Acquiring discharge estimates is crucial in hydrological studies, extreme event analyses, and water resources management. This study demonstrates the improved fluvial acoustic tomography system (FATS), a promising approach for automatically measuring streamflows with high temporal resolution for a long period. Unlike past hydroacoustic systems, the FATS enables continuous capture of the depth- and range-averaged water velocity with a single transducer set. Streamflow measurements were performed on November 26, 2015, in a mountainous river (depth: 0.8 m under low-flow conditions, width: 115 m). This paper presents a 127-day record of the flow. The average stream velocities and streamflows are automatically estimated from the acoustic data and water level data. The real-time flow data can be monitored by the Internet access. The continuous FATS estimates indicate that the streamflow does not change smoothly with the river stage. Analyses reveal that the streamflow may not be estimated accurately from a smooth rating curve (RC). The relative biases of RC reach $\sim \pm 20\%$ even under higher flow conditions. The FATS captures short-wave irregularities in the streamflow time-series.

This study investigates the tidal discharge division and phase difference at branches connected to a channel junction. The tidal discharge at three branches (eastern, western, and northern branches) was continuously collected using the fluvial acoustic tomography system (FATS). The discharge asymmetry index was used to quantify the flow division between two seaward branches (eastern and western branches). The cross-wavelet method was applied to calculate the phase difference between the tidal discharge and water level. The discharge asymmetry index shows that the inequality of flow division is obviously prominent during the spring tide duration, where the eastern branch has the capability to deliver greater amounts of subtidal discharge, approximately 55–63%, compared with the western branch. However, the equality of flow division between the eastern and western channels can be observed clearly during the neap tide period. The wavelet analysis shows that the phase difference at the western branch is higher than at the eastern branch, because the geometry of the western branch is more convergent than that of the eastern branch. Accordingly, the amplitude of the tidal wave at the western branch is more magnified compared with that at the eastern branch. Moreover, the phase difference at the northern branch is greater than at the two seaward branches, implying that the phase difference is slightly increased after passing through the junction into the northern branch.

Kota Pontianak terletak pada daerah dataran rendah, sehingga sangat rentan terhadap genangan banjir akibat air laut pasang. Tulisan ini bertujuan untuk memanfaatkan dan menganalisis data pasang surut untuk mengidentifikasi kenaikan muka air laut dan membakukan satuan muka air pasang surut. Data pasang surut jam-jaman diperleh dari diperoleh dari Stasiun Meteorologi Maritim Pontianak. Panjang data satu tahun diolah dengan metode analisa harmonik untuk mendapatkan konstanta pasang surut, untuk tahun 2016 dan 2020. Nilai konstanta tersebut akan digunakan untuk mengidentifikasi kenaikan muka air laut dengan cara menghitung tinggi muka air makimum, tinggi muka air rata-rata, dan tinggi muka air minimum. Untuk membakukan data elevasi muka air pasang surut, dilakukan konversi elevasi tinggi palm pasang surut menjadi satuan meter LWS dengan menggunakan waterpas untuk menghitung beda tinggi dengan elevasi lantai dermaga 01 Pelindo. Hasil analisis menunjukkan indikasi kenaikan muka air laut, dimana tinggi muka air laut rata-rata berubah dari 1.54 m LWS pada tahun 2016 menjadi 1.66 m LWS pada tahun 2020. Hasil nilai muka air maksimum adalah 2.6 m LWS dan hasil nilai muka air minimum adalah 0.93 m LWS. Beda tinggi antara elevasi puncak palm pasang surut dengan lantai dermaga menunjukkan perbedaan +0.810 m. Dengan demikian, elevasi puncak palm pasang surut setara dengan +3.0 m LWS, jika diukur dari lantai dermaga Pelindo.Kata Kunci: pasang surut, kenaikan muka air laut, mitigasi banjir, konversi elevasi palm.

This paper explores the dynamic interaction between tidal current and upstream discharge at the Kapuas River mouth. Long term time series data of tidal current and river discharge obtained from software Windwave 05 and hydrograph data, respectively. Three prominent parameters, i.e., river discharge, tides, and tidal current were analyzed using the wavelet method, Hilbert function, and low pass filter to evaluate the tidal characteristics and phase difference of M₂, M₄, K₁, O₁. The relationship between the tidal current and water level shows a mimic standing wave with the phase difference around ∼ -180 – 90⁰, indicating the tidal current leads the water level. The low-pass filter results indicate that the increasing river discharge hampers the tides and reduces the tidal current at the mouth. The Hilbert function result reveals the asymmetric tide and flood dominant flow which has the opposite direction with the seaward direction of the current. Moreover, the subtidal water level flows in a seaward direction. This happened because the net seaward current modulated by the river discharge. The currents at the mouth are affected significantly by the swell wave.