Chapter 5(Preview)

Hold the line

‘Holding the line’ is a phrase used in coastal management to describe a way of keeping the coastline in its current position and preventing the sea from encroaching where it’s not wanted.

On vulnerable stretches of coastline where holding the line is important, it’s critical to understand how coastal dynamics (how the currents, wave patterns, wind, tides and shifting sediment shape our coastline) and how different coastal defence options will respond to the physical conditions.

Before deciding what defences to build, engineers study and model coastal dynamics. They also look at how different defences will behave and try to predict how they will affect the natural processes along the coast (the coastal feedback loop). This is important because choosing the wrong coastal defence option can change the coastal dynamics and work against holding the line.

The hold the line strategy has been used in Borth’s current sea defences. The new defences include giant rock boulders and rock groynes, and fish tail shaped breakwaters, along with a reef, which also improves surf conditions.

Advance the line

This is where new defences are built further into the sea, extending existing defences and reclaiming land in the process.

Adaptive or planned retreat

Adaptive or planned retreat, is where the shoreline is moved backwards, with management to control or limit the movement of water from the sea. If an area is at high risk of erosion, adaptive or planned retreat could be an option.

Adaptive or planned retreat often involves the controlled flooding of low-lying coastal areas to relieve the coastal squeeze effect. In the Dyfi, this would require careful discussion and collaboration with any landowners and homeowners who have low-lying land or property.

In some cases, adaptive or planned retreat, combined with marine intertidal habitat creation, may be needed to compensate for the environmental cost of holding the line (where Marine Protected Areas are affected by coastal squeeze).

Although adaptive or planned retreat typically applies to low-lying areas at risk of flooding, it can equally be applied to cliff areas to help reduce the rate of recession for a period of time.

There are also some costs involved with adaptive or planned retreat. Some defences will need to be removed or redesigned, and land and property owners may need to be financially compensated.

But this strategy costs less compared to paying for new sea defences. It also creates a salt marsh, which can support many species and acts a natural defence against erosion and flooding.

However, through this strategy, land is reclaimed or changed by the sea. This will impact livelihoods, people’s homes and the history and culture associated with the land

What is coastal squeeze?

Coastal squeeze is the loss or deterioration of natural shoreline habitats – such as beaches and salt marshes – that stems from being trapped between man-made coastal defences and rising sea levels. This prevents the coast from moving inland as it normally would.