Dredging

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

Observations on Dredging and Dissolved Oxygen in a Tidal Waterway

Abstract: Evidence indicates that resuspension of oxidizable bottom sediments in a tidal waterway caused significant reductions in the dissolved oxygen (D.O.) concentration of the water. During dredging, D.O. was reduced between 16–83% below normal.

Resuspension and clearing of dredge spoils after dredging, Cleveland Bay, Australia

Abstract: During dredging operation, fine sediment is released in the navigation channel of the Port of Townsville, Australia, as a result of mechanical disturbance of the bed and of the overflow from the storage tanks of the dredger. Some of this sediment is advected away from the dredging site toward the beach and reef areas and could result in environmental damage if not managed properly. Field monitoring was conducted for salinity, temperature, suspended sediment, and acoustic profiles at several sites before and after dredging. Laboratory investigations on the effect of sediment concentration, turbulence, and floc size on the clearing of a suspension column were also undertaken

Coastal Land Loss in Texas--An Overview

Abstract: Nearly 1,500 acres of prime coastal real estate and productive wetlands are destroyed each year in Texas along the Gulf shoreline, near bay margins, and within alluvial valleys primarily as a result of erosion and submergence. Wetland losses constitute about 75 % of the total land losses. Historical analyses of maps and aerial photographs indicate that land losses are accelerating and that human activities are either directly or indirectly responsible for the increased losses. Natural decreases in sediment supply have been exacerbated by (1) river basin projects that reduce the volume of sediment transported to the coast and (2) coastal structures and navigation projects that prevent redistribution of littoral sediments along the coast. Erosion, caused by high wave and current energy and an inadequate supply of sediment, is responsible for higher local rates of land loss than submergence. Erosion losses are also more perceptible, especially after major storms when the greatest losses occur. Boat traffic causes substantial erosion along some navigation channels. The principal components of submergence are subsidence and the eustatic rise in sea level. Submergence converts uplands to wetlands and wetlands to open water. These surficial changes occur mostly on the coastal plain, but are also observed on barrier islands, on bayhead deltas, and within entrenched valleys. Recent accelerated submergence is induced by extraction of shallow ground water or production of hydrocarbons at moderate depths. Faults activated by the withdrawal of these fluids concentrate the subsidence near fault planes. Coastal land losses directly caused by dredging (marinas, subdivisions, canals, rig locations) are less than those caused by erosion and submergence, but they constitute a growing percentage of total land losses in Texas.

The behaviour of fines released due to dredging: A literature review

Abstract: In 2001a DIOC-projectwas started at Delft University of Technologyon the dispersion of fines during sand mining. In this project the behaviour and spreading of fines, which are released through the overflow of a dredging ship, is studied. Laboratory and field studies will be carried out to determine the behaviour and spreading of the fines. However, before any experiments are carried out, a literature study is done to determine the main focus of the subsequent research. This literature study is presented herein. It discusses the whole cycle of dredging, the release of sediment in the water, behaviour of sediment in the water column, sedimentation, erosion and impact on ecology. In the end it is decided that the subsequent research shal1focus on two subjects, namely the hindered settling of sand/mud mixtures and the sea/bed interaction.

The impact of dredging on macrobenthic invertebrates in a tributary of the Warri River, Niger delta

Abstract: The macrobenthic invertebrates of a canal, created from a tributary of the Warri River in the mangrove swamp of the Niger Delta, Nigeria, were studied before and after dredging. In the canal dredging resulted in at least a 93% decrease in the benthic population while the Margalef's diversity index reduced from 3.8 to 1.4. Of the 15 species identified during the pre-dredging studies, only Nereis operta and Baetis sp. were recovered after dredging. The site 500m downstream of the canal was also slightly impacted, showing a 31% decrease in population. We conclude that the drastic reduction of benthic species is due to the direct destruction of benthic species, larvae and habitat, as well as settling turbidity plumes, reduction of sediment nutrients, physical disturbance and, physiological and toxic stress. To conserve biodiversity it is recommended that mitigation measures should be put in place by stakeholders involved in dredging and that long-term monitoring of dredged canals is carried out to ensure that...