Estimation of Sediment Distribution Based on Bathymetry Alteration (2014-2016) in the Inner Bay of Ambon, Maluku, Indonesia

Abstract

The development of Ambon city is centered around Ambon Bay. As the major area of marine and social activities, changes occurred directly affect to the degraded of the bay water region. Sedimentation is the major issue that has been occurring. Marine ecosystem can be potentially disrupted by the high rate of sedimentation in the Inner Bay of Ambon (TAD). This study aims to determine the distribution of sediment volume within the bay. Bathymetry of TAD was surveyed by using transducer (Echosounder Echo track CVM Teledyne Odom Hydrographic Single Beam), which the depth of certain position was connected to GPS to record all the position data accurately. The field data are then analyzed spatially modelled in the form of 2D and 3D maps, overlaid with the past bathymetry data to calculate the difference between water depth and sediment volume during that period (2014-2016). The depth of TAD in 2014 ranged between 0 – -42 meters, whilst, in 2016 the water depth slightly changed to 0 – -44 meters. The reduction of the water depth is observed in the 25 – 125 m from shoreline, where the bed thickness alteration observed ranged from 0.1 - 1.4 m. Total volume of sediment augmentation reached 13,236,182 m3 that covers about 67.67 Ha. Tidal current speed ranged averagely from 0-1.2 m/s which has a tremendous influence on sediment transport in TAD. The bay mouth that is funnel-shaped enclosed area triggers a high transport mechanism on its surrounding. If ongoing, these conditions may endanger the environment and biota survival ability.