Siltation Rate and Mechanism in the North Harbour of Incheon, Korea

The development of North Harbour was initiated at a macro-tidal flat within the Harbour Complex of Incheon, Korea in 1997. To maintain the design depth of -14 m below ALLW (Approximately Lowest Low Water) from the tidal flat of 2 m above LLW, dredging operation has been repeated over the last 13 years within the unbalanced (disequilibrium) North Harbour. In efforts to reduce the siltation within the harbour, this paper deals with the estimation of siltation rate and the determination of the mechanism for the siltation within the North Harbour. The siltation rate was estimated and then confirmed by the following three independent methods: comparison of available hydrographic survey data (smooth sheet), radioisotope analysis of gravity cores and altimeter measurement of bed level. The sedimentation rate varied from 20 cm/yr in the far end of the harbour to about 70 cm/yr at the entrance. In order to determine dominant mechanisms for siltation, two ADCPs and two CTDs were deployed at the entrance and the far end of the harbour over a month, and examined flow mechanisms for a harbour basin. The preliminary results suggest that the mechanisms include Suspended Particulate Material (SPM) exchange by horizontal entrainment through the harbour mouth and trapping of SPM in the harbour basin.