tide & landscape
STORM SURGES ON THE WADDEN SEA COAST WHEN THE WATER RUSHES FORWARD
Many of the Wadden Sea coastal storm surge pillars mark the storm surge in 1636 The inhabitants on the Wadden Sea coast have always lived with the threat of storm surges that flooded their fields, caused devastating damage to their properties and, at the worst, loss of life. Still, storm surges were not only the ultimate fight in the past between nature and culture, but also future dramatic landscape challenges for the Wadden Sea region. A storm surge occurs when a storm causes the sea level on the ocean to rise faster than normal, thus causing devastating damage through flooding. The rise in the sea level is caused by a combination of water piling up, tidal flow and low atmospheric pressure. The water piles up when the ocean is pushed towards land by a strong onshore wind that causes the water to rise along the coast. The worst imaginable situation is therefore when a heavy storm hits the coast at the high tide after a long period with heavy onshore winds. Under normal circumstances, the atmospheric pressure near the earth’s surface is 1013 hPa on average, but during a storm it drops to 970-980 hPa. Since a drop of 1hPa in the atmospheric pressure will cause the sea level to rise by 1cm, such a drop in atmospheric pressure will increase the sea level with up to 0.4 cm. How or how long storm surges hit is therefore very diverse For example, the storm surge in 1981 developed over 4 or 5 high tides, while the tornado on Dec. 3rd in 1999 only lasted between 2 and 3 hours
See signs after storm surges in ... SPRING
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while also hitting at the low tide. In 1999, the increased sea level was caused by the effects of the water piling up and the drop in atmospheric pressure, and the piling up contributed with a 5.5 m rise in the sea level.
The Great Drownings
Two storm surges stand out in the history of the Wadden Sea. The Great Drownings in 1362 and 1634 caused huge changes in the Wadden Sea landscape, and they both caused devastating damage and a huge loss of life. The day in 1634, the second Great Drowning, is well documented and has left an indelible imprint not only on the landscape, but also in the consciousness of the people living on the coasts. The fishing village Sønderside, situated by the current Havnegrøft on Skallingen, had to be given up after the storm surge, and in Ribe Cathedral the sea level was marked on the stone pillar by the pulpit. Many of the storm surge pillars on the Wadden Sea coast also note the water level in 1636.
Klaus Melbye, Vadehavscentret & Anne-Marie Overgaard, Museum Sønderjylland Translation: Nanna Mercer, Sirius Translation
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