Net-zero carbon dioxide emissions in flood defence schemes

This paper compares the carbon dioxide emissions of constructing flood protection schemes with the emissions saved by providing flood defences. There is considerable information available on the carbon dioxide ‘cost’ of construction, but less on repairing flooded properties. Drawing on existing research into flooding, this paper identifies a carbon dioxide cost of repairs of 6 tonnes carbon dioxide equivalent per property flooded and uses this to provide a method to determine emission benefit for constructing flood protection schemes. While emission reduction should be the first priority, flood defences defend against future emissions. Using Stonehaven in the UK as a case study, this paper demonstrates that the carbon dioxide cost of constructing a flood protection scheme can be less than the carbon dioxide cost of undertaking repairs following flooding over the life of a scheme, with a benefit ratio of 2 identified for the case study scheme. The paper concludes with a review of the UK government appraisal process and cautions that the carbon value many not differentiate a flood protection scheme option when compared with capital cost. It is considered that an independent assessment should be undertaken to demonstrate that a net-zero-emission option is selected.