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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TL;DR: A 34-year record of dredging in a 484-km reach of the Middle and Upper Mississippi River documents the spatial and temporal patterns of bed aggradation in an intensively engineered river as discussed by the authors.
24 citations
TL;DR: Liverpool Bay, northwest UK, is a region of freshwater influence and hypertidal conditions used to demonstrate the impact of baroclinicity when considering sediment disposal, demonstrating the necessity of consideringBaroclinic influence even within a hypertidal region with low freshwater inflow for accurate particle tracking studies.
23 citations
TL;DR: The vertical stratification of sediment concentration and of animal numbers in the water column suggests that even if some of these species respond actively to the presence of the dredge, once entrained, they are transported more or less passively in the same way as the larger sediment particles.
23 citations
TL;DR: It is described here that mercury methylation was greater in the Eastern lagoon, indicating increased bioavailability of mercury, as probably facilitated by past dredging that decreased solid-phase retention of inorganic mercury.
Abstract: Surface sediments of the lagoons of Lome, Togo, were analyzed for mercury, methylmercury, and trace elements. Concentrations were greater than typical for natural lagoon sediments, and with greater variability within the Eastern lagoon compared to the Western one. The Eastern lagoon is larger and has been dredged in the past, while the Western lagoon, which also receives major waste inputs, has not been dredged and shows less tidal flushing. Accordingly, one naturally believes that the Eastern lagoon is cleaner and probably safe to use due to its natural resources, including fishes to eat. Unexpectedly, we describe here that mercury methylation was greater in the Eastern lagoon, indicating increased bioavailability of mercury, as probably facilitated by past dredging that decreased solid-phase retention of inorganic mercury. Urbanization has historically been more developed in the southern part of the lagoons, which is still reflected in contamination levels of sediment despite dredging, probably because sources of contamination are still more important there today. Such urban contamination emphasizes the need to regulate waste discharges and possible airborne contamination in growing cities of developing countries, and implements environmental and public health monitoring, especially in relation to misbelieves systematically associated with the cleansing effect of dredging activity.
23 citations
TL;DR: In this paper, the authors monitored nutrient transport in two drainage ditches for six years (2003-2008), during which two dredging activities occurred, and found that the nutrient losses from recently dredged reaches were generally significantly lower than the other reaches during the same year.
Abstract: Agricultural drainage ditches are vital for many agricultural landscapes in the U.S. Previous research has indicated that dredging agricultural drainage ditches may degrade water quality. In this study, we monitored nutrient transport in two drainage ditches for six years (2003-2008), during which two dredging activities occurred. Ditch reach nutrient loads were calculated on a monthly and annual basis for the two ditches, as hydrology and water chemistry were monitored daily during the growing season. When dredging activities occurred within the previous 12 months, reach loads were significantly reduced for all nutrients monitored, with net losses in the dredged reaches of NH4-N (-94 kg), soluble P (SP; -6.6 kg), and total P (TP; -5.4 kg). When examining annual reach loads, the nutrient losses from recently dredged reaches were generally significantly lower than the other reaches during the same year. The apparent improvements in water chemistry seem to be contrary to earlier reports of potentially degraded water quality immediately after dredging. We attribute this to: (1) oxidation of reduced sediments, (2) deposition of fresh sediments, (3) recolonization by filamentous algae and higher plants, and (4) formation of biofilms on the exposed sediments. To avoid the detrimental impacts on water quality immediately after dredging, and to maximize the benefit of ditch recovery, we propose that ditch managers work with agricultural producers to delay nutrient applications to adjacent fields for at least one month after dredging activities. This should allow the ditches sufficient time to recover their ecological function following dredging.
23 citations