How critical infrastructure can be made more climate-resilient

Whether it’s arrival and depar­ture boards show­ing can­celled trains because of flood­ing, or images of sub­merged roads in rur­al vil­lages, extreme weath­er events take their toll on infra­struc­ture and the peo­ple who rely on it.  

Glob­al­ly, the nar­ra­tive is a sim­i­lar one, with heat­waves and unprece­dent­ed rain­fall lev­els affect­ing every­thing from roads and rail­ways to bridges and sew­ers, lead­ing many ana­lysts to describe infra­struc­ture resilience in the face of cli­mate change as a time bomb. 

That sense of urgency has been high­light­ed this year by In Deep Water?, a report by think tank Bright Blue, which exam­ined how flood­ing endan­gers all types of infra­struc­ture in the UK. Its con­clu­sion was not opti­mistic and revealed that the UK is not ade­quate­ly pre­pared for the increased risk. 

“Flood­ing is the most seri­ous cli­mate-relat­ed risk to the UK in terms of the haz­ards it presents to com­mu­ni­ty func­tion­ing,” says envi­ron­men­tal and nat­ur­al resource econ­o­mist Helen Jack­son, the report’s author. “Cli­mate-resilient infra­struc­ture is key for dis­as­ter response. And infra­struc­ture which isn’t resilient can be unsafe and its fail­ure can ampli­fy the impacts.” 

This year’s report by the Inter­gov­ern­men­tal Pan­el on Cli­mate Change rein­forced the real­i­ty that cli­mate change is already caus­ing more fre­quent and more severe extreme weath­er events. It revealed that high­er pre­cip­i­ta­tion inten­si­ty could increase the risk of flood­ing and they iden­ti­fied bridges as one of the infra­struc­tures most at risk.

Engi­neers and plan­ners look at cli­mate mod­el­ling at the out­set of their projects and fac­tor fore­casts into their designs. Bridges are built to with­stand high­er mag­ni­tude flood events and sea-lev­el ris­es, with rein­forced foun­da­tions and greater height clear­ances from the waters below. Road con­struc­tion is also chang­ing, to accom­mo­date the dam­ag­ing impact of flood water as roads that are under­wa­ter for days can be impass­able even after the waters have reced­ed, caus­ing con­tin­ued dis­rup­tion for entire com­mu­ni­ties. 

Engi­neers are find­ing a way to weath­er­proof roads after a harsh les­son learnt in Queens­land, Aus­tralia, which expe­ri­enced sev­er­al extreme cli­mate events, includ­ing exten­sive flood­ing that dam­aged 19,000km of the state’s road net­work in 2010-11. 

“Queens­land used a process called foamed bitu­men sta­bil­i­sa­tion,” says Car­o­line Evans, chair of the cli­mate change and road net­work resilience com­mit­tee for the World Road Asso­ci­a­tion (PIARC). “The hot bitu­men is inject­ed with lim­it­ed amounts of air and cold water, which forms a water-resis­tant lay­er with­in the road itself. The process was in place in Queens­land by the time Trop­i­cal Cyclone Deb­bie hit the state in 2017 and when the waters reced­ed, the roads were still intact and need­ed min­i­mal main­te­nance.” 

Not all crit­i­cal infra­struc­ture is above ground. The Thames Tide­way Tun­nel project, dubbed the Super Sew­er, is in progress. A des­ig­nat­ed nation­al­ly sig­nif­i­cant infra­struc­ture project, the 25km tun­nel is being built to solve a his­tor­i­cal prob­lem that has been grow­ing more acute every year, as London’s Vic­to­ri­an sew­ers fail to cope with the amount of mate­r­i­al flow­ing through the net­work. Even driz­zle can cause untreat­ed sewage to spill into the Thames, cre­at­ing com­bined sew­er over­flows (CSO) inci­dents. With the prospect of increased rain­fall lev­els, engi­neers have future-proofed the tun­nel to cope with Met Office cli­mate pro­jec­tions that run to 2080. 

“There are cur­rent­ly around 50 CSO dis­charges per year, but the project is designed to restrict this to four or less,” reveals Roger Bai­ley, Tideway’s chief tech­ni­cal offi­cer. “The future per­for­mance of the tun­nel has been test­ed against rain­fall pre­dic­tions from the UK government’s medi­an emis­sions cli­mate pro­jec­tions for 2080. Parts of our new pub­lic realm are flood­able and com­pli­ant with the Envi­ron­ment Agency’s pre­dic­tions for ris­ing sea lev­els.” 

But the solu­tion to London’s sewage prob­lem pre­sent­ed plan­ners and engi­neers with a fresh one: how to min­imise the envi­ron­men­tal foot­print of the con­struc­tion phase? Hun­dreds of lor­ry jour­neys would be required every day to trans­port mate­ri­als to the site and embod­ied car­bon from it. The oper­a­tors turned to the Thames itself, rely­ing on riv­er barges rather than lor­ries. 

A 1,000-tonne barge pro­duces an aver­age of 90% less car­bon diox­ide than the HGV equiv­a­lent and by the end of the tun­nelling phase in April this year, more than one mil­lion tonnes of mate­r­i­al had been trans­port­ed by riv­er, sav­ing more than 115,000 HGV jour­neys. Tide­way esti­mates that more than 200 lor­ry jour­neys have been tak­en off the road each day. This inno­v­a­tive think­ing is crit­i­cal for a project’s legit­i­ma­cy and shows that the lev­el of cli­mate resilience can be estab­lished long before any ground is bro­ken.  

The same is true even for exist­ing struc­tures that require resilience to be retro­fit­ted. Take Dawlish in Devon, where the sea wall col­lapsed after storms in Feb­ru­ary 2014, forc­ing a full line clo­sure for eight weeks, cut­ting off the South West from the rest of the coun­try by rail. It was decid­ed that a new wall would be built in front of the old one, using new con­struc­tion tech­niques. Defences were twist­ed into the rock like a screw, rather than being dri­ven in, to achieve a depth that would with­stand future ris­es in the sea lev­el and tidal swells. 

But before any of this work start­ed, the height of the wall and pro­file of the cap­ping were analysed exten­sive­ly, with lab-based phys­i­cal mod­el­ling used to ver­i­fy the com­put­er-based mod­el­ling with an out­come that pre­dict­ed the project would be cli­mate-resilient for 100 years. 

The Dawlish and Tide­way projects show how old and new infra­struc­ture projects can be made cli­mate-adap­tive, shield­ing against the effects of rapid­ly chang­ing envi­ron­men­tal con­di­tions. The goal is to remove the weak links, even though the course of cli­mate change is unclear and we don’t know what’s com­ing down the road, the tracks or even the pipeline in the com­ing decades.