If you want a more up to date property search then check out my websites at http://www.RanchoElDoradoRealEstate.com or http://www.PinalCountyAZHomes.com where you find a search feature that is directly linked to the MLS. My sites also have a great deal of information about the city of Maricopa.
The wash poses no threat whatsoever. The only area that is considered to be in the 100 year flood plain is the subdivision of Desert Cedars. This home is in Senita. The wash actually adds value to the property as their are no neighbors behind you. I have lived in Maricopa for 10 years and have never even seen water in this wash.
If I can be of further assistance, let me know.