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  • Thomas Upton

Hiking to the top of Kohala via the Koai'a Corridor

Updated: Feb 2

A challenging Big Island hike I’ve been wanting to try for some time is the Koai’a Corridor trail which provides access to the top of the Kohala Volcano.


Koai'a Corridor, Mauna Loa, Hualalai and South Kohala Coast
Looking down the Koai'a Corridor trail with Mauna Loa and the South Kohala coast in the distance


Kohala is the oldest volcano on the island and is long extinct. The east side of the volcano is devoted almost totally to the Pu’u O Umi Wilderness area, a steep-sided series of canyons formed long ago by a giant landslide and eroded since into the lush valleys we see today. Reaching the summit of Kohala from this side would be difficult, if not impossible, for average hikers like me. The west side slopes more gently upward from the ocean across cattle ranches and many pu’us. Virtually all of this land is privately owned and access is not permitted. There is a public access route through this land however, called the Koai'a Corridor, which enables hikers to reach the Kohala summit with "relative" ease.


The Koai’a Corridor itself is a narrow strip of land on the west side that has been set aside for public access to the upper reaches of Kohala.


Mauna Loa, and Kohala slopes from Koai'a Corridor
Looking south from the Koai'a trail

It is stewarded today by the Kohala Watershed Partnership. It can be reached via the Kohala Mountain Road (State Highway 250, about 3.2 miles north of the junction with Kawaihae Road near Waimea) and begins right next to the Koai’a Tree Sanctuary, which you can read about here. Access to the corridor is via an unlocked but chained gate that opens to a 4WD track. This track leads straight up the hill to a parking area at the top of the corridor. The track is rough in spots but after about 1/3 mile or so, it transitions to a less-travelled, and therefore smoother track. We stopped our jeep just before a few ugly looking bumps at the 1/3 mile mark (partly at my urging), but it became clear as we walked from here (and spoke to others on the trail ) that you can drive all the way up to the top of the pasture.


The hike to the summit is in two parts. The Koai’a Corridor first climbs 1.7 miles through the pasture and provides entry into a rainforest at the top. You can drive or hike this portion as noted above. To reach the summit, a trek of an additional ~ ~0.7 miles through the rainforest is required. Overall elevation gain over the 2.4 miles is ~2300 feet.


We came to hike the whole route, and started up the track from our vehicle. Weather is an important factor, especially for the Corridor portion of the hike. The wind frequently comes straight down the mountain and can be so strong as to make progress difficult. We abandoned a previous attempt up the hill after more than an hour of being beaten up by these winds. Rain is also likely as the day wears on, especially in the rainforest. So, my strong recommendation is to start early on a day where the mountain is clear of clouds and hope for the best.


The pasture portion of the hike gains 1480 feet of elevation over it’s 1.7 miles. In most places, where such a trail would have switchbacks to ease the climb, this wouldn’t be a big deal. Here you are going straight up the hill over grades that vary in steepness. Be aware that the steepest are near the top. It's not difficult, but you will feel it. This part of the hike is well-documented on hiking websites. The good news is that the views looking down the hill behind you are stupendous, so stop and enjoy them along the way. Here are some examples:


View from the Koai'a Corridor on Kohala volcano
My hiking partners David and Sara pause on the trail


Clouds linger over Kohala and the Koai'a Corridor
Pretty common to be above the clouds when this far up the Koai'a Corridor trail


Kohala ranch land north of Koai'a Corridor
Private ranchland to the north of the corridor

These views are the reason I initially wanted to make this hike.


At the top of the pasture you will encounter a fenced area and a red gate. It will be obvious that you are entering a forested area. What’s in this rainforest is not well documented. You can find some good hiking accounts like the ones here or here, and most all refer to the trail within the forest as being poorly marked by blue flags (blue plastic tape tied to trees) once in the rainforest. Getting lost is said to be pretty easy. We chatted with a few hikers on the way up. One person said, “I walk the corridor all the time but I never go in the rainforest. My dogs would go crazy chasing pigs and disappear”. Another said, "I only went in once and it’s gnarly in there!”. Great!


