Suspended Sediment Plumes Research Articles

Impacts of suspended sediment on the ecosystem in Lake Michigan: A comparison between the 1998 and 1999 plume events

The impact of a reflective, recurrent coastal resuspension plume on the lower trophic food web system in Lake Michigan was examined using a 3‐D coupled physical and biological model. Numerical experiments were conducted for the March 1998 and 1999 plume events. The comparison between modeling results of these 2 years shows that the spatial distributions of the biological fields (i.e., phosphorus, phytoplankton, detritus, etc.) were closely coupled to the physical environment associated with wind‐induced three‐dimensional circulation and mixing. The influence of suspended sediment plumes on the lake ecosystem was reflected in heterotrophic (secondary) production rather than in the autotrophic (primary) production. Nutrients were maintained through nutrient release from suspended sediments within the plume, while it was supplied by current advection and diffusion in the interior. The cross‐shore flux of nutrients was driven by episodic wind events with a period of about 5–7 days. The flux was offshore during northerly winds and onshore during southerly winds. Comparisons between energy fluxes among biological variables suggest that the microbial loop (detritus‐heterotrophic bacteria and microzooplankton) played an important role in the ecosystem dynamics during plume events. Bacteria were good competitors with phytoplankton for inorganic phosphorus and were also a key supporter for growth of microzooplankton inside and outside the plume. As a result, the lower food web system could be divided into two decoupled loops: (1) detritus‐bacteria‐microzooplankton‐large zooplankton and (2) nutrient‐phytoplankton‐detritus.

Sediment transport and depth variation study of the Gulf of Kutch using remote sensing

Ocean Colour Monitor (OCM) data gathered onboard Indian Remote Sensing satellite (IRS P4), in eight VNIR bands covering Gulf of Kutch and adjoining regions were digitally processed using an image processing system. False colour composite images of actual data and principal components were generated to study sediment transport, depth variation and associated processes by mapping coastal and underwater geomorphic features and suspended sediment plumes. Submerged shoals, located as deep as 20 m below water level, were correctly marked. By studying turbidity distribution patterns and sediment transport indicators, sediment distribution and dispersion have been inferred. The study demonstrates that OCM data have been derived from up to 20 m water depth in the high-energy tide dominated Gulf and hence are useful for mapping underwater bedforms, sediment plumes, and other geomorphic features. The study indicates that the sediments are transported to the Gulf from the north as well as from the south and are mainly season dependent. It is concluded that the OCM data can be used for depth variation and sediment distribution studies.

Late Quaternary ice extent and glacial history from the Dj�p�ll trough, off Vestfirdir peninsula, north-west Iceland: a stacked 36 cal. Ky environmental record

Djupall is a O90 km long by 15 km wide trough which extends from Isafjardardjup to the shelf break above Blosseville Basin, north of the Denmark Strait. We present 3.5 kHz seismic profiles from this trough and data from cores collected in 1996 (JM96-1232 and ?1234) and five cores collected on cruise B997. We pay particular attention to B997-338 as this core recovered sediments ranging in age between 12 and 36 cal. Ky BP. This is the first such record from the Iceland continental shelf. Dating control is provided by AMS 14C dates and the occurrence of the Saksunarvatn tephra. X-radiographs of the cores enable us to quantify the input of iceberg-rafted detritus (IRD) and to describe the lithofacies. The sediment matrix is fine-grained and might represent either rain-out of suspended sediment plumes or distal turbidites. IRD is present from ca. 12 cal. Ky BP throughout the next 24 cal. Ky with some IRD-free intervals. Using sediment magnetic properties, sampled at 1 cm (o100 yrs/sample) resolution, we provide a stacked environmental record which includes marine isotope stages 1, 2 and part of 3. The sediment magnetic properties kARM and IRM(60), and carbonate and TOC, show multi-millennia quasi-periodic cycles, but there are no obvious events coeval with the North Atlantic Heinrich events. Our data indicate that at the Last Glacial Maximum on the Vestfirdir peninsula (VP), north-west Iceland, ice did not reach the shelf break, but was probably grounded near the mouth of Isafjardardjup. A rapid increase in the rate of sediment accumulation suggests that deglaciation of the VP occurred mainly between 11 and 15 cal. Ky BP.

