Putting a chimney cover or chimney cap on top of your flue can save you a lot of money in the long run. The covers keep out damaging moisture, which wears away masonry and steel chimneys - not to mention that they keep those birds and other critters out.
For protection against shallow flood waters, the washer and dryer can sometimes be elevated on masonry or pressure-treated lumber at least 12″ above the projected flood elevation. Other options are moving the washer and dryer to a higher floor, or building a floodwall around the appliances.
The furnace and water heater can be placed on masonry blocks or concrete at least 12 above the projected flood elevation, moved to inside a floodwall or moved to a higher floor.
Furnaces that operate horizontally can be suspended from ceiling joists if the joists are strong enough to hold the weight. Installing a draft-down furnace in the attic may be an option if allowed by local codes. Some heating vents can be located above the projected flood elevation.
Outside air conditioning compressors, heat pumps or package units (single units that include a furnace and air conditioner) can be placed on a base of masonry, concrete or pressure-treated lumber. All work must conform to state and local building codes.