How did Sediment-Laden Underflows Pass over the Subaqueous Hill?

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Dynamics of a unique behavior of sediment-laden underflows was examined in Peyto Lake, Alberta, Canada. As the characteristic basin shape, this lake has a subaqueous, traverse hill 7m high in the middle. The sediment-laden underflows should be driven only by the downslope component of gravity. Our previous studies of sedimentation in Peyto Lake, however, pointed out the possibility of the underflow passing over the hill and subsequently inducing sedimentation in the distal region. We thus examined the mechanism of the underflow's hill-passing by observing meteorological conditions, river sediment discharge and lake currents in the glacier-melt season of 1993. It is concluded that the underflow does not directly pass over the hill, but is produced downlake of the hill, due to the suspension storage in a proximal maximum-depth region by the continuous underflow and its consequent overflow on the hill. This overflow only occurred at mort than a critical river sediment discharge, and continuously produced sediment-laden underflow in a distal region.
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