Hmm. It appears to be artificial. The Wikipedia entry says "an artificial open channel" and 'Visit To Places Of Historic Interest In The Aberdeen Area Of Hong Kong Island' from 1967 (at https://www.jstor.org/stable/pdf/23890119.pdf) says:

"It was up this valley that Sir George Staunton, the eminent sinologue and Third Commissioner in the Amherst Embassy to Peking in 1816，strolled from the Aberdeen anchorage the following year to visit the village 一 in so doing to give his name to Staunton Creek now, 150 years later, being reclaimed from the sea."

I would not call that a river.

On the other hand, while researching the above I found that Lantau Island, Hong Kong at 147.16 km2 (56.82 sq mi) has the Tung Chung River.

Lantau Island - https://en.wikipedia.org/wiki/Lantau_Island

Tung Chung River - https://en.wikipedia.org/wiki/Tung_Chung_River

That's smaller than Suðuroy, and smaller than the "small island" of Rinca, making it seemingly a small island with a river.