Why were the sewers designed to overflow into the river in the first place?
By the time Sir Joseph Bazalgette started work, most of London’s rivers and streams were carrying both sewage and rainwater. Even at this time, separating the two would have been almost impossible and so he designed his new sewers to perform the dual function of dealing with ‘foul’ sewage and rainwater run-off from roads, roofs and pavements. After heavy rainfall the flows were greater than his sewers could take, so he designed the system to overflow into the River Thames when necessary, to prevent sewage from backing up and flooding streets and buildings. Of course, at that time, the river was ‘dead’ and his system was bringing big improvements, even though it overflowed from time to time. When Bazalgette’s network was built, the capital’s population was around 2.5 million. He planned for population growth of around four million, not the eight million we now serve. Nor did he predict climate change or that so many green spaces would be concreted over, preventing natural drainage.
