Coastal Deposition Landforms

When we talk about coastal deposition landforms, we're talking about much bigger things than sandcastles. We're talking about the vast sandy beaches around our coastlines, sand dunes, and other funky-looking sandy landforms you might be familiar with. The sea is constantly transporting sediment (sand and silt) and putting it in new places. Depositional landforms are essentially the different ways that this sediment is arranged. They're a bit like sandcastles but on a much larger (and maybe less fun) scale!

Get started

Millions of flashcards designed to help you ace your studies

Sign up for free

Review generated flashcards

Sign up for free
You have reached the daily AI limit

Start learning or create your own AI flashcards

Contents
Contents

Jump to a key chapter

    Coastal Deposition Landforms revision

    Before we look at the different landforms which are created by deposition, let's do a little coastal deposition revision. What is coastal deposition? What causes it?

    Coastal deposition is when the water in the sea loses velocity (slows down), and any sediment that the water is carrying (like sand or pebbles) gets dropped, as the water doesn't have enough power to carry it anymore.

    Deposition can occur for a variety of reasons on the coast:

    • When waves lose velocity after breaking.
    • When backwash is weaker than the swash.
    • At sheltered coastlines (caves) or when the water is shallower.
    • When freshwater meets seawater.
    • When water is sheltered behind a spit.

    The swash is when a wave breaks at the coastline and literally swashes its way up the beach. When the tide retreats, this is the backwash. This is how materials are transported.

    Make sure you take a look at the waves explanation!

    Coastal Deposition Landforms diagram

    Longshore drift is the main way sediment is transported by the sea. It happens when a wave breaks at an angle to the coast, rather than parallel (head-on) with it. This angle occurs because of prevailing winds.

    Prevailing winds are the winds that come from a certain direction, which is the most common.

    Because prevailing winds are mostly from one direction, longshore drift is usually in one direction too. These angled waves wash sediment diagonally up the beach. Gravity then pulls the waves straight down the beach (backwash). As this zigzag movement occurs, the waves transport sediment all along the coastline, which is how depositional landforms can occur. Take a look at the diagram below, which shows the process of longshore drift.

    Coastal deposition landforms, figure 1, longshore drift, StudySmarterFig. 1 - longshore drift diagram

    So, we've just revised a little about coastal deposition, but for more detailed information, make sure you read the explanations on Coasts, Coastal Processes, and Coastal Erosion and Deposition.

    Coastal Deposition Landforms types

    There are many different types of landforms created by coastal deposition, such as beaches, sand dunes, spits, and bars. Let's take a look at how some of these landforms are created.

    Beaches

    Beaches are the most common coastal depositional landform, and one which you will be most familiar with. They are found where the sea meets the land, and are made up of sediments that have been transported and deposited by the sea, such as sand, mud, silt, pebbles, and shingle.

    Sandy beaches

    Your typical sandy beach most often develops in bays. This is where low-energy, constructive waves are found, which move material up the shore and deposits it there, developing the beach.

    Coastal Deposition Landforms Sandy Beach Alaska StudySmarterFig. 2 - a sandy beach

    A constructive wave is a wave that is slow and long. Its swash is powerful, whilst its backwash is weaker; this means that more material is carried up the coast and deposited, which builds up over time, creating the beaches we see today.

    A destructive wave is a wave that is much steeper and has a more powerful backwash, with more power to erode the coastline.

    Over time, if constructive waves are dominant, the beach will build up (as more sediment is deposited), and the beach will become steeper. During the winter time, more destructive waves may become dominant, or even storm waves, which have stronger backwash, creating more gentle sloping beaches.

    Pebble or rocky beaches

    Pebble beaches are characterised by more powerful destructive waves. Larger sediment, like pebbles or rocks, cannot be transported so far up the beach, so it makes these beaches very steep or almost stepped. If it is stormy, the storm waves can throw heavy sediment towards the back of the beach. These beaches are also found in cliffed areas, where powerful waves erode the cliffs away.

    Don't forget: Constructive means that you are building (up) something; for coasts, this means that something is being created (in this case, by deposition). It is the entire opposite of destructive, which is demonstrated by erosional processes.

