From
http://www.heureka.clara.net/lincoln...dambusters.htm :
"In the long term, it proved to be little more than a minor inconvenience to the Ruhr's industrial output. A beneficial side effect was that 27,000 men were withdrawn from Atlantic Wall defences to rebuild the dams and 10,000 men were allocated to protect Germany's other dams in expectation of further raids, although no further dam raids took place.
Where the raid did have an impact, was that the pictures of the broken dams proved to be a huge morale boost to the Allies, especially to the British, suffering under German bombing. It also told the Germans, the British could strike at the heart of their war machine. Maybe even more important, it showed the Americans and the Russians, what the British were capable of."
So, as with many "elite force" operations, the direct impact may have been small, but the ongoing fear, and the re-allocation of assets that followed added to the pressure on the German machine. 10,000 men defending the dams who could have been in Northern France in 1944....