Understanding the dynamics of sediment transport and erosion-deposition patterns in the locality of a coastal structure is vital to evaluating the performance of coastal structures and predicting the changes in coastal dynamics caused by a specific structure. The nearshore hydro-morphodynamic responses to coastal structures vary widely, as these responses are complex functions with numerous parameters, including structural design, sediment and wave dynamics, angle of approach, slope of the coast and the materials making up the beach and structures. This study investigated the sediment transport and erosion-deposition patterns in the locality of a detached low-crested breakwater protecting the cohesive shore of Carey Island, Malaysia. The data used for this study were collected from field measurements and secondary sources from 2014 to 2015. Sea-bed elevations were monitored every two months starting from December 2014 to October 2015, in order to quantify the sea-bed changes and investigate the erosion-deposition patterns of the cohesive sediment due to the existence of the breakwater. In addition, numerical modelling was also performed to understand the impacts of the breakwater on the nearshore hydrodynamics and investigate the dynamics of fine sediment transport around the breakwater structure. A coupled two-dimensional hydrodynamics-sediment transport model based on Reynolds averaged Navier-Stokes (RANS) equations and cell-centered finite volume method with flexible meshing approach was adopted for this study. Analysis of the results showed that the detached breakwater reduced both current speed and wave height behind the structure by an average of 0.12 m/s and 0.1 m, respectively. Also, the breakwater made it possible for trapped suspended sediment to settle in a sheltered area by approximately 8 cm in height near to the first main segment of the breakwater, from 1 year after its construction. The numerical results were in line with the field measurements, where sediment accumulations were concentrated in the landward area behind the breakwater. In particular, sediment accumulations were concentrated along the main segments of the breakwater structure during the Northeast (NE) season, while concentration near the first main segment of the breakwater were recorded during the Southwest (SW) season. The assessment illustrated that the depositional patterns were influenced strongly by the variations in seasonal hydrodynamic conditions, sediment type, sediment supply and the structural design. Detached breakwaters are rarely considered for cohesive shores; hence, this study provides new, significant benefits for engineers, scientists and coastal management authorities with regard to seasonal dynamic changes affected by a detached breakwater and its performance on a cohesive coast.

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The issues of freshwater pollutions and the high demand of clean freshwater for daily human activities have forced developing countries such as Malaysia to continuously monitor the quality of the freshwater. The present study objective is to present the trend of water quality status in the Kelantan River downstream, Peninsular Malaysia from 2005 to 2018. Water samples were collected during dry and monsoon seasons from a sampling station located at downstream of the Kelantan River. Water quality parameters such as temperature, pH and dissolved oxygen (DO) were measured in situ while other parameters were analysed in the laboratory based on retrieved water samples. Water quality status was determined based on National Water Quality Standard (NWQS) for River in Malaysia by calculating the water quality index (WQI) according to the concentration of six water quality parameters involving pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (TSS) and Ammonia Nitrogen (AN). The results showed that Kelantan River had good water quality during the dry season classified in Class II at 2005. The water quality was found to be slightly lower during the monsoon season in year 2006. In addition, increasing the number of construction, human activities in the land use areas, land use changes and the sewage water from domestic, industrial, wet market and food outlets in the Kelantan State have declined the water quality in Kelantan River from Class II (in 2005) to Class III (in 2010 and 2011) and to become Class IV in 2017 to 2018. The results of the present study are expected to give valuable information for the water managers in order to deal with better strategies in controlling the quality of freshwater at the Kelantan River and minimize the incidence of pollution-oriented problems, thus the water can be utilized for various water uses with appropriate quality.

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Tsunami yang didasari oleh kejadian gempa bumi dapat menyebabkan kerusakan yang serius untuk penduduk wilayah pesisir pantai, terutama yang berada dekat dengan pusat gempa. Merujuk pada kejadian tsunami yang terjadi pada tahun 2004, pemerintah mulai mencanangkan pentingnya mitigasi untuk melindungi daerah pesisir pantai. Daerah Pesisir Barat Lampung merupakan daerah yang berbatasan langsung dengan lempeng Eurasia. Hal ini dapat menjadi salah satu pemicu kemungkinan terjadinya gelombang tsunami pada Pesisir Barat Lampung. Tujuan dari penelitian ini yaitu untuk memperlihatkan potensi penjalaran gelombang tsunami di daerah Pesisir Barat Lampung. Simulasi yang dilakukan dalam kajian ini meliputi dua tahapan: 1) simulasi dari penjalaran gelombang gempa dengan menggunakan data gempa pada tahun 2019 (magnitudo 5,1 di area sekitar Pesisir Barat Lampung) dan dengan mengasumsi magnitudo gempa sebesar 6,0; 7,0 dan 8,0 (simulasi dilakukan dengan menggunakan metode deformasi), 2) Simulasi penjalaran gelombang tsunami dengan menggunakan TUNAMI Modified (beta version). Berdasarkan hasil simulasi, penjalaran gelombang tsunami dengan magnitudo 5,1 tidak mencapai garis pantai pada daerah Krui dan Bengkunat. Sedangkan untuk gempa dengan magnitudo 8,0 menghasilkan gelombang sebesar 1,14 meter pada garis pantai Bengkunat. Walaupun penjalaran gelombang pada gempa 5,1 tidak mencapai garis pantai, namun perlu adanya simulasi potensial penjalaran gelobang tsunami untuk magtitudo gempa yang lebih besar guna pengambilan keputusan dalam penentuan mitigasi bencana di daerah Pesisir Barat Lampung.