Cwm Ivy Habitat Creation Scheme

Cwm Ivy Marsh in Gower is protected from the adjacent estuary by a large earth and stone embankment. In 2013, the embankment was damaged by storm tides and a small hole emerged. This allowed sea water into the marsh for the first time in over 300 years.

The constant passage of sea water at every high tide gradually opened the hole until a section of the wall and supporting embankment collapsed. Since then, the sea has begun to gradually reclaim the marsh and the breach in the sea wall has continued to grow naturally.

Challenge

We were commissioned by Natural Resources Wales to assess the best way to enable the marsh to reintegrate back into the wider estuary and develop into a saltmarsh of a standard needed to provide compensatory habitat. This would offset the likely loss of saltmarsh habitat in the future which is due to a combination of sea level rise from climate change, and the need for new coastal flood defences in the Lougher Estuary and Carmarthen Bay.

A range of project management, modelling and environmental assessment services were undertaken to support this exciting and ambitious project. The first of its kind in Wales, the project aimed to create 39 hectares (the equivalent of 55 football pitches) of new saltmarsh habitat.

Solution

We developed a range of saltmarsh development options by undertaking several detailed studies of the marsh. This allowed us to better understand the existing ecological and hydrological conditions, coastal processes and potential engineering constraints, both now and in the future.

The preferred option worked effectively with natural coastal processes, allowing the breach in the embankment to widen and fail naturally. This further deterioration in the embankment, and anticipated improvements in site drainage, are critical to the development of the saltmarsh habitat. An Ecosystem Approach was adopted to develop a robust business case and understanding of the associated wider costs and benefits.

In addition, we led the stakeholder engagement activities, liaising with statutory bodies, the public and other interested parties via public drop-in events, and meetings with Welsh Government, the local MP and local councillors.

Benefit

Providing a wide range of integrated services enabled us to lead the project whilst also providing specialist advice on the constraints, benefits and costs associated with different options. The preferred solution minimised the need for complex engineering or construction works, whilst facilitating a more natural reintegration of the marsh back into the wider estuary. This allowed a significant cost-benefit ratio and avoided the need for consents to facilitate its delivery.

Adopting an Ecosystem Approach ensured that the wider costs and benefits of the project could be identified and quantified where possible. This supported the development of the business case and enabled stakeholders to better understand the range of benefits that the project would deliver, and in doing so facilitate greater support.

Exciting changes are already taking place to the marsh. Saltmarsh plant species and other marine species are already beginning to colonise the site much quicker than anticipated, and the area has already become home to an array of bird species. The historic tidal creek pattern has quickly re-established across the site, providing a haven for marine fish and invertebrates.

Want to know more?

For more information on this project contact David Revill or visit the Natural Resources Wales website.

You can also find out more about our work on our environmental services web pages.



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