Showing papers on "Dredging published in 1981"

Sediment Management for Southern California Mountains, Coastal Plains and Shoreline. Part C: Coastal Sediment Delivery by Major Rivers in Southern California

Abstract: In southern California the natural environmental system involves the continual relocation of sedimentary materials. Particles are eroded from inland areas where there is sufficient relief and, precipitation. Then, with reductions in hydraulic gradient along the stream course and at the shoreline, the velocity of surface runoff is reduced and there is deposition. Generally, coarse sand, gravel and larger particles are deposited near the base of the eroding surfaces (mountains and hills) and the finer sediments are deposited on floodplains, in bays or lagoons, and at the shoreline as delta deposits. Very fine silt and clay particles, which make up a significant part of the eroded material, are carried offshore where they eventually deposit in deeper areas. Sand deposited at the shoreline is gradually moved along the coast by waves and currents, and provides nourishment for local beaches. However, eventually much of this littoral material is also lost to offshore areas. Human developments in the coastal region have substantially altered the natural sedimentary processes, through changes in land use, the harvesting of natural resources (logging, grazing, and sand and gravel mining); the construction and operation of water conservation facilities and flood control structures; and coastal developments. In almost all cases these developments have grown out of recognized needs and have well served their primary purpose. At the time possible deleterious effects on the local or regional sediment balance were generally unforeseen or were felt to be of secondary importance. In 1975 a large-scale study of inland and coastal sedimentation processes in southern California was initiated by the Environmental Quality Laboratory at the California Institute of Technology and the Center for Coastal Studies at Scripps Institution of Oceanography. This volume is one of a series of reports from this study. Using existing data bases, this series attempts to define quantitatively inland and coastal sedimentation processes and identify the effects man has had on these processes. To resolve some issues related to long-term sediment management, additional research and data will be needed. In the series there are four Caltech reports that provide supporting studies for the summary report (EQL Report No. 17). These reports include: EQL Report 17-A Regional Geological History EQL Report 17-B Inland Sediment Movements by Natural Processes EQL Report 17-C Coastal Sediment Delivery by Major Rivers in Southern California EQL Report 17-D -- Special Inland Studies Additional supporting reports on coastal studies (shoreline sedimentation processes, control structures, dredging, etc.) are being published by the Center for Coastal Studies at Scripps Institution of Oceanography, La Jolla, California.

Estuarine dredge and fill activities: A review of impacts

Abstract: Dredge and fill activities in estuaries have many environmental effects, most, although not all, of them deleterious. These effects include reduced light penetration by increased turbidity; altered tidal exchange, mixing, and circulation; reduced nutrient outflow from marshes and swamps; increased saltwater intrusion; and creation of an environment highly susceptible to recurrent low dissolved oxygen levels. Coral, oysters, and barnacles are particularly vulnerable to the effects of siltation. Both estuarine flora and fauna may be harmed by contaminants released into the water column by dredging operations. Ways to mitigate the effects of dredge and fill operations include careful pre- and post-construction environmental studies; use of bridging to create roadbeds where coastal wetlands cannot be avoided; use of a turbidity diaper and other means to control turbidity; dredging during periods of low benthic populations or during tides that would carry coarser sediments away from productive areas such as oyster reefs; and thoughtful disposal of spoil, such as locating spoil sites on the uplands with proper diking.

Effects of dredging on the macrobenthic infauna of Botany Bay

Abstract: The macrobenthic. infauna of dredged and undredged areas in Botany Bay were sampled. Data were analysed using tests of significance and computer classification. While dredging has not significantly affected average species density per sample, the benthic fauna of dredged areas differs from that of nearby undredged areas with respect to species composition and richness. both of which appear to be strongly associated with sediment type. Species richness. in particular. is generally higher in areas characterized by sand than in those characterized by, mud. Thus, where dredging has brought about a change in sediment type from sand to mud, species richness has decreased. This has occurred in the dredged areas near the Kingsford-Smith Airport extension and Port Botany revetment. However, in the region of the entrance to the bay, where harsh conditions of high swell and current exposure apparently normally limit benthos. the deeply dredged entrance channel supports a particularly diverse and abundant fauna. It is concluded that the major influence of dredging on the macrobenthos in Botany Bay has been indirect, through permanent modification of its physical environment. Extension of the present facilities at Port Botany are expected to lead to a significant decrease in the benthic species diversity of this area.

