Aquatic disposal field investigations Galveston, Texas, offshore disposal site. Appendix A: investigation of the hydraulic regime and physical nature of sedimentation

This report presents the results of a multifaceted investigation of the geological processes of deposition, erosion, and transport of dredged material within the area of the Galveston offshore Dredged Material Disposal Site (DMDS) during the period 6 March 1975- 20 November 1976. This study involved two major phases: a pilot study designed to rapidly survey the DMDS and environs, and an experimental study to delineate natural changes in the physical and geological characteristics of the study area after disposal had occurred. The latter study involved the monitoring of dredged material disposal at selected locations to determine the physical-geological processes active. Control sites were also monitored for comparison. Hydrographic data were collected to delineate current and wave effects within the DMDS, and flume experiments were conducted to determine the hydrodynamic characteristics of dredged material placed in the area. Comparisons are made between sediment and carbonate concentrations and bathymetric differences evident from data collected during the pilot and post disposal phases of the study. The differences determined are discussed in light of the hydraulic regime present. Estimates of current velocities required to redistribute DMDS bottom sediments are based on comparisons between flume experiment studies and on-site current meter data. Available data indicate that dredged material has been eroded from the shallow water portion of the DMDS and has been transported in a down coast-offshore direction; little erosion was noted in the deeper, offshore disposal sites.