Dude, where’s my beach?

One day it was there: a wide sandy beach firm enough to reverse a boat into the sea. The next it was gone.

All that remains of the beach at the southern end of Ngati Toa Domain is a deep, watery hole, surrounded by steep shingle and a sand bank.

Trevor Burgess and colleague John Kelly, who repair boats at the nearby marina, turned up on Monday morning to find what had been a beach the day before had gone. There were many opinions about what happened, but nobody seemed to know for sure.

‘‘It’s a lot of sand to be dragged away. It looks like a slip or a sinkhole,’’ Burgess said.

Greater Wellington Regional Council hazard analyst Iain Dawe said the disappearing beach was essentially just a case of nature doing what nature does.

While November’s Kaikoura quake probably played a part by loosening things up to allow water in, it was far from the only factor, he said.

A lot of recent rain had probably raised the water table, saturating the ground from beneath. Then come some big seas, and the sand essentially liquefied. ‘‘It can just slump away.’’ The sand would have gone out deeper in the inlet but, over the next year or so, would probably move back and refill the hole, or get distributed around the inlet, Dawe said.

Porirua City Council parks manager Olivia Dovey said the disappearance was a natural event, and the hole could well move again when conditions were right.

‘‘We’ve put up safety rails in front of the erosion area, and ask that people take care, particularly near the edge where it’s likely to be unstable.’’