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City's flood defences 'massively underdesigned'

Failed flood defences in New Orleans were massively underdesigned, a leading Dutch flood protection engineer said last month.

They were for one in 300 year storm events while those in Britain and the Netherlands are build to withstand one in 1,000 year events at least.

Theo Stoutjesdijk, a senior adviser on water defences at Dutch geotechnical consultant Geodelft, said principal dikes along Holland's coast and principal rivers are designed for 1 in 10,000 year storm events.

Levees protecting New Orleans anticipated one in 200- to one in 300-year events.

This meant the levees would inevitably be overtopped in a major storm surge, such as that accompanying Hurricane Katrina.

'Along the coast we can cope with water level 6m above normal, and waves of 6m to 9m on top of that, ' said Stoutjesdijk. 'But New Orleans' flood event strategy appears to have been based more on evacuation than on protection.' US Army Corps of Engineers liaison officer John Hall said New Orleans' defences had been designed to cope with 'a mild category three hurricane'.

Katrina was category four.

Of the 25 hurricanes to have hit the state of Louisiana in the last century, eight have been category three, with four measuring category four to five.

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