Northeast of Waimea on the Big Island, the trek along Hamakua Ditch leads to an overlook above the Waipio Valley. The trail was cut through the forest to build the ditch.
To reach the trailhead from Waimea, head east on SR19 for 3.5 miles. Past milepost 54, turn left heading north on White Road (aka Linsey Road) to the gate at the end. Park here off the side of the road (limited parking). There are plenty of signs indicating private property. The county states this is a public right of way through Hawaiian Homelands, but the Homelands Dept says its private. Check the current status and be friendly.
From the trailhead, the first 1.75 miles follows the dirt road through the forest. After crossing the ditch, the road turns into trail. At about 2 miles in, you should come to the edge of the gorge looking down into Waipio Valley. There is a treacherous trail that follows the edge of the cliff for another mile or so.
For the best views, start hiking early. Also, winter months tend to be better than summer months.
Overall, Hamakua Ditch is the 24th most popular hiking trail of all 45 hikes in Hawaii.