[k_sze]

Is intake into that discharge channel controlled?

Flash flooding is a thing. In Hong Kong, the Drainage Services Department puts up warnings and runs TV ads to tell people to stay clear of discharge channels, lest they get swept away by flash flooding during heavy rains.

So if intake into the discharge channel is not controlled, isn't it kinda dangerous to film there?

[thaeli]

The "temple" where filming is done is a secondary reservoir, it only receives water after the primary detention silos are full. So there is plenty of warning.