Hidrodinamik dan pengangkutan sedimen di muara Lagun Salut Mengkabong, Kota Kinabalu, Sabah

Bobita Golam Ahad, (2007) Hidrodinamik dan pengangkutan sedimen di muara Lagun Salut Mengkabong, Kota Kinabalu, Sabah. Masters thesis, Universiti Malaysia Sabah.

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Abstract

This study covered the hydrodynamics and sedimentary processes at the tidal inlet of Salut-Mengkabong Lagoon, located in the west coast of Sabah, Malaysia. Field measurements were conducted under different tidal conditions and monsoons aimed at determining water current profiles, water flux, suspended sediment concentrations and sediment flux across the main inlet as well as the entrance of Salut and Mengkabong Lagoon. Morphodynamics of the main inlet are illustrated through interpretations of profile measurements and field observation on adjacent coastline. Field measurements for water current and suspended sediment concentration were conducted in September 2005 (southwest monsoon) and February 2006 (northeast monsoon) covering both the spring and neap tidal cycles. Water surface elevations were measured using Tidalite at each transect for the complete tidal cycles during which field data were taken. Velocity measurements were conducted using Aquadopp profiler at three horizontal sampling points of each transects for complete tidal cycles at two hours interval. Water samples for measuring the suspended sediment concentration were collected at all sampling locations corresponding to velocity measurements. Beach profile were measured, using TOPCON Series ATG6, at six transects on the adjacent coastline during southwest, northeast and inter-monsoon. The measured water currents revealed that the inlet of Salut-Mengkabong Lagoon is ebb dominated. The time-averaged velocities during the spring tidal measurements were found to be higher in the main inlet, followed by the Mengkabong and Salut entrance. Neap tidal currents were found to be steady compared to spring tidal currents. Suspended sediment concentrations were found to be higher in February 2006 (northeast monsoon) compared to that in September 2005 (southwest monsoon). Sediment flux during spring tidal cycles were found substantially higher compared to neap tidal cycles. Spring tidal measurements revealed that, ebb tidal fluxes were higher than flood tidal fluxes, leading to large ebb shoals. The February 2006 (northeast) neap tidal measurement showed higher sediment flux during flood tide. Beach profile measurements at Karambunai revealed net erosion in areas away from inlet. The net change of the profile close to the inlet was found too small, indicating that deposited materials were mostly washed out by littoral drift toward the inlet or by cross-shore transport. The profile at the throat of the inlet showed net erosion. Substantial dune erosion was observed at Karambunai beach especially in areas near the inlet. Dalit beach was found to be depositional due sediment bypassing from the updrift Karambunai beach. Due to longshore drift and ebb dominated tidal current, there were substantial depositions at the ocean side of the main inlet. Two ebb shoals were found at locations offshoreward from the inlet mouth, which developed due to the discharge of sediment by strong ebb currents, and transport of sediment by longshore current flows around the ebb shoals.

Item Type:Thesis (Masters)
Uncontrolled Keywords:hydrodynamic, sedimentary process, tidal inlet, water surface, TOPCON Series ATG6, net erosion
Subjects:G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions:SCHOOL > Borneo Marine Research Institute
ID Code:9243
Deposited By:IR Admin
Deposited On:30 Jun 2014 12:59
Last Modified:30 Jun 2014 12:59

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