Analysis of seasonal and interannual river flows affecting whitewater rafting on the Franklin River in the Tasmanian Wilderness World Heritage Area

Abstract

We analysed river flows in the Tasmanian Wilderness World Heritage Area to understand how they affect commercial whitewater rafting. Respectively, two river gauges have recorded river flows since 1953 and 1980 on the middle section of the Franklin on the Mt Fincham Track and at the bridge on the Collingwood River, a major tributary of the upper Franklin River. We show river heights on the Collingwood River are suitable for whitewater rafting launches all year round. Low flows on the Collingwood River, which are less than ideal for large rafts, are uncommon except for the warmest months (January, February, and March) when they occur about 50% of the time. During the late autumn, winter, and early spring months (May through October) river flows on the Franklin River are frequently (>30%) too high for rafting through the Great Ravine, the crux of Franklin River journey. There is clear evidence of reduced rainfall across Tasmania since the 1980s, and predictions of further declines in summer and autumn rainfall, nonetheless, we find no trends in river heights and flows since 1953. We conclude that climate change is likely to broaden whitewater rafting season because of low river flows in the summer months combined with increasing bushfire risk that will periodically lead to World Heritage Area tourism being shut down.