Process-based modelling of the Maumusson inlet: Interaction between inlet, ebb-delta and adjacent shoreline

Process-based modelling of the Maumusson inlet: Interaction between inlet, ebb-delta and adjacent shoreline

Bergsma, E.W.J.

Stive, M.J.F. (mentor)
Walstra, D.J.R. (mentor)
Bertin, X. (mentor)
Luijendijk, A.P. (mentor)
Storms, J.E.A. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

Coastal Engineering

2012-03-16

In 2010, a realignment of the main channel of the Maumusson inlet, France, is observed. This breach of the ebb-delta is observed not long after a severe storm that afflicted the Charente-Maritime region in February 2010; Xynthia. A strong link between the breach and the Xynthia storm is expected: a storm event driven breach. In order to assess this hypothesis the impact of the Xynthia storm and the breaching process is investigated by use of a process-based numerical model, Delft3D. Two possible options for the breach are initiated, namely event-driven or a long-term development where the flow through the inlet becomes inefficient. In order to assess the two time scales, two scenarios are introduced for the numerical model; long (10 years) and short term (Xynthia storm). Hardly any input reduction is applied to the short-term scenario while the long-term scenario suffers extensive wave input reduction and the use of a morphological acceleration factor in the view of computational efficiency. Following the qualitative analysis; the results are in the line of expectations. The impact of the Xynthia storm turns out to be rather limited. During the long-term development of the ebb-delta (deflection of the main channel and elongation of the bypassing bar) the impact of the Xynthia storm event increases. When spill channels form and the ebb-delta is tending to breach, the impact of the Xynthia storm drops relatively rapid. In the long-term scenario, deflection of the main channel southwards is observed and simultaneously the bypassing bar elongated in the same direction. Finally, the flow through the inlet becomes inefficient and spill channels start to develop. The location of the new main channel is betrayed by the ebb and flood-tidal flows, making the bypassing bar relatively narrow on a specific location. Breaching of the ebb-delta at the Maumusson inlet is not caused by the 2010 storm driven event but was part of cyclic behaviour with an expected turnaround time in the order of decades. As a result, the littoral drift is significantly reduced by the new orientation of the main channel.

inlet
ebb-delta
breach
Maumusson
Civil Engineering
Coastal Engineering
long-term
modelling

http://resolver.tudelft.nl/uuid:0f25bdac-e89d-48c6-a6c2-d6cf72d674f1

Student theses

master thesis

(c) 2012 Bergsma, E.W.J.