Report reveals Scottish coastal flooding risk

A major new report offering for the first time a systematic study on coastal flooding in Scotland was launched at the University last month by researchers within the School of Social and Environmental Science.

'Coastal Flooding in Scotland: a Scoping Study' was commissioned by the Scottish and Northern Ireland Forum for Environmental Research on behalf of the Scottish Government, SEPA and SNH, in partnership with Scottish Environment Link and Comhairle nan Eilean Siar.

It was prepared by geographers Tom Ball, Alan Werritty, Rob Duck, Anton Edwards, Laura Booth and Andrew Black and represents the first systematic study on coastal flooding in Scotland which both assesses the risk and explores the management options.

'Until recently coastal flooding has attracted less attention in Scotland than floods affecting cities and the countryside," explained Professor Alan Werritty, who led the report team. "With sea level rise and the threat posed by storm surges, now is the time to assess the risk posed by coastal flooding and ways of managing that risk.

'The Scottish Government is currently bringing in a Flooding Bill which will radically change the way we manage flood risk in Scotland. This report is designed to assist the Scottish Government in changing the way we react to coastal floods.'

In assessing the risk, 304 separate coastal floods were recorded in an historical database and map which extends back to 1849 and itemises both the severity of the flood and its associated damage.

From this database it could be seen that many coastal areas have been flooded over the last 160 years with the Solway Firth, the Moray Firth, Aberdeenshire and the Firth of Clyde reporting the highest number of events. Storms driven in from the Atlantic Ocean during periods of strong westerly winds are the main cause of coastal floods.

Present-day flood risk arises from the combination of high tides, storm surges (driven by intense low pressure weather systems and superimposed on the tidal level) and wave action (driven by the wind). Over the past few decades water levels 50-60 cm above the highest predicted tide have been recorded at Aberdeen, Lerwick and Stornoway and 120 cm at Millport.

In response to recent sea level rise, mean surge levels are increasing at 1.17-2.18 mm per year for the Scottish mainland, but are slightly declining at 0.36 mm per year in Shetland.

Future flood risk depends on global mean sea level rise, regional uplift or depression of the land surface, and tidal changes. The best estimate of current global sea level rise of around 3 mm per year is expected to increase to around 4 mm per year by 2090. For much of Scotland, this is moderated by continued uplift of the land surface following the melting of the last Scottish Icesheet around 10,000 years ago. Thus by the 2080s we estimate that net sea levels will be around 20 cm higher in the Clyde estuary, 28 cm higher in Moray and Aberdeenshire and 32 cm higher in the Northern Isles. Given the uncertainties over future changes in surges and wave action, we have assumed these to remain unchanged in our map of future coastal flood risk.

The full report can be accessed from http://www.sniffer.org.uk using search code FRM10.