The quite flat low clay of Aldermaston's north has with exceptional rainfall led to flooding certain populous streets on three occasions – 1971, 1989, and 2007. The flood in 1971 caused by torrential rain was exacerbated by the non-porous tarmac and buildings of the Atomic Weapons Establishment which managed for the first time to overwhelm its balancing ponds. This happened again in July 1989, when an average of of rain was deposited across the parish in two hours; water rose above the ponds and broke through a brick wall. The destroyed wall was rebuilt with 17 grilles to avoid another build-up of water. A donation of £10,000 was given to the village by Blue Circle.