Numerical assessment of flushing time in Balikpapan Bay

Balikpapan Bay is a narrow bay waters and there are estuaries of rivers, as well as part of the Makassar Strait. One important factor in a bay is flushing time, which is the length of time a particle that enters a bay is released back into the open sea. The longer the flushing time in a bay, the more likely the bay will be polluted. If the rinsing time in a bay is fast, particles entering the bay will be quickly removed so the bay will tend to be clean. This study uses a numerical model to perform hydrodynamic and trajectory simulations in Balikpapan Bay, the hydrodynamic model used is the Regional Ocean Modeling System (ROMS) and the trajectory model is Opendrift. The simulation was carried out by releasing a number of particles at the mouth of the bay, and the simulation results showed that within 1 day the particles reached the farthest point, namely in the Kariangau area, then the particles tended to be stranded in Penajam. On the second day, all particles (100%) flowed and spread out to sea, up to the Makassar Strait. Balikpapan Bay flushing time based on numerical assessment is 70 hours.