i am working on the floodplain mapping of california,united states and i have downloaded the NFHL layer from the FEMA website.After extracting the data i can find different layers & attributes in the arc map.can anyone help me out with the layer & attribute to be selected for the floodplain mapping.Also i want to get the central valley watershed data.Can i get this data from NFHL data or do i need to download from other website.Please guide me regarding this. regards.