The Significance of Dredging and Dredged Material Disposal as a Source of Nitrogen and Phosphorus for Estuarine Waters

Abstract: Several hundred million cubic meters of waterway sediment are dredged each year in the United States to maintain adequate navigation depth. A significant part of this dredging and dredged sediment disposal takes place in freshwater tidal, estuarine, and marine waters. U.S. waterway sediments contain sufficient quantities of nitrogen and phosphorus compounds which, if released in available forms during dredged material disposal, could stimulate the growth of excessive amounts of algae and other aquatic plants in estuaries. This paper discusses the results of that portion of a comprehensive study conducted by the authors which assessed the significance of dredged sediments as a source of nutrients for U.S. estuarine waters.

Shallow dredging as a strategy for the control of sublittoral macrophytes: a case study in Tuggerah Lakes, New South Wales

Abstract: The effects of dredging the nearshores of the Tuggerah Lakes, on the central coast of New South Wales, to depths of 1.0, I.4 and 1.8 m, were investigated as a means of controlling aquatic macrophytes. The effects of this management strategy on the macrobenthic fauna and macrophyte growth were also evaluated.Recolonization of dredged plots by most of the 63 zoobenthic species present in control plots had occurred within 8 months of the treatment. All species of macrophytes had re-established in the shallowest (1.0 m) plot within 4 months but had failed to colonize the deeper plots up to 12 months after dredging. The removal of growing macrophytes from the water by dredging as a means of enhancing the shoreline is discussed, as are constraints relating to this method.

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.

Dredging-Related Mortality of Dungeness Crabs Associated with Four Dredges Operating in Grays Harbor, Washington.

Abstract: : From October, 1978, to December, 1979, entrainment and mortality of Dungeness crabs (Cancer magister) was estimated for two hopper dredges (PACIFIC and SANDSUCKER), a pipeline dredge (MALAMUTE), and a clamshell dredge (VIKING) operating in Grays Harbor, Washington. Sampling on suction dredges was accomplished by straining the discharged sediment through steel baskets or nylon nets, and visual observation on the clamshell dredge. Estimates of sampling mortality, actual dredging-induced mortality, and delayed mortality were made when possible. Entrainment rates were similar among the three suction dredges, but varied greatly with location in the harbor. Based on information from dredge sampling and crab trapping, recommendations were made concerning alternations in dredges and dredge scheduling which might reduce the subsequent crab mortality.

Transport of Dredged Sediments After Disposal Operational in Lake Erie

Abstract: A dredged material disposal operation was monitored on a location in Lake Erie 8 km offshore Ashtabula, Ohio, June to November, 1975. Some 200 sediment cores were collected in the periods before and after dredging and analyzed for the grain-size distribution of the sediments. Two current meters and a wave sensor moored nearby monitored the movement of the water masses. The sediments were dredged in the Ashtabula River and Harbor and discharged at a pre-designated location by a hopper dredge. A control site was established nearby. These sediments proved to be very similar to the ones from the lake bottom at the disposal site and the control site. Because of this similarity, it was extremely difficult to distinguish between the dredged material and the lake sediments without tagging the dredged material. Plotting the percentage of sand, silt and clay in several replicates collected at one site before and after disposal of dredged material allowed distinction between local and dredged sediments. Sediment transport could approximately be determined by the use of a modified computer program (SEDMOT), which calculates and plots progressive vector diagrams based on pre-assigned critical erosion and deposition velocities for specific grain sizes. The results showed that silt-sized sediments could have been transported over distances as large as 20 km. The main direction of transport was northeast and southwest, following the bottom topography. OHIO J. SCI. 81(1): 2, 1981 A dredged material disposal operation was monitored on a location 8 km offshore Ashtabula, Ohio, in Lake Erie. One of the objectives of the program was to study the movement of dredged sediments. In order to achieve this objective, the grain size population of the sediments from the Ashtabula Harbor and River, which was to be dredged, and of the lake bottom at the disposal site was analyzed. After dredged material was disposed, we again collected lake bottom sediments at the disposal site. With the aide of current meters and a wave sensor, we attempted to interpret the resulting differences in sediment distribution and to determine possible directions and distance of transportation. Many attempts have been made to determine the amount and direction of sediment transport in water environments similar to that in Lake Erie. Manuscript received 10 March 1980 and in revised form 24 July 1980 (#80-9). Three basic methods are generally used to estimate the sediment transport: 1. analyzing sediment grain-size distributions by use of moment statistics over several time intervals and estimating the direction of transport by comparing changes in the geographic distribution patterns (Pezetta 1975) 2. estimating the direction of transport by using measured water current values (McClennen and Kramer

