By Lisa Maria Garza and Jim Forsyth
DALLAS (Reuters) - Rivers in Texas flooded their banks on Friday after historic storms had pounded the state for more than a week, with the severe weather leaving at least 21 people dead, damaging more than 4,000 structures and prompting widespread evacuations.
Hundreds of cars were trapped on a suburban freeway blocked by floodwaters in Dallas, where rainfall reached about seven inches (17.8 cms) between Thursday night and Friday.
The National Weather Service issued a flash flood watch for Central Texas into Kansas, with additional rain swelling Texas rivers already at dangerously high levels.
The mayor of Wharton, about 60 miles (100 kms) southwest of Houston, issued a mandatory evacuation order for about 900 people living near the Colorado River, the Houston Chronicle reported. The river began flooding into the city on Thursday and has been rising steadily since.
Across Texas, people spent the night in shelters as this week's floods turned streets into rivers, ripped homes off their foundations and swept over thousands of vehicles.
The Brazos River overflowed its banks about 30 miles (50 kms) west of Fort Worth, forcing people out of homes in low-lying areas.
The rushing water also trapped people in cars and houses, and police and fire crews scrambled to rescue them.
"Some of those rescues have come from cars driving into water and getting stuck, and others are homes which have become inundated with water," said Jamie Moore, the emergency management director for Johnson County, southwest of Fort Worth.
In Central Texas overnight, Travis County firefighters rescued 21 people from a drifting houseboat, officials said.
Before Thursday night's storm, Texas climatologist John Nielsen-Gammon said so far in May the state had received 7.54 inches (19 cm) of rainfall on average. That breaks the record of 6.66 inches (17 cm) set in June 2004, based on records dating to 1895, according to Nielsen-Gammon of the Office of the Texas State Climatologist at Texas A&M University.
In Wimberley, near where at least seven people have been killed in floods, residents took time out from searches and clean-up for a graduation ceremony at their high school.
"Watching our kids for the past three days come and pick up shovels and go to neighborhoods and step in and help with clean up has just been awesome," said school district superintendent Dwain York.
(Writing by Jon Herskovitz in Austin, Texas; Reporting by Lisa Maria Garza in Dallas and Jim Forsyth in San Antonio; Editing by Susan Heavey, Bill Trott and Lisa Lambert)
