The debris — which includes corrugated roofing, hand-cut trees and green waste — is more than a foot deep in some places and extends for a three-mile stretch from Honokoa Gulch to Pohakuloa Gulch.

"It's a mess," said William Walsh, an aquatic biologist for the state Department of Land and Natural Resources Division of Aquatic Resources.

"The Kohala Coast is very vulnerable. Somehow we screwed up the natural drainage system," Walsh said. "There was nothing to absorb the run off, such as vegetation. These accumulated minor changes can have catastrophic results."

Low-lying coral in the area is covered by a layer of filamentous algae, which traps the finer sediment.

The sediment also smothered mollusks, worms and urchins.

Walsh said the fish can relocate to nearby areas but other marine life couldn't escape.

The reef has an amazing ability to regenerate and may clean out in about five years, but each event like this reduces the reef ability to respond, Walsh said.

The first sign something was wrong came Oct. 24 when researchers investigating coral settlement noticed unusual sediment in the water.

Kohala residents told Department of Aquatic Resources officials that people often cleared nearby land and dumped trash into the gulches.

They also noted a new residential area south of Waiaka'ilio Bay had dramatically reshaped the land.

Further, they recalled boulders had come tumbling down hills during a major rainstorm around the time a magnitude 6.7 earthquake struck off the Kohala Coast in October.

A preliminary investigation conducted by the Department of Health's Clean Water Branch said blocked culverts in Puu Kalalii and Keawewai Gulch could be responsible for the runoff.

The report didn't have enough evidence to pin the blame on any individual or government agency. But it did note the state Transportation Department had been carrying out construction activity by the Akoni Pule Highway that had a high potential for "sediment discharge."

State workers had been repairing the road after flash floods eroded the highway. Scott Ishikawa, a department spokesman, said workers did not install silt fences because of the urgent need to repair the road.

"We were in an emergency situation," Ishikawa said. "There was already a lot of dirt going into the ocean. At the time, we felt like we did not have a choice."

He added the department would follow better practices, installing silt fences, snake bags, and rubberized tubes used to divert silt and water no matter the circumstances or emergency.

Still Matthew Kurano, the Department of Health environmental health specialist that authored the report, said the runoff was "no one's doing" and was "an unfortunate situation."