A movable flood barrier wall system includes a housing assembly (12) that has an interior chamber (32). A barrier member (14) is made of a buoyant material having a selected density. The barrier member (14) floats vertically within the chamber (32) when a liquid is present. The barrier member (14) may be made from a closed cell foam core (34) that is clad with a fiberglass mesh material.The foam and fiberglass assembly may be infused with a resin material. Alternatively, the core (34) may be made from a plurality of elongated rods (38) that are individually clad and reinforced with a shear layer. The individaul barrier member modules (15) may be assembled in an end to end relationship with an elongated vertical seal member between adjacent modules. The barrier member (14) may be selectively raised prior to and in anticipation of a flood situation of a nearby body of water by a pump and control system that may be automatically or manually controlled. At least one passive backup system is provided for filling the chamber when the pump or control system fails. The system includes a second pump for selective removal of liquid from the chamber (32) when the barrier is to be lowered. The system also may include components to control silt contamination.
