Flood inundation and shoreline erosion have long occurred in Sayung, Demak area, the northern coast of Central Java Province, Indonesia. The people of Sayung planted mangroves to reduce the flood inundation and shoreline erosion in that area. They built the bamboo array to protect the juvenile mangroves from incoming waves. The bamboo acts as a breakwater and is considered an environmentally friendly permeable structure to reduce wave energy and stimulate sedimentation. This paper discusses three bamboo arrays’ effectiveness in wave reduction using Numerical Wave Tank (NWT). The interaction of regular waves with a permeable structure comprising a single row of vertical circular poles was conducted based on the Smoothed Particle Hydrodynamics (SPH) method. The effect of different waves and structural dimensions on the permeable structure was investigated based on the structure’s transmission coefficient (Kt) performance. The investigations have revealed that structures with the combination of Vertical-Horizontal formation (VH) attenuate more wave energy than Vertical Only (VO) and the combination of Vertical-Diagonal formation (VD). As the wave steepness increases, the transmission coefficient decreases. Likewise, the transmission coefficient (Kt) is decreasing when the wave height is increasing. On the other hand, the transmission coefficient (Kt) increases as the wave period increases. As the structure spacing ratio between end-to-end and center-to-center spacing (e/S) rises, the transmission coefficient (Kt) also increases. The diameter (D) has a slight effect on the transmission coefficient (Kt). However, the center-to-center spacing (S) has a more significant impact than the diameter on the transmission coefficient, affecting an inclination on the transmission coefficient (Kt) when center-to-center spacing (S) goes up.

Artificial reefs are commonly used to rehabilitate natural coral reef damage. Artificial reef serves as a new habitat for marine life and simultaneously protect the shoreline by reducing wave energy without reducing the aesthetics of the protected beach. As an artificial reef can serve as submerged breakwaters, the level of their effectiveness in reducing incoming wave need to be investigated. The new form hexagonal shape artificial reef is proposed then evaluated based on the transmission coefficient. The tests for various configurations of a hexagonal reef in a 1:10 scale were conducted in the wave flume of Department Ocean Engineering, Institut Teknologi Sepuluh Nopember, Surabaya. The result of tests was presented and showed that the new proposed hexagonal shape artificial reefs have better performance compared to cylindrical and cubical shape artificial reefs.

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Bawean is a small island located around 80 miles north of Gresik, East Java Province, Indonesia. In the recent years, the island is renowned as a new destination for marine and coastal eco-tourism. Sustainable eco-tourism management in a small island is a very important concept not only for increasing income of local people but also in protecting the island itself from environmental degradation due to natural and anthropogenic factors. This paper discusses the methodology of mapping the hydro-oceanographic condition of Bawean Island. In this respect a methodology to analyze the suitability of the island and formulate strategies towards sustainable management of Bawean Island as a coastal eco-tourism destination will also be discussed.

The floating breakwater is a protective structure that can absorb waves and can be used effectively in coastal areas with moderate wave environmental conditions. The stability of the floating breakwater is affected by the tension of the mooring line and the weight of the anchor. This research was conducted experimentally with a model scale of 1:10 on a floating breakwater with mooring systems and concrete anchor blocks with three types of configurations. The experiment was carried out on irregular waves with the following variations: wave height and period, mooring angle, structure width, and anchor weight. The results of this study indicate that at a wave steepness of 0.02–0.025 floating breakwater, which is installed with a mooring angle of 45 deg, configuration 3 has the largest stability parameter among other configurations. However, if the structure is installed at a mooring angle of 90 deg and cross, configurations 2 and 3 have almost the same stability. The test results also show that the relative width will affect the stability parameters. Configuration 3 (B = 30 cm) has the largest stability-parameter value among other configurations (B = 10 cm and 20 cm).