Lulumahu Falls was a once-forbidden 70ft waterfall sourced from the headwaters of Nuuanu Stream (near the Pali Lookout), where getting there wasn’t obvious.
The Jackass Ginger Pool is really more of a swimming hole than a waterfall attraction found by following the stream after deviating from the Judd Trail.
Likeke Falls is a pretty 30ft waterfall that was apparently the result of a broken ditch further upstream. So I guess you can say this waterfall isn’t natural.
Maunawili Falls is a small but popular 15-30ft waterfall and swim hole reached after a jungle hike with a few stream crossings that began in a residential area.