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Delta force holds back rising tide

By Matthew Knight for CNN

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(CNN) -- At the end of August 2005 Hurricane Katrina swept up through the Gulf of Mexico battering the coastline of the southern United States.

In New Orleans, Katrina wreaked unimaginable havoc, breaching the city's sea defenses and allowing seawater to engulf thousands of homes and claim hundreds of lives.

It came as no surprise that in early 2006 a U.S. delegation traveled to Europe to seek the expertise of Dutch engineers who had learnt painful lessons of their own when a catastrophic flood claimed 1,835 lives over half a century earlier.

The North Sea flood of February 1953 breached the dykes defending Zeeland in the southwest of the Netherlands, swamping 150,000 hectares of farmland and destroying 3,000 homes. It was the worst disaster the Netherlands has experienced in three centuries.

An earlier ruinous flood in 1916 had prompted plans to protect northern areas of low-lying land -- 70 percent of the country is either at or below sea level -- which resulted in the Zuiderzee Works.

Plans for this equally extraordinary engineering project were agreed in 1918. They served the dual purpose of flood protection and land reclamation.

A vast dam was constructed -- the Afsluitdijk -- stretching 32km across from the region of Wieringen to Friesland isolating 1,650 square km of shallow water and creating the Ijsselmeer (Lake Yssel).

With the aid of hydraulic drainage pumps and the construction of a complex series of dykes, new polders were created.

By 1950 work to protect the densely populated south-western areas of low-lying land had begun, successfully blocking the mouths of the rivers Brieles' Gat and Botlek. But the 1953 floods provoked an urgent rethink of the scale and schedule of the original project.

Three weeks after the floods the Delta commission was set up and quickly agreed on a new bolder initiative. By 1958 the first in a series of 13 dams and storm barriers -- which would be known as the Deltaworks -- was operational.

The storm barrier on the river Hollandse Ijssel east of Rotterdam protected the populous western area of the Randstad. By 1961 two more river mouths -- Veerse Gat and Zandkreek -- were blocked.

This necessitated the building of a succession of sluices -- 17 in total -- at the mouth of the river Haringvliet to regulate the flow of water from the river Rhine. Completed in 1971 the sluices were bolstered by the addition of the Brouwers dam which was completed a year later.

Engineers encountered unexpected opposition to the proposed damming of the Eastern Scheldt. Environmentalists and fishermen had raised objections to the dam on the grounds that it would damage the saltwater environment, literally killing off the profitable trade in mussels and oysters.

After successfully lobbying the Dutch parliament their protests changed the original plan from a dam into a storm surge barrier.

The Eastern Scheldt storm surge barrier proved to be one of the biggest structures ever built. It is 9km long with 62 openings, each of them 40m wide and twelve storys high. It also had a whopping price tag of €2.5bn by the time it was finished in 1986.

The Deltaworks were completed in 1997 when the Maeslant storm surge barrier was opened in the New Waterway between the Hook of Holland and Maassluis. It is moveable and wide enough -- 360m -- to allow ships going to and from Rotterdam to pass through comfortably.

It is estimated that the total cost of the project has been €15bn -- in today's money -- and has protected thousands of lives and livelihoods from destruction.

However, the growing threat from global warming may make one of the greatest engineering projects of the 20th Century redundant much sooner than anyone hoped. The Deltaworks' 21st Century successor will have to be even greater in its scope.

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