Coastal Characteristic and Abrasion Hazard in Putri Island, Nongsa, Batam

Abstract

Putri Island, Nongsa is the outer and frontier island of NKRI region bordering Singapore. Its existence is very important both economically and politically. The management of Putri Island should consider the coastal characteristic that describes character and physical of the beach as the result of interaction between marine influence and coastal condition, geophysical and anthropogenic elements. The purposes of the study are mapping the coastal characteristics as an effort to manage frontier island and describing the abrasion hazard that occurred in this area. The study area is Putri Island, Nongsa. Field survey was conducted in May 2014. Coastal characteristic method wes conducted through geological observation, coastal morphology and coastline character. Bathymetry measurement conducted by echosounder, tidal observation by peilschaal and wind observation by a weather station. The study results show the type of tide is mixed predominantly semi diurnal. The dominant current direction is to the northeastern. The bathymetry conditions between Putri and Batam Island have a depth of up to 20 with a slope of 2.50 and towards the Singapore Strait has a depth of up to 70 m with a slope of > 100. Coastal characteristics of Putri Island is divided into 5 types, ie sandy beaches, mangroves, coral, rocky and cliff. Generally, sandy beaches, mangroves, rocky, rocky have flat morphology and consist of sand, mangroves, coral reefs, gravel and boulder. Low-cliff beaches consist of conglomerates of various materials that are not well consolidated. The abrasion hazard threatens the Putri Island, Nongsa, especially in the north-western part of the island. The abrasion of Putri Island should be managed and performed based on the coastal characteristics of the area.

Characteristic of Shallow Subsurface Quaternary Sediment in Nongsa Isle, Part of Putri Islands, Batam, Based on Georadar Data Interpretation

“…The characteristics of sediments formed in this facies are thought to have a coarse grain size. If correlated with previous studies, this facies is comparable to Conglomerate Various Material (Hernawan et al, 2018) as a part of Tanjungkerotang Formation (Tmpt) (Kusnama, 1994).…”

“…However, based on the results of the P3GL investigation (2005) showed that during the Pleistocene -Holocene (Quaternary), Putri Islands are composed of reef limestone and coarse to fine fragments of sediment. This indicates that during this Quaternary time there were evolution of depositional environment from fluviatil into marine (Hernawan et al, 2018).…”

“…If correlated with previous studies, this facies is comparable to Aluvium (Qa) (Kusnama, 1994) with depositional environment similar to the present condition, namely the coastal area. The beaches in this area are dominated by sandy beaches with relatively flat morphology (Hernawan et al, 2018). All of these patterns can be seen on Table 1.…”

“…The last unit as the youngest depositional facies (Unit 1), this unit is characterized by a continuous parallel with strong amplitude reflector pattern dominated. This unit is the same unit as the present condition, which is a sandy beach area (Hernawan et al, 2018) with very fine sand -fine sand sediment grain size. The deposition process that occurred from Unit 1 -3 illustrates the influence of sea level rise (transgression), causing a change in depositional facies from fluvial -coastal plain (Table 1).…”

“…The islands lie in the most northwest tip of Indonesia Archipelago, as the outermost land of Singapore. Its coastal line has been changed significantly (Geurhaneu and Susantoro, 2016), and it is prone to abrasion hazard (Hernawan et al 2018). As the outermost island, Putri Islands are need to be protected, both from natural hazards and anthropogenic impact.…”