Lawrence Coates

Interactions between a benthic tripod and waves on a sandy bed

In the past the amount of local disturbance to hydrodynamic and sediment processes by instrumented benthic frames has not been investigated. Here, in a series of tests on sandy beds in a large wave flume, measurements of wave-induced flows, turbulence, bedforms and suspended sediments have been obtained from the large tripod frame STABLE and from a control site away from the influence of the frame. Present measurements show surprisingly small modifications by the frame to local hydrodynamic conditions, bed morphology and vertical profiles of suspended sediment.

Cohesive sediment transport on an inter-tidal zone under combined wave-tidal flow

Results are presented for cohesive sediment transport on a muddy inter-tidal zone at Portishead on the Severn estuary, U.K. Data for suspended solids concentration for calm and stormy conditions show the influence of waves in the surt zone, and further seaward. A turbulence model of the water column has been used to explain the turbulent transport mechanisms underlying a conceptual description of the vertical distribution of suspended solids concentration. The conceptual description for combined wave-current conditions proposes a near bed wave boundary layer dominated region, a region above the wave boundary layer controlled by turbulent diffusion effects and an upper region in which local bed generated turbulence is not of primary significance.