Abstract: An air inflation/deflection weir having an air bag made of a flexible film attached to the bed and the vertical bank of a river. The weir is adapted to be inflated and deflated by charging and discharging air into and out of the air bag, wherein the effect of the change of the atmospheric air temperature on the inner pressure of the air bag is eliminated and the inner pressure of the air bag is always maintained at predetermined valve. This inflates and raises the weir to a predetermined height in accordance with the detected water levels upstream and downstream of the weir. Maintaining the pressure inside the air bag, avoids abnormally high or low inner pressure of the air bag that would otherwise cause the air bag to burst or buckle resulting in a flood.

Abstract: An inflatable and collapsible dam arrangement including a flexible membrane weir element positioned so that when it is inflated, it will block a flow of water. The control chamber for the weir is divided into upper and lower sections. The upper section has at least a portion above ground and contains an apparatus for inflating the dam and making the weir element self-supporting. The lower control section includes at least a portion positioned underground and includes an apparatus for collapsing the dam.