidation of the sediment on the bottom are complex processes depending on many factors. In order to better understand the physics of the processes and hence to improve the mathematical models, FHR performs in situ and laboratory measurements and long term monitoring campaigns.
FHR has different models for the Belgian Coast and Scheldt Estuary based on open source and in house developed model software:

  • Delft3D
    • NeVla-type models for sand and cohesive sediment transport in the Western Scheldt and Sea-Scheldt
    • Idealised model for the Western Scheldt for long term morphodynamics (decades till centuries)
    • Scaldis: cohesive sediment transport model for the Sea-Scheldt
    • Scaldis-Coast: morphodynamical model for the coastal area and Scheldt mouth area (time-scale years till decades)
  • iFlow: Inhouse, in collaboration with TU Delft, developed software for idealised equilibrium modelling of sediment transports in estuaries
  • XBeach: local beach and foreshore area models for short term morphological evolutions (e.g. storms)
  • 1D coast-line models: midterm and long-term schematic models of the shore line evolution

Shipping traffic analysis

Flanders Hydraulics Research has a specific tool to analyse maritime and inland shipping traffic.

AIS data analysis tool

Flanders Hydraulics Research developed a tool to analyse Automatic Identification System (AIS) data in a flexible and effective way. AIS data contains information that can be used, for example, in the analysis of shipping traffic for operational purposes or for specific manoeuvres at specific locations.

Because data volumes are often very large, the AIS data analysis tool allows filtering of the data on vessel dimensions, on geographical restrictions or on voyage characteristics. To visualise the data, the AIS data analysis tool includes export options in various formats which are compatible with GIS viewers.

Computational fluid dynamicsnaar boven

Computational Fluid Dynamics (CFD) is used to study currents in liquids and gases (such as water and air) in a numerical manner using computers. The Navier-Stokes equations are solved in discrete form which allows us to simulate detailed flow patterns. CFD is used to determine the hydrodynamic forces on ships and structures and to simulate the flow through or in the vicinity of hydraulic structures.


The FINETM/Marine software package developed by NUMECA calculates the turbulent air-water flow around a vessel based on the Reynolds Averaged Navier- Stokes (RANS) equations. Flanders Hydraulics Research focuses its research on simulating experimental results obtained through research conducted in the towing tank (e.g. ship-bank interaction, ship-to-ship interaction and the behaviour of ships in waves). At the same time, in case Flanders Hydraulics Research has no appropriate experimental facilities available, we use this software to provide the necessary inputs (e.g. wind coefficients of ships) for ship manoeuvring models.


OpenFOAM is a free, open source CFD software developed by the OpenFOAM Foundation. The package includes multiple solvers to simulate specific flow problems. Flanders Hydraulics Research uses OpenFOAM mainly for the modelling of local flow processes through or near hydraulic structures.

DualSPHysics is a free, open source CFD software, based on the Smoothed Particle Hydrodynamics model named SPHysics ( The code is developed to study free-surface flow phenomena where gridded methods are difficult to apply. Flanders Hydraulics Research uses DualSPHysics mainly for the modelling of wave-structure interaction and is also actively involved in the further development of DualSPHysics.


Hydrostatics of vessels

Flanders Hydraulics Research can utilise a wide range of software for hydrostatic calculations of vessels, each with its own features and capabilities.naar boven


DELFTship Pro is a complete design package for applications in the maritime sector. It allows us to enter every possible hull shape and offers great flexibility. Because of its visual approach, it can be used for nearly any floating object.

Rhino and Orca3D

This programme calculates the hydrostatics and stability of a vessel and can manage a wide range of input and output files.

Hydrodynamics of vessels

We also have various research capabilities for the study of the hydrodynamics of vessels.naar boven


ROPES is a project that studies the effect of passing vessels on the movement of moored vessels. The size of vessels is constantly increasing and new terminals are being continuously developed along waterways and port access routes. It is therefore especially important for the planning and development of the operational activities in the port to properly identify the impact.


Flanders Hydraulics Research developed the ProToel software together with Ghent University’s department of Maritime Technology. It is a user-friendly application that determines the tidal windows of marginal ships sailing to Flemish ports based on both probabilistic criteria (maximum probability of touching bottom) as well as deterministic criteria (minimum keel clearances, maximum current velocity, etc.).

A user can simulate the desired voyage in the ProToel GUI by selecting the vessel, cargo condition, the route with the corresponding sailing speeds and the desired date(s) of departure. At each waypoint in the voyage, ProToel requests the predicted hydro-meteorological data (tide, current and directional wave climate) from a web service which Flanders Hydraulics Research hosts. For longterm calculations, it is possible to define astronomical hydro-meteorological data in the local database.

ProToel calculates the vertical motions of the vessel resulting from waves (dynamic vertical movement) and squat (stationary vertical movement) using a database of ship movement characteristics (obtained from model tests and numerical calculations).  

Filling & emptying locks

Flanders Hydraulics Research uses programmes that describe the lock filling and emptying process in schematic form. They calculate the variation of the water level in the lock chamber, the variation of the discharge through openings in gates or culverts and the variation of longitudinal forces on the ship in the lock chamber (transverse forces cannot be calculated), all as a function of time.naar boven


The LOCKFILL programme is provided free of charge by the independent research institute Deltares. The calculation method is based on scale model research, desk studies and previously developed calculation programmes. LOCKFILL was commissioned by Rijkswaterstaat and developed by Deltares in the period 1989-1993. This programme allows the filling and emptying of a lock through openings in the lock gates to be simulated and the longitudinal forces on the vessel in the lock chamber to be calculated. To a limited extent, it is also possible to study levelling systems with short culverts and a stilling basin in LOCKFILL.


Vul_sluis is a (Matlab) programme developed by Flanders Hydraulics Research and based on the available literature for the LOCKFILL programme. It was validated using measurement data from literature and additional measurement data from Flanders Hydraulics Research. This programme also makes it possible to simulate the filling and emptying of a lock through openings in the lock gates and calculate the longitudinal forces on the vessel in the lock chamber.

During the development of the vul_sluis programme, only the levelling through openings in the lock gates was taken into account. Levelling systems with short culverts and the longitudinal component of the force on the vessel as a result of differences in density are hereby not considered.

Impact of floods

In addition to determining physical parameters such as water levels and rising rates in flooded areas, Flanders Hydraulics Research also calculates the impact of floods by estimating damage and casualties. We do this to compare the risk before and after an intervention or, for example, to naar bovencalculate the effects of climate scenarios.


To calculate the impact of floods, Flanders Hydraulics Research developed a specific GIS tool in cooperation with Ghent University called LATIS. LATIS is used to determine flood damage and risks. The tool calculates both the economic risk (in euro/year) as well as the risk of casualties (in victims/year). This flood risk is the product of the probability of flooding and the damage caused by the flood. The damage caused by a particular flood is determined by the water depth and the maximum damage, which in turn depends on the type of land use and socio-economic context.

LATIS uses a very detailed land use map specified to plot level. The exact location of (residential and industrial) buildings, roads and other structures is identified. Based on this land use information and socio-economic data, it is possible to establish a potential damage map. This is combined with several flood maps for various repeating periods to create a single risk map. With the aid of damage functions, the actual damage is calculated based on the water depth as well as the current speed and the rate of the rising water.

LATIS plays an important role in meeting the requirements of the European Flood Directive (Directive 2007/60/EC). The package is built using Microsoft.NET with the aid of the Idrisi API (raster-GIS, Clark Labs). The user interface and the algorithm of the model are implemented in C#.Net.

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