Dredging

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

Assessment of Riverine Dredging Impact on Flooding in Low-Gradient Coastal Rivers Using a Hybrid 1D/2D Hydrodynamic Model

Abstract: The current study investigates the effect of large-scale channel modifications via riverine dredging on flood dynamics in low-gradient river systems located in inland-coastal flood transition zones. The study site is the Vermilion River in south Louisiana, US, which is characterized by complex flow regimes, reversal and bi-directional flows, presence of large swamps with significant river-swamp interactions, and large volumes of runoff contributions from lateral tributaries. The study aims to understand the interplay of these factors and how they modulate and get affected by different dredging approaches that vary in spatial extent and the modifications introduced to the channel. The study deploys a hybrid, one- / two-dimensional (1D/2D), hydrodynamic model that simulates flow and stage dynamics in the main river and its major tributaries, as well as the flow exchanges with the interconnected swamp system. Overall, the results show that the dredging activities can significantly alter the flow regime in the watershed and affect flow exchanges between the river and the swamp system. In terms of flooding impact, only dredging approaches that are extensive in spatial extent and modifications to channel longitudinal slope can result in sizeable reductions in flood stages. However, these benefits come at the expense of significant increases in the amplitude and inland propagation of the Gulf tidal wave. On the other hand, less-extensive dredging can still provide moderate and spatially limited flood mitigation; however, they further expose downstream communities to increased levels of flooding, especially during more frequent events. The results reveal that while dredging can increase the hydraulic conveyance of the river system, the large runoff volumes delivered by the urbanized tributaries seem to outweigh the added improvement in the in-channel storage, thus reducing the anticipated flood relief. The results suggest that a watershed-centered approach, instead of a riverine-centered approach is needed for flood management in these systems so that the relative benefits and tradeoffs of different mitigation alternatives can be examined.

Effectiveness of Spur Jetties at Siuslaw River, Oregon. Report I: Prototype Monitoring Study.

Abstract: : In 1985, the rubble-mound jetties at the entrance to the Suislaw River, Florence, OR, were extended offshore. In addition, on the ocean side of each jetty, one long spur oriented 45 deg to the main structure was constructed shoreward of the seaward end of each of the twin jetties. The spur system was investigated as a cost reducing alternative to significant linear jetty length extension which would reduce sediment shoaling and dredging requirements in the channel and improve navigability. Cost reductions were expected in reduced maintenance dredging and in actual construction and material cost. Monitoring and evaluation of the jetty system were conducted through the U.S. Army Corps of Engineers, Monitoring of Completed Coastal Projects (MCCP) Program by the Coastal Engineering Research Center (CERC) in coordination with the U.S. Army Engineer District, Portland (NPP). Data collected during field monitoring of the area are related to incident wave conditions. Spur-induced current patterns and sediment deposition patterns, along with annual dredging records are analyzed to evaluate structure performance. The favorable results of this MCCP study substantiate physical model test findings and indicate potential application of spur jetties at other sites.

A step-wise discriminant analysis of the effects of long term coal mine drainage and coal dredging on phytoplankton of the Guyandotte River

Abstract: Phytoplankton was sampled from the lower 60 miles portion of the Guyandotte River where three active coal dredging operations presently exist and five more permits are pending. Comparisons were made with phytoplankton from a similar stretch of the Mud River, a stream of minimal mine drainage and no coal dredges along its entire course. Diatoms were the predominant planktonic algae on both streams. The number of all phytoplankton species was 24% higher for the Mud River than for the Guyandotte River. Equitability and species diversity indices plus the distribution of mine water indicator algae show that the Guyandotte River is heavily polluted with domestic wastes and mine drainage. No correlation could be established for turbidity, specific conductance, or pH and locations of dredging operations, when the data were analyzed for differences among sampling stations. Step-wise discriminant analysis was used to compare the two streams and the biological, physical, and chemical variables. Based on coefficients for canonical variables, conductivity and pH are the two most influential variables in separating the two streams. Analysis of variance indicates that the canonical means of the stations on the Guyandotte River are significantly different from the Mud River stations.