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River dune dynamics under high and low flows

Start: 1-2020
End: 12-2023
Status: Active

Contact details

Lieke Lokin

University of Twente

Outcome

A river dune development model that can predict the development of these dunes in the coming days and make prognoses for climate change

Fig 1: example of a dune wave

Motivation and Practical Challenge

River dunes can be seen as waves of sand moving over the river bed. Their size, e.g. height and length, and how fast they mover with the discharge. During high flows these waves are high and move fast. During low flow, their height becomes lower and they move slower. Adaptation from high to low flow also takes some time. When a low flow period follow shortly after a high flow period the dunes are relatively high compared to the water depth. At those moments the dunes can be seen as bumps for shipping. Which implies that shippers cannot take on their full load.

My goal is to better understand the dynamics of these river dunes such that we can predict what the bed will look like in the coming days and also to study the effects of changing discharge regimes on the dune development in light of climate change.

Research Challenge(s)

My research questions are

  1. How do height, length and shape of river dunes change during a flood wave and the following months based on measurements of the riverbed?
  2. How accurate can dune dynamics be modelled throughout the all possible discharges in a river, while limiting the computational load of the model?
  3. To what extend can the model predict dune development? How can the these predictions be improved by using the measured data of the river bed?
  4. What are effective measures in river systems to mitigate the effect of a changed discharge regime due to climate change on dune development to ensure navigability and high-water safety?

Innovative Components

  • I developed a fast method to extract river dune dimensions from bed measurements (based on wavelet analysis, https://github.com/LiekeLokin/DuneDataAnalysis)
  • We have studied dune dynamics over 10 years of biweekly bed measurements, we were therefore able to study dune dynamics also during low and median flows which was not done before
  • We will built further on an existing dune development model, to also implement low flow dune dynamics
  • In order to predict the bed development, I will study different ways to incorporate the data in the model to improve predictions for the future
  • Together with students I study the effect of human activity on the dune dynamics, e.g. shipping, dredging and river interventions

Relevant for whom and where?

Potential users of my research may be river managers to improve their management with respect to dune dynamics, dredging companies to better plan their dredging activities in the rivers, shipping companies because the model I develop can help them see where and when the lowest navigable depths can be expected.

Findings and practical application

In the first part of my research I studied the dune dynamics in the Waal River over 10 years. The most important finding is that the dunes become longer while they decrease in height. For example during high flows, deep water and high flow velocities, the dune height is 1 to 1.5 m while the dunes can be 50 m long. During extreme low flows their height is 0.5 m but the length increases up to 120 m.

 

Last modified: 27/09/2022

Contributing researchers

Lieke Lokin

University of Twente

Supervisory team

Dr. Jord Warmink

Prof. dr. S.J.M.H. Hulscher

User group

Project outputs

Modelling strategies for low flow dune behaviour

13/04/2022 by Lieke Lokin

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