Topic: Title: “Adur Estuary Sediment Characterisation – Fate and Transport of particles”

Title: Adur Estuary Sediment Characterisation- Fate and Transport of particles"

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Introduction

Studying sedimentation on sandy-flats will give someone knowledge about tidal flows and waves that mostly influences the hydrodynamic forcing factors that operate the surface sediments. It is the tidal flows that influence the long-term evolution of tidal-flats due to the asymmetry of tidal regimes. These tidal current activities are mostly confined to the channels. Outside of the channels, mostly on the upper tidal-flats, tidal current velocities reduce and sediment entrainment is regularly ascribed to wave movement. The work of wave-induced procedures on intertidal-flat sediments is normally specified although it is rarely investigated due to methodological constraints.

Estuaries are areas that are partly enclosed by coastal water where river water it mixes with seawater. Therefore, the estuarine environment can be described using salinity borders and not geographic borders. The term estuary was derived from the Latin words 'aestud' which means the tide and 'aestuo' that means boil. Combine the make estuary that shows the impact created when tidal flow and river flow meets together. It is important to note and remember that the sea is salty while river water fresh. Hence, the estuary is the diluted environment and it is biologically more productive than both the adjacent river and adjacent sea since the water circulation here is special and traps plant nutrients to enhance primary production.

Adur estuary is a biological site that is of scientific interest to the western outskirts of Shoreham which is a sea in West Sussex. Part of it is a Royal Society that act of protection for birds. The whole Adur estuary is filled with saltmarsh where it meets mudflats which is the ideal roosting and feeding site for waders and wildfowl. The part of the river that is affected by tides and other marines that leads to procedures but void to salinity can be called a tidal freshwater river, a tidal river reach or a tidal river. The reaches seaward of the tidal river are in most cases brackish thus called estuaries and they can extend to cover hundreds of kilometers inland if the river is large enough. The upstream regime also is known as the region where the tide is almost at the extinction and tidal velocity oscillations occur around the equilibrium that is maintained by the discharge, the equations of motion are almost linear. As a result, multiple tidal waves propagate independently. The interactions among the tidal waves and the river flow are therefore strongest in the downstream stressing to the tidal river. On the other hand, the steam of this area of interaction is where individual tidal waves exist together.

There are many other papers where people have done a study on the same estuary. In most cases, the data given in this research paper were similar to the one in this paper. This implies that this paper can be used as a reference by other students and writers. Besides, this is also an indication that the data in this paper is accurate.

Methodology

Sieve technique is the commonly used method for particle separation. Each sieve stack has several sieves that have increased aperture size stacked on each other and it is placed on the topmost sieve. The stack is clamped to the sieve shaker and subjected to vibration for some time. Due to this, particles are distributed to the sieves in the stack depending on their sizes. Particles will pass through the smallest possible sieve apertures and with the smallest projection surface. Using the cubic particles as a model, this corresponds to the edge length of the cube. For lenticular particles, the size determined by the sieve analysis would be the value between the thickest and the diameter of the lense because the particle is introduced diagonally towards the sieve apertures. The advantage of this method is that it is fast and easy to handle. Besides, the results of the particle sizes are reproducible and accurate compared to other techniques because of the sieve aperture. It is also a time-saving method and the cost of these tools is lower than of other techniques. On the other hand, the disadvantage of using the method is that is can only work with dry particles with a minimum measurement of 50μm implying that the reduction of their sizes will cause an error.

Particle size analysis (PSA) is a complex procedure that includes sampling, dispersion and accurate use of instruments of particle separation. Since either of these operations can be performed alone it is important to measure the size distribution very carefully using expert laboratories. The advantage of using this method is that it is fast and cost-effective. Moreover, it increases the exposure of the poorly soluble particles by expanding their surface area which enhances dissolution rate. There is also less analysis time and particle sizes can be separated by the meshes. On the other hand, the cons of this method are that it is only the average particle size that is available and particle size distribution is unobtainable.

Data analysis was done using GRADISTAT, which is the commonly used tool in doing particle size analysis. Using this tool, one can run data in Microsoft Excel and it helps in calculating the particle size for sieve and laser granulometry data.

Results

The mean grain size is explained using the Udden-Wentworth grade scale. To make the terminologies in this scale consistent with silt and sand fractions, the size of gravels is given into five subsections that range from the very fine grains (2mm) to the very coarse ones (64 mm). Those that are bigger than 64 mm are considered to be boulders. In most cases like in this case the terms like granules, pebble and cobble are removed. The 'shingle' can just be described as rounded gravel.

Grain or particle size is a crucial textural parameter used in classifying rocks since it distributes information based on the conditions of transportation, sorting, and deposition of the sediment. It also provides some basic ideas of the historical events that happened at the depositional site before the last induration of the sediments. Identifying the sizes of the discrete particles that contain the sedimentary rock will be difficult mostly if the rock is strongly indurated.

These are the grain-size scales for the sediments in millimeters and when the United States standard sieve mesh is used.

Gravel

Ranges from 4,096, 1,024, 256, 64, 4, 3.36, 2.83, 2.38 to 2.00.

Sand

Ranges from 1.68, 1.41, 1.19, 1.00, 0.84, 0.71, 0.59, 0.50, 0.42, 0.35, 0.30, 0.25, 0.210, 0.088, 0.074, to 0.0625.

Mud is classified into two categories. That is silt and clay.

Silt ranges from 0.053, 0.044, 0.037, 0.031, 0.0156, 0.0078, 0.0039, 0.0020, 0.00098 to 0.00049.

Clay ranges from 0.00024, 0.00012 to 0.00006.

These are the standards used to classify sediments and sedimentary rocks using the millimeter-scale where each size of the grade is different from its predecessor by a content ratio of 1.2. Besides, each size class has a class name that is used to define particles even within themselves. This milimeter is called the Udden-Wentworth which is the scale of geometric grain-size scale because there is a content ratio in between the class limits and this gives a clear description of sediments in terms of gravels, sand, silt, and clay.

Discussion

There are many drivers of sediment distribution in River Adur Estuary but the most fundamental ones are those that generate a natural rhythm of diurnal or what is called semi-diurnal, bi-monthly and seasonal fluctuations because of the predictable variations in tides and weather. In this case, the catastrophic events like the late Pleistocene meltwater pulses as well as the tsunami started by the Storegga landslide are the key drivers. They lead to large but brief but speedy inundation occurrences of coastal regions and effects on human populations. Moreover, the episodic growth of channels mostly in the last 350,000 years might have led to numerous overtopping cases that are likely to increase the discharge in the extensive south North Sea proglacial lake held back by the Weald-Artois ridge. These lead to erosion of the ridge as well as the paleochannel creation in the east English Channel.

Conclusion

It is important to note that the suspended sediments and solids have a great impact on the quality of water in the water body as well as the water resources. These suspended sediments and solid can originate from either natural sources like wind erosion, rainfall, upland erosion, and rill erosion. Other sources include man-driven factors like farming, fishing, mining, and construction activities. These sediments can act as carriers of pesticides, nutrients, and radioactive materials and this affects the water quality.