Automatic dredge device for pump type dredger

Abstract: PURPOSE:To raise the efficiency and accuracy of dredging operation as much as possible as well as simplify the dredging operation and save its energy by a method in which set value suitable for the conditions of dredging site and detected value obtained in actual dredging operation are compared and calculated, and on the basis of the results, a dredger is automatically controlled. CONSTITUTION:A detector 17 by which to detect the suction negative pressure 26 and discharge pressure 29 of a dredging pump 24, the flow rate of mud water flowing in a dredging pipe 25, the sludge content 28 of the mud water, the load 12 to be applied to a soil cutter 4, the load 11 to swing a dredger 1, and the position of the cutter is provided. A setter 32 by which to set up upper and lower limiting values suitable to the conditions of dredging site and also the moving range of the cutter 4 is also provided. Furthermore, an arithmetic unit 31 to compare and calculate the set value and detected value is provided. On the basis of the calculation results of the arithmetic unit 31, the operations of a ladder 7, a swing winch 10m and a cutter 4 are controlled, and dredging work is automatically performed at given dredging width and depth.

Sediment Management for Southern California Mountains, Coastal Plains and Shoreline. Part A: Regional Geological History

Abstract: In southern California the natural environmental system involves the continual relocation of sedimentary materials. Particles are eroded from inland areas where there is sufficient relief and, precipitation. Then, with reductions in hydraulic gradient along the stream course and at the shoreline, the velocity of surface runoff is reduced and there is deposition. Generally, coarse sand, gravel and larger particles are deposited near the base of the eroding surfaces (mountains and hills) and the finer sediments are deposited on floodplains, in bays or lagoons, and at the shoreline as delta deposits. Very fine silt and clay particles, which make up a significant part of the eroded material, are carried offshore where they eventually deposit in deeper areas. Sand deposited at the shoreline is gradually moved along the coast by waves and currents, and provides nourishment for local beaches. However, eventually much of this littoral material is also lost to offshore areas. Human developments in the coastal region have substantially altered the natural sedimentary processes, through changes in land use, the harvesting of natural resources (logging, grazing, and sand and gravel mining); the construction and operation of water conservation facilities and flood control structures; and coastal developments. In almost all cases these developments have grown out of recognized needs and have well served their primary purpose. At the time possible deleterious effects on the local or regional sediment balance were generally unforeseen or were felt to be of secondary importance. In 1975 a large-scale study of inland and coastal sedimentation processes in southern California was initiated by the Environmental Quality Laboratory at the California Institute of Technology and the Center for Coastal Studies at Scripps Institution of Oceanography. This volume is one of a series of reports from this study. Using existing data bases, this series attempts to define quantitatively inland and coastal sedimentation processes and identify the effects man has had on these processes. To resolve some issues related to long-term sediment management, additional research and data will be needed. In the series there are four Caltech reports that provide supporting studies for the summary report (EQL Report No. 17). These reports include: EQL Report 17-A Regional Geological History EQL Report 17-B Inland Sediment Movements by Natural Processes EQL Report 17-C Coastal Sediment Delivery by Major Rivers in Southern California EQL Report 17-D -- Special Inland Studies Additional supporting reports on coastal studies (shoreline sedimentation processes, control structures, dredging, etc.) are being published by the Center for Coastal Studies at Scripps Institution of Oceanography, La Jolla, California.

