Deep inside the valleys on the north end of the Big Island of Hawaii exist tunnels through mountains, a surprising number of buildings, and a variety of other infrastructure. There are no roads or trails to these places, and the only reasonable access is by helicopter. But what are they for? How did it all get there? Why has no one else on the internet wrote about it? I made several multi-day backpacking trips to explore this remote, largely undocumented part of the island to discover its history and hidden infrastructure.
Hawaii’s Big Island is perhaps best known for its active volcanoes, beachside resorts, and world-class telescopes atop Mauna Kea. However, the north end of the island contains a series of deep, lush valleys. In ancient Hawaiian times, there were villages inside most of these valleys, and until the 1400s, many Hawaiian kings made Waipio (the largest and southernmost valley) their capital and residence. Today, Waipio is the only valley with any permanent residents--the other valleys have been abandoned, and the remnants of the old villages have mostly been overtaken by jungle, but traces can be found with some luck and searching. Paved roads end at the southern rim of Waipio and the northern rim of Pololu (the northernmost valley)--there is no vehicle access in between.
A full-island map with a box around the region containing the valleys.
A zoom to the boxed region of the previous map. I’ve labeled the valleys. The floors of Waipio and Pololu can be accessed by a short hike from their rims. It is possible to backpack from Waipio to Waimanu via a long, steep trail (I’ve done
this three times), but apart from this, there is no access to the middle valleys.
Given the lack of roads and trails in this area, I was shocked to discover a set of cabins over four miles up Honokane Nui Valley from the ocean while zooming around Google Earth one day. Considering how quickly the jungle overgrows everything, these looked to be in good condition. Someone had to be maintaining them.
The mystery cabins that caught my attention.
An overhead view of these cabins. There are no trails or anything else nearby! How did they get here? What are they for?
I did a Google search and found almost nothing. Some people sponsored by Black Diamond chartered a helicopter, flew to the cabins, and said they were for the Kohala Ditch. But that was a project 100 years ago, so why are the cabins still around and maintained? Some other guy mentioned that he hiked to the cabins but gave no details. I sent him an email asking for more information, and he didn’t respond...
I considered hiking to the cabins. Were they part of a huge, helicopter-supported marijuana growing operation? Were they some rich guy’s secret doomsday bug-out shelter? I did a search for information on hiking from Pololu, up the ridge on the other side, down into Honokane Nui, and then following the river up the valley to the cabins. I found this passage in a book:
A suicidal hike? You have my interest! (From The Rough Guide to Big Island of Hawaii by Greg Ward.)
I convinced Raiatea Arcuri to attempt the backpack with me, and we went for it during a 3-day weekend in early 2017. There used to be a trail from Pololu to Honokane Nui Valley, but it was destroyed by landslides during an earthquake in 2006. Since then, ropes have been tied to trees and there is a steep route down the cliff face. Our trip got off to a bad start when Raiatea and I promptly lost this route. We committed and just climbed the 500 vertical feet down into Honokane Nui, holding on to trees, brushing spiders and centipedes off ourselves, and constantly fighting with the extremely dense jungle. It took us hours to reach the valley floor, and we arrived barely in time for sunset. We camped on the Honokane Nui beach that night.
Off route, dropping down into Honokane Nui Valley, in one of the few sections where the jungle was sparse enough to see more than five feet.
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Sunrise on Honokane Nui beach.
After a brief jaunt through the spider-filled jungle to investigate Honokane Iki (the next valley over, and discussed in Section 4), we started following the Honokane Nui river upstream. It was a long hike. There were no smooth sections--just jumping from river rock to river rock. For the second half, due to the narrow valley and thick brush, the only place we could hike was in the water. How long can you jump from rock to rock, often in water, always covered in slippery moss, with a heavy backpack before you go completely insane? Fewer miles than the length of our route. How many spider webs can you take to the face before you resolve to never go outside again? I reached that point in the first quarter of the hike.
Only smiling because it’s the start of the hike.
When the only clear path is in the water, that’s the path we take.
Raiatea and I reached the cabins around sunset on day two of our three-day trip. The property had a new-looking fence around it to keep the wild pigs out. The cabins had clearly been painted in the last few years and there were fruit trees on the property. The cabins were locked, but we looked through the windows—the insides were spartan and covered in dust and mouse poop, so it seemed the cabins were not heavily used. We explored the area and saw no evidence of drug production. There was no sign of what the cabins were used for.
