Kaua‘i is an unusual island for corals to grow because we have a lot of rain and runoff from rivers and streams. This runoff usually carries sediment out to sea, along with logs, branches, farm chemicals, oil from cars and all kinds of land based pollution.
Kaua‘i is an unusual island for corals to grow because we have a lot of rain and runoff from rivers and streams. This runoff usually carries sediment out to sea, along with logs, branches, farm chemicals, oil from cars and all kinds of land based pollution.
All of these particles in the fresh water run off are bad for coral growth. Large coral reefs are usually associated with dry desert islands that build up coral barrier reefs over millions of years.
Kaua‘i has healthy corals even with a lot of rain but these corals only live in small pockets where they get the right combination of salt water, fresh water and sunshine.
Wainiha Bay on Kaua‘i North Shore is not the place where one would think a massive coral reef would grow. The Wainiha River flows directly into the bay and huge winter waves make the bay extremely rough. The name Wainiha means “wild waters” and the bay is so violent that it is hard to scuba dive there most of the time.
About 15 years ago on a calm day I decided to snorkel across the bay and expected to see a boring sandy bottom like Hanalei Bay, and then about half way across I saw something that just did not make sense. There is a lava cliff in the middle of the bay that is about 30 feet tall and this cliff is totally covered in giant corals the size of cars or even a small school bus! Huge mound and lobe corals usually grow in calm sheltered bays that have little wind or surf so why were they growing in the wild waters of Wainiha Bay?
It took me years of diving in Wainiha to figure out why the corals were there and just a few days ago I dove the spot with two friends and the corals were healthy and just stunning to look at. As a lifelong surfer the first clue came to me when the waves were 30 foot in the winter and friends of mine were tow-in surfing a half mile offshore of Wainiha Bay.
In the summer I dove on the same outer reef they surfed and the reef was only 15 feet deep out that far. In Wainiha Bay, close to shore the depth is 60 feet deep at the bottom of the underwater cliff. It turns out that the shallow reef outside of the bay attracts the full energy of the waves and keeps the inside bay calm, even on big swells. This makes the bay more like a lagoon even though the constant wind makes the sea surface of the bay rough.
My second clue as to why this giant coral garden lives in Wainiha Bay was the constant changing of where the Wainiha River enters the bay. For the last eight years I have used my drone to look at the river from above and it is quite dramatic. Some days the river enters the water on the left side of the bay and some days it enters on the right side of the bay and other times in the middle of the bay.
This meandering river is super healthy for the corals because mud and sediment are not deposited on the reef for very long before the river changes course. This gives the corals time to have the currents clean them and remain healthy. When a river is stabilized by rock jetties all of the sediment flows out onto the same part of the reef all years long and this usually kills all of the corals in that area.
In all my travels to every one of the main Hawaiian Islands, I have never seen anywhere like Wainiha Bay as these giant 1,000 year old corals have such a unique place to live and rarely ever get visited by us humans.
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Terry Lilley is a marine biologist living in Hanalei Kaua‘i and co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawai‘i go to www.reefguardianshawaii.org.
