There are depth markers at every crossing of every creek on Ft Hood. They may have been washed away by debris. All the more reason NOT to enter the water.
Depth markers don’t account for the erosion that often occurs instantaneously in a flash flood. I’ve seen six-foot torches cut through the desert in minutes. A stream that appears to be slightly higher than the road may be deep enough to swamp a vehicle.
My prayers to the families.