    Coastal Deposition Landforms Pebble Beach Alaska StudySmarterFig. 3 - a pebble beach

    Sand dunes

    On sandy beaches, you are also likely to find sand dunes. Sand dunes are big clumps of sand on the beach, usually found at the back of beaches. The material that is deposited by longshore drift, is blown around by the wind. Over obstacles, such as rocks or driftwood, sand is deposited, as a result of the wind slowing down. This forms an embryo dune. As the sand keeps building up, pioneer vegetation can grow, which actually helps to stabilise the dunes with their roots (stop them from being blown away). Foredunes are then formed.

    Pioneer vegetation is the plants that colonise an area first. They are pretty hardy plants, as the environments in which they colonise are barren (generally poor land for colonisation).

    This vegetation also forms soil from the nutrients when they die, which can cause further vegetation to grow. The sand dunes themselves become an obstacle for more sand to form around, creating more dunes in front of the first dune. Take a look at the diagram below, which shows a sand dune ecosystem.

    Don't forget: the stronger the wind, the bigger the dune!

    Spits

    Longshore drifts move sediments at an angle along a coastline. When the coastline comes to an end (or when the sea meets a river), wave energy slows down and deposition occurs. This can create a long stretch of sand that extends out into the sea. These are called spits.

    Spits are attached to the land on one end, with the other end sticking out into the sea.

    Spits continue to grow until they reach deep water, or the amount of deposition can't keep up with the amount of erosion.

    Coastal Deposition Landforms Homer Spit Alaska StudySmarterFig. 5 - Homer spit in Alaska, with human activity

    Wind can cause the spit to curve around at the end. The water behind this curve is calmer, as this area is a little more sheltered. Here, mud and other sediments are deposited, developing a salt marsh.

    Bars

    Bars, just like spit, are associated with the process of longshore drift. Instead of jutting out into the sea, like a spit, the sand deposition actually connects two sides of the headland that surround a bay. It's essentially just a long strip of land. This is known as a bay bar. Behind this strip, a shallow lake (lagoon) forms. As deposition continues to occur in the lagoon (due to low-energy water), a salt marsh can form.

    Offshore bars can also form off the coastline; destructive waves erode the sediment on a beach and drag it back towards the coastline, and deposit it, forming the offshore bar. The sediment makes it look like the seabed is raised in the middle of the water.

    Beach profiles can change over time; this change can be demonstrated by berms. Berms are little ridges in the sand across the beach profile. Formed by constructive waves, they can move around the beach with differing tides or even storms. During the winter, berms are eroded away by strong destructive waves (and can create offshore bars), whereas, in the spring or summer, constructive waves and movement of the offshore bar, can help to build the berms back up. Berms can also show where the high tide (or storm tide) marks are!

    Coastal Deposition Landforms features

    We just explored the many different types of depositional landforms formed on a coastline. Let's highlight a few features and characteristics that you might be able to squeeze into your exam answers!

    • For the coast to build up, there has to be more deposition than erosion.
    • There are other deposition landforms at coasts, such as mudflats, ridges, runnels, cusps and tombolos.
    • Coasts are very dynamic systems; waves, tides, wind etc. all continuously shape the coastal environment. Deposition landforms change all the time.

    Coastal Deposition Landforms example

    As you know, case studies are important in geography. For coasts, it is no different. Let's take a look at some examples of some of the deposition landforms that we've discussed.

    Dorset coast

    The Dorset coast has many great examples of coastal deposition landforms. Chesil Beach is one of them. Chesil Beach is a bar, created by longshore drift, which built up a spit, that eventually joined the Isle of Portland to the mainland. Behind this bar there is The Fleet lagoon.

    Coastal Deposition Landforms Chesil Beach Dorset StudySmarterFig. 6 - Chesil beach, Dorset coast

    Sefton Coast

    At the Sefton coast of Merseyside, which spans 20km from Liverpool to Southport, you can find the largest sand dune system in England. The coastline is characterised by a sandy beach, dunes, grasslands, and pine forest. The dunes are home to vegetation like dune heather and creeping willow, and some cool animals too, like sand lizards and dune tiger beetles!

