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A Land of Extremes

December 11, 2016

March 06 Flood

The March ’06 Flood filled the sinkhole with water.

Recent rain down at the cave has raised hope that the longest drought we have recorded there in over a decade is being broken, but so far it’s just a little “greening up” and not enough to make up the deficit.

The flooded stream at Makauwahi Cave Reserve.

In almost a dozen years of keeping daily rainfall records at MCR, a recurrent theme has been generally scant rainfall (from 23-50 inches per year), punctuated every few years by floods and droughts. The current drought is a doozy, lasting 33 months so far. Fortunately, most of our native plants growing so profusely on the Reserve today are well-adapted to drought, and often cope by dropping their leaves until rain returns.

By now we have learned quite a bit about the rainfall pattern down there, but we have been surprised on occasion, too. Overall there have only been eight instances in over 11 years in which monthly rainfall nearly reached or exceeded evaporation. But when it does rain… some individual rainstorms there are legendary, such as the March ’06 flood, when it actually rained about 40 days almost continuously for a total of 31 inches. That’s more than some entire years. Then there was one we christened the Leap Year Flood, because it was centered around Feb. 26, and continued into early March 2012. We saw the most rain in two hours we’ve ever seen down there, close to six inches.

Hurricanes and near-hurricanes can produce a big rain in late summer or early fall, ordinarily dry times. Coupled with storm run-up from the ocean, our lowlands could flood deeply in a hurricane as they have occasionally over the years.

We have interesting data on many other weather factors, such as the winds down there, too, thanks to the automated system operating in past years, installed by the Intelesense Corporation in connection with a National Science Foundation grant. And as you have perhaps read in earlier issues of this newsletter: “The Big Wave at the Cave” and “Making Waves”, the fossil record shows that on longer timeframes the area has also been hammered by at least one really big tsunami, about 430 years ago we think.

At least the little dormant volcanoes between the cave and the nearby town of Koloa have been behaving themselves, probably for tens of thousands of years!

By David Burney

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