The rain may have stopped falling, but South Carolina is still facing a precarious situation as floodwaters course through a complex network of creeks, rivers and lakes, breaching at least 18 dams and causing sudden flooding and evacuation orders in surrounding communities in the process.

Sixteen people died in the historic rainstorm, which was unprecedented in a state where weather records date back to the late 18th century. The death toll includes eight people who drowned from flooding, six who died in weather-related traffic accidents and two fatalities that occurred from heavy rain in neighboring North Carolina.

See also: South Carolina flooding is the type of event climate scientists have warned about for years

People stand on a bridge as homes sit in floodwater in Charleston on Oct. 5, 2015. Image: Mic Smith/Associated Press

South Carolina Governor Nikki Haley has warned residents that a huge surge of water is slowly working its way through waterways near the hard-hit capital city of Columbia and headed toward low-elevation areas along the coast. This extends the flood threat well beyond the return of sunny skies. State officials now say it may be weeks before things return to normal.

Hundreds of roads and bridges in South Carolina remain closed as engineers work to determine the safety of many thoroughfares after historic flooding. The state Department of Transportation says nearly 500 roads and bridges were still closed on Tuesday morning. Many of those are in the Columbia area, which registered record rainfall this week.

A 1,000-year rain

In some areas of the state, so much rain fell between Oct. 1 and Oct. 4 that four all-time rainfall records were obliterated. Charleston even set its record for the wettest October on record. The 20-plus inches of rain that fell rank as an event more rare than a 1,000-year rainfall event, according to the National Oceanic and Atmospheric Administration (NOAA).

A 90-mile stretch of Interstate 95 is still closed between Interstates 20 and 26 due to flooding and overall poor road conditions.

9 dams in the Midlands breached, 18 statewide. State and local officials are closely monitoring. #SCFloods #SCTweets — SCEMD (@SCEMD) October 6, 2015

Some rivers downstream are forecast to continue rising through Sunday. For example, the Santee River near Jamestown is not expected to crest until Sunday morning or later, possibly coming close to a record high.

Observed and predicted water levels for the Santee River in South Carolina. Image: NOAA

Other rivers have in fact set new records, and are now seeing water levels decrease. The Black River at Kingstree, for example, peaked at 22.33 feet at 11 a.m. ET on Tuesday morning, beating the previous record of 19.8 feet.

South Carolina has hundreds of small, earthen dams on public and private property, and, in many cases, not much is known about the likelihood that these dams will give way.

Water levels for the Black River at Kingstree, South Carolina, showing its record crest on Tuesday morning. Image: NOAA

Columbia Mayor Steve Benjamin said the city plans to expand the number of water distribution points. As many as 40,000 homes have no water service, and those with service have been told to boil the water for at least one minute before using it for drinking or cooking. Benjamin said that order is likely to be in effect for "quite some time."

He said the city is working to restore water service, a problem that has been complicated by a breach of a dam near a city water plant.

The deadly deluge that struck South Carolina was the result of a confluence of several atmospheric forces: long-term global warming that is adding heat and moisture into the atmosphere; Hurricane Joaquin that spun its way offshore, kicking a filament of moisture toward the Southeast; and a powerful upper-level, low-pressure system that helped force a warm, moist air mass to rise rapidly over the Carolinas.

South Carolina Flooding

Some information in this report was provided by the Associated Press.