Rivers and coasts, Year 10: landforms of deposition and managing the coast (Coastal landscapes option)

It is steeper (and usually narrower)

提示Water drains away quickly through the gaps between large stones.

为什么On shingle the backwash soaks down between the pebbles instead of running back over the surface, so material is pushed up the beach and stays there. On sand the backwash runs back and spreads the sand out into a wide, gentle slope.

A spit

提示Four letters; the same word is used for a roasting rod.

为什么Longshore drift carries sediment along the coast. Where the coastline changes direction, for example at a river mouth, the sediment is carried on in the same line and dropped in the open water. Over many years it builds a ridge above the level of the sea.

A change in wind direction brings waves from another side, pushing the end round

提示The weather is not the same every day; think what drives the sea's surface.

为什么The prevailing wind drives the longshore drift that lengthens the spit. From time to time the wind blows from a second direction and the waves it makes curve the tip. Old hooks left behind along a spit show where its end used to be.

bar; lagoon

提示The first is three letters and also means to block a way; the second is a calm pool that tropical islands are known for.

为什么A bar can only form where no strong river current keeps the gap open. The trapped water is cut off from the waves. Over time it may fill with sediment and become marsh.

An obstacle, such as driftwood or a clump of plants, that slows the wind

提示Think of snow piling up against a fence.

为什么Wind slows as it passes something in its way, and it drops the sand it was carrying. The small mound then traps more sand. Plants such as marram grass grow on it, and their roots hold the sand together, so the dune grows taller.

Rock armour (rip-rap)

提示The second word is what a medieval knight wore.

为什么The gaps between the boulders let water drain through, so the wave loses its energy instead of bouncing back. It is cheaper than a sea wall and quick to build. The boulders are often brought from far away, so they can look out of place, and they make the beach harder to reach.

A wire mesh cage filled with rocks

提示Imagine a shopping basket made of steel netting, packed solid.

为什么Gabions are stacked at the foot of a cliff or along a bank, where they absorb wave energy. They are among the cheapest hard defences. They are not very strong: storm waves and rust can break the cages open, so they do not last as long as a sea wall, and many people find them ugly.

Waves lose their energy crossing the beach before they reach the land

提示A long run-up tires out a sprinter.

为什么A beach is a natural defence: waves break on it and spend their force moving sand. The added sediment looks natural and gives tourists more beach. The sea keeps carrying it away, so it has to be replaced every few years, which is the main cost.

reprofiling

提示Start with the prefix for "again", then the word for a side view of a face.

为什么Storm waves drag material down the beach and flatten it. Pushing it back up makes the beach higher at the top, so it takes more wave energy. It is cheap and simple, but it has to be repeated often and only works while wave energy is low.

marram

提示Six letters, starting like the planet named after the Roman god of war.

为什么Dunes are a natural barrier between the sea and the land behind. Planting grass and fencing off worn areas lets them recover. It is cheap and keeps the coast looking natural, but storms can still damage the dunes, and fencing people out is unpopular.

The owners of the land that is allowed to flood (often farmers)

提示Ask whose fields are given up to the tide.

为什么In managed retreat (coastal realignment) the old defence is breached and the sea is allowed onto low-value land. Salt marsh develops and absorbs wave energy. The cost falls on the people whose land or homes are given up, which is why these schemes cause conflict.