Dredging

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

Summary of Available Guidance and Best Practices for Determining Suitability of Dredged Material for Beneficial Uses

Abstract: : The Corps of Engineers has the responsibility to maintain navigation of waterways across the United States. The Corps dredges more than 300 million cubic yards of sediment annually. Subsequently, methods to evaluate and determine environmentally and economically sound management alternatives are needed. Technological advances in equipment, treatment, and handling technologies continue to increase the options for beneficial uses (BUs). Ten categories of BU are: 1) Habitat development, 2) Beach nourishment, 3) Aquaculture, 4) Parks and recreation, 5) Agriculture, forestry, and horticulture, 6) Strip mine reclamation and solid waste management, 7) Shoreline stabilization and erosion control, 8) Construction and industrial use, 9) Material transfer, and 10) Multiple purpose. BUs of dredged material have a productive history resulting in over 2,000 man-made islands, more than 100 marshes, and nearly 1,000 habitat development projects. Corps islands provide vital habitat for rare, threatened, or endangered species. It is estimated that 1,000,000 birds nest on dredged material islands each year. BUs of existing dredged material in confined disposal facilities (CDF) should be considered along with all the alternatives available for CDF management. This report compiles current guidance and best practices useful to evaluate dredged material from ongoing dredging projects or CDFs for BUs.

Effects of dredging operations on the demersal fish fauna of a South American tropical-subtropical transition estuary.

Abstract: Changes in the environment and in the composition of fish assemblages in the Paranagua Estuary (South Brazil) were assessed by comparisons made before, during and after dredging operations, in the same months and areas studied in the previous year. Interactions between year and month were observed for salinity. During the dredging year fish total density was 2 individuals m(-2) and with a total biomass of 104 g m(-2) (among 31 species captured). For the same period the year before, 0·3 individuals m(-2) and 3 g m(-2) were captured (38 species). The number of species showed significant time v. month interactions, assuming that fish species composition varied for both year and month. Total mean density and biomass showed significant differences for interaction time v. month, and density and biomass in the dredging month September 2001 in the main channel were scientifically different from other months. Interaction times v. area were significant for Cathorops spixii (increased biomass), Aspistor luniscutis (increased density), Menticirrhus americanus (decreased biomass) and Cynoscion leiarchus (decreased density and biomass). This suggests that during the dredging process there is a change in the structure of the demersal fish assemblage. The impact (damage and mortality) induced by dredging on the macrobenthic animals along the dredge path attracted adults of C. spixii that reached densities 10 times greater than in the year before. On the other hand, sciaenid species practically disappeared. To contribute to the conservation of the estuarine fish fauna, and maintain fisheries production of the Paranagua Estuary and surrounding areas, it is recommended that, dredging should be done from the late rainy season to the early dry season. Decisions must take into account the ecological cycles of socio-economically important fish species and prioritize the safe disposal of dredged spoils.

Sediment resuspension during cutterhead dredging operations

Abstract: Sediments suspended during dredging operations impair water quality and can transport hydrophobic contaminants downstream. Suspended sediment transport models are available, but require an estimate of the rate of sediment resuspension resulting from the dredging operations. In this study, data from cutterhead suction dredging operations, an assessment of sediment resuspension mechanics during cutterhead suction dredging operations, and dimensional analysis are combined to develop empirical models of suspended sediment generation. The usefulness of the models for making a priori estimates of sediment resuspension rates associated with other cutterhead dredging operations is discussed. The sensitivity of the empirical models to variations in physical and operational parameters is investigated.

Changes in benthic community structure due to clam dredging on the Algarve coast and the importance of seasonal analysis

Abstract: Patterns in community structure of meiofauna and macrofauna in relation to Portuguese clam dredging were compared during a 2-y-period off Lagos and Vilamoura, south Portugal. SCUBA divers randomly sampled corer and quadrat samples before and immediately after simulating commercial dredge fishery. Univariate measures (abundance, number of taxa, evenness, diversity and biomass) and multivariate analyses (Cluster, MDS and SIMPER) revealed changes in the meio- and macro-benthic community structure caused by dredge disturbance (short-term effects), with a general decrease in all measures. Macrofauna were found to be more sensitive to dredge disturbance, and aggressive predatory behaviour was observed after disturbance in the continuously dredged area. Nevertheless, higher significant natural changes were found between seasonal periods, indicating that dredging may only cause a small-scale and short-term impact.