VIDEO: Cows struggle to stay afloat in Texas flood waters

Sheriff’s deputies in a county near Houston shot video of more than a hundred cows struggling to stay afloat in flood waters on Wednesday.

Hundreds of residents remained evacuated from their homes as the Brazos River reached 54.7 feet in Fort Bend County, where the video of the cows was shot. Officials there have had more than 300 water rescues the last four days.

But additional rain this week could mean it might take days or even weeks before the Brazos and other waterways drop to normal levels. The Neches River in East Texas and the Colorado River extending southeast of Austin also were overflowing.

Texas Gov. Greg Abbott declared a state of disaster Wednesday in 31 flood-affected counties including Lubbock County in West Texas, Hidalgo County in the Lower Rio Grande Valley of South Texas, and Jasper County in East Texas.

At least six people died in floods last week in Central and Southeast Texas.

The storms have prompted flooding in parts of Texas that two years ago had run dry because of drought conditions. They are the latest in a string of torrential rains since May 2015 that have put swaths of the state underwater.

Southeast Texas has been hit particularly hard and often, including storms in March that dumped up to a foot of rain in some areas and brought record flooding not seen since 1884 along the Sabine River. In April, more than a foot of rain fell in parts of Houston, submerging scores of subdivisions and several major highways, forcing the closure of schools and knocking out power to thousands of residents who were urged to shelter in place.

Fort Bend County's emergency management coordinator, Jeff Braun, said his biggest concern is the additional heavy rainfall in the forecast, which could delay evacuated residents from returning to their homes for up to a week because the water in flooded areas "will not have anywhere to go" with more rain.

State Climatologist John Nielsen-Gammon said the average annual rainfall in Texas over the last century has increased about 5 to 10 percent. But the severe weather over the last year was exacerbated by El Nino, which is the natural warming of parts of the Pacific Ocean that changes weather worldwide.

The El Nino period is dissipating but Nielsen-Gammon said the frequency of heavy rains likely will continue.

Elevated water levels could continue through the weekend as forecasts call for more rain. The National Weather Service has issued a flash flood watch for the greater Houston region where 8 to 10 inches could fall through Friday in some isolated locations. The Austin area is expected to receive 3 to 6 inches through Friday, while Dallas and North Texas is forecast to receive 3 to 5 inches by the end of Thursday.

The Associated Press contributed to this report.