North of Hilo and Honokaa on the Big Island, the scenic fruit laden Muliwai Trail is a 7 mile hike to the remote black sand beach of Waimamu Valley. Along the way, ascend the switchbacks up the valleys western wall. Pick lemon guava and avacados (best in summer). Stay overnight at the beach and explore the 800 feet Waiilikahi Falls, which is about an hours hike inland (the route is marked with surveryors tape). Expect to find wild pigs, wild horses and plenty of mosquitos. There are amazing waterfalls and pools to explore.
To reach the trailhead from Hilo, head north on SR40 for 49 miles to the Waipo Overlook. The trail starts about 1.5 miles down a steep dirt road (4WD required). At the bottom of the hill, turn right at the first dirt road. Follow this rutted dirt road to the beach and park.
Before starting, do not miss checking out Kaluahine Falls at the east end of the beach.
Head north on foot along the beach to the river. Cross the river to the northwest wall of the Waipio Valley on the beach. The trail starts here and heads up the valley floor . It passes a swamp and goes into the forest before starting switchbacks up 1350 feet. It goes up and down 14 gulches with 13 stream crossings. Around the 9th gulch, there is a shelter. From here the route generally heads down intto the Waimamu Valley.
This is a 2 or 3 day backpack trip. It takes roughly 10 hours to hike in.
Note: a permit is required for hiking and camping (808) 974-4221.
Here are some notes on adventuring in Hawaii. First, unlike mainland forests, the tropical island forests can grow very dense and can mask dropoffs. Plus, the trails can be very wet and slick most of the year (December to February is the main rainy season, but expect rain all year round). Stay on the trail to avoid disorientation. Second, speaking of disorientation, be aware that most Hawaiian topographic maps use the Old Hawaiian Datum. When trying to use the latitude/longitude from those maps with a GPS unit, you will think you are 0.4 miles south/southeast of where you really are. Kind of important in a dense jungle. Third, the bacteria Leptospirosis is found in the local waters and mud. It causes flu like symptoms within 2-20 days of contact, and can be fatal if not treated with antibiotics. Fourth, when hiking about, walking sticks can be very helpful for stablity in the slick conditions, for probing mud hole depths and clearing webs of the tiny crab spider.
Overall, Muliwai Trail / Waimanu Valley is the 11th most popular hiking trail of all 45 hikes in Hawaii.