Coastal seawalls can be designed to better protect lives and property endangered by storms, a new study suggests.

Scientists from the University of Edinburgh and Hokkaido University have developed a method of predicting what happens to the millions of tons of water inside big waves when they collide with cliffs, seawalls and buildings. Their findings could help engineers design coastal defenses that are better able to stop sea water spilling on to land, known as "overtopping," which causes damage to buildings, vehicles and transportation infrastructure.When a breaking wave collides with an upright structure, water is dispersed in distinct patterns. Image credit: Pixabay.When a breaking wave collides with an upright structure, water is dispersed in distinct patterns. Image credit: Pixabay.The researchers recreated stormy sea conditions in a 24m wave flume to gauge the impact of waves on vertical walls. A scaled-down version of a seawall was bombarded with waves, which researchers tracked using a high-resolution video camera.

When a breaking wave collides with an upright structure, a powerful jet of water is thrown straight up into the air. But the scientists also found that that water is dispersed in distinct patterns that vary depending on the size of the wave. These huge sheets of water split into several "fingers" before breaking apart into a spray of droplets that can hit people and property with real force.

Based on their findings, researchers developed a statistical model to calculate the pattern of spray produced by specific wave impacts. Use of the model could help inform the design of seawalls that, until now, have not taken into account the pattern of spray produced by waves, the team says.

"The UK and Japan are island nations on the edge of large oceans where storms can create very big waves," says David Ingram, of the University of Edinburgh's School of Engineering. "With climate change increasing the intensity and frequency of storms, a better understanding of the interaction of waves and our natural and engineered coast is critical."

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