Effects of Depth on Dredging Frequency. Report 2, Methods of Estuarine Shoaling Analysis

Abstract: : Whenever deepening of a dredged channel is under investigation, a prediction must be made as to the effect of the deepening on the existing dredging requirements. If the deepening is related to advance maintenance dredging rather than to an increase in authorized depth, the prediction becomes even more difficult because the project is allowed to shoal over a wide range of depth. Currently a variety of arbitrary, rule-of-thumb procedures are used for predicting the effect of increased depth on dredging requirements. The overall objective of this investigation was to evaluate the effectiveness of advance maintenance dredging in reducing dredging frequency and/or costs in the maintenance of coastal channels and harbors and to establish necessary guidelines for governing the practice. This report, the second of a series, presents an empirical method of shoaling analysis based on historical dredging and shoaling records that results in reliable predictions of future shoaling for deepened channel conditions resulting from either an increase in authorized channel depth or advance maintenance. The method presented was designed to be general enough so that it can be applied to most navigation projects without difficulty. The procedure was described step by step using an example (fictitious) project. To demonstrate how the method would be applied to real navigation projects and to point out problems that occur when evaluating real projects, selected Galveston Bay, Texas, navigation projects were evaluated and the results discussed. (Author)

Sediment Management for Southern California Mountains, Coastal Plains and Shoreline. Part B: Inland Sediment Movements by Natural Processes

Abstract: In southern California the natural environmental system involves the continual relocation of sedimentary materials. Particles are eroded from inland areas where there is sufficient relief and, precipitation. Then, with reductions in hydraulic gradient along the stream course and at the shoreline, the velocity of surface runoff is reduced and there is deposition. Generally, coarse sand, gravel and larger particles are deposited near the base of the eroding surfaces (mountains and hills) and the finer sediments are deposited on floodplains, in bays or lagoons, and at the shoreline as delta deposits. Very fine silt and clay particles, which make up a significant part of the eroded material, are carried offshore where they eventually deposit in deeper areas. Sand deposited at the shoreline is gradually moved along the coast by waves and currents, and provides nourishment for local beaches. However, eventually much of this littoral material is also lost to offshore areas. Human developments in the coastal region have substantially altered the natural sedimentary processes, through changes in land use, the harvesting of natural resources (logging, grazing, and sand and gravel mining); the construction and operation of water conservation facilities and flood control structures; and coastal developments. In almost all cases these developments have grown out of recognized needs and have well served their primary purpose. At the time possible deleterious effects on the local or regional sediment balance were generally unforeseen or were felt to be of secondary importance. In 1975 a large-scale study of inland and coastal sedimentation processes in southern California was initiated by the Environmental Quality Laboratory at the California Institute of Technology and the Center for Coastal Studies at Scripps Institution of Oceanography. This volume is one of a series of reports from this study. Using existing data bases, this series attempts to define quantitatively inland and coastal sedimentation processes and identify the effects man has had on these processes. To resolve some issues related to long-term sediment management, additional research and data will be needed. In the series there are four Caltech reports that provide supporting studies for the summary report (EQL Report No. 17). These reports include: EQL Report 17-A Regional Geological History EQL Report 17-B Inland Sediment Movements by Natural Processes EQL Report 17-C Coastal Sediment Delivery by Major Rivers in Southern California EQL Report 17-D -- Special Inland Studies Additional supporting reports on coastal studies (shoreline sedimentation processes, control structures, dredging, etc.) are being published by the Center for Coastal Studies at Scripps Institution of Oceanography, La Jolla, California.

Application of ecological dynamics for eutrophication control in kobe harbour area

Abstract: Numerical simulation of water quality in the eutrophicated Kobe Harbor area is examined for water pollution control using an ecological dynamics model which expresses phosphorus transfer in five nutrient forms, i.e., phytoplankton, zooplankton, detritus, inorganic matter, and sediment. The effects of measures in the water basin such as dredging bottom sediments and sea water filtration are evaluated by the model simulation, besides other basic countermeasures in land, namely, the reduction of discharged amount in inorganic or organic forms by means of advanced wastewater treatment, control in the use of synthetic detergents, and urban runoff control. Judging from the comparisons made among the effects of these policies, it is emphasized that each policy should be carried out in the appropriate time and space, supported by an intensive field survey, in coordination with other supporting actions.

