Green Infrastructure vs the Thames Tideway Tunnel — in pictures

Comparing Green Infrastructure (GI) with the Thames Tideway Tunnel (TTT) is a complex endeavour, which is why we’ve tried to put it into pictures.

The key issue that the TTT seeks to address is that extreme rain events cause sewers to overflow because most of the rainwater gushes down concrete surfaces straight into combined sewers. The TTT would perpetuate the flawed principle of allowing rainwater to mix with sewage.  The problem doesn’t go away and the TTT itself will run into capacity issues.  Indeed, it will still overflow several times every year, as soon as commissioned.

A key issue at the heart of the matter is climate change, which causes more extreme weather events, exacerbating overflows.  With its own substantial carbon footprint, the TTT would perpetuate a climate change vicious cycle as illustrated below. Because of this, its capacity shortages will get worse and it will spill raw sewage into the Thames more and more frequently. It’s clearly not a solution. At best, it’s a device to buy some time, but at what cost (both pecuniary and environmental)?

The Thames Tunnel perpetuates mistakes of the past - mixing precious rainwater with sewage in a single pipe - at an exorbitant cost for our wallets and the environment!

The Thames Tunnel perpetuates mistakes of the past – mixing precious rainwater with sewage in a single pipe – at an exorbitant cost for our wallets and the environment!

By contrast, it should come as no surprise that the GI solution, which actually addresses the root cause of the problem by striving to keep rainwater out of sewers and restoring the natural water cycle as much as possible, is considerably more environmentally friendly and constitutes a proper long-term solution:

Unlike the tunnel, Green Infrastructure mitigates a score of environmental issues as illustrated here.

Unlike the tunnel, Green Infrastructure mitigates a score of environmental issues as illustrated here.

Elsewhere in the world, cities are going full steam ahead with Green Infrastructure, due to all its side-benefits; some which are extremely relevant for London, such as:

  • Air quality
    • Urban air pollution is responsible for 29,000 premature deaths every year in the UK – this is likely a much more serious issue than water pollution…
    • London has recently been found in breach of the EU air quality directive and risks another set of substantial fines
  • Drought
    • You will remember hosepipe bans that were in force at the beginning of 2012…
    • The Institute of Civil Engineers rates London’s Water security as a 4 on a 10 points scale.
    • Drought risk will only worsen with growing population and climate change…
    • Again, it’s a really serious issue and continuing to pipe precious rainwater down combined sewers in this context is simply nonsense.
  • Surface flooding
    • London is prone to flooding; according to the EA, one in four property is at risk…
    • NYC has learned its lesson the hard way with Hurricane Sandy and are boosting an already robust GI plan to be more resilient next time…
    • London won’t be immune to extreme weather events forever, particularly if we continue to ignore the risks posed by Climate Change by building more outdated unsustainable infrastructure like the TTT
  • Climate Change
    • This is probably the single most underestimated environmental threat we’re facing.
    • Climate Change is actually a driver for the TTT: extreme weather events, such as intense, concentrated rainfall, have a bigger capacity to overwhelm combined sewers
    • Whereas the TTT would exacerbate Climate Change due to its substantial construction and operation carbon footprint, Green Infrastructure would do the exact opposite.
    • This vicious cycle is illustrated on the first infographic above; outdated grey infrastructure produces more greenhouse gases, which, in turn, exacerbate extreme weather events. An absolute own goal
  • Local green jobs
    • GI would foster local, long lasting green jobs, which are ideal for the long term unemployed workforce and those in need of additional qualifications.
    • Putting these people into long term jobs means that the cost of maintaining GI is long-term neutral to positive
    • This amount to substantial opportunity for the private sector to spark off a true “green collar” economy, which economists is the surest way out of the current gloomy economic climate.
    • By contrast, TTT jobs would come to an abrupt stop when the tunnel is (eventually) commissioned and TW have set themselves an “ambitious” target of employing 20% local workforce – enough said…
  • Quality of life for all!
    • Unlike the tunnel which is a sunk cost, Green Infrastructure is something that we’ll all enjoy during our everyday lives…
    • Imagine the amenity created by all the green roofs (rooftop football pitches, tennig court, urban farming)
    • The possibility to take advantage of road resurfacing to make them more cycling friendly; absence of gullies for one but also dedicated cycling lanes
    • Reduction of the urban heat island effect
    • Aforementioned mitigation of air pollution issues
    • Nicer neighbourhoods
    • But most of all, this would belong to the people paying for it, ie: Londoners; not some opaque offshore financial conglomerate that would be able to milk us for its maintenance for decades on end