Hydrodynamics Sabang Bay and Its Influence on Near Shore Sediment Transport, Weh Island, Indonesia

Sabang Bay is one of the significant areas in Weh Island that becomes a center of marine tourism. Recently, massive urban development in coastal areas impacts on the increase of marine pollution and sedimentation issues within the bay. This study aimed to determine tidal current patterns and their influence on evoking sedimentation within the bay. An Acoustic Doppler Current Profiler (ADCP) was installed within the bay for 30 days, which recorded surface elevation, waves, and sea currents. The numerical hydrodynamic model was developed to figure tidal current features out, validated using field observation data. Sediment transport along the coast was determined by comparing the sediment transport and wave energy component in the form of flux equation. Tidal current speed ranging from 0-0.2 m/s moves predominantly southeastward and northwestward during flood and ebb tides, respectively. Significant wave height (Hs) ranges from 0.18-1 m with a period span of 3.5 seconds propagates toward within the bay, resulting in enhanced sedimentation within the gulf caused by the wave-induced scour and turbulence. Sediment budget transported within the bay reaches 1,586.18 m3/year proving that the sediment movement remarkably occurs within the bay wherein the concentration of suspended sediment ranges from 5-35 mg/L and 2-25 mg/L during the high tidal and low tidal conditions, respectively. Scour and turbulence events induced by internal solitary waves generated from the Andaman Sea result in increased coarse-sized sediment deposition when the flood tide occurs. While, during ebb tide, the widespread distribution of suspended sediment will occur over the bay.

Velocity Components of Currents and Transport Mechanism in the Ie Meulee Waters, Weh Island, Indonesia

Weh Island has become an area of significance in which many developments are ongoing. Ie Meulee region was one of the developed areas where a new fishing port has been built which may impact to coastal instability. This study aims to determine the sea currents regime in the Ie Meulee waters and its relation to the transport mechanism. Field survey was conducted on March 2017 by which Tide Gauge and ADCP have installed within and without the port, respectively. Flow model was also simulated depicting current patterns for four extreme tidal conditions. The elliptical form of zonal and meridional components of current proves that the tidal current role takes place. The speed of tidal current ranged from 0-0.42 m/s and 0-0.85 m/s in the bottom and surface, respectively. The most prominent positive value of current components indicates that the transport mechanism is primarily surface ward during both ebb and flood tides. Reflection and diffraction are identified in the simulation testifying that the emergence of the fishing port has changed the hydrodynamic features. We also founded that the low-speed currents induced sediment settling within the jetty, so that it is essential to conduct regular dredging and bathymetry survey in the surrounding port.

TENDENCY FOR CLIMATE-VARIABILITY-DRIVEN RISE IN SEA LEVEL DETECTED IN THE ALTIMETER ERA IN THE MARINE WATERS OF ACEH, INDONESIA

Long-term sea level rise (SLR) leads to increasing frequency in overtopping events resulting from polar ice liquefaction triggered by rising global temperatures. Aceh province is directly bordered by the Indian Ocean, and is subject to the influence of ocean–atmosphere interactions which have a role in triggering temperature and sea level anomalies. Elevated sea level is possibly caused by temperature-induced water mass redistributions. This study aimed to prove that the Indian Ocean Dipole (IOD) and El-Nino–Southern Oscillation (ENSO) had an influence on sea level change in Aceh waters over the six years 2009–2015. Sea level anomaly (SLA) was identified using Jason-2 satellite data for the 2009–2015 period, to enable the mathematical prediction of SLR rate for further years. We found that SLR was approximately 0.0095 mm/year with an upward trend during the six years of observation. Overall, negative mode of IOD and positive phase of ENSO tend to trigger anomalies of sea level at certain times, and have a stronger influence on increasing SLA and sea surface temperature anomaly (SSTA) which takes place in a ‘see-saw’ fashion. Over the period of observation, the strongest evidence of IOD-correlated SLA, ENSO-correlated SLA and SSTA-correlated SLA were identified in second transitional seasons, with more than 50% of R2 value. The upward trend in SLA is influenced by climatic factors that successively control ocean–atmosphere interactions in Aceh’s marine waters.

