Determination of the relevant multibeam echosounder frequency to estimate the suspended sediment concentrations for environmental damage monitoring of mass movement

The problem of environmental damages in the river area can transform the morphology and threaten the ecosystem in it with one of the causes being natural factors such as suspended sediment. Retracing the medium form is fluid, the common instrument to determine the condition of the area is a sound wave-based instrument such as a multibeam echosounder. Considering the improvement of multibeam echosounder which can acquire areas using many frequencies at one time, noted as multi-frequency multibeam echosounder, now its application can reach various fields including environmental monitoring. Factors that can be considered in its practice include time efficiency, cost, and notably the accuracy of the data result. By converting the results of the acquisition into an estimate of the concentration of suspended sediment and integrating the results from several frequencies, it will be established the applicable frequency usage. It was concluded that a multibeam echosounder with a frequency of 450 kHz was recommended in a case study to determine the concentration of suspended sediment. This is supported by a correlation value of 89.18% or a very high correlation.

Sediment impacts on sponges and a deep-sea coral in New Zealand

<p><b>Increased levels of suspended sediment in the water column are important factors contributing to the degradation of marine ecosystems worldwide. In coastal waters, temporal variation in suspended sediment concentrations (SSCs) occurs naturally due to seasonal and oceanographic processes. However, there is evidence that anthropogenic activities are increasing sediment concentrations. The volume of sediment moving from land-based sources into coastal ecosystems and human activities in the ocean disturbing the seafloor, such as dredging and bottom-contact fisheries, have been increasing over the last century. In addition, offshore activities, particularly bottom-contact fishing and potential deep-sea mining, can create sediment plumes in the deep-sea that may extend over long distances. Elevated suspended sediment concentrations have detrimental effects on benthic communities, particularly for suspension feeders like sponges and corals.</b></p> <p>The aim of this thesis was to investigate the effects of increased SSCs that might arise from heavy anthropogenic disturbance on common shallow water and deep-sea sponges and a deep-sea coral in New Zealand, as these groups contribute to habitat structure in some benthic environments, including the deep sea.</p>

Sediment impacts on sponges and a deep-sea coral in New Zealand

<p><b>Increased levels of suspended sediment in the water column are important factors contributing to the degradation of marine ecosystems worldwide. In coastal waters, temporal variation in suspended sediment concentrations (SSCs) occurs naturally due to seasonal and oceanographic processes. However, there is evidence that anthropogenic activities are increasing sediment concentrations. The volume of sediment moving from land-based sources into coastal ecosystems and human activities in the ocean disturbing the seafloor, such as dredging and bottom-contact fisheries, have been increasing over the last century. In addition, offshore activities, particularly bottom-contact fishing and potential deep-sea mining, can create sediment plumes in the deep-sea that may extend over long distances. Elevated suspended sediment concentrations have detrimental effects on benthic communities, particularly for suspension feeders like sponges and corals.</b></p> <p>The aim of this thesis was to investigate the effects of increased SSCs that might arise from heavy anthropogenic disturbance on common shallow water and deep-sea sponges and a deep-sea coral in New Zealand, as these groups contribute to habitat structure in some benthic environments, including the deep sea.</p>

Tiakina Kia Ora: Protecting Our Freshwater Mussels

<p>Matauranga (traditional ecological knowledge) built up by Whanganui iwi during their long association with the Whanganui River provides information on local biota and anthropological changes to the river. This matauranga records a decline in one local species, the kakahi (Echyridella menziesii (Gray, 1843)). Reasons suggested for this decline include alterations to flow and desiccation following a hydropower scheme, sedimentation, domestic and agricultural pollution, gravel extraction and channel modification. Decline was confirmed by a survey of historic kakahi beds: decline was evident at 16 (73%) of 22 sites. Of those 16 sites, there were 7 sites where decline was so severe that the population had been extirpated. Of the 15 historic beds where kakahi are still extant, four (27%) were remnant populations. Evidence of recruitment was found at only four (27%) of the 15 extant populations, or 18% of the total number of sites searched. Effect of suspended sediment concentrations ranging from 5.5 to 1212 mg.L-1 on ka kahi feeding behaviour and physiology was explored. Both filtration rate and rejection rate increased with increased sediment load (from 1.62 mg.h-1 to 190.88 mg.h-1 and from 0.62 to 201.53 mg.h-1 respectively) but clearance rate decreased with sediment increase (from 0.42 to 0.20 L.h-1). Behaviour was unaffected, with kakahi filtering on average 78% of the time. As particulate organic matter increased, clearance rate decreased and filtration rate increased. Filtration rate declined with increasing % organic matter. Kakahi can continue feeding under very high sediment loads for short periods. Much remains uncertain about kakahi, from their early biology to reasons for decline. Restoration options were explored using an adaptive management framework within which different hypotheses can be trialled in an experimental manner. This proved difficult due to confounding factors. However, given the established link between vegetation clearance and sedimentation, an initial restoration focus which evaluates catchment revegetation and its impact on kakahi survival and growth is suggested.</p>

