River Surfing - Tidal Bores

Tidal Bores

Tidal bores occur in relatively few locations worldwide, usually in areas with a large tidal range (typically more than 6 metres (20 ft) between high and low water), and where incoming tides are funnelled into a shallow, narrowing river via a broad bay. Large bores can be particularly dangerous for shipping, but also present opportunities for river surfing. The funnel-like shape not only increases the tidal range, but it can also decrease the duration of the flood tide, down to a point where the flood appears as a sudden increase in the water level. Note the tidal bore takes place during the flood tide and never during the ebb tide.

A tidal bore can create a powerful roar that combines the sounds caused by the turbulence in the bore front and whelps, entrained air bubbles in the bore roller, sediment erosion beneath the bore front and of the banks, scouring of shoals and bars, and impacts on obstacles.

Tidal bores are being surfed along coastal rivers such as the pororoca on the Amazon River or England's River Severn.