Thames gateway - coastal flooding case study

Question 1

How can this risk be managed?

Answer 1

• In 2005, the Environment Agency was considering plans for a £20bn scheme that would see the construction of an ‘outer’ barrier along the Thames Estuary.
• Unlike the existing barrier, an outer barrier protection would extend beyond central London and into areas such as the Thames Gateway.

-This is an example of hard engineering.
Soft engineering strategies have also been implemented along the Thames Estuary. For example, Abbot’s Hall Farm has purposefully created breaches in its flood defences in order to allow low-value land to be flooded.

-This allows land to be reclaimed by salt marshes and reduces pressure on higher value land.

Question 2

What are the advantages and disadvantages of both proposals?

Answer 2

-The construction of an outer barrier along the Thames would incur a substantial £20bn cost to the taxpayer.

-Can this huge cost be justified?
Many argue the cost of hard engineering can be justified, because property along the Thames is worth an estimated £80bn.

• By allowing certain areas to flood (e.g. at Abbot’s Hall Farm), salt marshes are able to naturally migrate; protecting habitats for marsh birds such as Brent geese and Wigeons.
• English Nature and the Environment Agency support this approach.
• While soft engineering strategies such as managed realignment (Abbot’s Hall Farm) help to minimise the impact of flooding, they are rarely effective at preventing the actual event (unlike a physical barrier).

Question 3

Why is the Thames gateway at risk?

Answer 3

• Scientists predict that sea levels will rise by 86cm by 2080.
• Low-lying land surrounding the Thames Estuary (e.g. the Thames Gateway) will be put at risk as a result of such a significant rise in sea levels.
• In 2011, the government decided to build 160,000 new homes on the Thames gateway to meet growing housing demands in South East England.

-The resulting urbanisation and pedestrianisation makes the ground less permeable, and therefore raises the flood risk.
The Environment Committee of the London Assembly concluded that flood defences were ‘poor’ near the coast, leaving approximately 1.25m people at risk of flooding.

• Scientists estimate that the likelihood of a major storm sturge (such as the devastating 1953 surge that caused £5bn in damages to the Thames Estuary) will increase by 10-20 times as a result of climate change.
• Over the past 25 years, there has been a 40% decrease in salt marsh. This is a major issue for the Thames Gateway, because salt marshes absorb water and dissipate wave energy.
• Insurance companies estimate that the annual flooding insurance cost could increase from £1bn to over £20bn by 2080.