Flow and sediment dynamics of continuous turbidity currents in Lillooet Lake, British Columbia

This study examines turbidity currents, or sediment-laden underflows, generated by Lillooet River flowing into Lillooet Lake, British Columbia. Velocity was measured with acoustic velocimetry, and suspended sediment and grain-size using laser in situ scattering transmissometry. Turbidity current thickness increased and suspended sediment concentration decreased lakeward from the river mouth as a result of entrainment and sediment deposition. Turbidity currents were composed primarily of fine particles (<63 mum) which are responsible for sustaining the currents. Local wavelet analysis shows that the turbidity currents pulsate with periodicities of between ∼4--32 s and of ∼64 s, which are consistent with Kelvin-Helmholtz instabilities. Cross-wavelet analysis suggests that covariance between temporal changes in velocity and SSC is greatest at the interface as a result of the high levels of turbulence generated at this height. This study enhances our understanding of natural turbidity current dynamics and provides important data for testing laboratory and numerical models.