Miri River is the body of water that splits Miri Peninsula and the mainland Miri, flowing out to sea from inland, curving at Lutong Town. In one particularly popular but inaccurate online map service, the river is incorrectly marked as Sungai Baong. Others references online have confused it with Baram River.
The old Piasau bridge was a Bailey bridge at Piasau linking from the peninsular to Piasau at the point closest to the sea. The bridge, originally made of steel and wood with a single lane to handle the occasional vehicle traffic crossing, has seen several upgrades over the years.
In late December 1980, the weather had been relentless on Mirians and Lutongites. Strong winds, torrential rain, and heavy swells in the seas were incessant, the constant heavy rains causing water from the Miri River to burst its banks and flow into Lutong.