A caveat’s necessary to throw out at the start of any description of this path—sometimes simply called the “Mohihi Trail”—and it has to do with access. The trailhead is at the end of the Mohihi-Camp 10 Road, which is safely driveable only by a 4WD vehicle and which can be treacherous or outright impassable even for such a rig during wet weather. Don’t risk it during rainy periods. The road’s about six miles long; you could hike it instead (being wary of vehicles), but obviously, you’ll tack on that mileage to the Mohihi Trail itself.
The trail begins by passing through a stand of sugi (an introduced Japanese conifer). At a quarter-mile, it crosses the Mohihi Stream. In dry conditions, this is an easy ford, but, as with most Kauai streams, rainfall can swell the Mohihi dangerously. You hopefully aren’t tackling the trail in really wet weather, given the challenges of the access road, but be aware of the potential for flash-flooding on the Mohihi if unexpected downpours occur.
From the Mohihi, the trail climbs up Kohua Ridge and follows it into the Alakai Wilderness Preserve. The Kohua is an important regional landform, forming the divide between the Mohihi and Koiae streams. The Mohihi is a tributary of the Poomau Stream. The Poomau and the Koiae are tributaries of the Waimea River and form part of the great gorge system of Waimea Canyon.
These streams drain some of the huge amounts of water that fall on Kauai’s Olokele Plateau below Mount Waialeale. The Alakai Swamp, Kauai’s most legendary wilderness, sits atop the Olokele Plateau. This vast “swamp” is really more a blend of the high-elevation jungle or cloud forest broken by open mucky bogs. The Kohua Ridge, which rises more than 4,000 feet high, descends westward from the Alakai Swamp, then turns southwest to its foot above where the Koiae Stream runs into the Waimea.
The Mohihi-Waialae Trail follows the spine of the Kohua Ridge, which in places is quite narrow. Watch your footing! You’ll enjoy nice views over the canyon of the Mohihi Stream to the north and the Koaie Canyon to the south. The lush vegetation includes both native and non-native trees and shrubs. Tangles of the native uluhe and uluhe lau nui ferns—some of the symbols of the Alakai jungle—are highlights.
Metal signs mark the miles along the Mohihi-Waialae Trail. At 2.25 miles, you’ll reach a rain gauge. Past this point, the path’s a bit rougher and more overgrown, so some hikers might opt to turn around here for a five-mile round-trip ramble.
The trail continues beyond the rain gauge and eventually descends (steeply) down to the Koaie Stream. This is Koaie Camp, your endpoint, and you can overnight here if you have the proper permit. (This is the only place where you can legally camp.)
This out-and-back hike is an adventure. Given the remoteness and challenges of negotiating a sometimes overgrown, confusing ridgetop path, only experienced hikers should tackle the Mohihi-Waialae Trail. You could also seek out a guided hike, which has historically been available through the local chapter of the Sierra Club. Either way, definitely stick to the trail and bring a map and compass (and GPS unit, if you’re so inclined)!
-If you’re hiking with a dog, keep it leashed, and be aware you may run into hunters with their own dogs on this trail.
-The Mohihi Trail actually continues beyond Koaie Camp, but it’s not officially maintained—hasn’t been since the Alakai was battered by Hurricane Iwa in 1982, which toppled countless trees in the jungle. We definitely recommend turning around at Koaie Camp (if you didn’t already turn back at the rain gauge partway there).