Sand motors, also known as “sand engines,” are a sustainable alternative to beach nourishment for replenishing eroding coastlines. Though not an actual “motor,” they are sculpted landscapes that work with nature to maintain a healthy shoreline.
Instead of traditional beach nourishment — rebuilding the beach annually with new sand — sand motors extend one section of the shoreline out to sea at an angle that works with natural wave action to push sand out along the shoreline, spreading it for miles. This innovative new strategy is the brainchild of Marcel Stive, a Dutch coastal engineering professor at Delft University of Technology and the scientific director of the Water Research Centre Delft.
Photo Courtesy TU Delft
For years, governments have used traditional beach nourishment to combat erosion caused by tides, weather, and climate change. However, the problem is that the new sand also eventually washes away.
Sand motors address that issue by continually adding new sand to the beach in a way that only has to be redone every few years.
The new technique is particularly beneficial to countries that cannot afford to constantly replenish sand, even though many small nations require international assistance to fund the projects.
To start, engineers extend one section of the shoreline into the ocean at a unique angle. Over time, the waves essentially act as a motor that moves sand from that new landmass along the rest of the natural shoreline, spreading it evenly for miles. The sand motors cost more upfront than a singular beach nourishment session, but they protect far more land and last significantly longer.
“By mobilizing your dredging equipment only once, it’s cheaper to do one large nourishment rather than to return every two to three years,” Mark Klein, senior morphology engineer at Boskalis, told Grist.
Stive thought of the initial sand motor idea after watching the Netherlands government spend billions of dollars to bring new sand to its beaches over and over again. He worked with the dredging company Boskalis on a $50 million prototype along the shoreline near The Hague.
In that initial project, 28 million cubic yards of sand was removed from the ocean floor and sculpted into an eastward-curving hook along the beach.
The idea has continued to pick up steam, and the United Kingdom recently built a shifting sand barrier to protect a natural gas terminal in the coastal town of Bacton.
Photo Courtesy TU Delft
Sand motors are becoming increasingly popular in Africa. In 2016, Nigeria created a sculpted sandbar in a suburb of Lagos, and the World Bank announced a funding package to help the region adapt to the technology, including the construction of a sand motor in Benin.
The small nation is part of a coastline that faces a large erosion threat, with the potential for severe health and economic disruptions as sea levels rise. Beninese leaders chose to build the sand motor in a popular beachfront area. Boskalis built the project last May, vacuuming up more than 8 million cubic yards of sand to create it.
According to Peter Kristensen, a World Bank environmental economist, most countries can’t pursue sand motors without help because of the required money, sand, and dredging expertise. “In the U.S. and other countries, they can afford to replenish often; it’s harder for the African countries to afford that kind of replenishment on a regular basis,” he told Grist.
Overall, sand motors are a bold new solution for coastlines that can be saved and where development is not directly on the sand. In some American cities, most notably Miami, it may be too late for the technology, which works by distributing sand over years rather than immediately.
Photo Courtesy TU Delft
“In the U.S., we have lots of coastal resort communities where the houses are on the edge of the sea, right now, and we’re scrambling to keep sand in front of them,” Rob Young, a professor of geology at Western Carolina University and a leading expert on shoreline erosion, told Grist. “If you look at what is down drift of the sand motor on the coast of Holland, they don’t have buildings teetering on the edge.”
But for countries with sand and space, sand motors can make saving a coastline far less work and, in the end, less expensive. Stive’s new technology could potentially be a game-changer for numerous countries where erosion and rising ocean water are becoming an imminent threat to people and the economy.
