I have seen something like this before in Mandai Catchment. Very dense vegetation, but somehow it opens up at the stream. But sandy bed, not rocky like in your pic.. like nothing I've ever seen in Singapore.
I can give you the MGR if you need, but takes 2 hours of bashing through Primary Vegetation SW of Nee Soon Live Firing Range to get there.
upper thomson rd, turn into the road that leads to upper pierce reservoir park. the road will go downhill then uphill. about 100-150m from the entrance that u turn in, there is a drain that leads down to the reservoir.
most of the time, u can see rushing water (although the pipe can be switch off at times).
anglers call it the NEW ZEALAND RIVER, although its illegal to fish there.
i went to the HSBC treetop today. along the way from venus dr, there is a stream. the only thing is the water level not high and the flow is very slow. did not take any photo but i would think that after a rain fall, the water level should be height and fast enough for nice photo.