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What Transports Most of the Sediment in Beach Environments?

With 5 major oceans in the world, there are more than 682 beaches in the world. How many of them have you visited so far? Well, talking about oceans and beaches, do you know what are the sources of sediment at a beach and what force transports sediment along shore? Some of you may know the answer to the above questions, but can you tell me exactly what transports most of the sediment in beach environments? If not, then keep reading because today you will get to know about them all. 

1. What is Sediment and Where does it come from?

A material that occurs naturally after being broken down by the processes of weathering and erosion over a period of time is known as sediment. It means that the particles of sediments mostly come from the eroded soil which is transported from other places due to weather and other natural reasons.

However, in terms of water bodies, sediment can be clay, loose sand, soil particles, silt, and other particles that are settled at the bottom of the water body. It can be a form of the soil mixture as well. Sediments come from various natural factors like organic, geomorphic, and geologic. In the next segment, we will learn what transports most of the sediment in beach environments, so read on. (See What are Geologic Features?)

2. What is meant by Sediment Transport?

Photo by Lloyd Miraña on Unsplash

So, what transports most of the sediment in beach environments? The process of transporting organic and inorganic particles by water is termed sediment transportation. It has some significant environmental effects. These particles include mineral matter, chemicals, and pollutants. Moreover, there is a process of separating the particles and the sediments, called sedimentation, which takes place in still water where gravity will do most of the work. Sediment load is termed as sediment load as it consists of bed load, washes load, and suspended load from the sea bed.

  • Bed load: It is the portion of sediment transport that is rolling, bouncing, and sliding along at the bottom of the water body. It is not fully suspended and remains in contact with the sea bed. Bed load moves when a strong force of water overcomes the weight of the bed load sediments. Even if the water force is strong, the movement of these sediments is not at the same pace as that of water.
  • Suspended Load: The amount of sediment that is carried downstream by the flow of water and remains within the water column is known as suspended load. Moving water creates upward-moving currents which are essentially required by suspended loads to keep moving and stay above the sea bed. The stronger and faster flow will even lift the large particles, also but as it slows down the particles fall back to the sea bed.
  • Wash load: It is a part of the suspended load as it is made of the finest suspended sediments with a diameter of about 0.00195 millimeters. They are a bit different from the suspended load as the particles of the wash load do not settle at the sea bed if the flow is slow or even if the water is not flowing at all. Their particles are always in suspension because of their small size.

3. How are Sediments Transported?

Basically, sediments are transported by different sources, but their transportation mainly depends on the force of the carrying source and the size, shape, density, and volume of the sediments. However, the main agents of transportation are stream flow, estuaries, ice, wind, ocean currents, rivers, and gravitational transport. Erosion is one of the major factors which is responsible for the sediments being transported from one place to another. You are close to finding out what transports most of the sediment in beach environments. Let’s dive into the next segment. (See Why is Natural Erosion a Beneficial Process?)

4. What Transports Most of the Sediment in Beach Environments?

Waves transforming over a coastal profile and further generation of waves along with longshore currents create hydrodynamic conditions that result in the transport and deposition of the sediments in the beach environments. This transportation is termed littoral transport or drift. It is said that this type of transport mainly shifts cohesive sediments (for example sand) parallel to the shoreline along the coastal surfaces. So, what transports most of the sediment in beach environments? Seabed sediments are transported when they are exposed to a large force or extreme stress by the movement of water. (See What is the Very Bottom of the Ocean called?)

5. What are the Sources of Sediment at a Beach?

Photo by Polina Kuzovkova on Unsplash

Transportation of sediments is not a constant process because the quantity and type of sediment transported vary from time to time. Despite the changes from their occurring factors, the sediments at the active beaches are sourced from the following:

  • Longshore transport from adjacent coastal areas,
  • Erosion of older deposits on the inner shelf,
  • Erosion of upland rivers, and
  • Erosion of old beaches and deposits of shoreface.

