Flooding and subsidence in the Thames Gateway: impact on insurance loss potential

Flooded street 2007.

3D Geological model of the Dartford area showing the relationship between water levels and the underlying geology (Chalk in green, Thanet Sand in blue, Lambeth group in orange and London Clay in brown)

In the UK, household buildings insurance generally covers loss and damage to the insured property from a range of natural and human perils.

Consequently, insurers require a reasoned view on the likely scale of losses that they may face, to assist in strategic planning, reinsurance structuring, regulatory returns and general risk management.

The flood events of 2007 not only provided an indication of the scale of potential losses from an individual event, with £3 billion in claims, but also identified a need for insurers and reinsurers to better understand how events may correlate in time and space, and how to most effectively use the computational models of extreme events that are commonly applied to reflect these correlations.

In additional to potential for temporal clustering of events, there is a possibility that seemingly uncorrelated natural perils, such as floods and subsidence, may impact an insurer's portfolio.

Where aggregate losses due to the combination of perils such as subsidence and flood is increasingly important within the insurance company's strategic risk management process.

Future work

Spatial distribution flood areas

Areas within the Thames Gateway region where Holocene deposits are showing negligible subsidence at the present time may start to subside again under the weight of future flood water and sediment, or rehydration of sediments under flood water.

The latter mechanism may be particularly critical on sites where Holocene sediments are currently protected from flooding and are no longer subsiding; Holocene deposits tend to compress either under their own weight or under a superimposed load such as made ground, built structures or flood water.

Future work will identify areas at high risk of flooding and subsidence, and investigate the hydrogeological and geophysical links between flooding and subsidence events.

References and further reading

Royse, K R.   in press.  The Handling of Hazard Data on a National Scale: a case study from the British Geological Survey.    Surveys in Geophysics, 21.

Royse, K R, Horn, D, Eldridge, J and Barker, K.  2010.  Flooding and subsidence in the Thames Gateway: impact on insurance loss potential.   in Geophysical Research Abstracts 12, 2pp.

Contact

For further information contact Dr Katherine Royse or Enquiries