ENVIRONMENTAL AWARENESS
The importance of coastal engineering in the preservation of our coastlines
Coastal erosion has become a pressing concern for communities along the edges of our island, posing a significant threat to property, infrastructure, and seafront wildlife. John Rodgman - managing director of Borehole Solutions has delved into the pivotal role that coastal engineering plays in mitigating these challenges
W
e’re far from having a shortage of coastline in the UK. In fact, we’ve got 31,368km to be exact, and the vast majority of it has remained largely
unchanged over the past few centuries. The vast majority of our coastline, including areas such as Devon and Cornwall, is made up of hard, igneous rocks like granite, capable of withstanding weathering and erosion from the waves. The remaining landmass such as Norfolk, Suffolk and Dorset, however, consists of sedimentary-based coastlines, which are retreating at an alarming rate. If there’s any hope of preserving the future of these area’s coastlines, coastal engineering must come into play.
What is the coastal erosion crisis?
Coastal erosion – the loss or displacement of land due to natural forces such as strong waves, rising sea levels, and storm surges – continues to keep hold of the UK’s coastlines, with the natural impact of climate change dramatically speeding up the rate of erosion, with an estimated 7,000 homes expected to
be lost to the coastline’s retreat come the end of the century. One recent and alarming example of this is the 2021 collapse of the Jurassic Coast – the UK’s largest cliff collapse in over 60 years. Because of the naturally soft rock of the iconic Dorset cliffs, which when combined with the relentlessness of waves, wind and rain, caused a structural weakness in the cliff, leading to its collapse and as much as 10,000 tons of debris lost to sea. This is a risk faced by most the UK’s sedimentary coastlines.
What is coastal engineering?
Whilst being rather a broad term, coastal engineering refers to any form of man-made coastal defence. These can include, but are not limited to:
• Breakwaters and Seawalls: Both breakwaters (barriers submerged or partially submerged beneath the water) and seawalls (walls or embankments erected parallel to the shoreline) help protect the coastline against erosion.
• Wooden Groynes: These are long, narrow structured built out into the sea to limit the movement of sand and shingle along the coast.
• Beach Nourishment: This is the process of replenishing eroded beaches with sand and sediment to compensate for natural erosion and longshore drift.
• Living Shorelines: A living shoreline is a protected, stabilised coastal edge formed from natural materials such as plants, sand and rocks.
What information must be gathered prior to beginning work?
In order to fully understand the dynamics of the particular coastline, a comprehensive study must be undertaken. This is particularly relevant due to the long-term stability of engineering projects being impacted by the intersection
14 BUILDING SERVICES & ENVIRONMENTAL ENGINEER OCTOBER 2023
of air, land and the sea, with the conditions of each changing on a regular basis. Each must be observed in order to understand how the coastline responds to each element to ascertain the most effective engineering solution. Some of the factors which should be taken into account include:
• The range of tides for the specific coastline.
• Current and surge information. • The type of rock and sediment present along the coastline.
• Whether there is any natural protection from the elements.
Technical challenges to be considered with coastal engineering
Coastal engineering requires a multifaceted approach when it comes to combatting erosion. After all, powerful waves erode shorelines through longshore drift, rising sea levels intensify the rate of erosion, and the corrosive effects of saltwater must be withstood by various coastal structures. Any defence structure, whether a breakwater or wooden groyne, must take wave patterns, sediment transport, and long-term structural stability into account, with the most suitable materials and techniques utilised to maximise durability. Additionally, with the rate of erosion unlikely to slow down, adaptive designs and remediatory methods must accommodate future shifts in these factors.
The impact of coastal engineering on the Holderness coastline
The Holderness Coast – a 61km long coastline extending from Flamborough to Spurn Point along the east coast of England – has been rapidly eroding at a rate of 1.8 metres per year. This comes down to its soft clay and sandy composition, naturally narrow beaches which provide minimal protection to the coast, and
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