An arrangement for causing a water impermeable barrier conventionally lain on a ground surface to float above rising water or flooding, rather than being entrapped above the barrier, is shown and described. This invention applies particularly to ground coverings in building crawl spaces. In an embodiment, one or more floats are placed below the water impermeable barrier and above the ground. When flood waters recede, the float(s) and the water impermeable barrier return to their preflood locations above the ground surface. Floats may comprise blocks, sheets, strips, and other configurations of closed cell polymeric foam, for example. The float or floats may be coupled to the water impermeable barrier or alternatively, may be left decoupled therefrom.