Fluvial Recovery at Mount Pinatubo




My dissertation investigated how a fluvial system responds to extreme sediment loading and how the system recovers as sediment yields decline.   The project focused on Mount Pinatubo, which erupted in 1991, depositing 5-6 km3 of pyroclastic debris in basins draining the flanks of the volcano.   Through time, sediment yields are declining, essentially setting up a natural flume experiment that allows fluvial geomorphologists to study an end-member case of sediment loading and the processes by which rivers reestablish equilibrium conditions.  Data collected from a series of 5 rivers on the east side of Pinatubo from 1997 through 2003 show the processes by which channel recovery occurs.  My research examined fluvial recovery at multiple spatial scales, from longitudinal recovery of the valley to detailed studies of changes in bed texture and grain mobility at a site, linking the basin-scale observations with changes in the sediment transport regime.


I studied five basins on the east flank of Mount Pinatubo.  Most of my efforts centered on the Sacobia River and the Pasig-Potrero River, both of which had ~30% of the basin covered with pyroclastic debris as a result of the 1991 eruption.  In October 1993, the Pasig-Potrero River captured the upper Sacobia River drainage basin, doubling the basin area of the Pasig-Potrero River.   This led to an increase in drainage area without a corresponding increase in sediment load.  The result is that the Pasig-Potrero appears to be recovering at a faster rate than the Sacobia.


We were able to go back to Mount Pinatubo in summer 2009, winter 2009-10, and summer 2011 to investigate how the channels have evolved over the past 6 years, thanks to funding from the National Science Foundation and the University of Minnesota’s Office of the Dean of the Graduate School. 




Project Bibliography



This research was supported through grants from the National Science Foundation, the Geological Society of America, and the Dept. of Earth & Space Sciences at the University of Washington.   My funding came primarily from a STAR graduate fellowship through the EPA.



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