It seems that everyone - including the federal government, electric
power companies, Southwest politicians, rafters, environmentalists,
native Americans and scientists - has their eye on the operation of
Glen Canyon Dam, that controversial human creation which controls the
Colorado River's flow through the Grand Canyon.

For one, USC's Bernard Bauer is making what he considers a small but
potentially important contribution to the debate over managing the
dam. Bauer, an assistant professor of geography, is focusing on the
sandbars - the "beaches" where rafters set up camp at night - which
are thought to be eroding due to the dam operation.

Hundreds of sandbars along the Colorado support vegetation and
animals as well as providing the camping spots for river rafters. It
is believed that prior to the dam's construction, the Colorado River
floods would deposit sediments and build up the sandbars. But thanks
to the dam, the floods come no more. Furthermore, hydro-electric
production at the dam drives a cycle of water fluctuations that has
an impact on the downstream sandbars and the rest of the river
ecology.



Scientists have been studying the erosion of the sandbars for years,
but Bauer is adding a new wrinkle to the river research.

Bauer - who won a five-year, National Science Foundation Presidential
Young Investigator award in 1991 - is studying the river not in the
traditional manner of fluvial geomorphology (the evolution of rivers)
but from the perspective of a coastal geomorphologist: he believes
waves have something to do with the sandbars' erosion.

Most of Bauer's work has been concerned with oceans and the creation
of beaches and coastal sandbars. When visiting the Colorado River, he
said, "I was really struck by the fact that these systems almost look
like mini-beaches."

Bauer and a colleague at Utah State University, John C. Schmidt,
spent two weeks in May 1991 testing the idea that the waves of the
Colorado River, although tiny in contrast with ocean surf, affect the
sandbars. The scientists documented their findings in a paper
entitled "Coastal Perspectives on Fluvial Sandbar Erosion in Grand
Canyon, Arizona," which is expected to be published later this year
in the Annals of the Association of American Geographers. The river
research, funded through the Young Investigator award and an earlier
NSF grant, is the first work that quantitatively assesses the
importance of waves at the Colorado River, Bauer said.

"The contribution of this research is to point out that there are
other mechanisms here that we haven't considered in the past that
maybe we should take a closer look at."



In their research, Bauer and Schmidt studied the waves, river
currents and sandbars at two sites on the river: Stone Creek and Fern
Glen sandbars.

Their surveys of the sandbars revealed that between 47 and 61
centimeters of sand were eroding per day at Stone Creek, and that
Fern Glen sandbar was losing 25 to 30 centimeters per day.

The amount of erosion was higher than usual that week possibly
because of unusual "low flow" operations run by the dam in the
preceding weeks, in which the water levels were lowered to allow
scientific research to be conducted. While there is some question as
to whether the measurements are representative of long-term erosion,
they clearly show that erosion is occurring.

But what is causing it?

This is where the waves come in. Fluvial geomorphologists have
traditionally studied rivers from a unidirectional approach, meaning
they assume the current is moving in one direction; and that guides
their calculations of how the sediments are transported.

However, the Colorado River is riddled with eddy systems, in which
the flow of the river is separated from the main channel and creates
its own circulation system in pockets along the river's edge. These
eddies are created by debris, such as falling rocks, which build up
along the river and cause rapids, which in turn trigger small waves.

The magnitude of currents in these "eddy recirculation zones" are
weaker than those flowing through the main channel. But the
combination of the cross currents and waves is strong enough to carry
sediment, Bauer said.

"The waves coming into the sandbar environment are strong enough to
pick up sediments from the sandy bottom and move them around," he
said. "Ultimately they are transported back to the main channel and
they are lost from the sandbar system."



Bauer's and Schmidt's work will be noted in an Environmental Impact
Report on the effects of Glen Canyon Dam power operations being
prepared by the Department of the Interior.

In addition, Bauer said several agencies are aware of their work and
will consider it when planning future research and dam management
policies. The dam's operator, Western Area Power Administration, is
preparing a second EIR on how it sells power.

Bauer sees a strong connection between the releases of water from the
dam and the intensity of waves created. A lot of water flowing from
the dam would create stronger currents, rapids and waves - and more
erosion. Logic dictates, therefore, that the strategy for
discharging water from the dam ultimately affects the erosion
experienced by sandbars down the river.

People are grappling with how to come up with a management strategy
that balances the need for hydro-electric power with the interests of
rafters, native Americans and ecologists, whose concerns range from
preserving vegetation to saving the Humpback Chub, a type of fish.

"The question is: What is a reasonable discharge schedule for the
dam, given that waves generated downstream affect sandbar erosion?"
Bauer said, noting that there may be ways to alter the discharge
schedule to protect certain sandbars.

In the future, Bauer hopes to go back down to the Colorado and
broaden his research by doing an inventory of the wave-dominated
sandbars. Then he hopes to show how the discharge fluctuations from
the dam affect the waves at various sandbars.