Sunset at the cabins. Note the huge cliff face on the left—there looked to be a trail switchbacking up this.
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The cabins had a gazeebo that was perfect for setting up our tent in—no rain fly was needed.
Looking down the valley the way we came in.
We couldn’t stop staring at the colossal cliff face up the valley from the cabins. The cliff face was 2500 feet (800 m) tall and appeared to be zigzagged with a trail. What kind of trail switchbacks up a cliff this big? It would be brutal on the legs but have amazing views. Even the "99 Switchbacks" of Mt. Whitney is only 1700 vertical feet.
Are those switchbacks on the lower part of this 2500-ft-vertical cliff?
On the morning of our last day of the trip, Raiatea and I split up to cover more ground. I walked down the valley and got completely soaked climbing the 70-degree, dew-covered valley wall to get an aerial view of the area. Raiatea hiked in the stream farther up into the valley.
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The area is really quite beautiful.
When he returned, Raiatea said he had made several discoveries. He found an old dam and pump house dated 1933. Farther up the valley, he found several more structures, a modern dam, and even a backhoe tractor. Whoever was using this area clearly had heavy-lift helicopter capabilities. But who was funding this? What was the purpose? We hiked out, even more confused than when we entered.
1933 dam and pump house.
1933 pump.
Modern dam and support building.
In the months that followed the initial hike, I started discovering the pieces to the puzzle of the development in the valley. I spoke to Andrew Cooper, who runs the always-interesting A Darker View blog and has expertise in a variety of areas. He pointed out that the Kohala Ditch still exists, and in fact you can kayak a section of it. He suggested that the buildings we found were used by the workers who maintain the ditch.
The Kohala Ditch was constructed in 1905-1906 to bring water to the sugarcane fields of the northern tip of the island. Sugar growing was the dominant industry of Hawaii at that time. Carol Wilcox writes in Sugar Water: Hawaii’s Plantation Ditches:
In the remainder of this section, I will describe the portion of the Kohala Ditch we explored in later trips, roughly from upstream to downstream. Multiple trips were made in order to access the different parts of it. These areas are all extremely remote, so I recommend you do not try to access them.
The Kohala Ditch begins in the vast wilderness between Honopue and Waimanu Valleys and collects the water flow of each canyon it crosses as it travels west. A tunnel carries the water partway down into Honokane Nui Valley and then ejects it partway down the cliff as a 900-ft waterfall. The trail to access the tunnels inside the cliff is visible from the cabins on the valley floor.
The horizontal lines on the 2,500-ft cliff are the Kohala Ditch, which enters from the left, and the trails for accessing it. I tried to get up
onto these trails to see their condition (and get aerial photos of the valley), but there was impenetrable jungle where my topo map showed they
reached the valley floor.
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After the water traverses down the cliff in tunnels, it erupts as a 900-ft waterfall and flows to the valley floor.
After reaching the valley floor and merging with the (quite substantial) natural Honokane Nui stream, the water flows to the dam area. The dam contains a mesh section that enables the water, but not debris, to drop into a pipe. A remotely operated valve (controlled by satellite data connection? radio from a transceiver on the valley rim?) controls the volume of water flowing into the pipe. During our explorations of the various parts of the ditch, on several occasions we noticed the flow rate changing suddenly--this is apparently where the changes occur. When the water is not diverted into the Kohala Ditch, it instead flows down Honokane Nui Valley until it reaches the ocean.
The stream flow falls through the mesh and enters a pipe here.
In the photo above, most of the stream is entering into the pipe and therefore continuing in the Kohala Ditch, as evidenced by the lack of
a waterfall on the right side of the dam. They change the flow rate regularly, perhaps increasing the flow for the kayaking tourists, but
decreasing it at night to reduce erosion? While we were sitting here, they reduced the flow into the Kohala ditch, thereby diverting it
over the waterfall in the photo below.
This dam is relatively modern, and there is no obvious pumping equipment--I believe the flow is entirely gravity-guided. In the early 1900s, the stream flowed somewhat farther down the valley, reached a different dam, and then was pumped (to where? We didn’t see old pipes), at some point rejoining the current path.
The dam and pump house dated 1933 are farther down the valley from the modern dam. These are no longer in use. I don’t know where they were pumping
the water to, how the water flowed prior to their construction (the Kohala Ditch began operation in 1906), or when the modern dam was built.
