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Safety seal: a welder working on a section of a gigantic pipe that will help protect a coastal area of southern England from flash flooding.

Fresh patterns of climate change - causing more storms throughout the world - could make many coastal towns and cities vulnerable to flooding, according to forecasters.

One example of this was that coastal communities in southern England experienced a freak deluge this summer. More than three months’ of normal rainfall occurred in three hours. The historic town of Hastings experienced the heaviest rainfall since records began in 1865.

The regional water company has responded to the threat with a 10-point action plan costing 20 million pounds to help protect the famed city of Portsmouth and surrounding area.

Southern Water is installing a 2.2-metre-wide steel pipeline at its existing pumping station, helping to prevent it becoming overloaded during heavy rainfalls and storms.

The pipeline at Eastney will also connect a new 10 million pounds sister pumping station being built underground to an existing 1.8m sewer. The station sewer has four stand-by pumps capable of dealing with 9,000 litres of water every second.

Senior contracts engineer Dennis Taplin said: “We are making good progress with this scheme. When complete, the new pumping station will support the current pumping station, improving both response time and overall security to Portsmouth during storm conditions.”

Southern Water’s director of operations Andy Watson added: “Portsmouth is served by an ageing drainage and sewage system dating back to Victorian times and it also serves an area much of which is below high-tide level, so that most of the system has to be pumped to prevent flooding.

“Weather patterns are changing, with violent storms and intense rainfall occurring more commonly,” he added. “Our present pumping stations would not have had the capacity to respond effectively to the extreme weather events and flash floods we could experience.”

The Portsmouth district is densely populated and has little open land to soak away rainwater, as well as the possibility of thousands of homes being built under construction plans for the area.

The bedrock of Southern Water’s protection plan is the construction and upgrading of pumping stations, but it also includes an extensive programme of improvements to the sewer system.

There has been a comprehensive survey of the whole underground system with a view to seeing how it performs under different conditions. More than 500 sites have been inspected - in inaccessible areas using high-tech cameras being operated remotely - in what is thought to be one of the largest sewer surveys carried out in a city.

The water company is also looking at Rainfall Radar, a computerised technology linked to the UK’s Meteorological Office, allowing forecasters to predict the course of heavy rains.

Trained engineers would be able to chart the course of a storm developing in France and monitor it as it crosses the English Channel and heads for the coast.

This early warning would enable pumps to be primed and engines fired up early in the pumping stations that would be all set to react immediately.

Looking ahead, Southern Water is investing to try to minimise the effects of flooding generally in houses, gardens and open spaces in both rural and urban areas.