Design of a pilot dike on Cat Hai Island

Master project report. On behalf of, and in cooperation with the TU Delft and the MARD-CWRCT two dike designs are made for a pilot project on Cat Hai Island. Two different types of revetments are used, namely the Dutch block type revetment Basalton and the classic rip-rap revetment. The designs are based on the available boundary conditions, the new Vietnamese guidelines and the Dutch knowledge. The focus points of the technical design are the geometry, the revetment, toe construction and the settlement. Compared to the current Vietnamese dikes, the design is revolutionary due to the presence of an outer berm. Besides the technical part of the design, the logistics and finance for the pilot project is explored. The different possibilities of producing, placing and transporting together with a time and cost estimations are given. In addition a proposal is given for the maintenance schedule and how to monitor the dike. Eventually two optimal dikes are further investigated, this height is based on zero overtopping and the most economical feasible. The crest heights of the old Vietnamese dikes on Cat Hai Island are around 4,80 m and it has a dike footprint width of 40,20 m. The crest height of the Basalton dike will be one meter higher than that of the rip-rap dike and the rip-rap will be one meter higher than then old dike. Because Baslaton has a larger wave runup than a rip-rap dike. Therefor the footprints of both the new Basalton and rip-rap dike are almost twice as large as the old footprint. The reason for this is because of the use of a berm in the outerslope for the Basalton dike. An estimation of the cost of this project is for a riprap dike, roughly 24 billion VND and for the Basalton dike more or less 21 billion VND.