Original: By the next day, the river surpassed the 2008 flood peak level of 15.36 m/O. At the peak of the flooding, 80% of the town was flooded, the worst the town ever experienced.
Simplified: The next day, the river level rose above the 2008 flood peak level of 15.36 m/O. At the peak of the flooding, 80% of the town was flooded, the worst the town ever experienced.