Nate’s Adventures: Hike on the Kulanaʻahane Trail in Moanalua Valley (Red Hill)

by Nate Yuen | Reading time: 6 minutes

I led a Sierra Club hike on the Kulanaʻahane Trail in Moanalua Valley which is part of the Na Ala Hele System of Trails. The purpose of the hike was to reconnect people with nature, show where Oʻahu's drinking water comes from, and what we can do to protect this precious resource.

We met at Moanalua Valley Neighborhood Park and took this group selfie before the hike -- from left to right: Nate Yuen, Randy Ching, Dan Smith, Monica Nickolas, and Darriann Pittman.

Moanalua Valley is bounded by Tripler Ridge to the east and Kapūkakī Ridge to the west. Kapūkakī Ridge is where the Red Hill underground fuel storage tanks are buried in the mountain behind the Kaiser Permanente Moanalua Medical Center. Our plan was to hike 4.5 miles each way to a low point in the Koʻolau Summit Ridge – known as the Moanalua Saddle – which overlooks Haʻikū Valley on the windward side of Oʻahu. We would start on the Kamananui Trail (orange) – which is now a road – until we reached the Kulanaʻahane Trail (dark orange). There are about 27 stream crossings on the Kulanaʻahane Trail. The trail leads to the base of the Koʻolau Summit Ridge and climbs steeply to a low point in the Koʻolau.

Rainfall over the Koʻolau Mountains seeps into the earth, filters through layers of volcanic rock, and joins the ground water. Moanalua Valley is one of the valleys that supplies pure freshwater to the Pearl Harbor Aquifer -- which provides 40% of Oʻahu's drinking water. We scrubbed our shoes on brushes to remove seeds from invasive plants that might have been stuck on our footwear.

We crossed 7 bridges as we hiked up the valley many of which are covered with hau trees. Hau -- Hibiscus tiliaceus -- is the dominant tree in Moanalua valley which produces heart shaped leaves that glow in the sunlight.

Hau trees produce bright yellow hibiscus flowers. The flowers are remarkable in that they change color from yellow to red in a single day, and fall off the tree.

We saw many red flowers on the ground under hau trees as we made our way up the valley.

When we reached Pohakukaluahine -- the giant pohaku (boulder) with petroglyphs, we stopped to admire the carved figures. Randy shared with us that the mana and historical significance of this boulder stopped the construction of the H-3 Freeway in Moanalua Valley. The Sierra Club fought the development of H-3 in Moanalua Valley for almost 20 years. Ultimately, the H-3 highway was built although re-routed through neighboring Hālawa Valley.

As we made our way into the valley, the sweet scent of ginger filled the air. Ginger is an invasive species, but it was adopted into Hawaiian culture and was given a Hawaiian name – awapuhi.

As we hiked deeper into the valley, clouds over the Koʻolau Mountains were blown down the valley and briefly dropped its moisture on us. It was unusual to feel sunshine and rain at the same time. For Native Hawaiians, gentle misty rain -- ua noe -- is auspicious and is a blessing.

When we reached the Kulanaʻahane Trail, we veered off the road and took the trail further into the valley which crosses the stream about 27 times. There was no water in the stream – the dry season has started – and there has been little rain in Moanalua Valley lately.

The trail goes through a hau forest. Hau trees can grow into an impenetrable thicket of branches. Gravity continually acts on the branches to lower them and block the trail. Hikers have to duck under, squeeze through, and contort around branches. Maintaining a trail through a hau forest is a never ending task. Despite the trouble, hau leaves glow when illuminated by sunlight and are a sight to see. There is nothing like hiking through a hau forest.

When we came to the big pool, Randy remarked that it was the least water he had ever seen in the pool. I agreed with Randy -- there is usually way more water in this pool. The low water level is a result of less than usual rainfall over Moanalua Valley.

Randy had a catastrophic shoe failure when the sole separated from his shoe. Fortunately, he had duct tape so we were able to do a repair in the field. Duct tape is strong and has so many uses that it is a must in any first aid kit.

As we made our way up the dry stream bed it became apparent that the reduced rainfall over the Koʻolau Mountains this year could not have come at a worst time. The Red Hill fuel tanks have leaked into the Pearl Harbor Aquifer and several wells have been closed. Rainfall over the Koʻolau is less than usual and groundwater in the aquifer is not be replaced as the same rate it is being used.

We reached the last pool before the big climb to the summit ridge. This pool is a water source for backpackers doing the Koʻolau Summit Trail. Fortunately there is still water in this pool – although less than normal.

We started the 1,000 foot climb to the Koʻolau Summit Ridge through uluhe ferns and ʻōhiʻa trees.

The incline gets steeper as we climb up the ridge.

Just before we reached the top we came across ʻōhiʻa trees with lots of red lehua flowers.

And then we reached the top of the Moanalua Saddle! We looked over to the other side of the island. We could see Ha‘ikū Valley, H3, and Kāneʻohe Bay. Yellow-brown grass at the summit confirmed to me that rainfall over the Koʻolau Summit has been less than normal.

We admired the view as rain clouds began to gather over the Koʻolau Mountains. These clouds are the source of Oʻahu's water. Moisture laden air is blown against the Koʻolau Mountains and is forced upwards where the air is cooler and condenses into clouds. Rainfall over the Koʻolau is essential to the life on Oʻahu.

I was thrilled to see ʻōhiʻa trees with with red lehua flowers covered with orange lichen. This form of ʻōhiʻa appears to be part Metrosideros rugosa – lehua papa – a form of ʻōhiʻa endemic to O’ahu. My observation is that the leaves are not deeply furrowed enough to be pure rugosa.

We took a group shot with the ʻōhiʻa tree, ate lunch, and relaxed at the summit.

We descended the mountain and returned the way we had come. We past many hau trees and stream crossings as we made our way back to the front of the valley.

As we made our way back to the big pool, we remarked how the low water level in the pool is not a good omen for Oʻahu as the dry season begins. Ernie Lau at the Board of Water Supply said Oʻahu is under drought conditions and asked the public to conserve water. Water lawns less, take shorter showers, bathe every other day, flush only on 2, are some of the measures we can take to reduce our use of precious water during this time of drought.