A series of self-actuating flood guard units each including a buoyant gate flanked by a pair of the boundary walls and pivotable about a horizontal axis transverse to the flanking boundary walls runs along a shoreline of an adjacent body of water The axis is located at a selected elevation above ground inundated by the body water and is selected to cause the gate to buoyantly rotate upwardly between the boundary walls on rise of water above the selected elevation. The extent of rotation is limited by a restraint acting on the gate. The series of units may be continuous or contiguous and act as a whole to prevent onshore flooding from a rise of the body of water at the shoreline.