of the chalk formation the North Wessex Downs as part of the Thames Basin Heaths. The topography of the land in the parish generally slopes northward to the River Kennet. The soil in the parish is high in clay. Due to the parish's location within the Kennet Valley there is a high concentration of alluvium, with the content largely determined by the London Clay Formation, the Bagshot Formation, and the Bracklesham Beds. Flooding 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. In July 2007, torrential rain flooded some of the traditional village centre and primary school. The storm coincided with the annual Glade Festival and jeopardised the event. The festival gates were temporarily closed while organisers assessed the flooding, which submerged one of the stages. The festival's car park was incapacitated, with thousands of revellers stranded in the village and surrounding lanes. The floods also hit the Church of England primary school, with the Royal Berkshire Fire and Rescue Service evacuating pupils and staff from the school in life rafts. The evacuation used four rafts, rescuing pupils and teachers from the school through windows. The 165 people (140 pupils and 25 members of staff) were taken uphill to the parish hall, where blankets and sleeping bags had been provided. Thames Valley Police stated that the emergency services were "really stretched because of what happened over the county and the Glade event", that "the A340 road junction was two or three-foot under water", and predicted that "a lot of householders would be homeless." Demography The 1831 census showed that 68% of the employed population of Aldermaston were working class or "labourers and servants". 20% were middle class ("middling sorts"), 10% were upper class ("employers and professionals") and 2% were unclassified. In 1887 the population of the