Dredging

About: Dredging is a research topic. Over the lifetime, 3300 publications have been published within this topic receiving 28325 citations.

Settlement and Consolidation in the Laboratory of Steadily-deposited Sediment

Abstract: Large amounts of sediment are moved in suspension in water — in rivers and estuaries, for example — and then deposited onto the bed as the available energy reduces. An understanding of the settling behaviour and subsequent consolidation of the sediment is important for the analysis of siltation and dredging problems and for the disposal of slurried waste.

An Estuarine Ecohydrology Model of Darwin Harbour, Australia

Abstract: Throughout human history, the coastal plains and lowland river valleys have usually been the most populated areas over the world (Wolanski et al., 2004a). This is degrading estuarine and coastal waters through pollution, eutrophication, increased turbidity, overfishing, and habitat destruction (Lindeboom, 2002). The pollutant supply does not just include nutrients, but also includes mud from eroded soil, heavy metals, radionuclides, hydrocarbons, and a number of chemicals including new synthetic products. Darwin Harbour (Figure 1) is no exception. Taking the Harbour to include all waters inshore of Gunn and Charles Points, it covers 3,227 km, and the drainage is 2,417 km. The harbour is an estuary with three arms, each of which drains a seasonal river with negligible flow in the dry season. Several pollution sources exist in this estuary, mainly on the east side. Urbanization, industrialisation, dredging, dredge spoil discharge, sewage discharge, shipping, agriculture (fertilizers, pesticides, herbicides), aquaculture wastes, two harbours and several marinas, all represents threats to Darwin Harbour. By comparison, the west side is the least disturbed. To prevent major environmental degradation as happened in the other harbours described in this book, there is a need for a science-based integrated management plan that considers the whole Darwin Harbour catchment as the fundamental planning unit. For science to help in this process, it must provide useful data and tools. One such scientific tool is a model to quantify the human impact on the ecosystem health of the harbour. The health of an estuary or a coastal water body needs to include a number of potentially conflicting variables (Balls, 1994), requiring the use of modelling tools. This chapter describes such a model for Darwin Harbour. The model is kept as simple as possible to be practical while remaining realistic. In the model, flushing and mixing processes (that are readily measured in the field

Assessing Lead Contamination in Buffalo River Sediments

Abstract: The Great Lakes Water Quality Agreement between Canada and the United States has identified the Buffalo River as an Area of Concern. The watershed has a long history of heavy industrial activity that contributed to its overall pollution. Sediment core data collected by the New York State Department of Environmental Conservation in 2005 were used to determine lead sediment contamination in a section of the Buffalo River. The ordinary kriging spatial interpolation technique was used to generate surface and subsurface sediment contamination estimates. Due to the meandering nature of the river, two kriging models were used to analyze surface contamination: a global kriging model and a regional kriging model, consisting of three separate sections. The results show that both the global and regional kriging models display similar interpolated surfaces and do not vary significantly. Within the sediment, lead contamination in the surface layer is lower than at the various subsurface depths. In 2011, habitat restoration efforts commenced to remediate environmental damage due to years of pollution inputs from various sources. Sediment dredging operations were initiated that are expected to be completed in 2015. The goal of these operations is to remove heavily contaminated sediments and rehabilitate the Buffalo River. The kriging results provide area-wide estimates of contamination. When compared to the dredging plan, the results indicate that additional removal of contaminated sediments may need to be considered where no dredging has occurred or is not currently planned.

To preserve or to develop? East Bay dredging project, South Caicos, Turks and Caicos Islands

Abstract: The Turks and Caicos Islands are currently in the midst of an economic revolution from a marine-based provisional economy to a tourism economy. East Bay, South Caicos, is currently under construction with plans for a 160-unit condominium complex. Included in the project plan is removal of seagrass beds in front of the development to make a sandy beach for tourists. The aims of this study were to (i) describe the bathymetry and benthic habitat coverage of East Bay before dredging takes place and (ii) perform an economic valuation on the turtle grass beds that will be dredged using ecosystem valuation and emergy analysis techniques. The bathymetry survey revealed shallow waters (<1.5 m) until the reef drop off (∼650 m offshore). Benthic habitat exhibits zonation following the general progression: sand plain, algal plain, seagrass, coral rubble and seagrass, rock and turf algae, and reef flat. Ecosystem services valued the proposed dredging area at USD $28,807 per year, compared to emergy analysis, which valued the proposed dredging site at USD $32,060 per year. The baselines presented in the study may facilitate a quantitative assessment of dredging impacts on turtle grass once dredging is complete and an economical cost-benefit-analysis of the dredging project to see whether the economic gains outweigh the ecological costs of dredging in front of the East Bay development.