Retention basin Gissigheim

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The retention basin Gissigheim was a small flood retention basin near Königheim -Gissigheim near Tauberbischofsheim in the Main-Tauber district , Baden-Württemberg .

history

In the 1930s the Brehmbach between Brehmen and Gissigheim was straightened and the brook bed was reinforced. As a result, floodplain areas were lost and the flow velocity increased. In order to prevent parts of Gissigheim from being flooded in the event of heavy rainfall, an earth dam with a stone core and a man-high passage was built about halfway between Brehmen and Gissigheim at the end of the 1950s. The catchment area of ​​the structure was 12.6 km² and the usual storage space was 144,000 m³. The dam height above the ground was 9.7 m and the dam width was about 2 m. Using the photo in the weblink, on which people can be recognized, one can estimate a dam length of approx. 100 m. The Künzelsau water management office , which was responsible after the district reform from 1972, considered the condition of the retention basin to be inadequate and made several renovation proposals that provided for a widening of the dam crown to 5 m and a dam heightening by 1.3 m, as well as a second flood relief system. However, the proposals were rejected by the Königheim municipal council, most recently in February 1984.

Dam break on Corpus Christi day

Process and background

Today there is nothing to be seen at the blocking point

The dam of this retention basin broke on Corpus Christi Day , June 21, 1984, when it was overflowed with extremely high outflows during a flood as a result of heavy rain , because after a short time the bottom outlet clogged and its flood relief could not discharge the water masses after the grille cover of the relief system because of floating debris lost its efficiency considerably. Like most of the dams, the dam was not built so that it could be overflown and its air side was therefore not erosion-proof . The actual reason for the dam breach, however, was not retrograde erosion, but the integration of the relief system into the dam body, where the overflow structure was not interlocked and cavities were present due to the receding components.

The maximum water level in the basin was 10.7 m, the storage volume 0.144 million m³. At the beginning of the dam breach, 0.165 million m³ were dammed and there was an overflow height of 65 cm.

At noon, heavy rains began in Königheim and the surrounding area. At around 4:00 p.m. the water began to run over the dam of the retention basin. At 4:15 pm, about 54 m³ / s flowed over the dam crest. The dam broke at around 5:20 pm; the eyewitnesses later gave different times. The maximum breach outflow was approx. 80 m³ / s. At 5:42 p.m. the tidal wave reached the chain mill . Because of the retention effect (retention effect) of the widening valley, they could no longer be recognized as a single wave in Königheim in the general flood.

Damage

There were no fatalities due to the flood, but 9 injuries and major property damage. 55 large cattle and 700 small cattle drowned, 30 buildings were totally destroyed and 130 damaged. 80 vehicles became unusable. The damage to private property amounted to around 33 million DM , the damage to public facilities to around 6 million DM.

Despite the break, the basin prevented even greater damage in Koenigheim, as it held back the flood wave of the Brehmbach for so long that the flood waves from the side catchment areas below the rain retention basin could run ahead of it and the waves did not overlap.

The dam was not restored. The remains were dismantled after the accident. Today only the bottom outlet and the stilling basin can be seen. In the meantime, a new, larger pool is planned a few 100 meters below.

See also

Individual evidence

  1. ↑ a b c Anton Rupp: Failure of the Gissigheim dam.
  2. ↑ Karl Broich: Procedure for the hydraulic calculation of dike and dam breaks , see Table 3.1 on p. 9, (PDF; 665 kB)

Web links

Commons : Retention basin Gissigheim  - collection of images, videos and audio files

Coordinates: 49 ° 34 ′ 43.7 ″  N , 9 ° 34 ′ 3.5 ″  E