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Field measurements of tidal current velocities are used to infer sediment transport characteristics in the lower section of a large, tidally dominated estuarine system at Whangarei Harbour, New Zealand. Recent (2002) developments at the harbour entrance included a 32.6 ha intertidal reclamation and a 31.8 ha dredged turning basin. Residual distance vectors indicate that the postdevelopment, large-scale pattern of sediment transport dynamics remains consistent. Minor, localised modification of transport potentials has been observed immediately adjacent to the developments, however. These modifications include a slight realignment of current flows near the reclamation wall and some leakage from a previously identified transport loop near the dredged basin. The potential for scour is identified along the eastern margin of the dredged basin, which could act to remove material moving downslope into the basin from its western edge. These data are consistent with numerical model results that predicted minimal consequences resulting from the developments. Lower harbour sediment dynamics are consistent with established patterns for tide-dominated inlets, with separation of the channel into areas of ebb and flood dominance, and typical transport patterns over the flood tidal delta. Broad-scale inlet geomorphology has been maintained, which is consistent with other dredged tide-dominated inlets. [ABSTRACT FROM AUTHOR]

Redesign of Port Gisborne for the 21st century has encompassed a broad interdisciplinary approach. This procedure has taken into account the operational requirements of the port, effects of dredging and construction upon the benthic fauna, and wave activity within the port confines after the proposed development. Added amenity value of the development to the local community is an important ancillary redesign consideration. Initially, a major research project into the environmental impacts of the developments has been undertaken.The project, which commenced in 1996 and is still continuing, involves an iterative approach integrating the initial design and development options with the operational feasibility, construction constraints, environmental constraints, social acceptability, and economic practicality of the port; all of these require in-depth assessment to obtain the necessary planning and development approvals. This requires close liaison between the professional environmental research scientists, port management, port operation staff (pilots), construction engineers, planners, and the community interest groups.Numerical modelling of the hydrodynamics of Poverty Bay, simulating waves and current effects on the various initial designs options, and calibrated against data from a substantial field program, has been a fundamental tool. It was applied experimentally to determine the best option for the port layout, as well as to assess sedimentation impacts. Modelling results indicated a significant increase in maintenance dredging expected as a result of deepening the navigation approach channel. Because this may have an impact on the nearby sandy beach by inducing erosion, the best option for disposal of the sandy dredged material was determined to be disposal in the surf zone for subtidal beach profile renourishment. Textural analysis of the sediments trapped in the navigation channel demonstrated that they were suitable for this purpose. [Copyright &y& Elsevier]

A planned extension of the Port of Tauranga requires capital dredging of material containing significant amounts of silt and clay. The existing disposal ground located about 4 km offshore in water depths of15 to 25 m, is unsuitable as it was designed for slow migration of predominantly sandy materials onshore to nourish the adjacent beaches.Investigation for a new disposal site involved consideration of alternatives, but the 'best practical option' selected was offshore of the existing ground in water depths of 28-33 m. Site research included side scan sonar imagery of the sea floor, sediment sampling by SCUBA diving, and deployment of a current meter for several weeks during the spring season to obtain background hydrodynamic data. Analysis of the data indicated that motion of medium to coarse sands occurs duringperiods of high swell conditions. Calculations of potential transport of discrete mud 'clasts' suggest that small units (+/<2 cm) may move under large waves (Ts = 11 s, Hs = 1.6 m), but larger mud 'clasts' would be stable. It is expected that the existing high disposal mound immediately shoreward of the proposed new disposal ground would hinder onshore migration of muddy clasts. [ABSTRACT FROM AUTHOR]