During heavy rain, the park land (or river banks) that is integrated with the Kallang River at Bishan-Ang Mo Kio Park doubles up to channel rainwater downstream.
The public should move away from the river beyond the red markers when the warning lights and announcements are activated.
Backstory:
Yesterday, a concerned ASS reader wrote in expressing concern about the heavy ponding in Bishan Park.
https://www.allsingaporestuff.com/article/bishan-park-becomes-bishan-pond-after-once-50-years-flood