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Re-thinking the construction of the coastal edge

Helen McFadden


One Good Idea

Saltmarshes are complex wetland ecosystems which perform a vital role in attenuating wave action, sequestering carbon, and buffering the coastal edge. Human-instigated overgrazing and climate change have accelerated the depletion of Ireland's wetlands. But by carefully studying and adapting our historic coastal infrastructure, we can work with natural processes to preserve these crucial landscapes.

Timescape: saltmarsh – studies into saltmarsh evolution. Drawing: author

Sea level rise is surpassing sediment building or ‘accretion’ capacity and saltmarshes are ‘drowning’. When this happens, saltmarshes become mudflats, before disappearing beneath waters of expanding bays. The weight and force of the sea then breaks the sub-surface, releasing millions of tonnes of sequestered carbon into the atmosphere.

The immediate presence of the Atlantic Ocean is felt on any exposed edge of Ireland’s 7,678km coastline [1] where sea winds force their way many kilometres inland.

Physical systems acting on the geology of the western seaboard – from Malin Head, Co. Donegal to Bandon Estuary, Co. Cork – have created indentations which account for approximately 75% of Ireland’s coastline. These western indentations hold 203 of our 250 saltmarshes [2]. A saltmarsh is a low-lying distinct ecosystem in the upper coastal intertidal zone that is regularly flooded and drained by salt water carried in by tides.

Approximately half of Ireland’s salt marshes occur on the north-west quadrant of the island, from Malin Head to Galway Bay. Along this stretch, counties Mayo and Galway share the most indented coastline, with ninety-one saltmarshes.

Drone shot of Mulranny seascape showing causeway and saltmarsh to foreground. Image courtesy of Mulranny Park Hotel

Many of these saltmarshes are on mud or sand, but almost a third are on peat. This is highly unusual, both nationally and internationally. Examination of these peat substrates – usually two metres deep and often embedded with tree stumps – suggests these landscapes were originally freshwater-fed blanket bogs fed, but rising sea levels approximately 2000 years ago altered their composition, creating saltmarshes. These wetlands are constantly being authored by myriad forces: physical, cultural, ecological, geomorphological, technological, and political. They are dynamic landscapes, always evolving to become something else.

In a thriving saltmarsh, sediment carried in by the tide becomes trapped by grassy swards and peat soils accumulate as plants decay, allowing the saltmarsh to rise in tandem with sea levels while absorbing tides, attenuating waves, and buffering the coastal edge. This process supports a carbon sequestration rate of 218 g/m2 per year (In comparison, a forest sequesters 4 g/m2 per year) [3].

Recently, however, saltmarshes have become anthropogenic landscapes. Humans have adopted the role of time and two resultant accelerated changes are at work: overgrazing is causing saltmarshes to sink, and climate change is causing the tide to rise. When we thoughtlessly speed up and slow down natural processes, the effects cascade through time.

Today, sea level rise is surpassing sediment building or ‘accretion’ capacity, and saltmarshes are ‘drowning’. When this happens, grassy swards die, habitats disappear, wetlands holding 40% of the world’s ecosystems tumble, and saltmarshes become mudflats, before disappearing beneath waters of expanding bays. The weight and force of the sea then breaks the sub-surface, releasing millions of tonnes of sequestered carbon into the atmosphere.

Studies show Ireland has already lost 75% of its coastal wetlands [4] and we can lose no more. The saltmarshes come closer to vanishing with each tidal wash. This is a time of unprecedented change and urgency. Taking the view that problems get the solution they deserve, according to the terms by which they are created as problems in the first place, humans must repair what we have damaged and intervention is required. However, we must move away from our historic tactics. To quote architect and cultural geographer Dr. Anna Ryan Moloney, ‘when we see change happening, our language and actions tend to emerge from engineering. We try to “protect” our land and use “armour” to “defend” ourselves from the sea’ [5].

The Anthropocene demands a freshness of seeing and new ways of working. If we continue to adopt the role of time and if speeding up and slowing down landscape processes is a design challenge of our time, we need a structure through which theory and practice directly respond to each other. Interdisciplinary research should guide design-thinking when intervening in physical and cultural landscapes, or what sociologist and academic Barbara Adam calls ‘timescapes’ [6].

I am developing this theoretical and pragmatic structure while studying and working with the community in Mulranny – a historically, geographically and culturally significant village located on an isthmus between Clew Bay and Blacksod Bay in County Mayo. As a pilot Decarbonising Zone [7], Mulranny must reduce its carbon emissions by 51% before 2030.

Map of Mulranny Seascape. Drawing: author

Analogous to many coastal towns and villages, Mulranny’s coast has become culturally and physically estranged. Its saltmarshes, sand dunes and machair are depleting, and its pumphouse, causeway, bridges and pier have fragmented through neglect. Both as independent pieces and as a collective system, the wetlands and the associated infrastructural assembly have been pushed out of sync by anthropological forces.

