If the building is located in a flood zone, flood insurance is required.
You could have the parcel of land excluded from the mortgage but if you had to foreclose how marketable would that land be with the parcel excluded if it sits in the middle of your collateral – this is something you need to consider. Not that I’m recommending this, but I’ve seen borrowers tear down outbuildings/barns that have minimal value in order to avoid paying for flood insurance.