Just north of the cabins, Honokane Nui valley forks in two, and both valleys continue south. The cabins and the infrastructure described above are in the east fork. After the water enters the pipe at the modern dam, it flows through the ridge to the west fork. There, it crosses the valley in an elevated pipe, enters the valley wall, turns right (north), and flows in a tunnel just inside the valley wall for two miles. The original wood construction of the pipe is still visible, but it has been partially encased in modern metal in order to reduce its leakage.
Raiatea (center) provides scale as we head up the western fork of Honokane Nui.
The Kohala ditch crosses the western fork of Honokane Nui in an elevated pipe, then turns and proceeds down the valley in a tunnel just inside the
wall.
The century-old wooden pipe is visible inside the modern pipe.
We made a trip to the back of Pololu Valley to continue tracing the ditch’s path. I had heard that it is possible to enter a tunnel in Pololu Valley, walk through darkness for half a mile, and emerge on the other side of the valley wall in Honokane Nui. Reaching this entrance involved a horribly brutal bushwhack. The trail was carved out of the mountainside 110 years ago, but it has since been overgrown with trees and thorn bushes and destroyed by landslides and erosion. The brush was so thick that we needed to crawl in places, and our average pace was well under 1mph. We could rarely see more than five feet away due to the brush. I ran out of water at one point and was eating the wild apple guavas in order to stay hydrated...
We finally located the tunnel entrances in Pololu. What followed was a lot of wading through thigh-deep water in what would be a claustrophobe’s worst nightmare.
Ah yes, this hole seems inviting. Let’s wander into it.
This was one of the taller sections. The tunnel was clearly not built by six-foot-tall people.
Hiking the tunnel from Pololu to Honokane Nui. Note the light in the distance.
After passing through a few short tunnels on the Pololu side, we entered the main tunnel. It was perfectly straight, over half a mile long, and we could see the light of Honokane Nui on the other end. After walking against a strong current (the water was flowing quickly) for what felt like forever, the tunnel turned south (up Honokane Nui, where it eventually connects to the elevated pipe across the valley described above). The light we had been seeing was from a ventilation shaft—we decided to exit it. After slogging through knee-deep, man-eating clay, we crawled through a tiny hole in the mountainside and were greeted by an amazing scene: Honokane Nui Valley from 500 ft above the valley floor.
Looking into Honokane Nui after hiking through the dark tunnel for half an hour.
The ventilation hole in the cliff that we emerged from.
It was late in the day, so we didn’t follow the tunnel farther upstream; there likely would have been more ventilation holes with great views before the tunnel turned into the enclosed pipe across the west fork of Honokane Nui. We retraced our steps back into Pololu (walking with the current was much easier!), then continued to follow the ditch downstream. There was a small amount of open-air ditch, and then it entered another tunnel. We decided to follow this new tunnel.
A modern shelter for workers (above) and a very old structure (gauging station?) (below) in the short open-air run of the ditch between tunnels in
Pololu.
Another inviting hole in the mountain...
We entered this new tunnel apprehensively as night was setting in. We wandered through it in the darkness for a long time, trying to avoid the spiders, bats, and crayfish, and then finally emerged in amazement on the other side. A cabin, perched precariously on the valley wall, had been built directly over the ditch. A huge flume carried the water under the cabin and then across Pololu Valley.
The water flows from the bottom left, passes under the cabin, and then continues in the flume across the valley. The only flat spot was on the
porch, so this was our campsite for the night.
The water crosses Pololu Valley in this huge flume; the cabin is hidden in the brush on the left. The roof on the right prevents plants from
clogging the flume.
The cabin was a single room barely big enough for one person. The only access to it was through the tunnel—there were no discernable trails in the area. Most of the items inside the cabin were badly deteriorated, but we found some batteries with manufacture dates from the mid-2000s, so that's probably the last time someone came here. The cabin was so small that its purpose was unclear. At some point, a cantaloupe-sized rock had fallen off the cliff above it and hit the roof at high speed, causing significant damage through the initial impact and later rain intrusion. There was a set of boots and socks left hanging outside.
There wasn’t much inside the cabin, and most of it had badly deteriorated. Judging from the light, it evidently had electricity at one time.
At some point the cabin had been hit by a rock that fell off the cliff above it, and this caused major damage.
Yes, that’s a "For rent" sign in the window. There used to be a walkway across this side of the cabin, but it had rotted into oblivion.
After crossing Pololu Valley, the water entered a tunnel inside the valley wall and turned north. We did not continue following it; it eventually reemerges on the rim of Pololu before carrying the water to the kayaking tourists and farmers. The next section shows a geotagged map of the area and a lot more photos.
