You can find out about flooding by visiting the FEMA website at http://www.fema.gov
and looking at their flood maps. If you are looking at a resale property, flooding of a property or presence in a flood zone a disclosure item you will find noted on the seller's disclosure. Your insurance agent can also pull a report on the home and let you know if there have been any claims on the property regarding flooding or any other serious concerns.
As to crime, there are a few websites out there that are helpful, including sex offender data at the texas department of safety http://(www.records.txdps.state.tx.us
) and more general stats on melissadata.com and spotcrime.com.
When checking out a neighborhood, I also like to take a look at the school ratings, even if you don't have kids. You can find all sorts of information at http://www.tea.state.tx.us.
Last but not least, be sure to ask your Realtor for help! A buyer's agent can help you understand whether values in the neighborhood are increasing or decreasing, and answer any of your other questions about buying a home.