So here is the red gate at the top of the treeless grassy corridor, as captured in another hiker's good account.

















Looking back down the hill from in front of the gate provides this view:

Clouds on slopes of Kohala on the Big Island
Looking straight down the hill towards Kawaihae

And here is what you see immediately inside the red gate:


Rainforest view near Kohala summit
Looking into the rainforest from the red gate

Quite a difference! I’ve hiked rainforests all over the islands and this one is very dense! It is strange to go from wide-open pasture to dense rainforest in the space of a few feet. And yes, there are blue flags! And pink ones, and orange ones…


My hiking partners, David and Sara, are very experienced. David took the challenge of trying to follow the poorly marked trail through the forest. You can follow the flags, but like David, you will need to be able to determine which path is yours (via GPS and good tracking skills) when the blue flags are far apart. The various colored flags are supposedly the work of local hunters who may well be in the forest with you. Fortunately, we encountered no one with weapons. David tracked our path in and out via GPS and you can find his report here on Alltrails.com. With his permission, I reproduce his map here:


GPS map of the Kohala Corridor hike
GPS track for the entire hike to the Kohala "summit"

I haven't seen very many published GPS tracks through the forest, so please use his if you go.


Setting aside the poor markings, the trail itself is more narrow than normal and has various muddy and boggy sections, which is to be expected. A machete would have been nice at times. Most interesting to me were the massive spongy moss or lichen (sorry but I don’t know exactly what it is) mounds that increasingly lined the trail(s) as we continued. These mounds were up to 3 feet thick and very green.


Kohala summit trail in Puu O Umi reserve
Spongy moss lines the narrow trail in the rainforest

You feel that you could lie on them like a spongy mattress or step on them and sink in to your knees or more. The trail passing through them was less than 1 foot wide at times and looked more like a stream bed than a trail.


More spongy moss on the trail. Pretty damp!

I haven’t encountered this before on the Big Island. There are plenty of other interesting scenes, typical of a Big Island rainforest:


Ferns and grasses in Kohala rainforest
Looking uphill a few feet inside the red gate




Dense, jungle-like rainforest makes finding the trail difficult

The rainforest portion of the trail gains another ~800 feet of elevation. It became clear after a while that the summit was only going to be an “X” on our GPS map with no view other than surrounding rainforest. We continued, determined to reach the “X”. We wondered if there would be any old markings showing the summit location as others have reported. What we found was this:


Someone left these "trophies" very near the Kohala summit

While not exactly what we were expecting, we took these artifacts as sufficient evidence that we had reached the summit (or within probably 100 feet or so) and halted further search for the exact spot. We congratulated ourselves and had lunch. I took some abuse for having proposed this hike in the first place.


Perhaps more important, we could see that the forest fell away and opened a bit to the east of our position. More intrepid hikers might continue east to where the canyons of the Pu'u O Umi wilderness open to some probably wonderful views. Were I to repeat this hike (which I probably won’t) that would be my objective.


The return trip was uneventful. It is impossible to follow your exact path up in reverse, but the GPS track obtained by David was sufficient for us to stay close to it and get back to the pasture without incident. Do be prepared to have your hiking boots sink up to 6 inches in mud at times, however. When we got to the pasture, David and Sara found it easiest to just run down the hill, applying minimal knee brakes. My knees would no longer allow that.


Motoring down a steep section near the top of the Koai'a Corridor

I’m glad we did it and would recommend it to any hikers that want something out of the ordinary. That’s what the Big Island is about! Selfishly, I wish the the trail were much better marked and maintained as it could be turned into a wonderful wilderness and rainforest trail with some work. I understand, however, that the Kohala Watershed Partnership has other priorities and limited resources so trail improvement is unlikely in the near term. So buckle up your waterproof boots and give it a try. 🔼

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