The Government’s 2004 Foresight Future Flooding report took a long-term view of national flooding and coastal erosion risks to 2100. It estimated that future climate change, together with increased economic wealth which increases losses, could lead to potentially significant increases in future risk by the end of this century.
The Government advise the operating authorities to factor climate change effects into the design of present-day river and coastal defences. An allowance should be made for acceleration of sea level rise, as a result of climate change already locked in to the global system, from the current 2.5-4 millimetres (mm) a year to 13-15 mm a year by the end of the century, depending on location. As part of a precautionary approach, this advice also includes predicted land level changes as very gradually the south east of England has been lowering and the north of the country rising since the last ice age. Such guidance for flood and coastal erosion risk management activities has been provided since 1989 and is kept under review (most recently revised in October 2006).
Sensitivity tests are also recommended for a 20 per cent. increase in the river flows as a result of climate change. Increases in rainfall intensity are also recommended in planning guidance (PPS25) for new urban drainage.
On storm occurrence, the scenarios to be published by the UK Climate Impacts Programme in 2008 are expected to provide further insight into changes that may occur over the next century and these will be taken into account in future guidance.