The Waimanu Valley Trail is a strenuous 9-mile switchback trail. that climbs 1,200 ft to the top of ridge, then descends into the Waimanu Valley.
The views into Waipio Valley as you start up the trail (often called Z-Trail) are incredible.
Waimanu Valley is famed for much of the same kind of beauty as is Waipio Valley. Smaller Waimanu Valley was once well-populated and fertile, too. But Waimanu is now utterly uninhabited and wild. It’s preserved as the Waimanu National Estuarine Research Reserve.

Take this trip only during the “dry” season (roughly May through October) because of the large number of potentially dangerous stream crossings involved. Trail closures are frequent; check first. Even in the dry season, you must ford at least two good-sized streams on this trip: Wailoa Stream in Waipio Valley (nearly armpit-deep on me) and Waimanu Stream in Waimanu Valley (waist-deep on me). Be sure you and your backpack are prepared to get wet. Also be sure you have a rainproof tent: it will almost certainly rain at night in Waimanu.

Directions

N. side of Waipio Valley, roughly 100 yards inland from Waipio Beach.