Dredging

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

Restoration of Shellfishing Waters in a Tidal Creek Following Limited Dredging

Abstract: A moderately-developed tidal creek feeding the U.S. Atlantic Intracoastal Waterway was closed to shellfishing for a number of years because of high fecal coliform counts. An investigation was unable to determine an anthropogenic source for the contamination. Because dung piles and other wild animal signs were concentrated in the most affected area of the creek animals were assumed to be a major source of the coliform pollution. Over the years a sandbar had accumulated across the mouth of the creek, impeding flow into the creek. A coalition consisting of a concerned citizen's group, local government, and university scientists obtained permits to conduct limited creek-mouth dredging to improve flushing and increase salinity in polluted areas. Following dredging, fecal coliform counts decreased 35 to 60% creek-wide, with greatest decreases in stations midway up the creek. Nitrate concentrations decreased significantly and turbidity increased significantly at two creek stations. A continuous monitor located midway up the creek recorded higher salinities and less intertidal salinity variability following dredging than before dredging. The North Carolina Division of Marine Fisheries reopened the creek to shellfishing a year after dredging. While dredging proved to lower fecal coliform counts to acceptable levels, it did not remove the source of contamination; rather, it alleviated the symptoms.

Assessment of the Anthropogenic Sediment Budget of a Littoral Cell System (Northern Tuscany, Italy)

Abstract: In the present study we describe a straightforward and highly replicable methodology to assess the anthropogenic sediment budget within a coastal system (the Northern Tuscany littoral cell, Italy), specifically selected in a partially natural and partially highly urbanized coastal area, characterized by erosion and accretion processes. The anthropogenic sediment budget has been here calculated as an algebraic sum of sediment inputs, outputs and transfer (m3) within a 40 year time interval (1980–2020). Sediment management strongly influences the sediment budget and, even if its evaluation is crucial to assess the efficiency of a coastal management policy, it is often difficult to quantify the anthropogenic contribution to sedimentary processes. Different types of intervention are carried out by a variety of competent authorities over time (Municipalities, Marinas, Port Authorities), and the correct accountability of sediment budget is no longer known, or possible, for the scientific community. In the Northern Tuscany littoral cell, sedimentation is concentrated in a convergent zone and updrift of port structures, which have determined a series of actions, from offshore dumping and disposal into confined facilities (sediment output), to bypassing and redistribution interventions (sediment transfer); conversely, river mouths and coastal areas protected by groins and barriers are subjected to severe erosion and coastline retreat, resulting in many beach nourishments (sediment input). The majority of coastal protection interventions were carried out to redistribute sand from one site to another within the study area (2,949,800 m3), while the sediment input (1,011,000 m3) almost matched the sediment output (1,254,900 m3) in the considered time interval. A negative anthropogenic sediment budget (−243,900 m3) is here documented.

Fine sediments as a granular source for civil engineering

Abstract: Across the world, every year, several millions of tons of sediments are dredged in harbours. These sediments, which are sometimes polluted, represent an interesting granular resource for the civil engineering. For this study, fine sediments are chosen because of the difficulties to evacuate them after dredging, in comparison to sands, induced by their high water content, the presence of organic matters, their mechanical behaviour and, in some cases, the presence of pollutants. The paper shows the study carried out with fine sediments from harbours of the north of France. The authors propose recommendations to optimize the re-use of these sediments in considering technical, environmental and economical criteria. A re-use process has been studied in laboratory and tested on field site.