Jared Bramblett works on flood engineering in the flood-prone city of Charleston, S.C. So he was anxious this week when he stepped out of his home near King Street, the city’s vibrant central boulevard, and saw a low spot filling with rainwater from Tropical Storm Debby.

“I was worried about what was going to happen,” said Mr. Bramblett, a consultant for an engineering firm that does work with the city. “But then we got lucky.”

By midday Tuesday, the intensity of the rainfall had fizzled, and there was no storm surge — a sign that Charleston’s recently upgraded storm infrastructure had passed its first big test. But forecasters warned there was more rainfall to come.

From Tuesday afternoon through Wednesday morning, though, the rain came not in buckets but a steady drizzle, which appeared to allow the city’s drainage system to do its job without being overloaded, according to several local officials and engineering experts.

They credited the curfew imposed by the city’s mayor, as well as a network of blocked roads, as major reasons that no water rescues had to be made during the heart of the storm. Keeping the streets clear gave the authorities time to clear blocked drains, instead of responding to traffic accidents, they said.

“This was a really close call,” said Brian Haines, a meteorologist with the National Weather Service in Charleston. “Even now, with eight to 15 inches of rain, there are a lot of problems.”

Some roads remained blocked off by the authorities on Wednesday afternoon, and crews were removing debris from palm-tree-lined streets in the downtown area. Surfers were back on the shore, relishing the wind-whipped waves.

The rapid growth that Charleston has seen in recent years has prompted concerns over its central flaw: It floods easily because of its low elevation, its proximity to the ocean and to rivers, and its relatively flat terrain, which slows drainage.

Ever since its founding in 1670, Charleston has sought to mitigate that weakness with varying levels of success. The approach in the past decade has been multifaceted, especially because of the greater rainfall caused by climate change: Higher sea walls, bigger pumps and deeper drains.

But although the city continues to face a constant battle against nature, officials think the recent improvements have given them a fighting chance.

“We have no fear about a hurricane coming — I mean, we don’t want a hurricane, but our teams can handle it,” said Logan McVey, the chief policy officer for the city of Charleston. “They’re ready, they’re capable, and they just proved it.”