I finally found the in-laws zip...77388. Candleway Dr. Is that area likely to flood?
Go to this link, which takes a long time to load if you are on dial up and it gives you a big zip code map showing class four and five storm surge areas as well as 100 and 200 year flash flood areas:
http://www.houstontx.gov/category5.jpg
That area is just north of Cypresswood Dr., with Cypress Creek just to the south of Cypresswood Dr. That is a pretty good spot to gather some water, my friend. BUT, the really good news is if someone has a boat, the hospital is just real close!!!