Kelayakan Kualitas Perairan Laut Banda Aceh untuk Biota Laut

Perairan pesisir Kota Banda Aceh memiliki potensi dan sumber daya di bidang perikanan, terutama di bidang perikanan tangkap dan perikanan budidaya. Untuk mendapatkan hasil yang maksimal dalam proses budidaya perikanan, maka diperlukan suatu kajian parameter kualitas perairan yang sangat berpengaruh terhadap kelangsungan biota laut. Penelitian ini mengkaji nilai kualitas perairan Kota Banda Aceh yang meliputi parameter fisika, kimia dan logam terlarut sebanyak  20 parameter di 13 lokasi stasiun pengambilan data. Analisis hasil pengukuran dilakukan di Balai Riset dan Stadardisasi Industri Kota Banda Aceh, Laboratorium Universitas Syiah Kuala dan secara in situ. Hasil pengujian terhadap parameter kualitas perairan akan dilakukan pengujian kelayakan untuk kehidupan biota laut menggunakan baku mutu air laut KepMen LH No.51 Tahun 2004. Analisa hasil pengujian menunjukkan bahwa perairan Kota Banda Aceh memiliki nilai fosfat dan nitrat yang tidak memenuhi ambang batas baku mutu di setiap stasiun pengambilan data. Nilai fosfat dan nitrat yang terlalu tinggi akan mengganggu dan mempengaruhi kehidupan biota laut. Untuk parameter suhu, TSS, lapisan minyak, pH, salinitas, DO, BOD5, amonia total, fosfat, nitrat, sulfida, surfaktan, minyak dan lemak, raksa, Cr6+, arsen, kadmium, tembaga, timbal, seng dan nikel masih dibawah ambang batas dan memenuhi baku mutu air laut untuk biota laut

Tidal Ellipses Analysis Based on Flow Model Hydrodynamic Data Acquisition in Mandeh Bay, West Sumatera

Mandeh Bay is threatened by sedimentation issue caused by the rapid development of marine tourism area which strongly impacts to the environmental degradation. Due to the semi-enclosed area of Mandeh Bay, the tidal current has a significant role in triggering vertical and horizontal transports within the bay. This study aimed to determine the characteristic of tidal current during the southwest monsoon. We developed a hydrodynamic model based on Navier-Stokes equations using a flexible mesh and tidal forecast in which the validation is performed by ADCP data. The simulation results will be used as the basic data to develop a model which depicts the elliptical pattern of tidal current constituents. Offshore rotary tidal currents which are originally semidiurnal reiterate the elliptical pattern every 6 hours and 12 minutes. The strongest semidiurnal current speeds are observed in the bay mouth ranged from 0.1-0.5 m.s-1. The tidal constituent ellipses are oriented more meridionally and in several areas oriented zonally. The current speed of  is the highest at all which the  speed is averagely one third of  magnitude. While, the two main diurnal tidal constituents ( and ) have the maximum speeds approximately one fifth of  magnitude. Thus, the domination of semidiurnal constituents may trigger sediment distribution and accumulation within the bay because of its twice tidal oscillations entering the bay

An Overview of Surface Water Quality Influenced by Suspended Solid Content in the Sayung Waters, Demak, Indonesia

Abrasion which is occurred in the Sayung coast is triggered by a big role of climate change as well as the sea level rise and land subsidence. Resulting degradation ultimately affects changes in existing environmental conditions. This study has aim to determine the existing water based on biological and chemical content which is affected by increasing suspended solid content in the Sayung waters. Purposive sampling technique was applied, and data is analyzed both statistically and spatially. Suspended solid value has ranged 23,1-199,6 mg/L. Distribution of suspended solid was only simulated during low tide towards high tide phase with current speed has ranged 0-0.41 m/s. We found that dissolved oxygen value is quite high in several observation stations which indicates the fertile area with low pollution and blooming tendency. In the station which is dominated by a high suspended solid and turbidity found that the chlorophyll-a decreases. The increased rate of suspended solid is directly enhancing the turbidity and indirectly declines the photosynthesis activity and inhibits the oxygen cycle. Resulting in the primary productivity reduction in the Sayung water