I think the photos below explained or at least give you some idea why I mentioned before that one of the major reason of recent Sibu flood was caused by shallower riverbank.
Can you see how thick the sand precipitated at the riverbank? When low tide, this is what happened to the small boats. I guess these boats can only move away when the high tide come. Poor boats! Honestly, I never see such situation before where the boats were trapped on the shore.
As a conclusion, shallower Rejang river is a fact that nobody can deny. This is the main reason of frequent flooding in Sibu. Photos above only show a very minor part of precipitated sand in the river. In the mean while, abnormal low tide is something we may also need to pay attention to.