Hard and Soft Engineering Solutions to Flooding and Erosion in Coastal Areas.

Rising sea levels are one of the results of global warming. As the atmospheric temperature of the Earth continues to increase, the polar ice continues to melt thus making the sea-level rise. Along with many others, a major impact of this is the increase in major flooding and erosion in low-lying, unprotected coastal land.

A solution to protecting land from flooding and erosion is the implementation of coast defences. This involves the use of hard and soft engineering to mitigate the effects of the energy transfer that occurs between ocean waves and the land.

Soft Engineering Solutions

Some examples of soft engineering in coastal defence systems are beach nourishment, dune regeneration and cliff stabilisation.

Beach Nourishment

Beach nourishment is the process of manually adding truckloads of sand and shingle to the shoreline to either restore or create a beach. This man-made beach can be used not just as a tourist attraction, but as a technique in absorbing wave energy which reduces the impact of the ocean on the land resulting in less erosion.

The benefits of this type of coastal defence are that it is commonly considered to improve the look and quality of the shoreline, therefore having a positive effect on the quality of life in the area. Beach nourishment can also be viewed as sustainable as it often involves the re-use of unwanted materials. The sand and shingle are often sourced from areas where it is unneeded and considered as waste.

As an example, during the construction of the British Airways i360 on Brighton beach in the UK, 7200 tonnes of shingle and gravel were excavated to make room for structural foundations in the form of 4150 tonnes of reinforced concrete. The excavated material was then transported to another beach and used as a form of beach nourishment.

The negative side of beach nourishment is that the procedure produces a high amount of CO2 emissions. Dependant on the size of the beach, many large vehicles are required to transport the shingle from other parts of the country. Due to long-shore drift, the new sand and shingle is moved along the coast and taken away from the proposed area. The life span of beach nourishment is between 1 and 10 years so the process must be performed regularly which makes this coastal defence strategy expensive and unsustainable.

Dune Regeneration

Dune regeneration is an alternative form of a soft engineered coastal defence. Dune regeneration involves creating or restoring sand dunes around the shoreline. The purpose of these dunes is to provide a barrier between the waves and society and to absorb wave energy.

Vegetation is planted in the dunes to help stabilise the dune, also further increasing its ability to absorb wave energy. In order to allow these plants to grow without being disturbed by human activity, the dunes are sometimes temporarily fenced off, or wooden walkways are built over them so humans can avoid stepping on the sand.

Similarly to beach nourishment, dune regeneration is accepted socially and environmentally as it often improves the sight of the coast while re-using unwanted materials. However, dune regeneration also provides extra vegetation which improves the sustainability of the coastal defence.

The negative impacts of dune regeneration are also similar to that of beach nourishment as the transportation of materials produces CO2 emissions while also having a low life span.

Hard Engineering Solutions

Examples of hard engineering in coastal defence systems include the likes of sea walls, rock armour, groynes and cliff fixing.