Bypassing of dredged littoral muddy sediments using a thin layer dispersaltechnique

Maintenance dredging of the navigation approach channel to Pine Harbour Mar ina is necessary to remove muddy sediment which accumulates as a result of depositional processes due to flocculation and the littoral "turbid fringe" . Based upon analysis of the muddy sedimentation processes in the adjacent embayment a "thin layer" dredgings disposal method was instigated. This nov el technique required a detailed monitoring program based upon a wide range of field measurements including turbidity and suspended sediment loads, de tailed hydrographic surveys of the dredging disposal ground, high resolutio n side-scan sonar survey, SCUBA observations of sedimentation rods, and reg ular helicopter flights to obtain oblique air photo records. The results co nsistently demonstrated that thin layer disposal was achieved, and no mound of muddy deposits accumulated. Application of a 1-D numerical model of mud resuspension under storm waves realized suspended sediment concentrations similar to those measured in wat ers discharging from the adjacent catchment, and indicated that the erodibi lity of the bottom sediment in the disposal area was unlikely to change as a result of the disposal. It is thus most unlikely that muddy material woul d migrate from the disposal grounds to the adjacent beaches.