Laboratory model studies of flushing of trapped salt water from a blocked tidal estuary

Results are presented from a series of laboratory model studies of flushing of saline water from a partially- or fully-closed estuary mouth. Experiments have been carried out to determine the response of the trapped saline volume as a function of the fresh water river discharge Q, the density difference ∆p between the saline and fresh water and the estuary bed slope α. Flow visualisation and density probe data confirm that the transient behaviour of the plume can be represented well by the use of length and time scales Q 275 ∕(g’) ιz5 and Q ι / 5 ∕(g’) 3 / 5 respectively, where g’ = g(∆p)∕p o is the modified gravitational acceleration and p 0 is the density of the freshwater flow.