Storm tides and surges
If a storm, or hurricane, is pressing bodies of water against the coast, a storm surge can occur. On the North Sea coast of Germany, this mostly happens with northeastern winds. These winds press water into the German Bight. In addition to that, the mouths of rivers Elbe and Weser respectively form a sort of funnel. This leads to a further increase in water levels along the river courses. So if there’s flow tide, storm tides that exceed mean high tide by several metres might happen.
Dikes and barrages
To prevent flooding of the backcountry, higher and higher dikes had been built during the last centuries around coastal areas and river embankments. In the Bremen region, additional barrages have been built after the great flood of 17th February 1962. The hinterland of Hunte, Ochtum and Lesum is thus protected from surge events. However, dikes as well as barrages reduce compensatory areas for the water. So when a surge actually occurs, the water rises higher than before.
The storm surge of 17th February 1962 developed into a flood catastrophe with 340 casualties. At the Vegesack station, a high-water mark of 5, 23 metres above mean water level had been measured. At rivers Elbe and Weser and their tributaries, water levels that exceeded all figures ever recorded. Dikes were destroyed and vast areas flooded. The outcomes of this surge were newly-built barrages, and even higher dikes.
On January 3rd, 1976 another heavy storm surge occurred. An unfavourable weather constellation caused a prolonged hurricane. The water levels of 1962 at the Elbe and the Northern North Sea coast were exceeded. At the river Weser, figures stayed just below the previous peak. Vegesack recorded a highwater mark of 5,14 metres above mean water level. The compensation areas in Blockland and Niedervieland were flooded, also the whole of the Stadtwerder river island.
The storm surge of 28th January 1994, brought about the highest water level of all time in Bremen-Vegesack. It amounted to 5,33 metres about mean sea level. During the surge, all three barrages at Hunte, Ochtum were closed. Because the waters lacked now compensation areas, water levels rose accordingly.
An important surge event was caused by the depression Xaver. On December 5th and 6th, 2013, very similar weather conditions to the storm of 17th February 1962 prevailed, with a strong high in the South and distinct low pressure in the North. In Vegesack, the water reached a level of 5,16 above the mean.
The highest storm tides are recorded at the pillars of the signal station. They give an impression of the water surge at storm events. Every year, the Weser floods several times. Even moderate winds can cause, combined with spring tide water, relatively high water levels.