THE WAVE VANE - A DEVICE TO MEASURE THE BREAKER ANGLE

Estimation of the breaker angle in the littoral environmental observat ion (LEO) programme is still based on visual methods and therefore is subjective in nature. In the absence of a wave direction recording ins trument, a simple device called the wave vane as described here has be en developed to measure the breaking wave angle. The changes in the ho rizontal component of the orbital velocity under a progressive wave go vern the operation of the wave vane. The wave vane consists of a pair of fins, one responding to the velocity in the direction of wave propa gation below the wave crest, and the other to the velocity in the dire ction opposite to wave propagation below the wave trough. This results in wave vane orienting itself in the direction of the wave orthogonal . The performance of the wave vane was evaluated using the instrumenta lly recorded wave directional data as well as the visually observed da ta. The wave vane was found to give the wave directional information f airly accurate for the open coast where the influence of tidal current s was negligible.