Do you have more information on these places? Email me at sean@sgphotos.com.
Here's a custom map I generated containing placemarks, GPS logs, and photos from the area. A full-screen version can be viewed here.
Second, an album containing the photos shown on this page and map (and a lot more!) can be viewed here.
I’ll discuss in this section some interesting things that didn’t really fit into the previous sections.
Most of the Hamakua Valleys used to contain extensive Hawaiian villages that stretched for miles from the beaches. These were weakened when the native population collapsed following Western contact and pretty much ceased to exist after the Kohala Ditch diverted their water supplies starting in 1905. They have been mostly overtaken by invasive plants. However, ruins of them can be found in Pololu, Honokane Nui, and Honokane Iki.
Ancient ruins in Pololu.
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Ruins in Honokane Iki.
Raiatea with an adze he found. We left it.
Honokane Iki contains the Sproat Cabin near the beach, which was built in 1917 by Bill Sproat, whose family was instrumental in the history of the Kohala Ditch.
The Sproat family cabin in Honokane Iki.
Beach camping at Honokane Iki.
There’s an abandoned cabin about 3/4 of a mile up the ridge between Pololu and Honokane Nui Valleys. I genuinely have no idea what its purpose was. It seems too modern to have been affiliated with the Kohala Ditch construction, and also it is nowhere near the ditch. I found plastic motor oil bottles on the ground near the cabin, so it was inhabited after those entered use (1960s?). I also found lots of weird metal rails on the ground on the hike up to the cabin.
The mystery cabin on the ridge between Pololu and Honokane Nui.
Rails? Some of these were 10 feet long. One or two were upright and had been pounded into the ground.
There’s also another cabin on the rim of Honopue Valley where the Kohala ditch enters the valley. There are no trails visible in the satellite view or on any map that I’ve found. If you know a feasible route to this cabin, shoot me an email.
Lastly, there were multiple irrigation ditches dug in the early 1900s; the Kohala Ditch discussed here was the largest and most ambitious. Remnants of the other ditches can be found if you search in the right places...
A map from Sugar Water: Hawaii’s Plantation Ditches showing the various ditches.
Irrigation ditch, or water slide? Why not both?
A dam and pump for one of the other ditches, also far from where normal people stop hiking. This was taken as the rain was starting to pour and shortly before I
got lost and hypothermic in a jungle swamp.
Flumin' Kohala: You can kayak a portion of the Kohala Ditch. These people maintain the infrastructure that I described here, so please support them.
January 1949 Boys Life (the official magazine of the Boy Scouts): It describes Honokane Nui Valley and the Kohala Ditch. Bill Sproat, the author’s guide, managed the Kohala Ditch and owned the cabin that sits at the beach in Honokane Iki Valley. The rest of this magazine is super interesting, too. Things were very different in the 1940s.
USGS topo map archive. Click the map and then it will display the files that are available. In case the link changes, I’ve archived the 1982 topo .pdf and .kmz files. The route of the Kohala Ditch is clearly marked. These old topos are invaluable when it comes to trying to locate trails that have been buried under 100 years of jungle growth.
The USGS photo essay documenting the 2006 earthquake damage is a treasure trove of great aerial photos. See pages 106-135 in particular. An alternative link is here.
Sugar Water: Hawaii’s Plantation Ditches by Carol Wilcox (1996) was my primary source for the history of the Kohala Ditch.
Beaches of the Big Island by John R. K. Clark (1985) has an interesting description on pages 150-151 of the history of Honokane Nui and Honokane Iki Valleys, and the Sproat family’s role in them.
Hawaii The Big Island Trailblazer by Jerry & Janine Sprout (2014) briefly discusses the trails southeast from Pololu Valley.
Inevitably I'm going to receive semi-unhinged, all-capitals, ungrammatical emails from someone who is apoplectic in rage at me for publicly revealing secrets about an undocumented part of this island. In order to pre-emptively reduce that a bit (this probably won't be successful), here's a disclaimer.
I wrote this page in order to document a little-known aspect of the Big Island’s land and history. I encourage you to respect this area. If too many people go into here, resources will get damaged and the land will be closed off to explorers. We left the cabins and structures alone, carried out our trash, and did not take anything. Additionally, there are a few other things you should consider before trying to hike here:TL;DR: be respectful of the land, don’t damage the Kohala Ditch infrastructure, don’t attempt these hikes unless you are confident in your abilities, and be prepared for things to go wrong.