Important monitoring equipment fell victim to Maui flooding, forecasters say

Last week’s devastating flood on Maui swept away an important tool that helps forecasters warn the public to impending danger.

It’s called a stream gauge, which measures the volume of water moving through a stream and helps forecasters when it comes to issuing flash flood warnings.

There are currently 67 of them across the state.

Tom Birchard, a meteorologist with the National Weather Service, showed us a data chart of water flow the night the flash flood hit on Maui.

“When you see something like this, a rapid rise in water and then the data stops, you’re thinking something catastrophic happened to the gauge,” he said.

Birchard said the stream gauge at Wailuku River stopped working the night the flash flood hit.

“Does it make it easier to report or let public know about flash floods?” KHON2 asked.

“It does. It adds confidence when we issue warnings. It gives us confidence that yes, ground truth, this is what’s happening,” Birchard said.

He says they have other tools to monitor change in water flow, but the stream gauge helps, especially now that Wailuku River has changed.

Gov. David Ige said parts of the Wailuku River moved by more than 100 feet, about the length of a 30-yard line on a football field.

We’re told the water-level change means some homes in Iao Valley are now close to stream level.

Birchard says rainfall could raise the river, and there’s a chance nearby homes could flood.

“We’re not sure how much rain it would take now for that stream to cause problems for those properties,” he said. “Would it take just a little bit because of the changes, or will it take as much as before or more? We’re not sure. A lot of our information will be based on reports from residents.”

We asked Ige if he’d consider moving Wailuku River back to its original state. “The stream flow will always be different and I don’t think it will be the same as it was before the storm,” he responded.

We checked with the U.S. Geological Survey and were told right now a hydraulic model is being used to monitor the stream flow for flooding.

Will the gauge that got swept away last week be replaced? We won’t know for another few weeks.

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