Late Quaternary ice extent and glacial history from the Djúpáll trough, off Vestfirdir peninsula, north-west Iceland: a stacked 36 cal. Ky environmental record

Djúpáll is a Ø90 km long by 15 km wide trough which extends from Ísafjardardjúp to the shelf break above Blosseville Basin, north of the Denmark Strait. We present 3.5 kHz seismic profiles from this trough and data from cores collected in 1996 (JM96-1232 and ?1234) and five cores collected on cruise B997. We pay particular attention to B997-338 as this core recovered sediments ranging in age between 12 and 36 cal. Ky BP. This is the first such record from the Iceland continental shelf. Dating control is provided by AMS 14C dates and the occurrence of the Saksunarvatn tephra. X-radiographs of the cores enable us to quantify the input of iceberg-rafted detritus (IRD) and to describe the lithofacies. The sediment matrix is fine-grained and might represent either rain-out of suspended sediment plumes or distal turbidites. IRD is present from ca. 12 cal. Ky BP throughout the next 24 cal. Ky with some IRD-free intervals. Using sediment magnetic properties, sampled at 1 cm (ø100 yrs/sample) resolution, we provide a stacked environmental record which includes marine isotope stages 1, 2 and part of 3. The sediment magnetic properties kARM and IRM(60), and carbonate and TOC, show multi-millennia quasi-periodic cycles, but there are no obvious events coeval with the North Atlantic Heinrich events. Our data indicate that at the Last Glacial Maximum on the Vestfirdir peninsula (VP), north-west Iceland, ice did not reach the shelf break, but was probably grounded near the mouth of Ísafjardardjúp. A rapid increase in the rate of sediment accumulation suggests that deglaciation of the VP occurred mainly between 11 and 15 cal. Ky BP.

Radionuclides as indicators of sediment transport in agricultural watersheds that drain to Lake Erie.

An issue in evaluating the success of agricultural management practices is the speed that eroded particles make their way through the downstream waters. In this study at Old Woman Creek (OWC) and Rock Creek (RC), two largely agricultural watersheds in Ohio, the flux of sediment and radionuclides (7Be, 210Pb, and 137Cs) in thunderstorm runoff was examined to better understand transport of eroded agricultural soils. The hydrograph in an agricultural area under no-till was similar in timing, but of lesser magnitude, than the hydrograph from a similar-sized area under conventional tillage. The activities of 210Pb and 7Be are linearly correlated and are higher in suspended sediments derived from no-till subbasins than those derived from conventionally tilled subbasins. A suspended sediment plume, identified by its unique radionuclide signature, was traced through 17 km of OWC stream channel in approximately 13.4 h (0.35 m/s). The downstream exponential decrease of 7Be activities in suspended sediments 3 to 12 h after passage of the sediment plume was used to estimate transport distances of suspended sediment from 2 to 17 km, respectively. Transport distances of suspended sediments were also calculated from wave kinematics and indicate that at OWC suspended sediment transport distances were longer in streams draining areas of no-till (19-26 km) than in the streams draining areas of conventional tillage (6-15 km). Suspended sediments travel 7 to 22 km at RC. The transport distances are long relative to the lengths of the stream channel and indicate that erosion control methods implemented in the watershed should be reflected quickly in downstream waters.

The history of sediment flux to Atchafalaya Bay, Louisiana

Abstract The Atchafalaya became a free-flowing river system in the mid-nineteenth century. It progressively increased its diversion of waters from the Mississippi until, by the mid-twentieth century, it threatened to capture the total flow of the main river. The installation of control structures has, temporarily at least, prevented total diversion, limiting the flows to 30% of the Mississippi; water discharge and sediment transport into the Atchafalaya have led to deposition throughout the basin. A major system of lakes and bayous has become largely filled with deltaic sands and layered silts, so that the waters currently drain almost directly into the Atchafalaya Bay. The natural outlet and one artificially created outlet each carry waters from the system. As a result of major flooding in 1973, sediment was flushed from the Atchafalaya Basin and began the subaerial emergence of deltas, which had been slowly building below the bay water surface since the 1950s. The two deltas have provided, parallel growth one largely in natural form, and the other substantially modified by the dredging needed to maintain a navigable routeway to Morgan City and the interior of the basin. The sub-aerial deltas initially grew rapidly, a process apparently slowing, but the sediment transported to the depositional areas has not diminished, rather the area of deposition within the receptor basin is increasing, so that apparent growth inevitably slows. By 1994 the two deltas occupied an area of more than 153 km 2 above the −0.6 m measuring datum, created in approximately 30 years. In each case the sediments show upward passage from fine clays to laminated silts and fine sands, within a succession rarely more that 3 m in thickness, as defined by the original 1890 bathymetry of the Bay. Within the Bay itself resuspension of deposited fine sediment due to wave activity and water set-up and set-down in response to variations in the directions of coastal winds creates plumes of material that travel through the basin and may leave to form suspended sediment plumes on the inner parts of the continental shelf. A total of 20–25 such plumes annually drift initially east of the Bay outlet but later move west towards the chenier coasts of western Louisiana and Texas.

