Trimpley and Walthamstow illustrate an important principle in the design of bunded reservoirs: amenity land should be created at or above water level. Many of the Lea and Colne valley reservoirs have land in water company ownership which could be used for this purpose. Some of them are also underlain by sand and gravel deposits which could be exploited. Excavations would increase the volume of stored water and would provide material for the construction of new waterside mounds. It would also be possible to obtain inorganic fill material from the stream of trucks which transport wastes from London to suburban landfill sites. Material of this type was used in a reclamation scheme for Markfield sewage works in the Lea valley (Aldous 1972: 131). But even inert fill would have to be handled with the greatest care beside an existing reservoir.
Regent's Park and St James's park are surrounded by fine buildings. They gain from the parkview and the park gains a scenic backdrop from the buildings. This principle should be adopted in the design of urban reservoirs. The clubhouse at Queen Mother Reservoir demonstrates the structural feasibility of building on top of reservoir bunds, and there is scope for many other types of building. Since the Queen Mother Reservoir it less than three miles from Heathrow Airport it could provide a superb site for a hotel and conference centre. Windsor Castle can be seen over the water. Most of the airport hotels have drab sites and are hardly an advertisement for Britain.
The reservoirs and flooded gravel pits around Heathrow should be developed as a gateway waterpark for England. It would be used primarily as a visual amenity and to create sites for prestige buildings. Other urban reservoirs, when free of aircraft noise, could provide housing and hotel sites [Fig 5.15]. It would be possible to design Bakethinï¾type barriers to preserve the water level in the immediate vicinity of the buildings. The water companies could make more money out of property development than they do out of water. They need imaginative landscape plans.