This post is the second in a series focusing on the cycle of flood and drought which climate change experts are predicting for the future of the UK. MARIA JOSE YURISIC A, a Kingston University student, proposes a strategy to deal with rain water excess and scarcity in urban areas, creating a new typology of urban valley.
FLOOD & SEWAGE SYSTEM
“Like many older cities around the world, the vast majority of London is served by a combined sewerage system, collecting sewage (from toilets, sinks and washing machines etc) together with rainwater run-off from roads, roofs and pavements.The magnificent interceptor sewers, constructed by Sir Joseph Bazalgette following the ‘Great Stink’ of 1858, are still the backbone of London’s sewer network today. Rebuilding this system, using modern methods, would cost £50-60 billion today. The city’s natural drainage system, which is a network of waterways (the so-called ‘Lost Rivers’ of London, such as the Fleet and the Tyburn), had been built over and was already conveying sewage when Sir Joseph Bazalgette incorporated it into his design. The system was designed so that overflows would go into the River Thames, preventing the back up of sewage flooding people’s homes and streets”. Source: Why London need the Thames Tunnel
Flood is a major problem in London, especially if the climate change and rainfall predictions are included in the analysis. However, the problem is caused not just because the amount of rainfall has increased in the last years (which is also predicted that will still increasing in the next decades) but also because the city is no longer prepared to deal with that water. Together with the development of the city the non-permeable surfaces had cover an important part of what used to be soft surfaces, such us gardens, parks, squares and specially the Lost Rivers of London, all which was the hydrological network that used to be able to deal with the runoff water. On the contrary, nowadays all the rainwater goes through the streets to the (non permeable) sewage system, which transport the water rapidly and straight to the Thames. The Thames now is “doing the job” of all the other rivers, and is technically not capable of doing that. Therefore London floods.
The authorities have faced the problem proposing huge and expensive engineering interventions, such us the Thames Tunnel (also known as the Super Sewer) and the construction of new barriers in the Thames Estuary. Both of this “solutions” will require enormous amounts of money for the construction and maintenance and probably will have a certain period of operation, after which they will have to be replaced for another solution. What is needed now is a citywide strategy, more than a simple solution.
RIVERS + LOST RIVERS + CANALS: HYDROLOGICAL NETWORK
Natural connection between green areas in London.
Central London : “Lost Rivers” – Complete disconnection of the green infrastructure. A series of unconnected permeable areas (parks and others) don´t work properly against flooding. On the contrary, the runoff water is making the flood problem worst.
More frequent and intense storms, especially in summer, are adding to the problem, as is the loss of permeable surfaces able to soak up rainfall. As little as 2mm of rainfall can now trigger a sewage discharge.
CURRENT SITUATION: (HOW) LONDON FLOODS
FLOOD IN LONDON: PROPOSALS UNDER STUDY
- NEW THAMES BARRIER + AIRPORT
- THAMES TUNNEL
London proposed infrastructure
London Super Sewer