Rangsang Island is home to more than 48,000 residents. Climate change has been a critical issue to the Island and threatened the existence of the inhabitants. This study is proposed to identify the zone of the coastal area of Rangsang Island which is vulnerable to climate change. By mapping coastal vulnerability index (CVI) of the island, it is expected to be a reference of local government in planning their spatial management. The method of this study was by a direct survey for collecting data of geomorphology, beach elevation, sea level rise, tidal fluctuation, significant wave height, and changes in the coastline. To determine CVI, each parameter is divided into 5 categories and given a value level: 1 for very not vulnerable, 2 for not vulnerable, 3 for moderate, 4 for vulnerable, and 5 for very vulnerable. The results show that most villages on the island are classified as highly vulnerable to climate change, namely 9 villages. Even 2 villages are threatened very high risk because the village has CVI more than 12.5. Only 6 villages whose territory has moderate vulnerability index. Vulnerability level of coastal Rangsang Island is strongly influenced by geomorphological variable and coastal elevation. In addition, the variable coastline changes and sea level rise also contributed to the vulnerability index of the Island.

The Rupat Strait, a part of the Malacca Strait, is recognized as semi-closed waters and shows a high activity; thus, discovering the transport sediment mechanism of the strait as a consequence of ambient and anthropogenic forces is essential. Hydrodynamic and sediment transport modelling was constructed using the 2-Dimensional Explicit method which is averaged over depth. The results show that the dispersion of sediment at high tide is longer than that at low tide. This follows the hydrodynamic model in which current velocity at high tide is greater than the ocean current at the low tide. The previous sediment observation supports the results of transport sediment modelling, indicating that the anthropogenic factors are highly associated with the sedimentation in the Rupat strait

Siak river has a long history as a transportation lane in the east of Sumatera. From traditional to timber transportations are dependent on this river. Now the river is a severe suffering pollutant spill from many sources. Anthropological activities were higher contributions in the degradation of river environments. Many works were reported about pollution in Siak river. But how the distribution of model sediment transport in the mouth of the river is less to be explained. We consider hydrodynamics model of the mouth of Siak river for modeling the sediment distribution. This simulation gives a fundamental and clear understanding of how total solid sediment (TSS) distribution when flood and ebb tide happens. At ebb tide, TSS dispersion is higher than at flood tide. There is found that the sediment is concentrated in the plume of Siak river in Bengkalis strait. The composition of the sediment is dominated by organic matters.

The sediment transport model showing the sediment derived from the Mesjid River will be distributed to the Rupat Strait with different dispersion distances and concentrations depend on the tidal current pattern. The highest concentration of suspended sediment (0.0001 kg/m3 - 0.0013 kg/m3) can be found at a distance of 3.3 km from the Mesjid River Estuary toward the Rupat Strait. Meanwhile, at a distance of 3.5 km from the estuary, the concentration have returned to normal or there is no longer any sediment derived from the Mesjid River. However, at a distance of 2.8 km to 3.3 km, or at the coordinates 101,372 - 101,376 North Latitude and 1,744 to 1,750 East Longitude, sediment deposition occurs with concentrations ranging from 0.00027 kg/m3 to 0.00035 kg/m. Based on satellite images taken on August 2, 2006 and satellite images on January 5, 2020, sedimentation in the area has resulted in accretion with an area of ± 30,454 m2.

The coastal zone of West Rangsang is part of the Kepulauan Meranti regency, which directly faces Malacca Strait, which is one of the most crowded channels in the world. However, its shoreline is an open coast, which mostly undergoes local erosion as the defensive areas, encompassing coral rock and mangrove forest, are fragmented by nature and human exploitation. Therefore, this study aimed to investigate the relationship between the damaged coastline and the mangrove area changes in West Rangsang for the past 20 years. We propose a remote sensing method by satellite imagery to evaluate the coastline changes and the mangrove. Each year, the coastline positions were obtained using data processing involving geometric calibration, image cutting, and extraction. The changes were analyzed by inter-crossing the images of 1997 and 2017, further divided for four periods, i.e., 1997–2002, 2002–2007, 2007–2012, and 2012–2017. The results showed that varying erosion and accretion rates were due to shoreline exposure, strongly associated with the mangrove forests' devastation. However, this caused the physical function loss as an anchor against the coast's wear-out and as a breaker of waves and current approaching the island from the ocean. The stakeholder may use these research results to appropriate measures, such as replanting and creating mangrove-care societies, to conserve and maintain the coast.