Mounting evidence shows that recent sea-level increases have been caused by temperature rise. Rising ground-surface temperatures cause the melting of land-based ice, which ends up in the oceans and causes sea level to rise. Rising sea-surface temperatures cause a slight yet significant expansion of ocean-surface waters, also leading to sea-level rise. Most of the sea-level rise within the past few decades have been a result of this thermal expansion (Cabanes et al., 2001).

Sea-level rise during the 21stcentury is likely to have major negative effects on the world’s coasts and the 21% of the world’s population who occupy them (Gommes et al., 1997). Increased storm-surge hazards associated with sea-level rise will affect over 46 million people each year. A 1 metre rise in sea-level would increase this to about 118 million or more, as population growth is taken into account (Watson et al., 2001). The IPCC Reports (2001) state the sea-level is projected to increase 8-88cm between 1990 and 2100. However, more recent research indicates that sea-levels may rise between 1 metre and 3 metre this century (Dasgupta et al., 2007).

Warming oceans are also changing the world’s rainfall. In the UK rainfall events that would previously have occurred only once in a century are now likely to happen every eighty years in the south of England. This will mean far more frequent severe floods, as the UK has witnessed in recent winters. This will only get worse as global warming continues to rise (Harvey, 2014). In the winter of 2015/16, 16,000 properties were flooded and more than 75,000 lost electricity, causing more than £500 million in damages.

Despite the risks, UK government advisers say that construction on flood plains should go ahead. Flood plains tend to be flat and so are attractive to developers as they are easier to build on and with the UK facing a housing crisis, the pressure is on to build. Lord Krebs, the government’s statutory adviser on adapting to the effects of global warming, told an influential committee of MPs that although recent flooding has caused houses and other buildings to be inundated, property could continue to be constructed on flood plains. He said that the attendant risks and the possible devastation would have to be made clear to households, local government and developers (Harvey, 2016).

But what are the consequences of building or interfering with flood plains? According to the results of a recent 12-month study, a staggering 90% of England’s extensive floodplains are now not fit for purpose. Co-author of the study, George Heritage (2017) of Salford University said that “The changes to them mean water [from heavy rainfall] can flow much faster downstream and can flow at the same speed as the water in the rivers.” 

This accelerated flow has led to sudden and unstoppable deluges in recent years which have burst river banks. Normally, overflow from rivers, would spill out into flood plains which would act as natural sponges, soaking away the water through the vegetation. But now, intensive agriculture, increasing urbanisation and the draining of wetlands have altered the flood plains ability to act as a natural buffer against rushing water. They no longer have the ability to store water, leading to rapid flows into urban areas (Harvey, 2017).

Cabanes, C., Cazenave, A. and le Provost, C (2001) Sea level rise during past 40 years determined from satellite and in situ observations. Science, 249, 840-842.

Dasgupta,S., Laplante, B., Meisner, C., Wheeler, D., and  Yan, J. (2007) The Impact Of Sea Level Rise On Developing Countries: A Comparative Analysis Policy Research Working Papers.

Gomes, R., due Guerny, J., Nachtergaele, F. and Brinkman, R. (1997) Potential Impacts of Sea-Level Rise on Populations and Agriculture, Rome: FAO.

Harvey, F. (2014) ‘Climate change 'making extreme rainfall in England more likely’, Guardian, 30Apr 2014.

Harvey, F. (2016) ‘Build on flood plains despite the risks, say UK government advisers’, Guardian, 27Jan 2016.

Harvey, F. (2017) ‘Nine tenths of England's floodplains not fit for purpose, study finds’, Guardian, 01Jun 2017.

Heritage, G. and Entwistle, N. (2017) The Impact of Floodplain degradation on flooding in the UK. 37th IAHR World Congress, Volume: E-proceedings of the 37th IAHR World Congress August 13 – 18, 2017, Kuala Lumpur, Malaysia