Tidal impacts on the discharge division and freshwater transport in the Berau Delta, East Kalimantan, Indonesia

Abstract

Flow division at bifurcations is important in controlling material carried from the terrestrial to the coastal zone in tidally influenced deltas. The present study aims to identify the impacts of tides on flow division and freshwater transport in the Berau Delta, East Kalimantan. The Princeton Ocean Model (POM) is applied to simulate the hydrodynamics with forcing from river discharges and tides. Tides at open seas and observed river discharge at upstream locations were used to set model boundaries. Model validation was accomplished by comparing measurements of tidal elevation and salinity time series with model results. The model results reproduce the observed in temporal variations of tidal elevation and salinity. Model results highlight that the tidal amplitude has large influence on discharge division at the tidal junction. Tides enhance equal subtidal flow distribution in the river junctions, with the influence of tide is 15% on subtidal flow distribution in the bifurcations. Freshwater discharge at the Berau Delta flows mainly to the north and middle outlet with 90% of the total discharge. Based on an analysis model results, the decomposition of freshwater transport reveals that advection and tidal pumping are major factor, which are fluctuate in fortnight cycle.