Dredging

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

A Simplified Analytic Investigation of the Riverside Effects of Sediment Diversions

Abstract: : Coastal land loss is a striking reality in many coastal communities. The issue is especially acute in coastal Louisiana. Problems of land loss in coastal Louisiana have been extensively documented (Gagliano 1981; Britsch and Dunbar 1993; Boesch et al. 1994; Day et al. 2000).There are several factors that have been identified as causes of this land loss. Among others, these include the following: The rate of relative sea level rise in coastal Louisiana, which is generally faster than the rate of marsh accretion (due primarily to regional subsidence). The reduction of sediment loads in the Mississippi River. The decreased sediment supply to the wetlands due to the lack of hydraulic connection between the wetlands and the Mississippi River. The introduction of dredged canals that criss-cross the marshes and expose marsh vegetation to increased currents and salinity. Other factors, such as vegetation losses due, for example, to nutria, etc. As part of an effort to build land in coastal Louisiana, planners are considering the construction of sediment diversions. Sediment diversions typically consist of lateral water diversions, either controlled or uncontrolled, that are designed to capture and remove large quantities of sediment from a river. In coastal Louisiana, these diversions are intended to re-introduce sediment into shallow bays and degraded coastal marshes, in order to rebuild land in these systems (CPRA 2012). In order for a sediment diversion to be implemented successfully, a variety of factors need to be evaluated. A given sediment diversion must be able to divert and distribute sufficient sediment to effectively mitigate the causal land loss factors listed above. However, the diversion design is subject to several additional constraints.

3D CFD modelling of overflow dredging plumes

Abstract: 3D CFD simulations, lab experiments and field measurements are used to get more understanding of the turbulent near field overflow dredging plume mixing. The focus has been on the most often used dredging vessel: a trailing suction hopper dredger (TSHD). Near field overflow dredging plume mixing is important because it determines the far field dredging plume characteristics and deposition which are essential to know in order to be able to assess the environmental impact of a dredging project. The most important near field mixing processes have been identified in this study. The insights are translated to be usable in every day dredging engineering practise and used in the IMPROVE (IMPact Reducing OVerflow Extension) concept to reduce the environmental impact.

A Kinetic Model of Short-Term Dissolved Contaminant Release during Dredge-Generated Bed Sediment Resuspension

Abstract: Sediment particles can be displaced from the bed to the water column by both natural processes and human activities. Navigational and environmental dredging operations are known to generate particularly high concentrations of suspended sediment and have a significant environmental impact. Once contaminated particles are resuspended a fraction of particle-sorbed chemical is dissolved and equilibrium models are typically used to estimate chemical release. A kinetic model using a mass balance approach incorporating dredgehead particle generation, particle settling, biphasic desorption, flux from the sediment bed, and evaporation to air has been developed for plug-flow stream hydraulics. A key model output for steady-state dredging is concentration in water vs. distance downstream. Typical results for mechanical and hydraulic dredges operating at two sites, the Fox River and Indiana Harbor Canal, will be presented. The kinetic model shows lower concentrations than the equilibrium model in all cases. The most ...