IN THE newly released film Flood, London is swamped by a tidal surge. With uncertainty about the effects of global warming, it is a worrying scenario for the capital. Fortunately for its millions of inhabitants, Rachael Hill, technical strategy manager at the Environment Agency’s Thames Estuary 2100 project, is working to ensure that scenes of a submerged London are confined to disaster movies.

“There are 1.25 million people living in the Thames Estuary flood plain, and assets worth more than £80 billion,” Hill says, from her office overlooking the Thames Barrier. “Without the Thames Barrier and other flood defences, lowlying parts of the Thames Estuary, including parts of London, would be at risk of flooding twice a day with the rise and fall of the tides, and also from North Sea surges four or five times a year.”

But for how long will the existing defences be effective? Hill and her team produce flood risk management plans to take account of climate change, any degradation of existing flood defences and ecological changes in the estuary, plus variation of the numbers and range of people and property in the flood plain.

Flood risk assessment is a complex challenge, Hill says. The process involves understanding the risk source and existing flood-prevention assets, evaluating future flood-risk changes by looking at a range of variables, including different climate scenarios, and deciding what needs to be done. The team will present costed options to government in 2009.

It is good news so far. Given the most probable scenario of a metre increase in maximum water levels along the Thames Estuary by 2100, existing defences have greater safety standards than originally thought. “With the one-metre-change scenario, we don’t see any major engineering intervention on the estuary required until way after 2030,” Hill says. “Even then we would need only to adapt what we have at the moment.”

Not that Hill is complacent about her task. “The challenge is trying to look 100 years ahead; we are planning for an uncertain future.”

Explore Public Sector

• How to get a job

Times Recommends

• Inspirational leadership
• How to get a new job
• The reluctant CEO