Imagine a storm with the shredding power of Hurricane Hugo — only angrier — tearing through South Carolina.

Then imagine rain that just keeps coming for days, spreading flood waters a hundred miles inland and flowing 10, 15, and in some cases, 20 feet deep.

That's what would happen if a Hurricane Harvey-type storm made landfall in South Carolina and stalled.

"It would be a major catastrophic event," said Susan Cutter, the director of the Hazards and Vulnerabilities Research Center at the University of South Carolina. "It would overwhelm what Hurricane Hugo did. In some respects it's beyond our ability to imagine."

Flooding alone "would be like the 2015 flood on steroids," she said. 

To put it in perspective, Hugo in 1989 was a Category 4 hurricane at landfall, just like Harvey. It killed 35 people, left more than 50,000 homeless and stranded half the state without electrical power. It caused $6.5 billion in damage — at the time the costliest hurricane in U.S. history — without serious flooding away from the coast.

By comparison, Hurricane Harvey wracked the Texas coast with 130 mph winds at landfall Friday night. The difference is it has stalled there as a tropical storm, dropping around 24 inches of rain by Monday with the potential to reach 50 inches in the coming days.

If Harvey happened here, the depth of the flooding prospects are horrifying, smothering large swaths of homes, woods and farmland deep into the state's interior, just like what Houston is facing now some 40 miles inland.

It would begin with winds ripping up the coastal communities. Folly Beach likely would be cut in half by 20 feet of storm surge. The Charleston peninsula and most of the low-lying islands largely would be underwater. Inland areas would be wracked by the storm then watch their rivers rise to swamp them deeper than they have ever seen.

"Oh, that would be absolutely terrifying," said Carolyn Ganis, who lives in the Crichton Parish in the Oakbrook community outside Summerville near the Ashley River.

Water rose to within 1½ inches of her home during the 2015 flood.

"I would not have a home and most of my neighbors would not have a home," she added about a Harvey-type threat. 

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2015 Year in Pictures (copy)

Cynthia and Gregory Martin were rescue from their home in Shadowmoss on October 4, 2015, by Charleston Fire and Task Force One. FileLeroy Burnell/Staff 

In the historic 2015 flood, 19 people in South Carolina died and billions of dollars in damage was done to low-lying and riverland communities across the lower state. More than 500 roads and bridges were flooded out, including nearly 90 of them in Charleston, Berkeley and Dorchester counties. 

That was from 20 inches of rain. A Harvey-type storm would drop at least twice that.

Exactly how bad it could get depends on too many factors to say — how, where and what tide the storm comes in and where the heaviest rain falls.

"How much worse could it be? The simple answer is, that's impossible to answer," said meteorologist James Carpenter with the National Weather Service in Charleston.

"It’s possible the county could be split in half at Four Holes Swamp," said Mario Formisano, the Dorchester County emergency management director. "We experienced this for a period of time during the 2015 floods."

Flooding would engulf low-lying places like Oakbrook or Goose Creek.

"It would keep getting deeper and deeper. It would start washing away homes that just got wet in 2015," said Lee Lindner, College of Charleston environmental studies professor.

Entire towns could be swamped, particularly near rivers, like what happened to Andrews in the 2015 flood and to the Marion County town of Nichols after Hurricane Matthew in 2016.

Even larger, higher-ground towns such as Mullins, near Nichols, could go under. Mullins saw some swamping during Matthew.

Wanda Pittman, who lives in Mullins, had her apartment flooded out. A deeper flood, "it would just tear us down," she said.

Roads would be impassable for miles. For example, in the 2015 flood, 13 miles of Interstate 95 were closed. Shelters and emergency facilities such as hospitals — designed and selected based on storm surge or potential flood models rather than a combination — might be left in crisis.  

The disaster would be so extreme that no one Cutter is aware of has ever run a computer model disaster scenario like it.

"I don't think we've ever really thought about that kind of multi-hazard, multi-impact, multi-day event," she said. "But clearly we should be thinking about these kinds of events because we know they happen."

While the flooding would be the worst deeper in the state, the coast might not fare as poorly. Mark Wilbert, the city of Charleston’s director of Emergency Management and Resilience, said 4 feet of rain here would produce problems similar to what the region saw during the October 2015 floods.

“What the Charleston region has going in its advantage, at least along the coast, is when we get low tide, we do drain, which is good,” Wilbert said. “And we drain fairly quickly. The problem is there’s another high tide around the corner.”

The height of hurricane activity usually occurs in September.

Robert Behre contributed to this report.

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Science and environment reporter. Author of Washing Our Hands in the Clouds.