Round Trip Mileage: 16.2 miles
Elevation Gain: 7300 feet
Gear: If you choose to travel past Waipi’o Valley, you’ll be far from help. You need to bring enough gear to keep yourself and a partner alive in the rainforest, at least overnight. The hike is hot so shorts are a good idea that help with river crossings as well. I’d wear sturdy high-top boots for the entire hike because the trail is very steep and rocky. Bring extra water and food; you’ll underestimate the amount of effort this one takes. Treat all sources of water because there are agricultural pollutants entering the water from upstream.
Map: Topographical Map for Waimanu Valley
Overview: If you’re like me and you find Waipi’o Valley to be too developed and overused, and don’t like dealing with private property issues, Waimanu is for you. Literally translated, wai manu means “bird water” or “river of birds.” Located west of Waipi’o Valley along the windward side of Kohala mountain, this is one of the most difficult places to reach by foot on the Big Island. Indeed, many more people have viewed Waimanu Valley from a helicopter than on foot. Getting to Waimanu requires excellent fitness and above average routefinding. Most visitors camp at one of the permitted campsites in the valley, but it is possible to day hike out to Waimanu, despite what other sources tell you.
This is an extremely difficult day hike and should only be attempted the most fit and experienced outdoorspeople with a penchant for suffering and a self-masochistic streak. Take a look at the stats in the headline for this one: it’s more than sixteen miles and a vertical mile and a half. Those sixteen miles are mosquito-bitten, wet, steep, rocky, and unforgiving. You’ll need to cross one river where it meets the ocean and at least 13 other streams, all of which carry high flash flood danger and can become impassable at any time, stranding you. The trail has high rockfall danger and a fall in some spots could send you up to five hundred feet. Even splitting this hike up on a backpack is a very serious endeavor, requiring you to set a primitive camp in Waimanu valley.
Note that even doing a portion of this hike would be very rewarding. A challenging day is to start at Waipi’o and hike up and over the other side to view waterfalls and a part of the rainforest along the Muliwai Trail. If you choose to attempt any or all of this trail, especially if you try to go to Waimanu in a day, use these tips: start at dawn; choose a good day for high and low tide at Waipi’o river crossing; carry much more water than you think you need; set specific turn-around criteria and time; watch the weather and flash flood danger.
Getting to the Trailhead: From Honoka’a in the northern part of the island, take Hwy. 240 west to Kukuihaele. The road comes to a dead end at the Waipi’o Lookout. Parking can be difficult at the small parking area, and take care to park in an appropriate place if you park up the road. This is the trailhead for two-wheel drive vehicles, and is the place most tourists stop. There is a good overlook worth a stop near the parking area, although you can’t see much of the back of the valley. With a sturdy four-wheel drive vehicle and above average driving skill and nerve, you can drive down to the black sand beach. The road is narrow, impossibly steep (25% average grade), and rough. If you make it to the bottom in one piece, find an appropriate place to park and do not drive on the beach. A number of guiding services, shuttles, and horseback tours operate in Waipi’o and take visitors down to the valley floor.
The hike: The beginning of this hike takes you from the parking area for Waipi’o Valley and down the road for 0.7 mile into the valley. Follow the road toward the beach for a half mile, and proceed immediately to cross the stream. Cross the stream where it meets the ocean in the best place given current conditions. You can usually keep yourself pretty dry, but it’s deeper than it seems. After crossing the river, watch out for some yellow jackets that can burrow into the black sand. (I know it sounds crazy, but trust me). Look up at the cliffs in front of you and spot the big Z-like trail you’ll be on shortly. Continue to the opposite side of the black sand beach and look sharp for a faint trail that travels back from the beach into deep foliage. You’ll know you’re on the right trail if it shortly passes official state signs for the Muliwai trail. Check out any current warnings and persevere up 1300’ as the steep trail switches back several times in the sticky morning sun. This is probably the toughest part of the entire hike. One of these switchbacks has the best view of Hi’ilawe Falls, back across Waipi’o Valley (It's marked on the map above). After cresting the cliff into a cool Pacific pine rainforest, you’ll now need to cross about 13 different streams where you stay mostly 800’ – 1000’ above the ocean below, which you can rarely see. The Muliwai Trail gets less and less prominent as you continue toward Waimanu Valley, as it gains and loses elevation across the streams. Most stream crossings should be easy rock-hops, but always consider flash flood danger. A slip in many of these minor stream systems can produce a nasty fall. Eventually, you’ll reach your first vantage of Waimanu Valley. Be sure to take in every break in the rainforest as you descend into the magical valley: your best views of the waterfalls are actually from up here for perspective. The trail ends near the Waimanu Valley beach, where you’ll need to cross the Waimanu River to access the campsites and the other side of the valley. It‘s possible to explore further back into the valley off-trail, but the terrain is very overgrown.
If you’re heading back in a day, tonight’s forecast is going to be extended periods of pain. Repeat what you just did. The final road up to the parking area is especially hateful in the afternoon sun as you get passed by slack-jawed tourists in Jeeps.