Nigg Bay Nature Reserve

Introduction

Sea-level rise and storm surges due to climate change are causing coastal squeeze of the important habitat found in Nigg Bay, Scotland. Managed coastal realignment was undertaken where sea levels continue to rise, allowing the saltmarsh to re-establish naturally. This adaptation option provides multiple benefits, creating important coastal wildlife habitats which may naturally become high carbon stores. It also provides natural tidal and flood defences, thus lowering the construction and maintenance costs of increasingly threatened hard defences.

What are the issues?

Sea-level rise and storm surges due to climate change are causing coastal squeeze of this important habitat. Hard flood defences were becoming more vulnerable and expensive to maintain as a result of rising sea-levels and storm surges.

What has been done so far?

• Two 20 metre wide breaches in existing sea defences were built to allow the top of the tide to flood a 25ha field. Approximately 2/3 of this field is now under water at high water or spring tide.
• Preparation of field site through culverting drains linking to adjacent fields, removal of trees and reduction of terrestrial vegetation.
• A relict creek system still present in the field has been utilised rather than performing further earthworks.
• Repair and elevation of existing secondary sea wall in advance of tidal inundation.

Lessons Learnt

The RSPB undertook Scotland’s first coastal realignment project at Nigg Bay in 2003. The project has increased the area of saltmarsh and intertidal habitat for wading birds and wildfowl. A notable knock-on benefit is sustainable coastal flood protection against sea level rise and storm surges. The area has been successfully realigned creating new habitats and reducing the pressure on the sea wall to be maintained. By 2005, the area had developed three distinct vegetation zones: terrestrial grassland, colonising saltmarsh and a lower zone of fine sediments. Nineteen species of waders and wildfowl were recorded using the site during winter 2004/05, the commonest of which were redshank. Other common bird species are Canada barnacle and brent geese, knot, wigeon and bar-tailed godwit. The habitat shows the full range of saltmarsh zones, from grassland, through upper, mid and lower saltmarsh communities to mudflats. It has been recolonised more rapidly than expected and now hosts up to 20% of the birds that winter in Nigg Bay. The project is a sucessful demonstration of how managed coastal realignment can work.