The best way for homeowners to protect their homes from floods among the options given is relocating furnace and water heaters. By elevating these appliances above potential flood levels, homeowners can minimize damage and ensure they remain functional in the event of a flood.
The other options, while relevant to flood management and prevention, do not directly involve actions homeowners can take to protect their own properties in the same immediate way. Building near floodplains, for instance, increases risk, developing building codes requires broader legislative action, and helping build dams involves community or governmental efforts.