THE EFFECT OF INCREASING SEA LEVEL RISE ON FLOOD DEFENSES ALONG THE WESTERSCHELDE ESTUARY

摘要

Flood defense systems are designed and constructed to protect low-lying areas such as Zeeland Province, against flooding. Recent research indicates that a change of the Netherlands climate is likely. The change of the climate may have important consequences for the reliability level of flood defenses because of: a. A rise of the mean sea level. b. An alteration of the wind climate in the form of a changed frequency and intensity of storms. c. A change of the mean amount and the variability of the rainfall. The crest elevation of the existing dyke system along the Westerschelde shoreline in the Province of Zeeland is designed so that the dyke withstands the 4,000-year flood event. The 4,000-year flood event is based on the extrapolation of historic water level data. It is expected that climate change would cause an increase of sea level at the Dutch coastline of a maximum of 0.85 meters (m) in the next 100 years. For a typical site along the Westerschelde, the 1 million year water level was computed in 1991 to be 7.3 m NAP. In the summer of 2011, the 1 million year water level was computed using an extended water level dataset to be 7.6 m NAP. In addition to the sea level rise, the increasing intensity of winds would cause higher run-up level at the flood defenses due to the expected increase in storminess in the North Sea.