Girdwood Trip - Bore Wave

On August 8th, 2010 we traveled to Girdwood, AK for documenting a tidal bore wave in the Turnagain Arm. Equipped with a professional video camera and a 400x zoom picture camera, our group climbed 1820 ft up the Rainbow Ridge, located between Beluga and Bird Points, to capture the phenomenon.

At around 4:15 pm on August 10th the wave became visible at our site. Dina and Deven employed a 48x zoom video camera to film the tidal bore, while Jennifer and Prof. Rybkin, who were positioned approximately 39 ft higher (coordinates 61.008849 N 149.659122 W), took photographs. Odile, Marina (Prof. Rybkin's wife) and Jessica made up the supporting crew and captured the wave from a different angle and a lower location - altitude 912 ft, coordinates 61.005221 N 149.655826 W. With combined efforts we have covered a significant portion of the distance the wave has traveled.

More about the the bore waves...

A turbulent bore is characterized by a turbulent wave front followed by a steady, uniform stream.

An undular bore is characterized by a smooth wavefront followed by a train of stationary waves.

Often times you see both types of bores propagating at the same time. The type of bore that will occur depends on the initial water depth in the river or estuary and the elevation difference between the incoming tide and river or estuary. Shallow water and a large initial difference in height most often produce a turbulent bore whereas undular bores form in deeper water where the initial difference in water heights is small.