Significant, springlike flooding is ongoing along much of the southern stretches of the Mississippi River and its tributaries, inundating homes and businesses and forcing evacuations. As of Tuesday morning, flood warnings and advisories stretched more than 500 miles from Mississippi to as far north as Illinois. The hardest-hit areas remain under a flash-flood watch as additional rounds of torrential rain eye the beleaguered Southeast.
Most noteworthy has been flooding in and around Jackson, Miss., which is expected to see “major” flooding through at least late Tuesday, according to the National Weather Service.
The Pearl River, which passes about 50 miles east of the Mississippi, crested at 36.67 feet Monday, overflowing its banks in several parts of Jackson. Monday’s crest was the third-highest observed at the station, the highest crest being 43.28 feet on April 17, 1979. Data from the river gauge dates to the 1800s.
Hundreds of homes have been damaged by the flooding, according to the Mississippi Emergency Management Agency, with authorities conducting at least 16 water rescues. Social media video shows streets impassible and submerged beneath feet of water.
Businesses were in jeopardy on South President and South Farish streets in Jackson, while Sidney Street was flooded. Once the water rises to about 36 feet, “water is close to entering homes in Northeast Jackson,” the Weather Service wrote.
Fortunately, earlier projections of water levels nearing 38 feet did not bear out; at 38 feet, homes would begin to flood in northeast Jackson, while water would seep its way into structures downtown. Marty Pope, senior service hydrologist at the Weather Service in Jackson, said he thinks the city dodged a worst-case scenario.
“We’re doing pretty good as of now,” Pope said. He said the flooding was not as bad as it could have been, thanks to some quick thinking by engineers at the Ross R. Barnett Reservoir, just northeast of the city.
“Generally you keep your water level very high all the time, but they kept their water level pretty low this year,” Pope said. As a result, there was room to capture some of the river’s inflow before it threatened the city.
“Even though we got 83,000 to 90,000 [cubic feet per second] coming into the lake, they were able to [reduce the outflow] to 75,000,” Pope said. “When you get to that point, every 1,000 cubic feet per second makes a huge difference. They kept a lot of people’s belongings and things safe from flooding.”
Pope said that the reservoir was actually not designed for flood control. But it made a world of difference in this episode.
Other forces were at work, too.
Even once the flow rate out of the reservoir increased to 78,316 cubic feet per second, the river’s crest corresponded to a flow rate of only 76,550 feet per second at the river gauge downstream, Pope said. Moreover, flooding that occurred there in 1983 — when the reservoir’s discharge rate was nearly identical — produced a river crest about three feet higher.
So how did Jackson get lucky this time?
“The river is more efficient which means the river could be much deeper after past floods have carried away the silt out of the bottom of the stream,” Pope wrote in a public information statement issued by the Weather Service. “Another possibility, the clearing of trees along the flood plain after the 1983 flood. This would allow the river to flow faster not being impeded by trees. This situation has benefited those in downtown Jackson where the river is much lower than expected.”
Pope did say there was more significant flooding north of downtown Jackson near the levees, which were installed in the 1960s.
“It’s interesting what happened upstream, up above Jackson just above our reservoir. A lot of the areas north of Jackson reached what they did in ’83,” he said, noting the lack of a second river gauge for upstream monitoring.
While floodwaters will recede through late week in Jackson, soppy soils and swollen creeks were leading to issues elsewhere, too. In Bentonia, just northwest of Jackson, the Black River crested at more than 31 feet; a major flood stage occurs there at 29 feet. Pope’s team was concerned that additional rainfall, on the order of one to two inches, could spur additional flooding this week.
In Savannah, Tenn., multiple homes collapsed as landslides claimed several cliffs overlooking the Tennessee River. More landslides are possible in the coming days.
It’s been a waterlogged start to the year in the Southeast, with persistent periods of heavy rain kicking off flooding weeks ahead of the typical flood season.
Jackson has already recorded 19.9 inches this year, the greatest year-to-date rainfall in at least half a century of record-keeping. Rainfall in Birmingham, Ala., is also high, after deluges brought its total to 17.02 inches.
Unfortunately, more heavy rain is in the offing as an active weather pattern continues to dominate. Another one to two inches are possible through Thursday along the Interstate 20 corridor in Mississippi, Alabama and western Georgia — with higher amounts possibly falling in eastern areas.
Longer-range models are also indicating the potential of additional bouts of heavy rainfall late this weekend or early next week, and again in about eight to 10 days.
In other words, forecasters such as Pope will be anxiously watching river gauges for some time to come.