On the predictability of the notional permeability of breakwaters as a function of core properties

To determine the nominal diameter of armour rock for a rubble mound breakwater, the ‘Van der Meer’-formula is frequently used. It requires the so-called 'notional permeability' parameter P, which has been defined for a limited number of structures. Often designed structures deviate from these defined lay-outs. To determine the notional permeability of these intermediate structures, various hypotheses have been proposed. In this thesis, the IH-2VOF numerical model is used to predict the notional permeability for a range of intermediate structures based on the various hypothesizes. The hypothesizes used are indirect methods based on the ‘hypothetical’ flow into the core and prediction of the reflection coefficient. Numerical simulation have been made for structures with varying core layer (thickness and nominal stone diameter) loaded by varying wave periods.Civil Engineering and GeosciencesHydraulic Engineerin

Project Hue: Report and field study on the water related problems and solutions in and around the Cau Hai lagoon and the Tu Hien inlet, Vietnam

The Tam Giang-Cau Hai lagoon system, lying in the Thua Thien-Hue province in central Vietnam, is affected by a tropical monsoon climate. This among others is the reason the Cau Hai Lagoon area has a long history of floods and other water related problems. Inhabitants are very dependent on the lagoon, as the main sources of income of people living in the region are fishing, agri- and aquaculture. The project goal has been formulated as follows: Finding an economic as well as technical feasible solution to reduce the water related problems, specifically navigability, salt intrusion and floods, in and around the Cau Hai Lagoon and the Tu Hien inlet and thereby improving the economic development of the region. Concerning flood risk, navigability and salt intrusion the inlet stability and size are important aspects. Using an echo sounder the bathymetry of the inlet has been measured. The measured size of the inlet was one of the input parameters for the hydraulic model that has been set up. This basic model of the Cau Hai basin system was made to test some alternative solutions for the Tu Hien inlet. The different solutions were simulated for five different scenarios. These scenarios include average dry season conditions, average wet season conditions and multiple extreme events. The output of the model for the different alternatives was used to rate the alternatives for a couple of criteria in a Multi Criteria Analysis. Other criteria of the MCA are qualitatively rated. The most promising alternative proved to be the one including a jetty at the northern side of the Tu Hien inlet in combination with a bank protection at the other side. In this way a large part of the littoral drift is blocked, enlarging the equilibrium cross-section of the inlet. This in turn results in a better flood evacuation capacity, navigability and water quality in the lagoon. For both mentioned elements a preliminary technical design is made, resulting in the stone class needed for the armour layers, dimensions of the toe and characteristics of the filter.Hydraulic EngineeringCivil Engineering and Geoscience