Restoring the estuarine character of the lower Saâne valley
Client: Syndicat des Bassins Versants Saâne, Vienne et Scie - Scale: 1:80
Background
The Saâne is a small coastal river that flows into the sea via a conduit crossing the dike supporting the coast road, against which there is a pebble beach.Saâne River upstream of the outlet
The discharge capacity of this system is insufficient when the river is in flood, and the lower valley upstream of the mouth is subject to frequent flooding.
A physical movable-bed model was used to study a new outlet that would also help to restore the estuarine character of the lower part of the valley, restore functional natural habitats and reinstate free passage for migrating fish. The model simulated the movement of pebbles under wave action with a view to examining and defining development works to stabilise the river mouth and limit tidal ingress upstream of the estuarine section to be restored.
The coastline at the mouth of the Saâne river
Model characteristics and contributions
Undistorted model of the pebbled coastline
Pebble ridge represented by fine sand
Representation of changes in the pebble ridge under the action of waves and ebb currents in the Saâne
Testing of several scenarios offering alternatives to a conduit fitted with a non-return valve, including a free-surface outlet
Testing of tidal ingress in the restored estuary.
Modelling of the shingle coastline
The sedimentological scale model of the sea mouth of the river Saâne
