Every winter on the north shore of Oahu, an island in Hawaii, the Waimea river is blocked by sand creating a natural dam where the river flows into the ocean. This happens due to heavy rains in the valley, combined with a high surf during the winter season. The locals, have taken it upon themselves to dig a trench through the dam in order to alleviate the bloated river and preserve the local ecology. In the past few years, they have received help from groups of surfers, who use the trench to their advantage to prepare for the BIllabong Pipemasters Competition. Watch how this tiny trench turns into an amazing surfing event.

via tvwaves