Coastal erosion can have a profound impact on coastal infrastructure, coastal communities and ecosystems. Conventional ‘hard’ engineering methods of coastal protection such as revetments and sea walls are increasingly viewed as potential intrusions into sensitive ecosystems. Ecologically-sustainable techniques are sought for use in coastal zones that can provide both effective protection from erosion and environmental improvements.
Arup collaborated with Iarnród Eireann (Irish Rail) to identify medium- to long- term coastal protection methods and to assess and compare them using multi-criteria analysis. The assessed methods included offshore techniques (such as breakwaters and planting artificial seaweed to encourage retention of sediment), lower shore techniques (such as groynes, beach nourishment, artificial headlands, and beach drainage) and upper shore techniques (such as artificial dune building, dune fertilization, marram grass planting, sand trap fencing, revetments and cliff stabilisation). The weighted, ranked assessments took account of the environmental impact and climate change resilience of each method in order to identify sustainable coastal protection solutions for use at specific locations on the Irish Rail network where there is a risk of erosion and encroachment on the existing railway.
Coastal management requires a holistic approach that assesses the interactions between the coastal protection mechanisms in operation within a section of coast, and also considers interference or synergies that may arise between different parts of the coastline.
The selection and design of medium- and long-term coastal management techniques must take account of changing trends in climate parameters including rainfall, storm intensity and sea levels.
An assessment of provisions for coastal protection, including adaptation for climate change effects, can benefit from active co-ordination with a strategic flood risk assessment for the relevant area, particularly at interfaces between critical infrastructure and potential flood and ponding zones.
For any infrastructure asset that is vulnerable to coastal processes, the development of a stormwater and coastal defence asset register using a GIS (geographical information system) tool can significantly assist long-term asset management and planning for the infrastructure.
This project identified environmentally sustainable approaches to coastal protection, as distinct from traditional ‘hard’ engineering solutions. The project case studies focused on a particular stretch of the east coast of Ireland, but the methodology adopted for evaluating coastal protection techniques, and techniques themselves, are potentially applicable at any coastline.
The coastal protection techniques and evaluation methodology addressed in this project represent a strategy for future-proofing that can help ensure continuity of service and minimise damage and disruption to the rail network due to coastal erosion. The techniques used in this study can be applied elsewhere in order to support long-term asset management and to inform decision making for the prioritisation of maintenance funding. The techniques are adaptable for many types of infrastructure projects worldwide.
The research highlights the importance of climate change in any decisions made by infrastructure rail authorities for future design works to ensure resilient infrastructure.
The research has helped form the basis for developing a strategy for coastal erosion management that includes medium- and long-term erosion control and coastal protection techniques that provide environmentally sustainable solutions for effective protection of coastal infrastructure.