Why is dredging necessary?
Most U.S. ports are located on rivers or in estuaries that have natural water depths less than required for the larger vessels commonly used in domestic and international shipping. Terrestrial surface water runoff, wave action, and tidal currents carry sediments from the erosion of rock and soil and deposit this material in downstream areas of the rivers and estuaries including navigation channels and ship berths in ports. This erosion and deposition cycle is a natural process, which has been enhanced by increased land development. Today’s modern ships require deeper drafts to move goods more economically. Removal of the sediment material from the navigation channels and berths by dredging allows more fully loaded ships safe passage into and out of berthing facilities. Shallow draft clearances (shallow depths) in navigation channels and berthing facilities forces shippers to carry less cargo increasing the effective shipping cost of the delivery. In the case of tanker ships carrying pe
