Extreme Runup and Clifftop Boulder Transport During Super Typhoon Haiyan

Typhoon Haiyan (2013), with estimated 1 minute sustained winds of 170 knots and hindcast significant wave heights of almost 19m, generated extreme runup and consequent boulder transport along a 4km section of cliffed coastline in Eastern Samar, Philippines. Post-storm field measurements showed thousands of clifftop boulders transported to distances up to 250m inland, with largest estimated masses exceeding 200t, and largest lengths ~8m. These distances and sizes exceed significantly maximum values stated to be possible in the literature, and overlie the megatsunami range. These discrepancies arise not only due to the extreme hydrodynamics during Haiyan, but because inland boulder transport occurred on infragravity scales of O(100s of s) rather than the incident wave scales of O(10-15s) assumed in the literature. A clear fining trend was seen, with largest boulders deposited near the coast and smaller boulders able to be transported farther inland.

For some boulders, evidence was found for transport by multiple events separated by time scales long enough for boulders to partially re-cement to bedrock. This earlier event may have been an 1897 storm that was in many ways similar to Haiyan.