Coastal Defences - IELTS Reading Answers & Explanations

You should spend about 20 minutes on Questions 1-14, which are based on Reading Passage 1 below.

Coastal defences

The world's coastlines are constantly being reshaped and reworked by the sea. Coastal erosion is one of the natural phenomena that contribute to the creation and destruction of our shores and one of the main processes that form beaches, dunes, mud flats, reefs and marshes along the coast. These different shoreline features have a wide range of functions: they provide habitats for wildlife, prevent flooding and protect fresh water resources inland, and, of course, they provide opportunities for leisure activities like sunbathing. As human activity along the coast continues to increase with the development of towns and industries, managing erosion is becoming a problem of growing importance. The risk of flooding due to rising sea levels, attributed to the effects of global warming, makes finding a solution to erosion a priority. As well as protecting natural habitats, coastal management involves saving homes and businesses from damage or destruction, and failing to do this can have severe consequences for society and the economy.

Coastlines are changed by the sea in two ways: erosion and longshore drift. Erosion happens through different processes, but essentially the action of the sea wears down features of the coastal landscape such as cliffs, beaches and sand dunes before washing them away. Longshore drift happens when waves approach a beach at an angle and move sediment along the coast until eventually the beach changes its shape. The beach may even disappear from its original location and re-form (as sediment is deposited) further down the coast.

There are three basic approaches to coastline management. The first one is to maintain the existing coastal defences but not to build new ones. The second is to build new defences further out at sea in order to reduce pressure on existing defences and even extend the coastline. The third is to retreat, in other words, to move people, homes and businesses away from disappearing coastlines. When the preferred option is to attempt to stop coastline erosion, either hard or soft engineering options can be used.

Hard engineering options are expensive and, in all probability, short term. They tend to have a significant effect on the landscape and environment because of their size 'and visual impact. Furthermore, they are expensive to build and maintain. Common coastal hard engineering methods are to build a sea wall or groynes; each type of barrier is designed to combat an aspect of coastal change, and in some places more than one type of sea defence can be seen. Sea walls are built at the edge of a coastline and are usually made from reinforced concrete to make them stronger. The walls prevent the sea from washing away the bottom of cliffs, causing the cliffs to fall into the sea. The walls can be vertical, curved or mound walls. Vertical walls were mainly used in the past and are the simplest type of wall. Unfortunately, they are also the most easily damaged by waves as their foundations can be undermined by the sea. Curved seawalls serve to push the waves back out to sea, and the curve prevents water from crashing over the top of the wall. However, deflecting the energy of the waves simply means that erosion takes place further down the coast. Mound sea walls use a mixture of loose material, such as rock and concrete, which has the advantage of absorbing the energy of the waves rather than deflecting it, and cost much less to build. However, they are less effective in storms and have shorter lives than solid sea walls.

Groynes are low walls built at a right angle to the coastline and are used to minimise the effect of longshore drift. They can be built from wood, stones and/or concrete, and are used in groups to break the beach into sections. As a wave hits the side of a groyne, its power is reduced and the material being carried by it is deposited at the side of the groyne. Groynes are less expensive than sea walls to put in place but like mound sea walls, they have a short lifespan.

The alternatives to hard engineering schemes are soft engineering techniques. They are low-cost solutions that have little immediate effectiveness against coastal erosion but are much more sustainable. There are two main kinds of soft engineering options. The first is beach nourishment, which replaces the sand and pebbles washed away by the sea. This avoids the need for expensive sea walls but sand needs to be moved constantly to maintain the beach. Unfortunately, because this option does not stop natural erosion by the sea, a larger quantity of material is deposited further down the coast. The second option, managed retreat, avoids coastal management and construction projects and allows areas of the coast to erode and flood naturally. Managed retreat usually takes place in areas of low economic value. The advantage of this method is that it encourages the development of beaches and salt marshes, two kinds of environments that are natural defences against the sea. The second advantage is, of course, that it is cheap.

Coastal management is difficult as local people, farmers and the agricultural industry, environmentalists, tourist authorities and other economic interests will have different opinions about what should be done. The importance of the issue is obvious from just one statistic: 45% of the world's population live within 100 kilometres of the coast. As sea levels rise and storm energy increases, the problems of coastal management are going to become ever more intense and pressing.