DIKE ENGINEERING - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 298

Scheldt was excepted, as it connects the sea with the harbour of Antwerp. In 1976
under the influence of the environmental lobby, which was then at the height of its
strength, it has been decided to keep the Eastern Scheldt partially open in order to
conserve the tidal environment of this estuary. This was realised by building a very
costly open dam. In 1983, the government wanted to cut public expenditure by
back-pedalling on the river-dikes reinforcement program. There were sincere
protests all round, but the most vociferous opposition came from the water boards,
the public authorities responsible for managing the sea and river defences. To
relieve the cost of continuous inland dike maintenance the government decided to
construct a moveable closure, the Maeslandt Barrier (Fig 17.3), in the main
entrance canal to the harbour of Rotterdam, the only vulnerable open sea
connection left. This closure has been completed in 1996. The government has kept
its promise made in 1953 that the sea defences will be of the required height and
strength. The project took 40 years! Billions of guilders have been spent on the job
and a gigantic amount of work has been done.
The Delta-river project
The struggle against the water continues. Several hundreds of kilometre of river
embankments, lake and canal dikes are waiting in turn for proper improvement.
New insight uncovered the fact that design water levels have risen significantly. In
the last decades, public opinion changed. Landscape, natural and cultural values
should be preserved in balance with safety requirements. The public protested
fiercely against sacrificing old villages to dike enforcement measures. Several
governmental Committees advised the parliament about acceptable lower norms
and suggested development of sophisticated smart redesign methods and
construction. Dike enforcement became subject to law, the Environmental Impact
Assessment Act, which delayed the river dike improvement program drastically.
water boards did not posses enough money, wanted to save maintenance costs and
preferred a less expensive conventional technology. Latent danger laid in waiting!
When in 1995 and 1996 high-river water levels threatened again to destroy the
weak dikes and a massive evacuation of some hundreds of thousands of man and
cattle had to be undertaken, the government reacted quickly with special
legislation. The Delta Act Large Rivers was launched, and 370-km primary river
dikes were reinforced in an accelerated tempo with a more integral design
approach. With costs varying from 5 million euro per kilometre (conventional
groundwork) to 15 million euro per kilometre ('smart' methods) this project required
an investment of more than ten billion guilders; it was completed in 2000.
Besides, the attention also focuses on problems related to polluted river beds,
storage of contaminated sludge, restoring the natural habitat of rivers, estuary
dikes, unstable sea-dike slope protection, introduction of the new integral approach
and the development of a broad public and politic platform for a modern and
consistent safety norm, i.e. not just the likelihood of flood but also incorporating
the subsequent damage by inundation. A continuous great effort is dedicated to the
improvement of the Dutch water-defence system by exploring new methods and
ways, by developing new insight and experience and by inspiring a true and
balanced political and social awareness about the matter of safety (see Fig 17.7).
There is consensus that a water-defence structure represents a multi-functional