Update 7 a.m.: In a nighttime message, Ascension Parish officials underscored the need for residents to evacuate from the flooding threat in Sorrento and the Ridge Road area off Bluff Road, saying a "a major impact" is expected.
In Sorrento area, high water was expected to overtop Airline Highway and nearby railroad tracks and inundate the town.
At 10:30 p.m. Monday, officials said in a statement that impacts were expected in six to eight hours, or early Tuesday morning.
"I cannot stress to our residents enough the magnitude of this situation," Meredith Conger, parish homeland security planning and intelligence officer, said in the statement Monday. "This type of historic flooding has never been seen before and we are not out of danger yet."
Voluntary evacuations had already called for in those areas earlier on Monday.
Parish official also said the Marvin J. Braud Pumping Station had shut operations for several hours to clear intakes of debris. The station was expected to resume pumping at midnight.
Parish officials re-emphasized the risk of flooding from Bayou Narcisse, Bayou Francois, New River Canal or Black Bayou because these waterways are not able to drain normally. Voluntary evacuations had been called for already in those areas as well.
Conger added that the water is not expected to leave for several days into late this week.
For information on shelters, road closures or help to get out of homes, call the parish emergency operations center at (225) 621-8360.
Original: Close to a third of all homes in Ascension Parish were flooded by Monday as important pieces of the parish's flood protection system along the Amite River were overcome by the inundation from historic levels of high water along the Amite, Bayou Manchac and other tributaries.
While the critical Marvin J. Braud Pumping Station continued to operate Monday, a parish emergency official acknowledged the possibility of the high water eventually forcing the pumps to stop as well.
As a result, parish officials expect water to continue to creep into swaths of the parish and called for further voluntary evacuations in the town of Sorrento and the Ridge Road area on the western side of east Ascension, in addition to earlier evacuations along Manchac, the Amite and other inland bayous.
"Flooding across Ascension Parish is widespread, and we are not out of danger yet," Meredith Conger, parish homeland security planning and intelligence officer, said in a videotaped emergency message Monday.
Though levels in some parts of Bayou Manchac were starting to recede, Rick Webre, director of the parish Office of Homeland Security, said the threat remains great.
"The next 24 to 48 hours is going to be a significant indication of just how much risk the parish remains in," Webre said in the emergency statement.
Like a big, stretched-out wave heading downstream toward Lake Maurepas, record-breaking crests on the Amite from the severe run of rain last week began to reach Ascension late Sunday and Monday after large swaths of Baton Rouge, Zachary, Baker and Central were flooded.
Meanwhile, an array of multi-parish and state boats and vehicles continued to rescue people stranded by high water as official rescue teams were joined by a volunteer boating force affectionately known as the "Cajun Navy."
"I'm from the bayou, man, and I know what it's like to be flooded," said Raymond Meladine, a civil engineer who came up from New Orleans with his friend to volunteer.
Once rescued, many evacuees were being taken by school bus to the Lamar Dixon Expo Center near Gonzales.
The high water had already sent nearly 600 people to shelter at the gym in the parish-owned Expo Center. Parish officials plan to make another building in the complex available to more evacuees. The complex is also housing stranded pets.
Ascension emergency officials are asking for donations of a variety of items, including socks, aloe lotion, child and adult diapers, baby items, dog and horse food, ropes and buckets for horses.
Ascension Parish public schools will remain closed for the rest of the week as at least five schools have been affected by high water. Schools officials said Monday they planned to make decisions Wednesday about when school would resume.
"We will not know the full extent until the flood waters recede," school officials said in a statement.
The Amite at Port Vincent was cresting Monday at nearly 17.5 feet, almost 3 feet higher than the all-time record from the great flood of '83, which has been the benchmark of collective memory for years in Ascension and a starting point for the design of the parish's flood protection system.
Parish officials estimated as many as 15,000 homes and businesses had been flooded, mostly in Galvez and St. Amant. Ascension has about 45,000 housing units in all, a mid-2015 census estimate shows.
"The damage is unreal, and the water is still coming up. It hasn't even stopped," St. Amant Fire Chief James LeBlanc said.
Conger said high water on Sunday overtook the Henderson Bayou floodgate, which protects the Galvez area against backwater flooding from the Amite. On Monday, water began overtopping the Laurel Ridge levee in the St. Amant area.
Both form part of the parish's protection from high water in the Amite, along with natural ridges to which the structures are connected.
"The protection basin is slowly filling with water due to the overtopping of the Laurel Ridge levee," Conger said.
Parish officials battled false rumors that the six diesel-powered pumps at the Marvin Braud station weren't operating, but Conger acknowledged in an interview that the historically high water could eventually shut down giant pumps.
"That is possible. It is possible it will get to that point that it is no longer functional," Conger said.
Located at the confluence of New River/Bayou Francois and the Severio Canal, the pumps in the southeast corner of Ascension are farther down stream along the Amite than where the river was said to be cresting on Monday.
The pumps in the McElroy Swamp drain runoff from 76 square miles of the parish, including St. Amant, Gonzales and parts of southern Prairieville.
But on Monday, the combined civilian and official forces worried about the here and now and helping those in need.
Ascension Parish Sheriff's Maj. Lee Anderson said that by partnering deputies with civilian boaters, officials were able to stretch their forces. It doesn't matter who makes the rescue as long as residents are safe, he continued.
During a short interview at the command station, the major was twice interrupted by boaters offering to lend a hand.
The civilians have been providing extra watercraft, and the deputies have radios and know where people need to be rescued. The deputies also know the lay of the land, since many of the boaters came from elsewhere in the state.
Meladine and his buddy Alan Harris put in Monday near St. Amant on La. 431, a corridor devastated by Amite River flooding. Within minutes they floated past a drifting coffin, not the last they'd encounter. They pushed forward amidst sunken cars and ruined houses.
They eventually lent a helping hand to Dustin Bergeron, who lives in the St. Amant area but had been helping with evacuations all along the river in places like an apartment complex in Denham Springs and to the north in Watson where boaters could sail over sunken buses.
However, after running his boat for three days, a belt broke, and Harris and Meladine had to tow him to higher ground.
Nearby, Austin Holton was leading two of his neighbor's horses out of the floodwater. He had already fled the area, but when his brother-in-law said the whole neighborhood was going underwater, he returned for the animals. They had to be comforted before crossing the deepest water, but they eventually made it to dry land.
"I couldn't just leave them," Holton said.
It became apparent that the cost of service is a thousand aggravations. Boaters must inch forward to keep their wakes from pushing into already-flooded houses and to avoid running up on fence posts, driveways and other sunken debris. Islands of dry spots have to be circumvented. Spiders and insects drop from the trees. It's hot and rainy, and everyone works in stressful conditions with limited information.
"Nobody knows what's going on," said Wade Wolsing as he stood on the highway in the area where boaters were setting out.
Wolsing's friend was out in their boat; he stayed ashore to leave extra room for evacuees. He passed the time instead by directing traffic and helping people setting out or coming in. With dozens of boats, the scene was crowded and a bit chaotic.
Despite the hard work, boaters made repeated trips into the flood. John Falcon and Paul Randazzo Jr. rescued three children and two adults from a house that was about to flood and began preparing to head in again. Randazzo, a crane operator, had taken a vacation day at work — he had the ability to help, so he wanted to offer his time.
Others offered help by feeding the evacuees and the volunteer rescue force. Parishioners at The Church in St. Amant flagged down boaters heading into or out of the flood zone to hand meals of red beans and rice through windows or toss a water bottle to people riding in the beds of trucks.