Every New Yorker or New Jerseyan remembers all too well the deadly storm surge caused by Hurricane Sandy in 2012.

The storm came ashore in late October of that year with hurricane-force winds of about 90 miles per hour, but the water proved most dangerous. A 14-foot high tide in New York Harbor topped the seawall in Lower Manhattan and inundated key infrastructure — and an even higher tide devastated parts of Staten Island. Dozens drowned in the city.

Ultimately, Sandy was blamed for nearly 150 deaths, mostly water-related.

While many focus on the wind and rain during a hurricane, in many ways the storm surge is the greater risk.

What is a storm surge?

Storm surges are different from normal tides. In fact, the basic definition of a storm surge by the National Hurricane Center is “an abnormal increase in water produced by a storm that exceeds predicted astronomical tides.”

Simply put, the winds of a tropical storm rotating in a cyclone push the water towards the shore. Because the land underwater rises at an angle toward the coast, it rises higher when it hits land as the storm pushes more water.

Imagine a wave of water rising 15 feet high on the coast, as the NHC has predicted. Now imagine one-story houses in the path of this wave.

The water would rise to the roofs or even above them.

It’s not just low-rise houses, but also the infrastructure. According to the NHC, more than a quarter of all roads in the Gulf Coast region are at or below 4 feet.

Even a 1.5 meter high water level could submerge these roads, making evacuations – and rescue operations – much more difficult.