Samenvatting

Gili Ketapang is a small island located in East Java, Indonesia. The island is currently experiencing environmental changes due to coastal erosion and the decline of its coral reef ecosystem. At the same time, the population is growing, and economic activities centred around fishing and tourism are expanding. This increases the pressure on the ecosystem, the island, and the community, making it challenging to maintain a quality of life and build resilience for the future.

This thesis research investigates the potential of artificial reefs as a protective measure for the coast of Gili Ketapang. The primary objective of this research is to evaluate the effectiveness of various artificial reef configurations, focusing on hexagonal reef models. The study aims to identify, based on six different artificial reef configurations, the model that achieves the highest reduction in wave energy and sediment transport, considering the current conditions of the island.

To achieve this, the research begins by defining the problems in Gili Ketapang and outlining the potential benefits that an artificial reef can offer the island. Comprehensive data is collected to create a bathymetry of the study area, providing essential information about the underwater topography, as well as data on tidal and wave characteristics for Gili Ketapang.
The core of the study involves conducting 63 hydrodynamic flume tank simulations using the software application DualSPHysics. These simulations are designed to recreate the interaction of waves with different reef configurations and scenarios. A total of seven different reef scenarios were modelled, including one that represents the current situation without an artificial reef, which serves as the baseline for comparison. Each reef scenario was subjected to nine different wave and tidal characteristics, allowing for an investigation of the performance of the reef configurations under various conditions. Therefore, it is essential to note that each simulation generated a wave from a single direction without incorporating other complex hydrodynamic factors.
The output of these simulations was subjected to data analysis based on particle velocity at a cross-section within the simulated environment. The wave energy and estimated sediment transport were calculated for each individual simulation using established formulas, with the primary goal of this analysis being to identify differences in these parameters compared to the original modelled situation without an artificial reef. This identified the most effective configurations for reducing wave impact and sediment transport.

Beyond the physical model, this research also included a literature-based review of the potential ecological and socio-economic benefits of artificial reefs for Gili Ketapang and its community. This involved reviewing existing literature and research to identify how artificial reefs can support marine life, fisheries, and tourism while considering potential challenges.
Finally, a multi-criteria analysis was conducted, focusing on the overall economic feasibility of each artificial reef configuration. With the aim of determining the most effective reef layout by weighing the potential economic resources against the reductions each configuration provides, thereby identifying its economic feasibility.