we lived in the Portland area during the 1996 big flood and the best structure protection was wrapping the structure (purchase a home improvement store by the roll)then stretching it up as high as desired and affixing it to the structure, leaving an 2-3Ft apron in front on the ground, THEN putting 2-3layers of sandbags on top of that apron right against the structure. Plywood over any window where needed because the pressure and weight of the water probably would break the window if the water was high on it. So as the water rises it seals the plastic against the structure, so if everything stays intact the water damage would be significantly less that sandbags which in my opinion does nothing because the water goes around and thru those bags.......good luck