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.