What is a spit?

A spit is an area of sand or shingle which either extends at a gentle angle out to sea or which grows across a river estuary. Many spits are characterised by a hooked, or curved end. Spits develop in places where:

• Longshore drift moves large amounts of material along the beach
• There is a sudden change in the direction of the coastline
• The sea is relatively shallow and becomes progressively more sheltered.

Introduction:

Dawlish Warren is a coastal spit which extends across the mouth of the Exe estuary in South Devon. Longshore drift moves from west to east along the south coast, and is interrupted by the Exe estuary.

At Dawlish Warren, the spit has formed over many years as materials is deposited which has been sourced from cliff erosion, sandbanks offshore and river deposits. In recent years it has seen a reduction in size due to a number of factors

The spit performs three main functions:

1. Defence

The spit protects the inner estuary from powerful waves that could cause erosion and flooding. This has meant that the land behind has been developed for housing, farming and infrastructure

2. Habitat

It supports a sand and gravel beach and a sand dune ecosystem. The spit has meant that mudflats and a salt marsh has become established behind the spit which supports varied flora and fauna.

3. Tourism and Leisure

The area has a popular bathing beach and golf course. It also has a nature reserve, café, shops, car park, amusements and a railway station - all of which bring people to the area and helps support the local economy.

Problems:

There is a problem with sediment supply. There is more sediment being lost from the spit that is being fed into by longshore drift. It is likely that this is the result of coastal erosion. Due to pressure on other areas in the coastal zone, more has been done to protect cliffs updrift and keep sediment and sand on the popular beaches down the coast. As a result, the supply of sediment has been reduced and erosion rates have increased on the spit.

In addition, the railway line along the coastline needed to be protected by rip rap and a sea wall, which interrupted the natural flow of sediment to the spit.

Gravel and sand extraction on the spit in order to provide building materials also accelerated the reduction in the size of the spit in the 1920s. At the point where the spit joins the original coastline heavy engineering has taken place in the form of a sea wall, revetments, rip rap, gabions and rock armour in order to reduce the likelihood of flodding and a breach of the spit.

Summary

The railway line has allowed access to the area and the spit, but it has starved the beach and spit of sediment, increasing the rate of erosion on the spit

The sea wall protecting the railway has reduced the sediment supply to the spit which has meant that hard engineering solutions have needed to be applied

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D.Drake 2011

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