Biological Effects of Suspended Sediments: A Review of Suspended Sediment Impacts on Fish and Shellfish with Relation to Dredging Activities in Estuaries

Abstract Objective assessment of the effects of increased concentrations of suspended sediment caused by human activities, such as navigation dredging, on estuarine fish and shellfish requires an integration of findings from biological and engineering studies. Knowledge is needed of (1) the suspended sediment characteristics typical of both ambient and dredging-induced conditions, (2) the biological responses of aquatic organisms to these suspended sediment dosages, and (3) the likelihood that organisms of interest will encounter suspended sediment plumes. This paper synthesizes the results of studies that report biological responses to known suspended sediment concentrations and exposure durations and relates these findings to suspended sediment conditions associated with dredging projects. Biological responses of taxonomic groups and life history stages are graphed as a function of concentration and exposure duration. The quality and taxonomic breadth of studies on which resource managers must rely when...

Monitoring suspended sediment plumes by optical and acoustical methods with application to sand capping

There is a need to rapidly survey plumes of suspended sediment and to determine the quantity and transport of disturbed material that might arise from industrial and remedial activities in lakes and harbours. The example of sand capping of contaminated bottom sediments is used to illustrate the methodology. Capping of contaminated bottom sediments is one strategy for immobilizing contaminants. In a pilot-scale project, a 0.34 m thick cap of clean sand was deposited over a one hectare area in Hamilton Harbour. The objective of this study was to determine if in-place sediments could be disturbed by the capping operation. In the first of three approaches, the suspended sediment plumes created during the capping operation were monitored for evidence of suspension of bottom materials with underwater acoustic and optical profilers and other moored instruments. In-lake calibration of the instrumentation was based on the collection of over 300 grab samples. Three-dimensional rendering of a dense network of acoustic backscatter profiles revealed that there was no evidence that bottom sediment was resuspended. The density current flowing downslope close to the bottom caused by the capping material was examined and found too weak to erode bottom sediments. Finally, a quantitative estimation of the amount of sediment suspended in the plumes indicated little evidence for resuspension of in-place sediments. The methodology developed could also be applied to estimate the concentration and quantities of contaminants in sediments suspended by other remedial activities such as dredging. Key words: suspended sediment plumes, underwater acoustics, optical measurements, sediment remediation, harbours, lakes.

Monitoring suspended sediment plumes by optical and acoustical methods with application to sand capping

Monitoring suspended sediment plumes by optical and acoustical methods with application to sand capping

The Persistence of Anthropogenic Turbidity Plumes in a Shallow Water Estuary

Increased turbidity and light attenuation (Kd) in the suspended sediment plumes created by hydraulic clam dredging were examined in Chesapeake Bay, MD, U.S.A. Turbidity andKdvalues were measured along transects in areas with and without dredge plumes. The turbidity andKdof individual plumes were tracked as they returned to background levels using both Lagrangian and Eulerian techniques. Existing aerial photographs and a geographical information system (ARC/INFO) were used to examine plume sizes and dredge boat locations in relation to bathymetry.Hydraulic clam dredging produced plumes with significantly higher turbidity and light attenuation compared to background values. Plume characteristics were determined primarily by bottom sediment type and water depth. The greatest increase in turbidity and light attenuation occurred when dredges operated in shallow water (<1·0m) where bottom sediments had increased amounts of silt and clay. Plume turbidity andKddissipated exponentially over time. The initial change in concentration of suspended sediments was rapid as the coarse sediments settled to the bottom. The rate of plume decay slowed as diffusion and resuspension acted on the finer sediments remaining in suspension. Some Lagrangian rates of plume dissipation were faster than Eulerian rates due to resuspension in shallow waters. Examination of aerial photographs indicated that 72% of the dredge boats digitized in the Chester River were operating in less than 2m water. The area of a plume measured per boat in the Chester River was highly variable, ranging from 0·01 to 0·64m2.

A review of remote sensing for the assessment and management of tropical coastal resources

This article reviews applications of remote sensing to the assessment of tropical coastal resources. These applications are discussed in the context of specific management objectives and sensors used. Remote sensing remains the only way to obtain synoptic data for large coastal areas uniformly in time and space, repeatedly and nonintrusively. Routine applications to tropical coastal management include the mapping of littoral and shallow marine habitats, change detection, bathymetry mapping, and the study of suspended sediment plumes and coastal currents. The case studies reviewed suggest that wider use of remote sensing in tropical coastal zone management is limited by (1) factors that affect data availability, such as cloud cover and sensor specification; and (2) the problems that decision makers face in selecting a remote sensing technique suitable to their project objectives. These problems arise from the difficulty in comparing the capabilities of different sensors and the limited amount of published ...

