Transforming Conventional Seawalls into Marine Habitats: Eco-Engineered Coastal Structures for Philippine Urban Waterfronts
Keywords:
Biodiversity, coastal infrastructure, eco-engineering, living seawalls, Manila Bay, nature-inclusive design, Philippines, urban waterfrontsAbstract
Philippine cities require dependable coastal protection, yet conventional smooth seawalls simplify intertidal habitat and can intensify ecological losses associated with marine urbanization. This integrative literature review examines how eco-engineering can retrofit or redesign vertical coastal structures to retain their safety function while providing habitat. Thirty-one peer-reviewed and institutional sources were synthesized across four themes: ecological effects of shoreline armoring, performance of habitat-complexity interventions, structural and maintenance requirements, and transferability to Philippine urban waterfronts. Evidence consistently favors small-scale additions of pits, crevices, ledges, textured panels, shaded cavities, and water-retaining pools; responses nevertheless vary with tidal elevation, wave exposure, material, pollution, propagule supply, and maintenance. A context-sensitive design is proposed in which the reinforced-concrete wall remains the primary load-bearing system and replaceable habitat panels are zoned vertically, fixed through inspectable corrosion-resistant connections, combined with lower-intertidal water-retaining units, and separated from structurally independent toe protection. Manila Bay is used as the principal application context because flood exposure, subsidence, dense infrastructure, degraded water quality, and large planned coastal investments make ecological co-benefits both valuable and difficult. The review concludes that eco-engineered seawalls are not substitutes for mangroves, tidal flats, setback, or pollution control. They are a pragmatic harm-reduction and habitat-support strategy where hard protection is justified and space is constrained. Philippine pilots should use reference sites, before–after-control–impact monitoring, native-species safeguards, life-cycle maintenance plans, and explicit structural acceptance criteria.
Downloads
References
M. G. Chapman and A. J. Underwood, “Evaluation of ecological engineering of ‘armoured’ shorelines to improve their value as habitat,” J. Exp. Mar. Biol. Ecol., vol. 400, pp. 302–313, 2011.
L. Airoldi and M. W. Beck, “Loss, status and trends for coastal marine habitats of Europe,” Oceanogr. Mar. Biol., vol. 45, pp. 345–405, 2007.
K. A. Dafforn et al., “Marine urbanization: An ecological framework for designing multifunctional artificial structures,” Front. Ecol. Environ., vol. 13, no. 2, pp. 82–90, 2015.
L. B. Firth et al., “Ocean sprawl: Challenges and opportunities for biodiversity management in a changing world,” Oceanogr. Mar. Biol., vol. 54, pp. 193–269, 2016.
F. Bulleri and M. G. Chapman, “The introduction of coastal infrastructure as a driver of change in marine environments,” J. Appl. Ecol., vol. 47, no. 1, pp. 26–35, 2010.
R. Rodolfo and F. Siringan, “Global sea-level rise is recognised, but flooding from anthropogenic land subsidence is ignored around northern Manila Bay, Philippines,” Disasters, vol. 30, no. 1, pp. 118–139, 2006.
G. Herrera-García et al., “Mapping the global threat of land subsidence,” Science, vol. 371, no. 6524, pp. 34–36, 2021.
Asian Development Bank, A Region at Risk: The Human Dimensions of Climate Change in Asia and the Pacific. Manila, Philippines: ADB, 2017.
National Economic and Development Authority, Manila Bay Sustainable Development Master Plan. Pasig City, Philippines: NEDA, 2021.
E. M. A. Strain et al., “Eco-engineering urban infrastructure for marine and coastal biodiversity: Which interventions have the greatest ecological benefit?” J. Appl. Ecol., vol. 55, no. 1, pp. 426–441, 2018.
K. A. Browne and M. G. Chapman, “Ecologically informed engineering reduces loss of intertidal biodiversity on artificial shorelines,” Environ. Sci. Technol., vol. 45, no. 19, pp. 8204–8207, 2011.
