Outburst flooding at Franz Josef Glacier, South Westland, New Zealand

Abstract During February and March 2003, a series of unusual events involving supraglacial flooding and ice collapse affected an area of Franz Josef Glacier, South Westland, New Zealand. This paper describes these events and examines rainfall and river stage data in order to explain their occurrence. Relationships between rainfall events, supraglacial flooding, and stage of the Waiho River suggest that subglacial water was rerouted to a supraglacial position, most likely resulting from blockage of the subglacial route by ice collapse near the base of the main icefall on the lower part of the glacier. Review of previous literature reveals that a variety of flood and ice collapse events are frequent at Franz Josef Glacier. While this is only one of several natural hazards in the Franz Josef area, it is of considerable importance because of the large number and significant duration of tourist visits to the terminus and onto the lower part of the glacier.