The Dutch have long been masters of "hard infrastructure": miles of earthen works, dikes and levies that keep the North Sea from flooding the country, much of which lies below sea level. Yet Europe’s low-landers are trying a new tact to defend against the ocean’s slow rise: designing with nature, instead of against it.
Every engineer faces the fact that even the best designed structures inevitably collapse when faced with nature’s power. The tsunamis in Japan and the rushing tides flooding New York’s low-lying areas are only the latest examples.
For the Netherlands’ latest coastal defense, engineers are harnessing nature rather than resisting, it by creating what they’re calling a "sand engine": about 750 million cubic feet of dredged sediment, enough to fill several stadiums, that stretches for almost a mile out into the ocean. This hook-shaped peninsula, at times peaking 20 feet above sea level, is designed to be washed away. New dunes and beaches will form as the sand, first relocated by dredging sand from six miles offshore, is gradually eroded and deposited along the coast.
The $91-million, government-backed project is replacing traditional sand nourishment approaches. Typically, dredges will dump a much smaller amount of sand along a beach every five years, only to see it wash away again. The sand engine, reports Yale Environment 360, will supply beaches for about 20 years at half the price.
And more of the same thinking is coming. Natural or green infrastructure is making its way into the blueprints of urban planners, engineers, and others who are designing the urban environment of the coming century. Although the Netherlands’ sand engine is one of the largest examples, U.S. cities are also turning to natural infrastructure such as trees, wetlands, and vegetation to manage storm water, air pollution, and heating cities rather than looking at concrete or "hard" solutions.
The Natural Resources Defense Council says Philadelphia is leading the way with public investments of more than $1.67 billion over the next 25 years to retrofit its stormwater management system. The city’s fee and credit systems gives project developers incentives to keep stormwater runoff out of the municipal pipes (which are often overwhelmed during a storm) by retaining the first inch of rainwater on their property through green practices. New York City ($1.6 billion over 20 years), Los Angeles (about $200 million in the next two years) and even Detroit ($50 million over 20 years) are looking into similar measures.
Sand, trees, and wetlands may soon take their place along bulldozers and concrete in the engineer’s toolbox.