Glaciomarine facies from the western sector of the last British ice sheet, Malin Beg, County Donegal, Ireland

The coastal margins and mountainous core of County Donegal, Republic of Ireland have been areally scoured and deeply-eroded along structural lineaments by major Late Devensian ice streams which moved generally westwards onto the continental shelf. A raised glaciomarine sequence is selectively preserved along a gully at Malin Beg and comprises mud/muddy diamict, sand and diamict. (1) The mud, which was deposited from suspended sediment plumes, passes upwards into muddy diamict, which reflects an increase in ice-rafting. The muds contain a redeposited foraminiferal assemblage of ice-proximal origin pumped into the water column by jets reworking previously deposited outwash. The presence of Middle Devensian shells have been identified from the mud by amino-acid analysis. This suggests a Late Devensian age for the succession. (2) The overlying sand indicates an increase in traction current activity at the site. (3) There is a sharp planar contact between the sands and the overlying tabular diamict unit. (4) A surficial sheet of coarse-grained breccia is attributed to intense periglacial weathering along the slopes of Leahan mountain. This sequence and those at other sites in western Ireland (e.g. Belderg, Co. Mayo) provide a record of deep isostatic depression and sedimentation in a peripheral trough at the north-western margin of the last British ice sheet. Directional indicators including drumlin fields and major troughs indicate that the north-western sector of the ice sheet was drained by major ice-streams. These ended in calving bays. Ice marginal response to ice wastage depended largely on catchment factors such as the magnitude of the ice reservoirs and the length of flow lines. Ultimately calving led to accelerated ice flow and areal down draw and collapse of the north-western sector of the ice sheet.

Behavior of a Glacier-Derived Suspended Sediment Plume in a Small Arctic Inlet

The changing configuration of a glacier-derived, turbid surface meltwater plume was observed over a 40 hr period in a small marine inlet in Spitsbergen. Factors controlling plume position (tides, winds, and melt stream discharge) were also monitored. Tidal forcing was the dominant control on plume behavior over the study period, when winds were calm or light. The plume spread over much of the inlet on the flood and around high tide, and was restricted to the north side on the ebb and at low water. Winds were generally <5 kts and only influenced plume position when reaching over 12 kts. Coriolis effects were unimportant. Sediments on the inlet floor fined progressively with distance from glacier-fed stream effluxes. Short cores showed that deposition was mainly in the form of structureless sands and silts.

Seismic reflection investigation of Kalamalka Lake: a "fiord lake" on the Interior Plateau of southern British Columbia

A uniboom seismic reflection profile survey has revealed the nature of bedrock relief and the acoustic character of Pleistocene glacial sediment fill beneath Kalamalka Lake in southern British Columbia. Despite its continental interior setting, Kalamalka Lake basin has many attributes of coastal fiords, such as being overdeepened below sea level and having closed bedrock depressions and a thick sediment fill.The bedrock surface beneath Kalamalka Lake has been eroded as much as 417 m below lake level (26 m below sea level) and is characterized by a series of closed, glacially overdeepened depressions. We suggest that the location of the lake basin is structurally controlled but was overdeepened by rapidly flowing ice that drained the interior portions of the Cordilleran ice sheet during repeated Pleistocene glaciations.Up to 272 m of sediment has been deposited beneath Kalamalka Lake. The greatest thickness of the sediment fill (up to 237 m) is a seismically transparent unit that overlies a thin (up to 20 m), discontinuous lower stratified unit and is overlain by a thin (up to 15 m), continuous upper unit that is well stratified. The sedimentological nature of the lower stratified unit is not known but could represent a discontinuous coarse lag. The thick, middle transparent unit is interpreted as a massive silt deposited rapidly in a proglacial lake from suspended-sediment plumes during deglaciation. The thin overlying stratified unit may be correlative with laminated glaciolacustrine "white silt" deposits that outcrop extensively across central and southern British Columbia, suggesting a common history of deglaciation and sedimentation.An ambitious research program focused on seismic stratigraphic definition, coupled with direct drill-core sampling, is needed to take full advantage of the extensive sediment record that exists beneath the large, glacially overdeepened lakes of southern British Columbia.