6. How do Longshore Currents deposit Sediments?

The approaching waves are parallel to the shoreline, and before they reach the coast the waves reach an area where there is a rise in the seabed. This area is termed a breaker zone where the waves become higher and steeper. This region breaks the waves that create turbulence leading to the suspension of the sediments in the water. These sediments are then carried by longshore currents on the beach. (See What are Factors affecting Soil Weathering?

7. Why is Inner Shelf considered the Source of Sediments on Beach?

The inner shelf is another factor in what transports most of the sediment in beach environments. An inner shelf means an area that has been submerged in shallow waters for the past several years and even centuries. Beaches receive significant amounts of sediments from the erosion of these inner shelves. According to the evidence provided by Wehmiller and other researchers, about 75% of the clamshells that are found on beaches are fossils. Large waves can erode rocky materials from inner shelves and take them up to the Grand Strand Beaches. Hence inner self is considered one of the sources of sediments on the beach. (See What are Some Physical Factors Examples?)

8. Is Inner Shelf Erosion the Major Source of Sediments?

Yes, based on the researcher’s evidence, the sediments derived and deposited after the erosion of the inner shelf are only a fraction of the sediments on the beach. However, these inner shelves are a potential source of sediments on the beach but not excessively. (See What is the Importance of Turnover in Temperate Lakes?)

9. How can Old Beaches be a Source of Sediment?

Photo by Sumner Mahaffey on Unsplash

While discussing what transports most of the sediment in beach environments, note that Earth is renewing itself occasionally and beaches are not lacking behind. Researchers like Gayes found that the years and months-old segments or profiles of the beach tend to lose some materials from their top layer. This erosion takes place over months and years after which the sediment thus obtained is transported to the new beach which is not eroding but gathering the sediments. Must see What causes Breaking Down of Rocks into Fragments?

10. How Upland River Erosion Works?

Rivers provide sediments to the beaches only in areas found in the northern and southern boundaries of Long Bay. From the North Cape Fear River, the Great Pee Dee River from the south enters Long Bay and brings the sediments. However, various dams and shipping channels effectively trap most of the sediments and only a limited number of sediments reach the shore. (See How has the Removal of Wetlands Impacted Rivers and Streams?)

11. What Force Transports Sediment Along Shore?

As you are aware of what transports most of the sediment in beach environments, now take a look at the number of factors affecting the transport of sediments along the shore, namely, water, wind, water level, weather changes, and human influences:

  • Water Flow and Water Level: This is the most important force in the transportation of sediments. It is the flow of water that picks up the sediments, moves them, and deposits them. To initiate the transportation, flowing water is required. The speed of the flow determines the type and amount of sediment it would carry. Water flow is affected by the water level prevailing in the water body at the time of transportation. 
  • Wind: Another force that is notably mentioned in transporting sediments is the wind. This force is considerably important for the low-lying spits that border tidal lagoons. However, the wind is not much important for transporting predominantly cliffed coastlines. The force of the wind can influence the factors that transport most of the sediment in beach environments.
  • Weather Events: Different events like precipitation, storms, etc., affect the water flow along with the water level. More precipitation means more water levels and storms mean a considerable change in the water flow. Both weather events are the factors affecting the transportation of sediments. However, snow melting in a glacial-rich area will increase the amount of glacial silt. Overall, season and weather events are responsible for a change in water flow and water level that determines the amount and type of sediments that will be transported.
  • Human Influences: The construction of dams and altered land influence the amount of sediment transport. The restriction caused by these constructions results in less deposition of sediments in areas beyond them and more built of sediments on this side of these constructions. 

So, today you learned about what transports most of the sediment in beach environments. You can now mention the sources of sediment at a beach easily and what force transports sediment along shore is also known to you. (See How are Levees Beneficial to Human Settlements?)


Written by Alex Williams

Alex Williams is a PhD student in urban studies and planning. He is broadly interested in the historical geographies of capital, the geopolitical economy of urbanization, environmental and imperial history, critical urban theory, and spatial dialectics.

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