European Commission, Environment DG

Managing the twin risks of flooding and erosion in coastal areas

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Source: European Commission, Environment DG

Coastal areas are naturally at risk from erosion and flooding, but this risk is increased by the effects of climate change. A recent study has examined choices for regulators and coastline managers and suggests that successful management in high risk areas needs a fully integrated approach involving all stakeholders.

Managing the interactions between the natural environment and socio-economic activity of coastal areas has become even more complicated by climate change, which threatens to increase coastal flooding and erosion through higher sea levels and more severe storms. In the EU, these issues are being tackled through integrated coastal zone management approaches1.

Coastal erosion and flooding are typically assessed independently, but this study provides evidence that these seemingly two separate problems are in fact interdependent and management should be fully integrated.

The researchers investigated a 72 km stretch of coastline in Norfolk in the south east of the UK. A number of scenarios were modelled for the coming century that included the influence of global and regional climate change, particularly sea level rise, wave height and direction, together with local socio-economic development and coastal defence options.

For the first time, it was possible to estimate how much sediment would be released from the soft cliffs and foreshore and understand the role that it plays in protecting nearby low-lying coast from flooding. The study expressed risk in terms of expected annual damage, which allowed the impacts of cliff erosion to be directly compared with flood impacts.

Sediment from the eroded cliffs form beaches, which are continually moved along the coast. These beaches diminish the impact of the waves and help protect low-lying inland areas from flooding. However, man-made defences, such as sea walls which have been constructed to prevent cliff erosion, restrict the flow of sediment to the beaches. The beaches therefore decrease in size and offer less protection to inland flood plains. Some beaches in Norfolk are currently becoming shorter by up to 2.5 metres a year.

Overall, the study found that the risk of flooding and cliff erosion both increase over the next 100 years, largely the result of higher sea levels. The risk of flooding was potentially more damaging than the increased risk of cliff erosion. The trade-off between different management choices suggests that, although cliff protection reduces the risk of erosion, it could also rapidly increase the risk of flooding where no additional flood protection measures are implemented.

The authors suggest that by removing cliff defences and allowing the coast to return to a more natural state, a greater problem of flooding would be reduced. However, this has significant implications for cliff-top communities and housing plans need to be integrated immediately into coastal management. Whilst further work is needed to better understand the socio-economic issues associated with coastal risk management, visualisation of the results from these simulation models provides a potentially powerful tool for motivating and engaging policy makers and stakeholders.

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