Environment Agency publishes long-term flood investment scenarios to 2125

The Environment Agency published its Long Term Investment Scenarios 2026 on 13 November, an economic assessment of what flood and coastal erosion risk management in England could look like over the next 50 and 100 years.

The report, known as LTIS, considers the next 50 years, to 2075, and 100 years, to 2125. The Environment Agency previously produced editions in 2014 and 2019.

The agency said current government investment in flood and coastal erosion risk management (FCERM) is about £1.3bn to £1.4bn a year. It said the 2026 study uses more sophisticated methods and takes account of the best available evidence, including its National Flood Risk Assessment, and described it as a major step forward.

The assessment

The agency said LTIS explores what can be achieved for different levels of investment, describing outcomes in terms of reduced economic damages and wider benefits. The study covers three sources of risk: river flooding, coastal flooding and surface water flooding.

Its design climate scenario is based on 2°C of warming by the middle of the century and considers 4°C of warming by the end of the century. The agency said an extreme climate scenario is also used for stress testing.

The scenarios include significant maintenance activities for refurbishing or replacing existing assets, but the agency said routine maintenance costs are not accounted for in the results. The report also estimates wider benefits from investment, such as reduced carbon emissions and improvements to nature, and estimates how benefits are distributed in terms of social equity.

The Environment Agency said LTIS does not assess where the funding would come from or which funding sources would be most appropriate.

The previous edition, LTIS 2019, put the overall benefit-cost ratio at about 5 to 1, with about £5 of property damage avoided for every £1 invested. Its annual average investment was calculated over the 50-year period 2014 to 2063.

Properties at risk

According to the 2026 report, about 6.3 million homes and businesses are currently in areas at risk of flooding in England, a figure that could rise to about 8 million, or around one in four properties, by mid-century.

The 6.3 million total matches the agency's National Flood Risk Assessment published on 17 December 2024, which put about 2.4 million properties in areas at risk from rivers and the sea and about 4.6 million in areas at risk from surface water. That assessment reported an 88% increase in the number of properties at the highest levels of risk compared with the previous assessment.

The current programme

The scenarios sit alongside spending the government has already committed. On 17 March 2026 the government and the Environment Agency announced £1.4bn of investment in flood defences in 2026/27, with more than 600 projects being funded. The government said a £7.9bn capital investment over the next decade will benefit 840,000 properties, and that at least £10.5bn will be invested between 2024 and 2036.

The Environment Agency's programme page states that the £7.9bn capital commitment covers 10 years from April 2026 to March 2036. Its business plan for 2026 to 2027 says it is investing £1.4bn in the next generation of flood and coastal erosion risk management, and that 70,000 properties will benefit from flood protection by March 2027.

The LTIS 2026 report is available on GOV.UK in HTML and as a 29-page PDF, alongside the 2019 and 2014 editions.