Closing the Gap

On one calamitous day early in 1953, a howling northwester teamed with a wild spring tide. The resulting floods were the most disastrous to afflict The Netherlands in five centuries. Hardest hit were 1,300 square miles of Rhine and Meuse delta lands in The Netherlands' southwest, where tidal surges roared up estuaries and rivers, shattered 67 dikes, drowned 1,800 people and engulfed 375,000 acres of farmlands. In the aftermath, the public alarm was profound, and engineers swiftly blueprinted a $650 million plan to safeguard the delta forevermore by damming up four of the region's principal sea arms (see map). Fortnight ago the Delta Plan marked its first milestone: the damming of the 2,000-ft.-wide Veersche Gat.

Sunken Caissons. In a country where three-fifths of the population live on land reclaimed from the sea, the closure was a national event. Dutchmen the nation over sat glued to their TV sets; Queen Juliana herself was on hand aboard the royal yacht Piet Hein.

Already in place were six sunken, 5,000-ton concrete caissons developed from types used by the Allies in World War II as assault jetties at Normandy beachheads. Four tugs heaved at the seventh caisson, precisely long enough to fill the remaining 140-ft. gap, fighting the surging tide to keep it poised over its eventual resting place atop an asphalted nylon mat that anchors the shifting sands of the sea's bottom. Precisely at the moment of the tide's turn, when the water was completely still, 25 workmen aboard Caisson 7 frantically twirled at the watercocks. The waters rumbled into the hollow insides of the caisson, and after four minutes it sank surely into place.

"It sits, boys," cried the boss of the tugs. "Blow your horns!" The spirit of the occasion even moved the staid Queen Juliana. She tossed her purse to a surprised cop, waved away courtiers clucking in alarm, waded ankle-deep in the construction-site muck to reach the ladder and clamber to the top of Caisson 7.

20,000 Concrete Piles. At the Eastern Scheldt 72 caissons will be needed, and at the Brouwershavensche Gat, 32. The most challenging project is the three-mile-wide Haringvliet inlet, through which an estimated 50% of the combined waters of the Rhine and the Meuse pour out to the sea. The plan is to close Haringvliet with massive sluices anchored to the sea bot tom by 20,000 concrete piles. In the winter and spring, the 400-ton sluice gates will open to vomit out ice sweeping down the rivers.

Main purpose of all four dams is to fend off the sea and its damaging flood tides. But with the salt water blocked off, the estuaries will slowly fill up with fresh water from the rivers. By means of five smaller dams farther inland, the sweet water can be sluiced northward into the Rotterdam Waterway. The waterway provides ocean-going vessels with access to The Netherlands' greatest port, but, in the process, also allows salt water to pass far inland, damaging surrounding farmlands. In effect, the five smaller dams of the Delta Plan will be used to hose the salinity out of the waterway with sweet water sluiced up from the southwest.

Finally, an enormous, 700-ton steel "guillotine" floodgate has been constructed on the Hollandsche Ijssel River. The huge gates can be clamped down on eight minutes notice when approaching tidal surges threaten the lowlands around The Hague and Delft, where 3,500,000 Dutchmen live. Expected completion of the entire Delta Plan: 1978.

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