Karakteristik Transformasi Pasang Surut di Delta Berau, Kalimantan Timur

Abstract

Karakteristik gelombang pasang surut akan mengalami transformasi ketika menjalar dari laut lepas ke perairan dangkal seperti pesisir pantai, estuari dan delta. Penelitian ini bertujuan untuk mengkaji transformasi elevasi pasang surut dari hilir ke hulu di Delta Berau meliputi komponen pasang surut utama semidiurnal dan diurnal (M2, S2_, K1, dan O1), serta komponen pasang surut perairan dangkal M4 dan MS4. Metode analisis harmonik pasang surut menggunakan program T-TIDE di empat lokasi titik pengamatan (Tanjung Redeb, Batu Batu, Semanting dan Muara Tumbuk). Data elevasi pasang surut yang digunakan merupakan hasil observasi data lapangan pada waktu pengukuran dari 31 Mei – 27 September 2007. Hasil penelitian diperoleh bahwa amplitudo elevasi pasang surut mengalami peredaman dari arah hilir menuju hulu delta, komponen pasang surut semidiurnal M2 dan S2 berkurang 25%. Amplitudo komponen pasang surut diurnal O1 dan K1 berkurang 22%, sedangkan amplitudo komponen pasang surut perairan dangkal (M4 dan MS4) bertambah 370% dan 220% dari hilir ke hulu delta. Ketidaksimetrisan pasang surut diperlihatkan dengan perbedaan durasi waktu ketika menuju pasang (4-5 jam) dan menuju surut (7-8 jam) di Tanjung Redeb. Rasio amplitudo M4 dan M2 (Ar) diperoleh nilainya bertambah dari hilir ke hulu, dengan rasio maksimum bernilai 0,1 di Tanjung Redeb.

The characteristics of tidal waves will transform when they propagate from the open sea to shallow water such as coast, estuary and delta. The present study aims to examine the tidal transformation from downstream to upstream in the Berau Delta, including the main tidal components of semidiurnal and diurnal (M2, S2, K1, and O1), as well as the tidal components of shallow waters M4 and MS4 are using the T-TIDE harmonic analysis method at 4 locations (Tanjung Redeb, Batu Batu, Semanting dan Muara Tumbuk). The tidal elevations were obtained from field observations in the period from May 31 to September 27, 2007. The results showed that the tidal elevation amplitude decreased from downstream to upstream of the delta, and the M2 and S2 semidiurnal tidal components decreased by 25%. The amplitude of diurnal tidal components O1 and K1 decreased by 22%, while the amplitude of shallow water tidal components (M4 and MS4) increased by 370% and 220% from downstream to upstream of the delta. Tidal asymmetry is indicated by the difference in the duration of high tides (4-5 hours) and low tides (7-8 hours) in Tanjung Redeb, and the difference in duration of high and low tides decreases (more symmetry) from upstream to downstream of the delta. The ratio of M2 and M4 amplitude shows that the value increases from downstream to upstream, with a maximum ratio of 0.1 in Tanjung Redeb.