Topic
Dredging
About: Dredging is a research topic. Over the lifetime, 3300 publications have been published within this topic receiving 28325 citations.
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01 Jan 1996
TL;DR: In this paper, the risks of dredging polluted sediments are shown to depend on the risk of dispersion and on the mode of occurrence of the pollutants, i.e., when the pollutant occurs as single molecules dissolved in water.
Abstract: The growing environmental concern in the world is also noticeable in the dredging world, especially in relation to dredging polluted sediments. The knowledge obtained during the last decades of the behaviour of pollutants in aquatic systems has been used to manage the environmental quality of aquatic systems. The situation during dredging differs from the regular situation, due to processes with short time scales and very heterogeneous environmental conditions. In this article the risks of dredging polluted sediments are shown to depend on the risk of dispersion and on the mode of occurrence of the pollutants. During dredging, shifts in mode of occurrence may occur which affect the availability for uptake by organisms (the bioavailability) and consequently the toxicity of the pollutant. The toxicity is highest in the free mode of occurrence, i.e. when the pollutant occurs as single molecules dissolved in water. General descriptions are given of the behaviour of the two main classes of pollutants: heavy metals and organic micropollutants. Evaluating the processes occurring during dredging revealed the conditions and activities causing environmental risks.
32 citations
01 Jan 2007
TL;DR: The cumulative effect of fishing can lead to overfishing with a consequent decrease in the abundance of targeted species, the fisheries that depend on them and significant impacts on ecosystems as mentioned in this paper.
Abstract: The sustainable existence of particular fishing activities in a certain area depends on the maintenance of the stock of the target species in that area. The cumulative effect of fishing can lead to overfishing with a consequent decrease in the abundance of targeted species, the fisheries that depend on them and significant impacts on ecosystems. Ecosystem changes caused by fishing are mostly associated with mobile bottom gears, especially dredges, which impact the benthic habitat and associated assemblages of species. The magnitude of impacts from such fishing depends on factors such as the fishing frequency, towing speed, gear type, gear penetration into the sediment, time of year, local environmental conditions (such as water depth, tidal strength and currents), nature of the substratum and the structure of the benthic communities affected (de Groot 1984; Churchill 1989; Mayer et al. 1991). The environmental effects of shellfish dredging have received special attention throughout the world in recent decades (e.g., Caddy 1973; Conner and Simpson 1979; McLoughlin et al. 1991; Eleftheriou and Robertson 1992; Dare et al. 1993; Hall et al. 1993; Jennings and Kaiser 1998; HallSpencer and Moore 2000). These gears re-suspend and rework bottom sediments, move and bury boulders, reduce microtopography and may leave long-lasting grooves (e.g., Caddy 1973; Churchill 1989; Mayer et al. 1991). Sediment re-suspension by towed gears can alter the composition of sediments (usually to coarser grain sizes), reduce chemical exchanges in the water-sediment interface and increase water turbidity with deleterious effects on planktonic productivity (Hayes et al. 1984; LaSalle 1990; Coen 1995). Along with the target species, dredges also catch algae and other epifauna and infauna, many of which have no commercial value and are therefore discarded either alive or dead.
32 citations
15 Apr 2006
TL;DR: The storage loss due to reservoir sedimentation has been found to exceed the storage added worldwide by the mid 1990s, and the storage loss is estimated to range between US$ 10 billion and US$ 20 billion per year, not accounting for the growth in world population.
Abstract: The storage loss due to reservoir sedimentation has been found to exceed the storage added worldwide by the mid 1990s. Recovery of this lost storage is estimated to range between US$ 10 billion and US$ 20 billion per year, not accounting for the growth in world population. Reservoir sedimentation does not only impact water supply and power supply reliability, but also has significant impacts on the environment, including downstream river degradation, and impacts on recreation, flood management, infrastructure, and the economy. The article illustrates how sediment is trapped in reservoirs, provides empirical techniques for calculating the volume of sediment that can be trapped by reservoirs, outlines sediment management techniques, which includes flushing, dredging, dry excavation, hydrosuction, and bypassing, and introduces the life-cycle management approach. This approach to reservoir sedimentation management is in contrast to the conventional design life approach, which is inappropriate for the design, construction, and management of dams and their reservoirs. Numerous references for further reading are listed.
Keywords:
sedimentation;
reservoir;
flushing;
dredging;
dry excavation;
reliability;
water supply;
life-cycle management;
density current;
sediment transport;
delta;
topset slope;
frontset slope;
sediment management;
storage loss;
environmental impact;
sediment trap efficiency;
design life;
hydrosuction removal system;
bypassing
32 citations
32 citations
TL;DR: The findings show that creation of the artificial island with the underwater explosion sediment removal technique would greatly impact the marine environment, however, the impact for the silt dredging technique would be less.
32 citations