However, there is still time for innovation. As a first step, I conducted a site-specific M.Arch. thesis which examined how Mulranny’s historic coastal infrastructure could be used to help natural processes in the wetlands meet decarbonisation objectives for the future. This ‘one good idea’ was explored by mapping, modelling, drawing and photographing the relationship between the seascape and technical infrastructural details, which contain embedded ideas from generations within the community and thus represent ‘material culture’ [8].This approach sought to balance Mulranny’s cultural and physical context to help the community meet its objective of creating a thriving biosphere for future generations to build on.

Satellite View of Mulranny. Image: Google Earth

The proposition saw conservation interventions, guided by local ancestral constructive-logic, intended to attune the existing coastal infrastructure to today’s environment. For example, extending the pier landwards to protect a drumlin from tidal undercutting; raising the causeway level above spring tide; and fitting cross-drains to prevent saltmarshes from being flooded. Proposals at the bridges included flap sluice gates which mediate between, and respond to, the weight and force of the sea and river on either side, while mixing freshwater and seawater to form brackish water for the saltmarshes to thrive on.

These protection measures represent a starting point for more work to be done. There will be no ‘one-size fits all’ ­solution to every coastal challenge presented, as all landscapes, communities and built environments require their own site-specific approach. However, lessons learned from this thesis can be carried forward.

The protection measures demonstrate that when coastal challenges arise, rather than building imposing seawalls that stop the sea from entering the wetlands, or standing back and hoping natural processes repair human damage, we need instead to consider alternative protection measures which, in performing their function, could balance the cultural and physical context to ‘provide new spatial forms and experiences that combine use with beauty in ways paralleled by the historic lighthouse, harbour, pier, and promenade’ [9].

1:200 model of Clew Bay coastline from Mulranny to Newport. Model: author

Historic coastal infrastructure can be adapted to help natural processes in the wetlands meet decarbonisation objectives for the future.

One Good Idea is a series of articles which focuses on the simple, concise discussion of a complex spatial issue. Each piece is presented as a starting point towards a topic that the author believes should be part of broader public discourse. For all enquiries and potential contributors, please contact

One Good Idea is supported by the Arts Council through the Architecture Project Award Round 2 2022


1. R.J.N. Devoy, ‘Coastal vulnerability and the implications of sea level rise for Ireland’. Journal of Coastal Research24, 2008, pp. 325‐341. *The full length of Ireland’s coastline is disputed. Devoy’s 7,678km is used in SAC reports from the NPWS and this piece is written accordingly.

2. T.G.F. Curtis and M.J.S. Skeffington, ‘The SaltMarshes of Ireland: An Inventory and Account of Their Geographical Variation’, Biology and Environment: Proceedings of the Royal Irish Academy, 98B (2),1998, pp.87–104. Available at:, accessed 18 October 2023.

3. E. Trégarot, M. Andriamahefazafy and C. Cornet,  ‘Salt Marshes to Fight Climate Change’, Macobios, 2022, Available at:, Accessed 18 October 2023.

4. K. O’Sullivan, ‘Ireland Worst in World for Wetland Depletion over Last 3 Centuries, Global Studies Finds’, The Irish Times, 2023, Available at:, accessed 18 October 2023.

5. A. Ryan Moloney, ‘Buildings at the Coast: An Architect's Viewpoint’, in The Coastal Atlas of Ireland, R. Devoy, V. Cummins, B. Brunt, and S. Kandrot, Cork, Cork University Press, 2021, p. 760.

6. B. Adam, Timescapes of Modernity, London,Routledge, 1998, p. 54. ‘Timescapes combine natural and cultural activities into a unified whole. It is inclusive; it gathers up sources of knowledge from both material and immaterial, visible and invisible sources. Such transcendence of dualistic approaches becomes crucial for understanding a world of globalised local human activity that creates holes in the ozone layer, changes the level of CO2 in the atmosphere…’

7. Circular Letter LGSM01-2021 from the Department of Housing, Local Government and Heritage, dated 10 February 2021, requires each local authority to identify a pilot ‘Decarbonising Zone’. ‘A Decarbonising Zone (DZ) is a spatial area identified by the local authority, in which a range of climate mitigation, adaptation and biodiversity measures and action owners are identified to address local low carbon energy, greenhouse gas emissions and climate needs to contribute to national climate action targets.’

8. H. Glassie, Material Culture, Bloomington, Indiana University Press, 1999, p. 41 ‘Material culture is culture made material; it is the inner wit at work in the world’.

9. A. Ryan Moloney, ‘Buildings at the Coast: An Architect's Viewpoint’, in The Coastal Atlas of Ireland, R. Devoy, V. Cummins, B. Brunt, and S. Kandrot, Cork, Cork University Press, 2021, p. 760.


Helen McFadden

Helen McFadden is a PhD Researcher and Sustainability Scholar at the University of Limerick, focused on “Re-thinking the Construction of the Coastal Edge in the Face of Climate Change” (Supervised by Dr. Anna Ryan Moloney, Dr. Declan Phillips, Dr. Eimear Tynan and Dr. Steve Larkin). She holds an M.Arch. from SABE TU Dublin and follows interests in landscape, culture, climate, and construction through drawing, photography, and writing.


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