Comparison of Grain-Size Profile and Depositional Process in Mandeh and Nyalo Bar, Mandeh Bay, West Sumatera, Indonesia

Abstract

Shipwreck of MV Boelongan Nederland situated in offshore of Mandeh Bay of West Sumatera is announced as potential area for tourism destination. Many studies were produced in term of its archeological and historical side but there is no significant work in sedimentological aspect. It is critical to understand depositional process of study area regarding the design of construction to minimize the impact of dynamic activity of waves within the area. Moreover, some areas along Mandeh Bay are covered by Cubadak Island as a protection for wave action derived from Indian Ocean that can produce more complexity in depositional process and will reflect to its characteristic of grain-size profiles. Utilizing thirteen sediment samples in two areas that correspond to inside (Mandeh Bar) and outside (Nyalo Bar) coverage of Cubadak Island, this study attempted to compare and contrast both grain-size profiles as well as interpretation of depositional process based on well-known analysis such as bivariate scatter plots, Linear Discriminant Function plot (LDF), Log probability curves and C-M diagram. Result of this study can be integrated by other researches to gain better policy in maintaining the shipwreck conservation. High energy of Indian Ocean wave supported by strong current clearly dominated depositional process in Nyalo Bar with coarser grain-size; good sortation, lower Y2 of LDF plot; extremely high population of traction materials and lower range of C-M. By contrast, presence of Cubadak Island disrupted the wave effectively and created lower and fluctuated energy in Mandeh Bar. This phenomenon was clearly depicted in its characteristic of finer grain-size with higher Y2 value; high abundance of saltation materials and greater ratio of C-M value.

Prediksi Akumulasi Sedimen Berdasarkan Survei Batimetri dan Hidrodinamika di Pesisir Teluk Mandeh, Kabupaten Pesisir Selatan, Sumatera Barat

“…Jumlah tersebut tersebar secara tidak merata pada kawasan perairan laut teluk mandeh sedangkan ketebalan sedimen rata-rata adalah sebesar 0.30 m dengan luasan penelitian sebesar 78,52 km 2 . Sebaran ketebalan sedimen tertinggi ada pada sisi sebelah utara dan sebelah selatan perairan teluk mandeh dengan ketebalan antara 0.7 sampai dengan >1.5 meter yang ditunjukkan dengan warna kuning hingga ke merah (Gambar 10), selain itu pada sisi sebelah utara terdapat muara sungai Mandeh dan Sungai Nyalo yang merupakan salah satu penyuplai sedimen paling besar yang berasal dari darat (Hidayat and Rozamuri, 2016).…”

Marine-Sediment Characteristics and Thickness Over The Eroded Sayung Coast, Demak, Indonesia

“…Coarse sediments reflect the strong currents influence and vice versa. This statement is espoused by (Hidayat & Rozamuri, 2016) that grain size is an indication of currents and waves strengths that work in the deposition environment.…”

Value estimating of the sedimentation rate at the shipwreck sites (MV Boelongan Nederland) the Mandeh Bay Region-Pesisir Selatan Regency

“…Several previous research related to sedimentation has not been done much. [12] analyzed granulometry in the Mandeh river and Nyalo river, which showed medium to coarse sand grain sizes. In addition, [13] simulate tidal currents and their effects on sediment distribution in the Mandeh bay region.…”