The Coastal Environment
Beaches have three main components:
1. Nearshore: Where the land begins to affect the
sea.
2. Foreshore: The surf zone.
3. Backshore: Usually above the high tide mark.
1. Nearshore: Where the land begins to affect the
sea.
2. Foreshore: The surf zone.
3. Backshore: Usually above the high tide mark.
The gradient of the beach is typically steeper in the summer due to the constructive waves which are more common within the summer months. The strong swash associated with constructive waves deposits large sediment at the top of the beach resulting in even weaker backwash and very little transportation. This is because the water drains away by percolation through large sediment, rather than by running down the beach.
The Action of the Waves
> The strength at which the wind is blowing and > How far the wave has travelled (I.e. The Fetch)
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Destructive Waves
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destructive_waves_vid.mov | |
File Size: | 1323 kb |
File Type: | mov |
Constructive Waves
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The Tides
- Tides are complex daily oscillations in sea level around the world, that range from barely noticeable to several metres.
- As tides flood (rise) and ebb (fall) the daily migration of the shoreline causes significant changes that affect the sediment erosion and transportation.
- Tides are created by the gravitational pull of both the moon and the sun. The sun's influence is only half of that of the moon.
- Tides appear to move in and out along the shoreline but they actually don' t. The Earth's surface rotates in and out of relatively 'fixed' tidal bulges.
- As the Earth rotates through two bulges within 24 hours, most coastlines experience two high tides and two low tides.
- A weak tidal current or a small tidal range will determine the shape and size of a beach profile. This will also influence the rate at which erosion occurs.
- There are two tides which have the most significance - the 'Spring tide' and the 'Neap tide'.
> Increases the tidal range by heightening the high tide and lowering the low tide. > Caused by the alignment of the moon and the sun, aligning the gravitational pull.
> Produces a low tidal range, with a high tide lower than 'normal' and a low tide which is higher than is 'normal'. > Occurs because the gravitational force of the sun and the moon are acting against each other. |
Sediment Sources and Cells
Sediment Types |
Sediment Cells |
There are four different types of sediment it is possible to see in the coastal environment:
> Clastic Sediment: This comes from weathering rock and varies from very small clay particles to sand, pebbles or boulders. > Biogenic Sediment: Skeletons and sediments of marine organisms. > Non-Cohesive Sediment: Larger particles (for example, sand) moved grain by grain. >Cohesive Sediment: Very small clay and mud particles that bond together. There are many sources and ways in which sediment can make its way to the coastal environment and become part of the systems that take place in this area. These include: > Rivers entering the sea, including deltas. > Cliffs. > Wave erosion. > Mud, sand and shingle. |
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Rock Strata
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