Flood Risk and Climate Change: Developers Must Respond to Greater Uncertainty

The Met Office has provided its first major update on climate change in almost 10 years, warning of significant increases in rainfall, flood risk and coastal sea level rise in the decades ahead. This stark warning means planning authorities and communities will assess location for the long term on flood risk.

The UK Climate Projections 2018 study is the most up to date assessment of how the UK may change over this century. The 2018 heatwave will become the norm while winter rainfall increases by more than a third.

In launching the report, Michael Gove, the Environment Minister, backed the scientists behind the projections.

The Report was launched on the 10th anniversary of the UK’s Climate Change Act. This ground-breaking strategy, which commits the country to cutting greenhouse gas emissions by 80 per cent by 2050, shows the UK currently well ahead of many other nations in curbing carbon emissions.

But set in the global context, our contribution will do little to change dramatic changes in the course of our children’s lifetimes, said the Met Office.

Higher Sea Level Rise

The Met Office highlights that a general increase of at least 1m in sea level rise is almost certain.

Sea levels in the Thames Estuary could raise flood tides by up to 1.15 metres by 2100, while Edinburgh, Cardiff and Belfast all face water rises of over 90 cm, if greenhouse gas emissions continue unabated. And even if emissions are cut in line with the Paris climate agreement to curb temperature rises to well below 2C above pre-industrial levels, sea levels could still be up to 70cm higher in the capital.

The report says many coastal communities are particularly vulnerable to flood risk because populations in coastal areas are often poorer and older than the UK average. At the same time, The Committee for Climate Change (CCC) has said that current shoreline management plans are unfunded and far too optimistic.

It highlights the issue of land-slips on the coast. It says 100,000 cliff-top properties could be at risk from coastal landslides, but the public don’t have clear and accurate information about the issues and there’s no insurance or compensation for people who lose their homes.

Transport, energy and waste infrastructure are also exposed to coastal flood risk and erosion.

Approximately 7,500km of road, 520km of railway line, 205,000 hectares of good farm land, and 3,400ha of potentially toxic historic landfill sites are currently at 0.1% or greater risk of coastal flooding in any given year.

Power plants, ports, gas terminals and other significant assets are also at risk. The report says the government needs to focus on protecting these assets, as well as saving people’s homes.

What’s more, coastal defences are likely to be at risk of failure as sea levels rise.

A rise of just 0.5m is projected to make a further 20% of England’s coastal defences vulnerable to failure. The risk will be even higher if the current rates of deterioration of salt marshes, shingle beaches and sand dunes continue.

In England, 520,000 properties (including 370,000 homes) are in areas with a 0.5% or greater annual risk from coastal flooding.

By the 2080s, that figure could rise to 1.5 million properties (including 1.2 million homes). In addition, approximately 1,600km of major roads, 650km of railway line, 92 railway stations and 55 historic landfill sites are at risk of coastal flooding or erosion by the end of the century.

Greater Flood and Drought Risk

The increased temperatures will bring greater humidity and therefore more rainfall. Scotland, Northern Ireland and The North of England could receive as much as a third more rain in the winter, while the South of England could see an average 5C temperature rise in the summer, with the corresponding water supply and drought problems.

Gove highlighted that a new long-term approach would be needed on dealing with flooding, warning “it will not always be possible to prevent every flood. We cannot build defences to protect every single building or reinforce every retreating coastline”.

This could lead to an acceptance of managed retreat more widely from some of our most vulnerable coasts to deflect flood risk in any one area. Natural catchment management and upstream solutions, such as dams and riparian planting to slow the flow would also dissipate impacts to communities downstream.

But there is also a real possibility that communities may need to be permanently relocated and estates abandoned should persistent inundation be unavoidable, especially with combined tidal and fluvial flood events.

To tackle droughts, Gove also said new policies would help drive the construction of new water infrastructure such as reservoirs.

Developers and architects must realise (and quickly) that local planning authorities and home owners are increasingly looking to the long term with how and where they will create and be part of communities. Climate change and planning responses are at the heart of this.

Guidance and legislation on mitigating flood risk are tightening all the time and verifying the right site is now a crucial part of economic viability.

GeoSmart provides architects, planning consultants and their developer clients with a comprehensive range of flood risk and drainage assessments to ascertain conditions ahead of full planning submission.  These account for past extents, land use zoning and allowances for climate change.

These can provide essential pre-screening of sites for potential risks, through to providing a forensic approach to risk from surface, river and groundwater flooding and how these could affect site drainage.

For more information contact us on 01743 298100 or email info@geosmartinfo.co.uk