Numerical modelling of flood control areas with controlled reduced tide.

Maria João Teles, Sven Smolders, Tatiana Maximova, Ivan Rocabado, Joris Vanlede

Monday 29 june 2015

16:36 - 16:48h at South America (level 0)

Themes: (T) Special session, (ST) Scheldt Estuary physics and integrated management

Parallel session: 3J. Special session: Scheldt Estuary physics and integrated management

Estuaries are an important link between overseas trading and local economy. They provide great opportunity, but behold also great risk. Storm surges can propagate far inland and induce flood risk for all those living close. In Belgium, the Scheldt estuary is also subjected to storm surge treat. The safety plan of the Belgian part of the tidal river Scheldt is called the (Actualised) Sigmaplan (W&Z, 2005), which aims for satisfying safety and ecological needs along the river Scheldt in a sustainable way. Therefore different restoration techniques are elaborated which combine safety with estuarine restoration, eg. dike strengthening together with more space for the river, flood control areas (FCA) with or without a controlled reduced tide (CRT). FCA’s with CRT is an innovative option were a limited tidal range is realized in the FCA through exchange of water between estuary and FCA through culverts, as such creating new intertidal habitats such as mudflats and marshes. The elevation and specific shape of these culverts determine the amount of water that can enter daily. This is called Controlled Reduced Tide (CRT). When the storm of 6th of December 2013 entered the Scheldt estuary, 13 of these areas were active. In the future there will be more than 40 areas active. It is thus becoming essential to include these areas and structures in numerical models. The present paper focusses on the numerical modelling of these structures along the Scheldt estuary and coastal zone for the storm event of 6th of December 2013. For that purpose the three-dimensional hydrodynamic circulation model Telemac-3D (v6p3) was used. A new culvert functionality had to be implemented in the code in order to better represent the hydrodynamics in the Scheldt estuary close to these areas. Existing source and sink terms were paired and used as a culvert. The theoretical background to represent the different kind of flows through the culvert was based on the work of Bodhaine (1968). Additionally different head loss coefficients were introduced according to different geometric features of the culverts. The implementation of these new structures inside the 3D numerical model was validated using water level measurements in the estuary and inside the flooding areas for the named storm event. For a normal spring neap tidal cycle water level and discharge measurements were available for model validation.