How do storm surges work and why are they so devastating?
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Basically it’s when an off-shore storm like a hurricane *pushes* a massive amount of water towards land. This water floods the land and if combined with high-tide can create a super hightide flooding the shore.
It’s devastating for two reasons – the first being that humans have built homes and towns in areas where this stuff happens, meaning *duh* they are going to get flooded. But also in building things where storm surges occur we also destroy the natural barriers like plants and earth that naturally protected the area in the first place. Many storm surge prone regions have natural conditions that deal with them, such as wet lands and mangrove forests. When you demolish those to erect a beachside down you’re sort of doubling down on the damage.
The other problem is that the water might not clear super quickly after the storm. This means you have tons of dirty water filled with debris and things that can hurt people but also have a risk of things like sewage backing up and water borne diseases. So it’s not just the damage to the property, the people who live there are now exposed to things like dysentery and cholera and all sorts of other “old timey” illnesses that proper sewage treatment and water treatment takes care. In most cities the sewage systems are connected to the rainwater/gutter system. Even a mildly heavy rain can overflow this and cause raw sewage to be pumped directly to the nearby bodies of water. Combine that with a storm surge and now you have all the sewage just sitting around stagnating in people’s homes, streets, and towns.
There are two things that contribute to storm surges. One is the low pressure of the storms. The air pressure can be as much as 10% below normal near the center of the storm. That’s like putting an extra metric ton of weight on every square meter of water surrounding the storm that isn’t at the center, so the water in the center rises.
The second really big contributor is the way the winds spin around the storm. As the storm makes landfall there’s one side has wind going offshore and one side has it coming onshore. Wind can push water a lot, piling wave on wave, and driving it up and over the land.
What can make the so devastating is that water is heaving, and when waves of it start hitting buildings, the force is very, very high. It takes a specially constructed building to withstand it, and even then, it might have its footings washed out from under it.
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