This difficult 2- to 3-day backpacking adventure -- only for the hardy -- takes you to a hidden valley some call Eden, with virgin waterfalls and pools and spectacular views. The trail, which goes from sea level to 1,350 feet and down to the sea again, takes more than 9 hours to hike in and more than 10 hours to hike out. Be prepared for clouds of bloodthirsty mosquitoes, and look out for wild pigs. If it's raining, forget it: You'll have 13 streams to cross before you reach the rim of Waimanu Valley, and rain means flash floods.
You must get permission to camp in Waimanu Valley from the Division of Forestry and Wildlife, P.O. Box 4849, Hilo, HI 96720-0849 (tel. 808/974-4221). Permits to the nine designated campsites are assigned by number. They're free, but you're limited to a 7-day stay. Facilities are limited to two composting pit toilets. The best water in the valley is from the stream on the western wall, a 15-minute walk up a trail from the beach. All water must be treated before drinking. The water from the Waimanu Stream drains from a swamp, so skip it. Be sure to pack out what you take in.
To get to the trail head, take Highway 19 to the turnoff for Honokaa; drive 9 1/2 miles to the Waipio Valley Lookout. Unless you have four-wheel-drive, this is where your hike begins. Walk down the road and wade the Wailoa Stream; then cross the beach and go to the northwest wall. The trail starts here and goes up the valley floor, past a swamp, and into a forest before beginning a series of switchbacks that parallel the coastline. These switchbacks go up and down about 14 gulches. At the ninth gulch, about two-thirds of the way along the trail, is a shelter. After the shelter, the trail descends into Waimanu Valley, which looks like a smaller version of Waipio Valley but without a sign of human intrusion.