Tiakina Kia Ora: Protecting Our Freshwater Mussels

<p>Matauranga (traditional ecological knowledge) built up by Whanganui iwi during their long association with the Whanganui River provides information on local biota and anthropological changes to the river. This matauranga records a decline in one local species, the kakahi (Echyridella menziesii (Gray, 1843)). Reasons suggested for this decline include alterations to flow and desiccation following a hydropower scheme, sedimentation, domestic and agricultural pollution, gravel extraction and channel modification. Decline was confirmed by a survey of historic kakahi beds: decline was evident at 16 (73%) of 22 sites. Of those 16 sites, there were 7 sites where decline was so severe that the population had been extirpated. Of the 15 historic beds where kakahi are still extant, four (27%) were remnant populations. Evidence of recruitment was found at only four (27%) of the 15 extant populations, or 18% of the total number of sites searched. Effect of suspended sediment concentrations ranging from 5.5 to 1212 mg.L-1 on ka kahi feeding behaviour and physiology was explored. Both filtration rate and rejection rate increased with increased sediment load (from 1.62 mg.h-1 to 190.88 mg.h-1 and from 0.62 to 201.53 mg.h-1 respectively) but clearance rate decreased with sediment increase (from 0.42 to 0.20 L.h-1). Behaviour was unaffected, with kakahi filtering on average 78% of the time. As particulate organic matter increased, clearance rate decreased and filtration rate increased. Filtration rate declined with increasing % organic matter. Kakahi can continue feeding under very high sediment loads for short periods. Much remains uncertain about kakahi, from their early biology to reasons for decline. Restoration options were explored using an adaptive management framework within which different hypotheses can be trialled in an experimental manner. This proved difficult due to confounding factors. However, given the established link between vegetation clearance and sedimentation, an initial restoration focus which evaluates catchment revegetation and its impact on kakahi survival and growth is suggested.</p>

Effects of River-Ice Breakup on Sediment Transport and Implications to Stream Environments: A Review

During the breakup of river ice covers, a greater potential for erosion occurs due to rising discharge and moving ice and the highly dynamic waves that form upon ice-jam release. Consequently, suspended-sediment concentrations can increase sharply and peak before the arrival of the peak flow. Large spikes in sediment concentrations occasionally occur during the passage of sharp waves resulting from releases of upstream ice jams and the ensuing ice runs. This is important, as river form and function (both geomorphologic and ecological) depend upon sediment erosion and deposition. Yet, sediment monitoring programs often overlook the higher suspended-sediment concentrations and loads that occur during the breakup period owing to data-collection difficulties in the presence of moving ice and ice jams. In this review paper, we introduce basics of river sediment erosion and transport and of relevant phenomena that occur during the breakup of river ice. Datasets of varying volume and detail on measured and inferred suspended-sediment concentrations during the breakup period on different rivers are reviewed and compared. Possible effects of river characteristics on seasonal sediment supply are discussed, and the implications of increased sediment supply are reviewed based on seasonal comparisons. The paper also reviews the environmental significance of increased sediment supply both on water quality and ecosystem functionality.

Field measurement and monitoring of hydrodynamic and suspended sediment within the Seven Mile Island Innovation Laboratory, New Jersey

The Seven Mile Island Innovation Laboratory (SMIIL) was launched in 2019 to evaluate beneficial use of dredge material management practices in coastal New Jersey. As part of that effort, the Philadelphia District requested that the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, collect data to characterize the hydrodynamics and turbidity within the central portions of the SMIIL prior to and during dredge material placement. Pre-dredge monitoring found that apart from punctuated wind events, the study area waters were generally calm and clear with small waves, <0.25 m, slow current speeds (~0.1 m/s), low turbidity (~10 ntus), and low suspended sediment concentrations (~10–20 mg/L). In March 2020, 2,475 m³ of dredged sediment was placed on the northern portion of Sturgeon Island within the SMIIL. Turbidity in the waters surrounding the island was monitored to quantify extent of the sediment plume resulting from the placement. Observations found little to no turbidity plume associated with the dredging operations beyond 20 m from the island and that the plume was largely limited to areas near a tidal creek draining the placement area. Additionally, turbidity levels quickly returned to background conditions at times when the dredge was not in operation.