The Sabine River at Deweyville, Texas, broke the unofficial highest river level set over 130 years ago and is headed for an even higher crest, completely isolating the small Newton County town of about 1,200. Mandatory evacuations were ordered in Deweyville after a week of heavy rain pushed the Sabine River over historic flood levels Monday evening.

By Sunday morning, water crept into town by about two blocks, storm chaser Erik Fox told weather.com. More than 400 Newton County homes have been flooded by the swollen Sabine, and officials told NBC Dallas-Fort Worth that they fear all of Deweyville's homes will be flooded.

"No residents of the town have ever seen a flood in Deweyville like what's occurring," said weather.com meteorologist Jonathan Erdman.

(MORE: Historic Floods Ongoing in the South)

Upwards of 18 inches of rain fell in the Sabine River Basin from a weather system that lingered over the area for five days. By Tuesday evening, the river is expected to rise near 35 feet and is projected to break the old record by nearly three feet.

The Coast Guard has advised boaters to stay off a 25-mile stretch of the rain-swollen river amid flood and safety concerns. A Coast Guard statement Sunday afternoon said all mariners should avoid the Sabine River between Orange and Bon Wier until Friday due to extreme flood currents linked to last week's rainstorms.

Deweyville residents know what their river can do, and many made preparations to leave well before evacuations were ordered. 

"We're taking virtually everything from our house," Deweyville resident John Bickam told KFDM.com. "We're moving it to higher grounds in hopes that, you know, when all this is over we'll have a house to come back to." 

With the help of 100 agencies, emergency crews in Newton County rescued people via boat and by air as floodwaters continued to rise, KBMT-TV reported. About 45 people were rescued on Friday, according to the Trout Creek Fire Rescue assistant chief.

The mandatory evacuation ordered by Newton County Judge Truman Dougharty went into effect for multiple areas near the Sabine River; a list of affected areas and shelter locations has been posted by KBMT-TV. A curfew also went into effect at midnight on Friday at 7 a.m. and will last until March 19.

The Sabine River Authority lowered the nine gates at Toledo Bend Reservoir to 20 feet open on Friday, KOGT.com reported. The gates had been left completely open at 22 feet for 31 hours, sending 208,000 cubic feet of water per second down the river. The decreased release has 190,000 cubic feet per second. At 6 p.m. Friday, they dropped the gates down to 18 feet.

(MORE: Impacts From Catastrophic Flooding in the South)

Evacuations were also recommended for residents living on the Louisiana side of the Sabine River. According to KATC.com, Calcasieu Office of Homeland Security and Emergency Preparedness director Dick Gremillion is urging residents to take immediate action, as "entry and exit routes to these areas will be limited due to safety concerns" and "public services and emergency services may also be limited during this flooding event."

One reason why the Sabine will see such a huge rise in the coming days is because it is a funnel for so many other tributaries. When all of those rivers and lakes become full at the same time, history has shown that the flooding can be destructive for Deweyville.

"Two large reservoirs on the Sabine River – Lake Tawakoni, east of Dallas, and the larger Toledo Bend Reservoir, south of Shreveport – are both over 2 feet above full pool as of Friday," said Erdman. "All that water has to flow somewhere, and it's headed downstream toward Deweyville and Orange, Texas."

Most Deweyville residents size up flooding events to the 1989 Sabine River Flood, when the river swelled to 29.15 feet in early July. It's the fourth-worst flooding event ever recorded for the Sabine River at Deweyville, topped by a 29.5-foot recording in 1913, a 29.98-foot event in 1953 and a reading of 32.2 feet in 1884, according to historical data from the National Weather Service.