Tree-Planting for Damping Waves and Flood Control

With more than half the country below sea level, the Netherlands controls rivers and the sea through a network of dikes while allowing the water room to expand when needed. Dutch research institution Deltares has started an experiment with a different method of flood protection, using willow trees to break waves, limiting the damage water can do to the surrounding environment.

Delta Flume

The Delta Flume in action during a test using willows to break waves

The Netherlands is world-famous for its innovative flood risk management solutions. Considering the challenges of climate change and a growing world population, keeping coastal-and riverside-areas safe has become an important issue.

Conflicts in nature conservation and flood risk management exist, for instance, when trees along the river are cut for aesthetic reasons instead of being preserved for use in floodwater risk management. Trees play a critical role in reducing coastal and soil erosion by breaking waves and maintaining soil structures.

To learn more about how trees can break waves and protect nature and people, researchers from Deltares started to batter 32 willow trees with 4 meter high waves. All in a controlled environment of course. They used the world’s largest artificial wave machine – or flume - as their tool. The Delta Flume is 300 meters long, 5 meters wide and 9 meters deep and used to simulate waves. The wave machine is also great for surfing.

Several types of trials and trees

The research will contain several types of trials – without trees, with trees; willow trees, with and without leaves, and finally a test with thinned crowned trees. The goal is to determine the role of trees, leaves and branches in dampening waves.

Willow trees are used for this research test because this type of tree can be readily found in most of the Netherlands. The species grow well if planted on the slope of a levee.

However, the aim is to conduct similar tests with mangrove trees. Mangrove trees are common in (sub)tropical climates. By running these experiments, the Dutch can share knowledge with countries where this type of tree is indigenous.

The tests will last for 12 days and will be followed by a data analysis phase.

Crowdfunding

Although institutions like Deltares, Delft Technical University, NIOZ, Boskalis, Van Oord and Rijkswaterstaat are associated with the project – there is still need for more financial funds, €50,000 to be exact. The organizers try to involve the general public and raise the remainder of the financial needs through crowdfunding.