Protection against flooding from the sea

Description

The ecosystem service “protection against flooding from the sea” through energy dissipation and sea defenses is of enormous importance in Flanders, which has 67 km of coastline and 150 km of macrotidal estuary (with a tidal range of more than 4 m). Most of the Belgian coastal plain is 2 m below the level of an average annual storm of +5.5 m TAW (Second General Water Passing), while the high water level on the Belgian coast during the storm surge of 1953 rose to +6.73 m TAW amounted to.

Beaches play an essential role in protecting the coastal plain against flooding because they can (partially) extract the energy of impacting waves. This reduces the erosive force of waves that reach the dune base or the dike and reduces the amount of dune erosion or reduces the risk of dike instability during storms and therefore also the risk of breaches forming.

Dunes mainly provide protection against flooding because on the one hand they extract wave energy and on the other hand they form a physical barrier that can hold back seawater. Dunes that are not closed off from tidal forces by hard sea walls can also ensure that the natural coastal defenses continue to grow. Dunes that are cut off from tidal action no longer receive a supply of sand, while wind erosion can further break down the dune. However, depending on the erosive or accreting effect of the coastal strip, tidal action can also break down the dunes (De Ronde and Houthuys 2007 in Van der Biest, 2008).

Currently, there are no directly applicable methods available to value this service.