Environmental Effects of Hydraulic Dredging for Clam Shells in Lake Pontchartrain, Louisiana,

Abstract: : The approach taken in the present study was to select two sites in proximity that would also be representative of the area subjected to the perturbation cause by dredging operations. One site would serve as the control site and not be dredged; the second would be the experimental site and would be dredged in a manner approximating normal operations. Each site would be sampled in a quantitative manner both before and after dredging on a logarithmic time scale for the first year and on a quarterly basis thereafter. Ideally, the two sites would be located somewhere in the mid-lake region and would not ever have been dredged. Unfortunately, because dredging operations have occurred pretty much at random over the past 45 years with few, if any, records having been kept, it was virtually impossible to ascertain that any particular area had never been dredged. The next best alternative was to select an area that had not been dredged recently and that would be protected from being dredged again before the completion of the study. Such an area that had not been dredged recently and that would be protected from being dredged again before the completion of the study. Such an area exists along a two-mile wide swath, one mile on each side of the Lake Pontchartrain Causeway, which was first open in 1956.

Dredging method for dam storing reservoir

Abstract: PURPOSE:To conduct dredging efficiently and economically by a method wherein a sedimentation basin is installed at a location lower than a storing reservoir, a top section of a bank body of a dam is made up in a top section of a siphon and dredging is conducted CONSTITUTION:A sedimentation basin 11 is constructed outside a dam storing reservoir at a level lower than a section at which the earth and sand 2 to be dredged of the reservoir deposit, and the soil and sand 2 are dredged by means of a suction pipe 4 with a suction nozzle at a nose of a working ship 3 A sand transporting pipe is mounted to buoys 6, and communicated with the sedimentation basin 11 through the surface of water of the reservoir W, a top section of a bank body of a dam and a discharging pipe 10 Thus, since the sand transporting pipe forms a siphon 5, the soil and sand can be dredged by utilizing water in the reservoir W of the dam

Policy analysis of water management for the Netherlands. Vol XVIII: Sedimentation and dredging cost models

Abstract: When water is extracted from rivers to supply users such as agriculture, the resulting sedimentation may cause costs for shipping or dredging. This volume describes three models, the Sedimentation Model, Dredging Cost Model, and Sedimentation Loss Function Model, built to estimate these costs for tactics which involve extractions from the Waal River. These models help determine procedures which result in the lowest costs and to estimate these costs when different water management tactics are used.

An Assessment of Water Quality Impacts of Maintenance Dredging on the Upper Mississippi River in 1979.

Abstract: : In connection with the 1979 maintenance dredging season, the Corps of Engineers, St. Paul District, investigated the water quality impacts of hydraulic and clamshell dredging operations at five selected sites on the Upper Mississippi River. Turbidity values and suspended solids were monitored at all sites, and selected chemical parameters were monitored at two hydraulic dredging sites. At most sites, dredging and disposal operations produced minor and localized changes in water quality. No statistically significant increases in chemical parameters were noted due to hydraulic dredging operations. However, effluents from the disposal area did cause some elevations of heavy metals (cadmium, lead, nickel, zinc, copper, chromium) and total ammonia. None of the chemical parameters tested exceeded their maximum permissible level proposed by Federal Water Quality Criteria. The five monitoring studies generally indicated that rapid settling and dilution occurred near and downstream of dredging and disposal operations.

Self-immersing jet pump

Abstract: A jet pump which is used in dredging situations and includes a series of water nozzles which create a slurry in a sand mass by erosion thereof, the slurry being conveyed to a receiving station

The effects of elevated highway construction on water quality in Louisiana wetlands : final report.

Abstract: This study is to determine by physical, chemical, and biological means, the effects of bridged highway construction techniques on water quality in wetlands. Water quality was monitored before, during, and after construction. The data shows the increase in pollution that occurred during construction. The areas where construction has been completed have shown gradual improvement towards the preconstruction ambient. The information obtained may be useful in predicting the degree and duration of impacts of future construction projects on wetland environments. (FHWA)