TRANSFORMATION OF BED SURFACE STRUCTURES AFTER A SERIES OF RELATIVELY SHORT HYDROGRAPHS
ABSTRACT: This paper reports
on a laboratory experiments in which a bimodal sediment bed was exposed to an
antecedent flow hydrograph followed by a stability test. The applications of
these hydrographs were intended to observe the development of bed
surface structures after
certain duration of
exposure by the
flow. Probability
distributions of bed
surface elevations was carried
out to estimate
the level of
grain exposure and the variations of bed
surface level. Bedload transport rates
were also observed
to obtain correlation
with the changes
in bed topography.
The results suggest
the changes in bed topography
from original condition
to the final
form. It is
evident that the
bed surface structure
has changed considerably during antecedent flow in which the average bed
surface elevation decreased by almost 2.792 mm. Highly exposed areas appeared
on the bed after antecedent flow test were removed and no longer exist after
stability test. At this stage further erosion continued but with a mere 11.82 %
decreased in the bed surface elevation. This indicates the level of
erosion during antecedent
flow test was significantly different than
that during stability
test. This study also reveals
that the transported bedload during the stability test was dominated by grains
in the coarse mode.
Author: Yusron Saadi
Journal Code: jptsipilgg090007
