Sources and Pathways of Extreme Coastal Floods -A “Pre/Post-Event” Perspective of the Storm Surge of 1962, German Bight Coast
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Fakultät für Forst-, Geo- und Hydrowissenschaften Sources And Pathways of Extreme Coastal Floods -A “Pre/Post-Event” Perspective of the Storm Surge of 1962, German Bight Coast - General Types of Failure (Pre) Event Conditions General Arrangement For Sea Dikes of Dikes Plan of December 1963 •Wave overtopping: high waves The significant failure processes In December 1963 the General running up at the seaward side during the storm surges in 1962 and Arrangement Plan for dike waves are higher than the dike 1976 were wave overtopping and enhancement, dike shortening and overflowing that led to damage to coastal protection was proclaimed in the landward slope and regressive Schleswig-Holstein. erosion. •Dike shortening –Dammingthe Due to a high preciding tide in 1962 Eider the dikes were already soaked when the actual event occurred. Figure 1: Wave overtopping Furthermore the dikes were to low and the slope angle to steep, so that •Overflowing: waterlevel at the water spilling over the dike lead to seaward side higher than the dike, erosion. 70 km dike out of 560 km water flows over the dike were destroyed and 80 km significantly damaged. Situation on Eiderstedt Figure 6: Eider Barrage Peninsula The storm flood in 1962 lent Figure 2: Overflowing urgency to a dam at the Eider river. •Breaching – from seaward side: From 1967 to 1973 the Eider due to wave impact the seaward barrage was erected. The Eider dam slope is eroded, creating holes and is close to the mouth of the river cliffs that lead to breaching between Hundeknöll and Vollerwiek. Each of the five 40-m-wide openings has two radial floodgates. One for protecting the hinterland from tidal Figure 5: Removed dunes near St. Peter waves and one to hold back water Ording on the river. The Eider barrier, used During the flood event in 1962 the as a secondary coastal defence line, sea dikes between Brunsbüttel-koog is a reduction of the length of the Figure 3: Dike breaching from seaward side and Husum were affected in an dike from 60 km to 4.8 km. •Breaching – from landward side: extremely hard way. Besides many due to overflowing and infiltrating other places, where people had to •Dike enhancement: Higher dikes water the landward slope is eroded, be evacuated, the dikes of the Köge with slight slope angles followed by sliding of the clay cover in the north of the peninsula •Coastal Protection: Construction of and breaching Eiderstedt were damaged extremely dike defence ways severely. The dunes in front of St. Peter Ording were partly removed. Conclusion Dikes alone cannot prevent storm surges from destroying the assets along a coast. A well-balanced pool of measurements is essential. Figure 4: Dike breaching from landward side Figure 7: Dike defence ways International Teaching Module Students Team A FLOODmaster Theresa Järschel Integrated Flood Risk Management of Extreme Events Cornelia Kurbjuhn Romy Marschner Manuela Rödel Réka Sesselmann Sources supported by Germany today – Damming the Eider, 1974 Die Sturmflut vom 16./17. Februar 1962 an der Schleswig-Holsteinischen Westküste Bericht des Ministeriums für Ernährung, Landwirtschaft und Forsten - Landesamt für Wasserwirtschaft - Schleswig-Holstein Die Sturmflut vom 3. und 21. Januar 1976 an den Küsten Schleswig-Holsteins Risikoanalyse an der Nordseeküste - Fallstudie St. Peter-Ording.