The Dams Raid

Dams of the Ruhr Valley

Map from the front page of The daily Telegraph 18th May 1943

People today think that Barnes Wallis came up with the idea to destroy the dams of the Ruhr valley. This is not true; the Air Ministry had dicussed the matter back in 1938, just in case Germany went back on the war path. The committee laid down clear objectives should the matter arise.

  1. Cut water supplies for industrial and domestic use.
  2. Cause flooding and damage to industrial plants, railtracks and water ways in the valley.
  3. Prevent sufficient supplies of water for use in the inland waterway systems.

The dams that were under discussion were the Mohne, Eder,Sorpe and the alternative sites of the Ennepe, Lister, and Diemel dams. The Mohne being the most important of them, the reason being this dam near Dortmund was a catchment type dam its role was to collect rainwater and to prevent flooding of the valley. It also provided water for industrial and domestic use and inturn generated hydro-eletricity for the Ruhr valley. The Eder was used to feed the important Mittelland Canal, prevent flooding and generating hydro-electricity, the others worked like the Mohne only smaller.

The idea was on the table but no one had any idea how to carry out such a task and so the idea was shelved.

The Mohne dam

Situated at Gunne and 25 miles east of Dortmund, construction started in 1909 and finished in 1913. The wall was made of limestone rubble masonry and was protected against seepage. This construction stood 112 feet high and had a base thickness of 130 feet tapering to 25 feet at the top and is 2100 feet long. The dam holds back 135 million cubic metres of water, covering an area of 3229 acres. It was protected by 2 anti torpedo nets in the water and anti aircraft guns.

After the raid over 2,000 workers took just 4 months to rebuild the wall ready for refilling, the power station was never re-built at the base of the dam.


The Eder

This was yet another very impressive dam being the largest masonry dam in Germany, it reached 138 feet into the air and was 119 feet thick at the base tapering to 20 feet at the top and a lenght of 1310 feet. The Eder is some 25 miles east of the Mohne dam. The Reservoir was much larger than the Mohne it could hold up to 7100 million cubic metres of water


The Sorpe

This dam was built between 1927 - 1933, and was a completely different type of construction. This one consisted of an earth work embankment and a concrete core. The wall height was only 58 feet but had the capacity to hold 72 million cubic metres of water. It is situated six miles south of the Mohne and even Barnes Wallis indicated his bomb would not work on this type of construction.

The Ennepe

This masonry type dam was built between 1902 - 1905 it has a wall height of 45 feet and holds back 15 million cubic metres of water.


The Lister

The Lister built between 1909 - 1911 with a wall height of 35 feet it was also of the masonry type "ideal for the bouncing bomb", this dam had a capacity of 22 million cubic metres of water.

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