E. C. Heery et al., “Identifying the consequences of ocean sprawl for sedimentary habitats,” J. Exp. Mar. Biol. Ecol., vol. 492, pp. 31–48, 2017.
M. G. Chapman and D. J. Blockley, “Engineering novel habitats on urban infrastructure to increase intertidal biodiversity,” Oecologia, vol. 161, pp. 625–635, 2009.
L. H. L. Loke et al., “Area-independent effects of water-retaining features on intertidal biodiversity on eco-engineered seawalls in the tropics,” Front. Mar. Sci., vol. 6, art. 16, 2019.
L. H. L. Loke and P. A. Todd, “Structural complexity and component type increase intertidal biodiversity independently of area,” Ecology, vol. 97, no. 2, pp. 383–393, 2016.
M. A. Vozzo et al., “Ecological effects of habitat complexity vary with intertidal elevation and spatial scale,” J. Appl. Ecol., 2025.
L. B. Firth et al., “Between a rock and a hard place: Environmental and engineering considerations when designing coastal defence structures,” Coastal Eng., vol. 87, pp. 122–135, 2014.
R. L. Morris et al., “Design options, implementation issues and evaluating success of ecologically engineered shorelines,” Oceanogr. Mar. Biol., vol. 56, pp. 169–228, 2018.
I. Perkol-Finkel and R. Sella, “Ecologically active concrete for coastal and marine infrastructure: Innovative matrices and designs,” in From Sea to Shore—Meeting the Challenges of the Sea, London, U.K.: ICE Publishing, 2014, pp. 1139–1149.
M. S. Perkol-Finkel et al., “Ecological enhancement of concrete based coastal and marine infrastructure,” Ecol. Eng., vol. 120, pp. 213–224, 2018.
A. Glasby et al., “Nonindigenous biota on artificial structures: Could habitat creation facilitate biological invasions?” Mar. Biol., vol. 151, pp. 887–895, 2007.
M. A. Vozzo et al., “Making seawalls multifunctional: The positive effects of seeded bivalves and habitat structure on species diversity and filtration,” Mar. Environ. Res., vol. 165, art. 105243, 2021.
R. L. Morris et al., “From grey to green: Efficacy of eco-engineering solutions for nature-based coastal defence,” Glob. Change Biol., vol. 24, no. 5, pp. 1827–1842, 2018.
B. G. Reguero et al., “Comparing the cost effectiveness of nature-based and coastal adaptation: A case study from the Gulf Coast of the United States,” PLoS ONE, vol. 13, no. 4, art. e0192132, 2018.
S. Temmerman et al., “Ecosystem-based coastal defence in the face of global change,” Nature, vol. 504, pp. 79–83, 2013.
M. W. Beck et al., “The global flood protection savings provided by coral reefs,” Nat. Commun., vol. 9, art. 2186, 2018.
Intergovernmental Panel on Climate Change, “Cities, settlements and key infrastructure,” in Climate Change 2022: Impacts, Adaptation and Vulnerability. Cambridge, U.K.: Cambridge Univ. Press, 2022.
United Nations Environment Programme, International Good Practice Principles for Sustainable Infrastructure. Nairobi, Kenya: UNEP, 2021.
Department of Environment and Natural Resources, Operational Plan for the Manila Bay Coastal Strategy 2017–2022. Quezon City, Philippines: DENR, 2017.
National Climate Change Commission, National Climate Change Action Plan 2011–2028. Manila, Philippines: Climate Change Commission, 2011.
L. Airoldi et al., “An ecological perspective on the deployment and design of low-crested and other hard coastal defence structures,” Coastal Eng., vol. 52, no. 10–11, pp. 1073–1087, 2005.
Published
How to Cite
Issue
Section
Categories
Copyright (c) 2026 Zuraida Julhiji Bara, Al-Rashiff Hamjilani Mastul , Muhammad Hasnain Khan, Nazia Ehsan
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
