A1) Hydraulics and morphology of LTDs

Timo de Ruijsscher

"Studying how the longitudinal training dams (LTDs) influence flow and morphological patterns using both field observations and a physical scale model"

Practical motivation

In the Dutch river system, measures are taken to keep the river system sustainable for the future. One way of doing this, is by replacing transverse groynes in the inner river bend by so-called longitudinal training dams (LTDs). As a pilot project, LTDs are constructed over a ten-kilometre stretch in the Waal River. LTDs are expected to reduce long-term subsidence, increase the lowest water levels, increase the discharge capacity during floods and create ecologically more favourable conditions. However, existing knowledge about the effects of LTDs on erosion/deposition and regional flow patterns is highly limited.

Management phase: Implementation & Monitoring |

Management goals: Morphological understanding |

Schematic view of a longitudinal training dam (LTD) and the remaining groynes (Source: Rijkswaterstaat).

Research Aim

The main aims of this research are to understand:

  • the effect of the intake geometry of an LTD on the morphological patterns and associated flow structures in the inflow region,
  • the morphodynamic evolution of the bed in both the main channel and the side channel after construction of an LTD,
  • the dynamic behaviour of subaqueous dunes in the Waal River, and the influence of the LTD construction thereon and,
  • the physical mechanisms governing exchange processes in LTD openings.

To achieve these goals, both physical scale model experiments and field measurements will be used.

Temporal scale: Seasonal measurements |

(a) Picture of the line laser scanner measuring a profile. The red light on the profile is the line emitted by the laser. (b) Overview of the experimental set‐up. c) Physical scale model of the upstream section of a longitudinal training dam (1:60) in a 2.5-metre-wide flume. Arrow indicates flow direction. (Source: Adapted from Figure 1; de Ruijsscher et al. 2018; https://doi.org/10.1002/2017WR021646)


  • In order to prepare the experiments, a 1:60 physical scale model is built. In this scale model, polystyrene lightweight granules will be used as substitute sediment.
  • A so-called line laser scanner is used to reconstruct the bed profile. A red laser line is projected on the bottom of the flume, which reflection is recorded by a 3D camera (top right in the Figure).
  • Problems that occur using this method are data scatter and missing data. Both are reasonably resolved by using an interpolation and smoothing algorithm, which also appears to be a useful tool for filtering bed forms of different spatial scales.

Data-collection methods: Field survey measurements | Physical and laboratory experiments | Remote sensing |

Main progress and next steps

  • Implementation and analysis of a line laser scanner as a new non-intrusive measurement method for measuring sub-aqueous bed forms in flume experiments.
  • The scale model experiments are ongoing. Analysis will follow during spring and summer 2018.
  • Two Horizontal Acoustic Doppler Current Profilers (H-ADCPs) and Optical BackScatter (OBS) devices were mounted at a traffic pole at the upstream side of the most downstream LTD to measure horizontal flow velocities and turbidity at two different heights from end of May 2017 onward. These measurements are daily accessible and still continuing.
  • First data gathered by Rijkswaterstaat is accessible, which allows for analysis of the morphological data.

Study areas

Key study areas: Waal River (Netherlands)

Last modified: 10/06/2018

Main researcher

Timo de Ruijsscher

Supervisory team

dr. ir. Ton Hoitink


dr. ir. Bart Vermeulen


dr. ir. Erik Mosselman


Prof. dr. ir. Wim Uijttewaal


Contributing partners

Rijkswaterstaat Ministry of Infrastructure and Water Management


HKV Consultants

Royal HaskoningDHV

Witteveen+Bos Engineering and Consulting

Wageningen University & Research

Radboud University Nijmegen

Delft University of Technology

NWO Applied and Engineering Sciences

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Featured Outputs

Application of a line laser scanner for bed form tracking in a laboratory flume

08/03/2018 by Timo de Ruijsscher et al.

Contains: Data repository access Journal publication Modeling tool access

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Other outputs

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Conference abstract



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Conference proceedings




Symposium on River, Coastal and Estuarine Morphodynamics 2017 in Padova (Italy)

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News and Press

ITV Border Special Report: Living with the River

18/02/2016 by dr. ir. Ton Hoitink

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Fishing along the dam newsletter editions

01/12/2017 by Laura Verbrugge

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Project group
Project A

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Timo de Ruijsscher

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