Sediment simulation in intakes with Multiblock option (SSIIM)

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Quick summary

Figure 1: Flow chart of the executable SSIIM (NTNU).
Figure 2: List of all available parameters in SSIIM (NTNU).

Developed by: NTNU

Date: 2018

Type: Tool


SSIIM is a numerical model to simulate the hydraulics and sediment transport including bed changes as well as various other parameters related to water quality in fluvial environment. It solves the Reynolds-averaged Navier-Stokes equations in all three directions and calculates the turbulent kinetic energy and dissipation through the standard k-espilon model. The calculated bed changes are directly coupled to the time steps in the hydraulic computations. SSIIM can use both, an unstructured and a structured grid to discretize the domain of interest.


After downloading the SSIIM executable from the webpage mentioned below, the text files "control" and "koordina" have to be established. The control file lists all the control parameter which SSIIM is supposed to execute. There are various parameters depending on the results the user wants to achieve. The koordina file is used to describe the geometry of interest.

Figure 1 shows the flow chart in which way SSIIM is working.

The application of the user does not require any coding, however, the user has to specify certain parameters and the geometry as text in the above mentioned files. These files are generated with any text editor and linked to the main executable. A detailed description can be taken from the manual (Olsen, 2018). The application varies from the most basic simulation of a steady state hydraulic computation to the most complex one, when combining unsteady flow with multiple sediment sizes and wetting and drying of parts of the geometry.

INPUT: To start a most basic version of a time dependent sediment transport model of a river reach you have to have the geometry in terms of a point cloud file, the discharge Qin=out, the waterlevel height at the downstream end of the reach and the prevailing sediment grain size distribution at the river bed.

OUTPUT: All the available output parameters can be displayed in the graphical user interface and copied into the clipboard (Figure 2). In addition, it is possible to use a separate post processing tool, like freeware Paraview ( or commercialized Tecplot (

Relevant mitigation measures and test cases

Relevant measures
Baffle fishways
Bottom-type intakes (Coanda screen, Lepine water intake, etc)
Bypass combined with other solutions
Construction of a 'river-in-the-river'
Construction of off-channel habitats
Drawdown reservoir flushing
Environmental design of embankments and erosion protection
Fish guidance structures with narrow bar spacing
Fish refuge under hydropeaking conditions
Mechanical removal of fine sediments (dredging)
Migration barrier removal
Mitigating rapid, short-term variations in flow (hydro-peaking operations)
Mitigating reduced annual flow and low flow measures
Mitigating reduced flood peaks, magnitudes, and frequency
Other types of fine screens
Placement of dead wood and debris
Placement of spawning gravel in the river
Placement of stones in the river
Pool-type fishways
Removal of weirs
Restoration of the riparian zone vegetation
Skimming walls (fixed or floating)
Vertical slot fishways
Relevant test cases Applied in test case?
Anundsjö test case -
Bannwil test case -
Gotein test case -
Las Rives test case -
Schiffmühle test case Yes
Trois Villes test case -

Other information

The numerical model can be download free of charge at the webpage listed below. There is a large user group and information is available at many places.

Relevant literature

Contact information