Shell dredging sedimentations in Galveston and San Antonio Bays 1964-1969.

Sedimentation on oyster reefs caused by hydraulic mudshell dredging was studied at seven sites in Galveston and San Antonio Bays. Silt baskets, core tubes and oyster tongs were used to monitor rates of sedimentation. Important factors in reef sedimentation were oyster reef contours, sediment composition, direction of current flow and the number of shell dredges discharging sediments. No sedimentation was found on a reef rising 0.91 to 1.22m (3 to 4 ft) above the surrounding bottom while a shell dredge operated 91.4 m (300 ft) from the edge. A reef with a flat profile received deposits of dredge sediments when the nearest of five dredges was 1,798 m (5,900 ft) away. Sediment deposits of 10.2 to 15.2 cm (4 to 6 in) caused oyster mortalities. It was concluded that each dredging site contained particular characteristics and that regulations providing inflexible minimum distances between dredges and reefs were not appropriate.