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.

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.

SIMULASI NUMERIK GELOMBANG (SPECTRAL WAVES) DAN BENCANA ROB MENGGUNAKAN FLEXIBLE MESH DAN DATA ELEVATION MODEL DI PERAIRAN KECAMATAN SAYUNG, DEMAK

Pesisir Kecamatan Sayung merupakan wilayah abrasi di Kabupaten Demak yang terkena dampak paling parah dari kenaikan muka air laut. Tujuan penelitian ini untuk mengetahui dinamika gelombang yang terjadi pada setiap kondisi pasang surut dan pengaruhnya terhadap rob serta overtopping yang terjadi. Metode penelitian adalah deskriptif kuantitatif menggunakan persamaan numerik, simulasi MIKE 21 dan model elevasi ArcGis. Hs tahun 2016 pada pasang purnama 0,015 – 0,359 m dan pada surut purnama 0,009 – 0,358 m. Hasil pengolahan data menunjukkan ada perbedaan yang drastis genangan yang terjadi pada saat pasang dan surut. Luas area model genangan rob pada tahun 2016 sebesar 7200,36 Ha. Untuk jarak terjauh genangan rob dari garis pantai pada tahun 2016 sejauh 10826,7 m. Terdapat peningkatan tinggi gelombang termasuk kondisi pasut purnama dan perbani tiap tahunnya. Hal ini menunjukkan abrasi terjadi di pengaruhi oleh kikisan gelombang yang terjadi secara terus-menerus. Kenaikan muka air laut yang terjadi setiap tahunnya berbanding terbalik dengan luas genangan yang dihasilkan, sehingga perlu dilakukan tindakan yang preventif pada proses tata kelola ruang pesisir.  Kata kunci: model elevasi, gelombang, model numerik, banjir rob, SayungNUMERICAL SIMULATION OF SPECTRAL WAVES AND ROB DISASTER USING FLEXIBLE MESH AND DATA ELEVATION MODEL IN WATERS OF SAYUNG DISTRICT, DEMAKCoastline area in subdistrict Sayung is an abrasion area in Demak which has the worst affected of sea level rise. The purpose of this study to determine the wave dynamics that occur in any tidal conditions and their effects on tidal flood and overtopping happened. The research method is quantitative descriptive using numerical equations, MIKE 21 simulation and ArcGIS elevation models. Hs 2016 on a tide 0.015 to 0.359 m and in full retroactively from 0.009 to 0.358 m. The results of data processing showed no drastic difference puddle that occur at high tide and low tide. The area of tidal inundation model in 2016 amounted to 7200.36 Ha. To the farthest distance from the shoreline tidal inundation in 2016 with a distance of 10826.7 m. There are an increasing wave heights including a full moon and neap tide conditions each year. This shows abrasion occurs is influenced by the piling up of waves that occur continuously. Sea level rise that occurs annually is inversely proportional to the resulting inundation area, so we need a preventive action on the processes of governance of coastal areas. Keywords: elevation models, waves, numerical models, tidal flood, Sayun

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

The Coherency and Correlation between Sea Surface Temperature and Wind Velocity in Malacca Strait: Cross Wavelet Transform and Wavelet Coherency Application

This study tried to observe the correlation and coherency between sea surface temperature (SST) and wind velocity in the Malacca Strait at the year of 2015. The SST and wind velocity data with 6 hours interval step have been used in this study. S-Transform, the Cross Wavelet Transform, and the Wavelet Coherency were applied to observe the influence of the variation of sea surface temperature to the wind velocity in Malacca Strait. These methods could produce the phase lag and the time of occurrence between them. S-Transform was used to show the spectrum energy of the sea surface temperature variation. The strongest correlation between them has the period of 32 days during July to August and October to November at each point with significance level of 95 %. The coherency of them has the range of 4 to 64 days at each point. The last result is the spectrum energy of SST variation that has the period of 5 to 50 days at each point. It was similar to the result of the correlation and coherence period between the wind velocity and the SST dat

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

ANALISIS JULAT PASANG SURUT (TIDAL RANGE) DAN PENGARUHNYA TERHADAP SEBARAN TOTAL SEDIMEN TERSUSPENSI (TSS) DI PERAIRAN TELUK PARE

ANALYSIS OF TIDAL RANGE AND ITS EFFECT ON DISTRIBUTION OF TOTAL SUSPENDED SOLID (TSS) IN THE PARE BAY WATERSPare Bay conditions is closely related to the mechanism of circulation in Makasar Strait. One of the problems that occur in Pare Bay waters is increased turbidity and low dynamics of transport inside the bay, which caused silting in some parts of the bay. The aim of this study was to determine tidal range characteristics and the influence of suspended sediment distribution as analysis of the sedimentation process and siltation at Pare bay. Descriptive quantitative method was used and the survey location was based on purposive sampling method. Tidal type in Pare Bay water was mix mainly semidiurnal tides with Formzahl Value was 0.895. The value of the water level below the lowest tide (Z0) was 1036.44 cm. Mean sea level (MSL) value was 1107.97 cm. The vertical datum of MHHWS and MLLWS were 1143.47 cm and 1072.47 cm. Tidal range cycle in spring condition was 102-129,56 cm bigger than cycle in neap condition ranged from 55.53-82.47 cm. TSS concentrations ranged from 0-7.0 mg/L in the surface and ranged from 0- 10.0 mg/L in 5 meters depth. At high tide down, sediment was settling and at the time of high tide, sediment mixed back.Keywords: Pare Bay, suspended solid, tidal range, tide.ABSTRAKKondisi perairan di Teluk Pare sangat berkaitan dengan mekanisme sirkulasi di Selat Makasar, Permasalahan yang terjadi di Teluk Pare salah satunya adalah tingginya tingkat kekeruhan dan rendahnya dinamika transport didalam teluk yang menyebabkan pendangkalan di beberapa bagian teluk. Tujuan dari penelitian ini adalah mengetahui karakteristik julat pasang surut dan pengaruhnya terhadap sebaran sedimen tersuspensi sebagai analisis proses sedimentasi dan pendangkalan di perairan Teluk Pare. Metode penelitian yang digunakan adalah deskriptif kuantitatif, metode penentuan lokasi titik pengambilan sampel air yaitu metode purposive sampling. Tipe pasang surut Teluk Pare adalah campuran condong harian ganda dengan nilai bilangan formzahl sebesar 0,895. Nilai muka air dibawah surut terendah (Z0)  sebesar 1036,44 cm. Nilai mean sea level (MSL) sebesar 1107,97 cm. Datum vertikal MHHWS dan MLLWS memiliki nilai 1143, 47 cm dan 1072,47 cm. Julat pasang (tidal range) siklusan saat siklus pasang purnama yaitu 102–129,56 cm lebih besar daripada siklus pasang perbani yang berkisar 55,53-82,47 cm. Konsentrasi TSS berkisar antara 0-7,0 mg/L pada permukaan dan berkisar antara 0–10 mg/L pada kedalaman 5 meter, pada saat pasang turun sedimen sudah mulai mengendap dan pada saat pasang naik sedimen teraduk kembali.Kata kunci: julat pasang, pasang surut, sedimen tersuspensi, Teluk Pare