The flood-ravaged Bishopsford Road bridge will be demolished and rebuilt at a cost of £2.7 million.
After days of heavy rain, the northern arch of the bridge, which crosses the river Wandle, partially collapsed in June last year, given the erosion of its foundations and the surrounding river bed.
Nearby residents suffered longer commutes and higher travel expenses in the 8 months since the crucial crossing was damaged.
Deidre Sutton, 59, relied on the bridge to make family visits and commute to Ikea where she works as a salesperson.
She said: “It affects me every single day so I am fed up.
“The council aren’t even sorting out potholes on the roads that are now overused, and because our road is empty we have racers, which is another problem.”
Merton councillors dismissed cheaper alternatives for restoring the bridge during a Cabinet meeting on February 24.
In a statement, Merton Councillor Martin Whelton defended the high-cost of reconstruction plans.
He said: “A quick-fix solution may have meant further work having to be carried out in a few years’ time, causing further disruption.”
The decision was made in the wake of Storm Dennis, with the Met Office reporting that almost all of England’s rivers were recording unusually high water levels.
The UN Intergovernmental Panel on Climate Change (IPCC) says climate change will lead to heavier rainfall and increased flood risks across the UK.
Construction of the new bridge is due to start in summer 2020, with plans to open in spring 2021.