The Shoreline

The shoreline or beach is the point at which the land
meets the sea. It can be sandy, muddy or stony or a
mixture of these. It consists of the land either side of
the high tide line.

The high tide line is marked by the strand line, which is
the highest point that the tide reaches.

As the tide comes in, it carries material floating in the water
such as seaweed, dead plants and animals and human rubbish.
Some of this material is left stranded as the tide turns. The height
of the tide changes with the phases of the moon and the weather
so there can be more than one strand line.

Below the strand line the top of the beach is only covered by water at high tide whereas the bottom of the beach is covered by water most of the time. This is why you will find different plants and animals at the top and bottom of a beach. Not many species can cope with these conditions, but it is a good place for those that can, so there maybe thousands of tiny spire shells (Hydrobia) and or a thick layer of seaweed.

Dell Quay shore
Dell Quay shore

The area above the strand line is mostly dry except for the very highest tides so a different range of plants and animals are able to live here but they must still be able to cope with the occasional soaking with salt water!

The shoreline at Dell Quay

The shoreline at Dell Quay is shingle at the top of the beach and becomes increasingly muddy further down.

The strand line can produce some interesting finds! In among rubbish carried by the tide such as old boots, bits of string and wood you might find white cuttlefish bones. This bone forms the inside skeleton of a fascinating animal which looks a bit like an octopus and can change colour when it wants to!

Small white crab shells are not what they seem. They are not dead crabs but are the shell left by the crab after it has grown a new bigger one. It sheds the old one, takes in water to expand the new one and then hides until the new bigger one has hardened.

Sandhoppers are about 2 cm long and live among the debris of the strandline feeding on dead and decaying matter. They are able to jump and may land in your lunch box if you are picnicking too near the high tide line!

Wading birds such as the redshank and turnstone enjoy foraging among the bladderwrack, seaweed and under pieces of wood looking for things to eat.

Sea beet
Sea beet

Above the high tide line plants are better able to grow. Sea beet grows in the shingle and can tolerate the salt spray. It is edible and is related to spinach and beetroot.

Below the strandline many of the animals that live in the mudflats also live where the mud is mixed with shingle. These include crabs, cockles and periwinkles.

Food chain

Dead Plants -> Sandhopper -> Turnstone


The shoreline, especially the strandline can be badly affected by pollution such as oil and other harmful substances as it can become concentrated among the debris of the strandline.

Boats on legs
Boats on legs

Shorelines like that at Dell Quay are heavily used by people for keeping and launching boats. Quay, jetties and pontoon are built across the beach to help access to deeper water. Bits of boat and old structures are left behind from days gone by. Some of these are interesting, others ugly and potentially dangerous.

Human litter from beach users and rubbish washed up by the tide can affect the shoreline.

Rising sea levels are also a problem. Sea walls and other sea defences have been built to protect houses and farmland, so the beach gets smaller as the water level rises.


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Chichester Harbour Conservancy Education
Harbour Office, Itchenor, Chichester, PO20 7AW.   Tel: 01243 512 301