Rolling side drum

OK, its not the rolling surf of the Pentland Firth at Thurso where the UK element of the surfing championships are taking place this weekend but this surf has an interesting feature. It is one of the longest drum rolls of surf I have ever heard.

If you have a beach that shelves parallel to the shore, waves roll in and curl over on the break giving off a booming noise as the wave breaks in one over its length.

This beach shelves at a shallow angle to the shore. As a consequence, when the swell rolls into the inner firth the wave builds and breaks away to the right of the picture and is then a continuous break from right to left. In the right conditions the break can be nearly half a mile from start to finish. If you stand in the centre spot you can hear the doppler effect like you do when a train passes a stationary listener. This sounds like a guy stood on a trailer being driven past at speed as he executes a prolonged drum roll on a snare drum. At the end, you expect to hear the National Anthem start up.