Results of the experimental study on the influence of the permeability of a spur dike on a scouring are presented in this paper. Experiments were carried out for impermeable and permeable spur dikes to compare several parameters influencing the flow and scouring. Surge flow was chosen for the experiments. This flow pattern exposed the effect of the permeability, as all the processes were characterized by greater intensity than in the stable flow conditions. Three dimensional velocities, water level, scour profile, as well as data of pressure pattern, excess pore water pressure, liquefaction and seepage force were measured and investigated. For each parameter, the influence of the permeability of the structure was recognized. The most important advantage of the permeable structure is to reduce the final scour depth.

The goal of study described in this paper is to develop the three dimensional analytical model to simulate a flow around a porous structures. The VOF method was used for the free surfacce flow field considering the future applicability to the rapid changes of the flow such as a surge flow. The flow in porous media was modeled by the Brinkman-Forchheimer extended Darcy's equation. As the experimental verification, three dimensional velocities around a spur dike were measured by using Acoustic-Doppler Velocimeter (ADV). The numerically obtained flow profile around a permeable spur dike was compared with the experimental results. It is confirmed that agreement between proposed numerical result and experiment is good under sub-critical flow condition. Some limitations according to mesh size and boundaries were exposed, nevertheless applicability of the model was proved. The present study enables the future simulation of rapidly varied flow around permeable hydraulic structures.

Detailed measurements of pressure and scouring depth were performed to improve understanding of the water flow and its influence on the riverbed around a spur dike. Two sets of hydraulic conditions and 20 measuring points located at the spur dike gave an image of how the pressure changes in time when a wave is passing around. The other factor tested was the delay of pressure change at several points on the spur dike structure. After passing the wave, the scouring depth was measured for each flow setup. Those measurements brought doubts in the assumption of the existence of a direct correlation between excess pore water pressure and the scouring of the area near the spur dike.