Coastal Protection - Soft Engineering

The approach of soft engineering is to manipulate and modify natural systems to bring about desired consequences rather than trying to impede or interrupt them.

Soft engineering coastal protection (erosion)

The key techniques of soft engineering can be summarised as follows:

Beach nourishment

Replacing lost beach material from a natural store either offshore (beach rebuilding) or from downshore along a stretch of longshore drift (beach recycling)

Benefits

Reproduces what natural systems would do – but at a faster rate. Sediment is not removed from the system – just redistributed. Low cost intervention over short term Maintains natural shoreline without artificial intrusions

Issues

Requires repetition over the year (3x) and each year Regular costs accumulate over the long-term Can be disruptive to beaches (local amenity and tourist economy) while engineering takes place

Beach reprofiling

Re-shaping the cross-sectional profile of a beach to ensure it offers maximum protective gradient and width against destructive wave action

Benefits & Issues

As above for beach nourishment

Living shoreline barrier

Planting shoreline vegetation (mangrove) or shellfish colonies (oyster reefs) to absorb wave energy between shore and sea

Benefits

Enhances shoreline habitats Encourages wildlife More attractive for locals and visitors Can be modified with different species to adapt to rising sea level

Issues

May be harmed by pollution events May not adjust to rising ocean temperatures/acidityCan be devastated by extreme storm events

Soft engineering: protection from coastal flooding

Living shorelines offer some protection against storm/tidal surges by absorbing the forward movement of water, although extreme tidal heights will still make their way inland.

An increasingly favoured soft engineering strategy to cope with more extreme storm events and anticipated rising sea level is to redirect flooding from coastal areas that are valued (homes, industry and key infrastructure) onto areas that have less significance with correspondingly less damage. This is achieved through ‘managed retreat’ (coastal realignment):

• New coastal embankments are constructed further inland on slightly higher land behind low-value shoreline
• Existing embankments are breached
• When higher sea levels are experienced the water floods onto the specified area
• New tidal saltmarsh/mudflats develop over time, absorbing flood water and providing essential wading-bird feeding habitat