Potential Benefits of Pneumatic Barriers in Estuaries

Pneumatic barriers (or bubble screens) have been proposed or actually used for a variety of purposes, including reduction of the extent of saltwater intrusion in estuaries, the reduction of saltwater intrusion through navigation locks which separate a saline water body from a freshwater body, to accelerate movement of warmer bottom water to the surface to reduce ice formation around piers, to diminish wave heights, and to increase turbulence as a means for inhibiting the deposition of sediments in critical areas. This paper summarizes the potential benefits which might accrue from construction and operation of pneumatic barriers in estuaries, describes briefly the results of hydraulic model experiments of such devices made to date, points out the need for additional research to develop model laws and scaling factors for transference of model results to prototype dimensions to aid in design and economic evaluation of barriers, and mentions research efforts planned for the immediate future at the U. S. Army Engineer Waterways Experiment Station. The paper also points out certain detrimental effects on estuarine phenomena which might result from indiscriminate operation of pneumatic barriers without careful study and evaluation of all effects of such devices.