    Coastal Deposition Landforms Sand Dunes Sefton StudySmarterFig. 7 - sand dunes at Formby Point, Sefton coast

    Coastal Deposition Landforms - Key takeaways

    • Deposition of sediment on the coast occurs when the water slows down and doesn't have enough energy to carry sediment, so drops it.
    • Longshore drift is the main way that sediment is moved and deposited along a coastline.
    • Depositional landforms include beaches (sandy and pebble), sand dunes, spits, and bars.
    • Some great examples of coastal depositional landforms can be found on the Dorset coast and the Sefton coast.

    References

    1. Fig 2, a sandy beach (https://commons.wikimedia.org/wiki/File:2020-12-18_Sandy_Beach,_NSW_3.jpg), by Maksym Kozlenko (https://commons.wikimedia.org/wiki/User:Maxim75) Licensed by CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/).
    2. Fig 3, a pebble beach (https://commons.wikimedia.org/wiki/File:Pebble_beach_in_the_evening_with_a_mountain_town_on_the_horizon.jpg), by Aleda12, Licensed by CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/).
    3. Fig 5, homer spit in alaska (https://commons.wikimedia.org/wiki/File:Homer_Spit_1.jpg), by Scott McMurren (https://www.flickr.com/photos/alaskatravelgram/) Licensed by CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/).
    4. Fig 6, chesil beach dorset coast (https://commons.wikimedia.org/wiki/File:Chesil_Beach_from_New_Ground.jpg), by BennH (https://en.wikipedia.org/wiki/User:BennH) Licensed by CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/).
    5. Fig 7, sand dunes at formby point (https://commons.wikimedia.org/wiki/File:Sand_dunes_at_Formby_Point_-_geograph.org.uk_-_2586058.jpg), by Rob Noble (https://en.wikipedia.org/wiki/User:BennH) Licensed by CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0/).
    Frequently Asked Questions about Coastal Deposition Landforms

    What landforms are created by coastal deposition? 

    Beaches (sandy and pebble), sand dunes, spits, and bars are all coastal landforms created by deposition.

    What is an example of coastal deposition?

    Chesil beach, on the Dorset coast, is a great example of coastal deposition; here you can find a beach/bar, built from a spit, and a lagoon.

    What are depositional landforms? 

    Depositional landforms are landforms that are created by material that is dropped by water which has slowed down and lost energy.

    What are the 5 types of deposition? 

    Deposition can occur when:

    1. Waves slow down after they break

    2. When swash is stronger than backwash

    3. Shallow water or sheltered coastlines 

    4. When seawater and freshwater meet

    5. When water is sheltered behind a spit

    What are the coastal depositional features? 

    Deposition is higher than erosion and coasts are incredibly dynamic, changing continuously over time.

    Save Article

    Test your knowledge with multiple choice flashcards

    True or False: for longshore drift to occur, waves have be angled against the prevailing winds

    Which of the following is not a reason for deposition occurring?

    True or false: landforms created from deposited sediment are not very dynamic, and don't change very often.

    Next

    Discover learning materials with the free StudySmarter app

    Sign up for free
    1
    About StudySmarter

    StudySmarter is a globally recognized educational technology company, offering a holistic learning platform designed for students of all ages and educational levels. Our platform provides learning support for a wide range of subjects, including STEM, Social Sciences, and Languages and also helps students to successfully master various tests and exams worldwide, such as GCSE, A Level, SAT, ACT, Abitur, and more. We offer an extensive library of learning materials, including interactive flashcards, comprehensive textbook solutions, and detailed explanations. The cutting-edge technology and tools we provide help students create their own learning materials. StudySmarter’s content is not only expert-verified but also regularly updated to ensure accuracy and relevance.

    Learn more
    StudySmarter Editorial Team

    Team Geography Teachers

    • 10 minutes reading time
    • Checked by StudySmarter Editorial Team
    Save Explanation Save Explanation

    Study anywhere. Anytime.Across all devices.

    Sign-up for free

    Sign up to highlight and take notes. It’s 100% free.

    Join over 22 million students in learning with our StudySmarter App

    The first learning app that truly has everything you need to ace your exams in one place

    • Flashcards & Quizzes
    • AI Study Assistant
    • Study Planner
    • Mock-Exams
    • Smart Note-Taking
    Join over 22 million students in learning with our StudySmarter App
    Sign up with Email