In recent decades, Denmark has experienced several floods caused by torrential rain and storm surges—each time at great cost.
Major torrential rain in Copenhagen in 2011 caused an estimated DKK five billion damages. In 2013, the storm Bodil flooded large areas along the Isefjord and Roskilde Fjord, while a storm in October 2023 flooded large areas in south-eastern Denmark. Each of these storm surges cost over a billion Danish kroner.
DTU has made the first Denmark-wide calculation of how much damage we can expect from torrential rain and storm surges in the next 100 years and how much we can save by investing heavily in climate protection.
"It will cost billions to climate-proof nationwide, but it will definitely pay off," says Kirsten Halsnæs, professor of climate economics at DTU Management, who, together with climate researcher Per Skougaard Kaspersen and others, is behind a new report they have prepared for the Danish trade association for insurance companies and pension funds, F&P, and the CIP Foundation.
The researchers have calculated flood scenarios for all of Denmark at a very detailed level, linked to economic models for the consequences of flooding, and then looked at the costs and benefits of climate protection.
406 billion is a conservative estimate
The report shows that over the next 100 years, the total expected damage to homes, holiday homes, commercial buildings, transport, agriculture and tourism will amount to around DKK 406 billion, converted to present value. The costs are distributed with an estimated DKK 157 billion for torrential rain and approximately DKK 249 billion for storm surges.
Other societal values, such as health, nature and total production in the business sector, are not included as the data is too uncertain. So, according to the researchers, the DKK 406 billion is a conservative and low estimate of the costs.
They also calculated what the floods could cost year by year.
"The expected annual costs of torrential rain and storm surges are currently around DKK 7 billion annually. But we know that there will be more and more of these events, so if we don't implement ambitious climate protection measures, our calculations show that the costs will rise to DKK 12 billion per year around 2050 and to around DKK 27 billion per year in 100 years," says Per Skougaard Kaspersen.
Billion-dollar investments in climate protection can pay off
The report also assesses how far Denmark as a society should go to protect itself against flooding. Overall, it is clear that relatively high levels of protection can pay off.
"In most cases, the cost of climate adaptation will be lower than the expected damage costs, so we can achieve significant savings by investing in climate protection now. But several billions need to be put on the table," says Kirsten Halsnæs.
For example, adequate protection against a 20-year torrential rain event would cost DKK 69 billion but save us DKK 112 billion in damage costs.
In the case of a storm surge, which today would be viewed as a 100-year event, the cost of protection would be DKK 37 billion, while the potential damage costs are DKK 67 billion.
The researchers behind the report emphasize that their estimates are meant as input to make broad, national decisions. There will be local differences in the specific consequences of flooding – for instance, whether it's fields or houses being flooded – and whether there are local benefits through nature-based solutions such as stream restoration.