Biofacies and sediments in an emergent Late Pleistocene glaciomarine sequence, Skerries, east central Ireland

Late Devensian sedimentation (ca. 18 ka B.P.) on the coastal margins of the Irish Sea Basin occurred in shallow-water glaciomarine environments around retreating tidewater ice margins. High relative sea levels were the result of glacioisostatic crustal depression around the periphery of the last British ice sheet. At Skerries, in east central Ireland, ice-proximal glaciomarine diamict, mud, sand and gravel facies are selectively preserved in a bedrock depression. The coastal exposure, about 500 m long, can be divided into three lithofacies associations. (1) A diamict/gravel association resting on bedrock was emplaced by sediment gravity flows and records the downslope reworking of glacial debris released from a retreating ice margin. (2) An overlying mud association was deposited from suspended sediment plumes, with minor ice-rafting, and records ice retreat and increasing distality of the site. Muds contain a mixed foraminiferal microfaunal assemblage typical of open-water shallow-marine shelves. Species can be grouped into reworked temperate, cosmopolitan and well-preserved boreo-arctic elements and indicate mixing of derived and retransported temperate species with an in-situ glaciomarine fauna. (3) At the top of the section a gravel association, derived from a nearshore fan delta, rests on planated muds and is attributed to wave reworking and slumping of the fan delta front in shallow water during rapid basin rebound. This and other sequences elsewhere in the Irish Sea Basin is a record of rapid evacuation of the basin by calving tidewater glaciers and the uplift and erosion of glaciomarine sedimentary sequences in response to rapid late glacial crustal rebound.

Sedimentation patterns and facies geometries on a temperate glacially-influenced continental shelf: the Yakataga Formation, Middleton Island, Alaska

Abstract The 5 km thick Yakataga Formation of the Gulf of Alaska provides the longest and most accessible record of late Cenozoic glaciation in the world. The formation consists of interbedded marine and glacimarine sediments of late Miocene to Holocene age and is well exposed on offshore islands and in the coastal mountain ranges as a result of the convergent margin setting of the Gulf. About 1.3 km of early Pleistocene Yakataga Formation sediments are exposed on extensive intertidal platforms around Middleton Island which is sited close to the modern continental shelf edge. Variably graded gravels and sands at the base of the Middleton Island succession were deposited by sediment gravity flows and represent the fill of a large submarine channel. The remainder of the succession is dominated by thick (up to 100 m) planar tabular units of fossiliferous diamict containing a series of striated boulder pavements and shell-rich beds (coquinas). Diamict facies formed predominantly by the settling out of fines from suspended sediment plumes together with ice-rafting of coarser debris; foraminiferal biofacies data indicate palaeobathymetries of between 20 and 250 m. Boulder pavements are lag surfaces which developed in relatively shallow water and were subsequently faceted and striated by a grounding ice sheet extending to the continental shelf edge; coquinas record episodes of current winnowing in shallow water (20–50 m) but also contain ice-rafted debris. Extensive mud units formed in relatively deep water during periods of reduced ice volume and are similar to ‘mud blankets’ accumulating on the modern shelf. The Yakataga Formation on Middleton Island contains a rich record of changing palaeobathymetry and ice volumes in the Gulf of Alaska.

Seasonal dynamics of suspended-sediment plumes from the Tana and Sabaki Rivers, Kenya: Analysis of landsat imagery

Landsat imagery of the Kenya coast, in conjunction with meteorological, oceanographic, and river discharge data, was used to analyze coastal movement of suspended sediment from the Tana and Sabaki Rivers. The distribution and relative concentration of suspended sediment in each image were mapped by tracing the perimeter of turbidity features visible at MSS bands 6, 5, and 4. Turbidity plumes appear seasonally, during and immediately following the two rainy seasons. Their subsequent movement is primarily, affected by local wind and tide conditions. The largest sediment pulse, produced by the long rains in April–May, is transported north from the river mouths by prevailing southern monsoon winds and currents. The smaller sediment plumes generated by the short rains in November may be carried southward along the coast by weaker northern monsoon winds, despite the usual continued northward flow of the East African Coastal Current.

A model for the estimation of the concentrations and spatial extent of suspended sediment plumes

A simple model is presented for the spatial structure of suspended sediment plumes produced by over-board pipeline disposal of dredge spoil in shallow waters. The model is based on a solution to the advection-diffusion equation for a continuous vertical line source. It provides information on the variation of both centerline concentration and the second moment of the lateral distribution with distance from the source. The structure of the plume is described by only two parameters: one proportional to the settling velocity of the suspended material and the other equal to the ratio of a diffusion velocity to the advective velocity of the ambient flow. The model has been applied to represent the structure of observed suspended sediment plumes at three separate shallow water sites.