Establishing vegetated foreshores to increase dike safety along lake shores

Vegetated foreshores in front of existing dikes can contribute to the overall reduction of wave loads on the dike. In order to test this concept in large shallow lakes a field pilot was constructed along the Houtribdijk in Lake Markermeer (the Netherlands) in 2014 to gain experience with construction, stability, maintenance and governance aspects. A large scale monitoring programme was set up to follow the hydrodynamic forcing, morphological changes and vegetation development on the pilot. The pilot is located on an exposed south-westerly direction, and experiences substantial wave impact. As a result the desired vegetation on the land-water interface has not been able to establish, but a rather dynamic sandy beach is currently the main feature along the waterline of the site. Higher up the slope planted reeds, and a mixture of willows has well established itself in the first growing season. The exposed position of the location makes that hardly any natural pioneer vegetation has settled, only in small sheltered areas some annuals were able to germinate and maintain themselves

Establishing vegetated foreshores to increase dike safety along lake shores

Vegetated foreshores in front of existing dikes can contribute to the overall reduction of wave loads on the dike. In order to test this concept in large shallow lakes a field pilot was constructed along the Houtribdijk in Lake Markermeer (the Netherlands) in 2014 to gain experience with construction, stability, maintenance and governance aspects. A large scale monitoring programme was set up to follow the hydrodynamic forcing, morphological changes and vegetation development on the pilot. The pilot is located on an exposed south-westerly direction, and experiences substantial wave impact. As a result the desired vegetation on the land-water interface has not been able to establish, but a rather dynamic sandy beach is currently the main feature along the waterline of the site. Higher up the slope planted reeds, and a mixture of willows has well established itself in the first growing season. The exposed position of the location makes that hardly any natural pioneer vegetation has settled, only in small sheltered areas some annuals were able to germinate and maintain themselves

Measuring (Oblique) Wave Run-Up and Overtopping with Laser Scanners

Wave overtopping is commonly measured using overtopping tanks. In this paper, an alternative system is developed by using two laser scanners. It measures wave run-up, as well as layer thicknesses and front velocities, both during normally and obliquely incident waves on a dike in the field. The paper considers the first field validation tests with the system, with normal and oblique waves generated by the wave run-up simulator on a grass dike slope. Furthermore, a range of environmental conditions are simulated, to determine the robustness of the system. From the measured distance and reflection, the run-up is determined, which corresponds well to the observed run-up. From the data, the layer thickness and front velocity are determined as well. Layer thicknesses and front velocities are determined reliably with the laser scanners. Also, the (virtual) wave overtopping discharge can be calculated, which corresponds well with the most commonly used overtoppingequations.Hydraulic Structures and Flood RiskEnvironmental Fluid Mechanic

Proces-based modeling of the overflow induced growth of erosional channels

A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a noncohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally. The flow modeling is based on the shallow water equations. For modeling the channel growth, a set of closed equations describing the channel growth in both vertical and lateral direction has been derived in connection with several new morphologic parameters such as the representative channel width and the channel cross-sectional growth index. The approach has been applied to simulate the breach growth in sand-dikes and the morphological development of wave overwash across sand barriers. The computational results bear fairly good resemblance with existing experimental data.Hydraulic EngineeringCivil Engineering and Geoscience