Coastal areas brace for high tide in March 2018 as a strong storm moves through Scituate, Massachusetts.
CNN  — 

Almost half of all deaths from tropical cyclones come from storm surge.

While many people focus on the wind speed of storms, the danger often comes from the water flowing in from the ocean.

“A storm surge is a rise in water level caused by a strong storm’s wind pushing water on shore,” said CNN meteorologist Brandon Miller. “The wind literally piles up the ocean water and pushes it on the land.”

And storm surge accounts for nearly half of all hurricane-related fatalities, according to the National Oceanic and Atmospheric Administration.

All that water has nowhere to go

Storm surge also can exacerbate flooding. As the water piles up along the coast, rivers and streams that typically drain into the ocean can become clogged farther upstream, forcing water levels to rise.

That water doesn’t just leave. Depending on how much water was pushed ashore and the area’s watershed, it may hang around, causing further damage to communities.

Due to climate change, storm surge has become an even greater threat in recent years.

“Sea levels have risen in most places by about 1 foot over the past century. The higher baseline ocean level allows storm surges to reach even higher, increasing their destructive capabilities,” Miller said.

Rates of sea level rise are increasing as ocean temperatures climb to new highs every year, which will continue to increase the threat to coastal communities, especially during significant storms.

‘Reverse’ storm surge can be dangerous

“Reverse storm surge” also can happen during strong storms. This is when the water actually recedes away from the shoreline back into the ocean as winds push water out of shallow areas.

Just before a hurricane’s landfall, the water recedes along the coast as the storm’s winds blow from the land out toward the ocean, exposing land usually under water.

Ultimately, that water comes back onshore with much greater force, inundating coastal communities.

This can be dangerous because people often will go out to the bare or uncovered land to take photos, grab seashells, etc. But the water can come back in just as quickly as it went out, catching people off guard.

CNN’s Gene Norman, Judson Jones and Emily Smith contributed to this report.