That is a BRIDGE???
Low water bridges are common in both the Texas Hill Country and West Texas.
In the Hill Country they go over small streams/Creeks that are probably between ankle and mid thigh deep at that point. They are designed so that flood waters will flow over them and hopefully not be damage by debris.
I went to Camp Arrowhead the (first term) summers of 78 and 79 (I think I was a sub deb the first year and JR deb 2nd). During the 2nd term of 78 there was huge flooding in the Hill Country. I remember watching the news as those helicopters with 2 sets of blades and long body air dropped supplies to the camp. When we went back the next summer you could still see the debris up in the trees. Daddy was 6' 6" tall. He stood under one of the trees and held a 6 foot pole from the RV up over his head with his arm fully extended. The debris was a good deal higher up than the end of the pole. The low water bridge into the camp had been undamaged on the top, but had to be replaced because the bottom of the creek had been dug out around the supports.
In West Texas the go over creek beds that are dry, unless you get a gully washer there or up stream then the water rushes down.
I was "raised" on stories of people who did not heed warnings and tried to cross these during floods, only to be swept away and drowned. The reason I always pay attention to locals warnings.