SEEPAGE
EROSION FROM DAM REGULATED FLOW - THE CASE OF THE GLEN CANYON DAM
Muniram Budhu and Roger Gobin
ABSTRACT
Seepage erosion, in particular, slope failures (bank slumps, mass wasting)
is prevalent on most sand bars downstream of the Glen Canyon Dam. The public
is concerned about the loss of the extant bio-mass and recreational facilities
on these sand bars. It is alleged that the operation of the Glen Canyon Dam
is responsible for the erosion of the sand bars. In this contribution, a simple,
approximate analysis is developed to determine the extent of slope failures
due to seepage of bank stored water from transient dam flow. The analysis
is intended to assist environmentalists, dam operators, planners and others
to predict zones in which riparian habitat and recreation use will be negatively
impacted by fluctuating flows. The affected area of a sand bar was found to
be dependent on the range of flows, the rate of rise of river stage, the duration
of the peak discharge, and the permeability, friction angle and cohesion of
the soil. Comparison of the predictions of the analysis with field data show
good agreement.