Dredging

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

Effects of dredging and reclamation on the sediments of Botany Bay

Abstract: Bottom sediments in Botany Bay were surveyed and analysed for particle size using a wet-sieving volumetric determination. Sediments are predominantly clean sands. although substantial changes in sediment type have occurred in the northern region of the bay since 1968. Large areas which were formerly clean sand, now contain significant amounts of mud. This increase in fine sediments is particularly marked in the dredged areas protected by the Port Botany revetment and the Kingsford-Smith Airport runway extension. These changes have not been the result of exposure by dredging of silt and clay lenses within the underlying sediments, but have probably been caused by the combined effects of deposition of fine material discharged during dredging and reclamation, and increased deposition of fluvial suspended matter due to changes in tidal circulation following the development of port and airport facilities. Sediments in the Port Botany harbour area are expected to become progressively more muddy. Water turbidity in turn may increase as a result of resuspension of fine material by shipping movements.

Sediment Transport near Ship Shoal for Coastal Restoration in the Louisiana Shelf: A Model Estimate of the Year 2017–2018

Abstract: Ship Shoal has been a high-priority target sand resource for dredging activities to restore the eroding barrier islands in LA, USA. The Caminada and Raccoon Island pits were dredged on and near Ship Shoal, which resulted in a mixed texture environment with the redistribution of cohesive mud and noncohesive sand. However, there is very limited knowledge about the source and transport process of suspended muddy sediments near Ship Shoal. The objective of this study is to apply the Regional Ocean Modeling System (ROMS) model to quantify the sediment sources and relative contribution of fluvial sediments with the estuary and shelf sediments delivered to Ship Shoal. The model results showed that suspended mud from the Atchafalaya River can transport and bypass Ship Shoal. Only a minimal amount of suspended mud from the Atchafalaya River can be delivered to Ship Shoal in a one-year time scale. Additionally, suspended mud from the inner shelf could be transported cross Ship Shoal and generate a thin mud layer, which is also considered as the primary sediment source infilling the dredge pits near Ship Shoal. Two hurricanes and one tropical storm during the year 2017–2018 changed the direction of the sediment transport flux near Ship Shoal and contributed to the pit infilling (less than 10% for this specific period). Our model also captured that the bottom sediment concentration in the Raccoon Island pit was relatively higher than the one in Caminada in the same period. Suspended mud sediment from the river, inner shelf, and bay can bypass or transport and deposit in the Caminada pit and Raccoon Island pit, which showed that the Caminada pit and Raccoon Island pits would not be considered as a renewable borrow area for future sand dredging activities for coastal restoration.

Bottom Fauna of a Shallow Eutrophic Lake, Lizard Lake, Pocahontas County, Iowa

Abstract: The State of Iowa is carrying on a dredging program in an attempt to rehabilitate many of the lakes in the northern part of the state. Most of these lakes are of glacial origin and are in the later stages of succession. They are of little value for boating and swimming because of the shallow depth and heavy growths of aquatic vegetation. The fish populations in many of them cannot be maintained because of their vulnerability to winter kill. By means of dredging, the life of these lakes is prolonged and sufficient depth is provided to support a fish population throughout the year. The increased depth and decrease in aquatic vegetation makes them more suitable as recreational areas. Conditions in these lakes are radically altered as a result of dredging and it is desirable to know what effect this has on the biological productivity. The bottom organisms are directly affected by dredging and it is believed that they can be used as an index to measure any changes in the productivity of these lakes. Lizard Lake was selected for a bottom fauna study because it will be dredged in the near future. This paper deals with the data gathered from Lizard Lake in the summer of 1951, before dredging of the lake, and will provide a basis for comparing the productivity in terms of bottom fauna after the lake has been dredged. Several sampling techniques were used to determine which would give the best results in dcifferent types of habitat. Lizard Lake, located in Lake Township, Pocahontas County, Iowa, has a surface area of approximately 268 acres (fig. 1). The maximum depth found in July, 1951, was 5 feet and much of the lake was between 4 and 5 feet deep. There are no docks or cottages around the lake and the surrounding land is devoted entirely to agriculture. Most of the land in the immediate vicinity of the shoreline is wooded or open pasture. The main inlet flowing into the shallow bay at the southwest corner of the lake provided water throughout the summer of 1951. The outlet is at the north end of the lake and drains into the west fork of Lizard Creek and thence to the west fork of the Des Moines River. Chemical and temperature readings indicated very little stratification from top to bottom during most of the summer. By the middle of August most of the surface of the central part of the lake was covered with a dense growth of sago pondweed, Potomogeton pectinatus. Methyl orange alkalinity ranged from 180 to 230 parts per million during the summer. Turbidity was almost entirely due to silt suspended in the water after periods of high wind. 0n calm days the Ekman sampler could be seen on the bottom at a depth of 4 feet.