Wailuku River, Big Island Hawai’i; The Wailuku River is the longest river in Hawai’i stretching 28 miles long. The island river’s course lies mostly along the divide between the lava flows of Mauna Kea and those of Mauna Loa to the south. It arises at about the 10,800 feet elevation along the eastern slope of Mauna Kea . It flows generally eastward, descending steeply from the mountain and entering the Pacific Ocean at the ocean front of Hilo Town.


Wailuku River State Park is located along the lower reach of the river. One attraction of the park includes Rainbow Falls (Waiānuenue-literally “rainbow water”). The 80 foot high Rainbow Falls got it’s name from the fact that, on sunny mornings as the east rising sun shines on the falls, rainbows can be seen in the mist thrown up by the waterfall. Behind the waterfall is a lava cave, home to Hina, Hawaiian Goddess of the moon.

About a mile mauka (towards the mountain) is another significant part of Wailuku River State Park, it’s known as Peʻepeʻe Falls and an area called the Boiling Pots which are a series of small falls and pools.


The upper and middle reaches of the river are known for hunting of introduced game animals, predominantly wild boar. Wailuku River is also a good source of providing Hawaiian crawfish/crayfish and freshwater shrimp called opae. Hawaii has three types of native freshwater shrimp, all with close ties to the ocean. One type lives in lava ponds with underground connections to the sea. The other two spend the first part of their lives at sea and the rest in streams or estuaries. It is these two species that people like to eat.Susan Scott

The lower reach of the river is also used for the generation of hydroelectricity. The flow at Hilo averages 275 cubic feet per second with peak flows 40 times as great. The Wailuku River provided power to the Hilo Boarding School, first building structure in Hilo to feature electricity.

Lower Wailuku River is also a popular destination amongst Locals for swimming, tubing, and cliff & bridge diving/jumping. However the Wailuku River (which includes Boiling Pots) accounts for 25% of the river drowning deaths in the Hawaiian Islands. You’ve been warned. In the Hawaiian language, wai means fresh water and luku means destruction, so it means essentially River of Destruction. During rain storms the river can rise into the trees and drop back down very fast.The high flood marks can be seen dated in concrete, on the stairs going down to the river behind the Hilo Public Library. With it’s rapid waters the river carries an average of 10 tons of suspended sediment into Hilo Bay each day.