Much of the multi-use trail network in the DFW area was built along flood plains, or near/along streams. After hard rains, these areas tend to flood, sometimes by many feet. You must pay attention to the weather conditions and have secondary routes available in case the trail gets flooded.
You can get a rough idea how bad conditions are in the McKinney area by checking the water level of the East Fork Trinity River in McKinney, here.
Here are some pics taken along the trail in Cottonwood Creek, in Allen TX (near Allen Premium Outlets). Even one more foot of water would have washed out this crossing.