The ex-Houston Texans running back still has a home in the area -- and his entire street has been hit hard from the storm.

"Neighbors took a video of our crib from across the street," Foster wrote while posting video showing several homes submerged ... while the rain continues to pour.

So far, at least 5 people have died from the storm and thousands of residents have been forced to leave town -- including Foster.

Foster's former teammate, J.J. Watt, has kick-started a campaign to help hurricane relief ... and is hoping to raise $500k for flood victims.