Skip to main content
Nature-Based Flood Relief Scheme

Case Study:

Nature-Based Flood Relief Scheme


Dublin City Council initiated the Environmental Improvement Scheme for Crumlin Village in 2018. This included realignment of footpaths and road resurfacing works, while also taking into consideration road safety, flood risk and amenity issues. The design included the management of surface water runoff in a sustainable way, rather than using a conventional piped system. This approach was taken to meet the requirements of the current City Development Plan and provide resilience to climate change, through implementing a nature-based solution for managing surface water. A softer, greener, ‘engineered’ approach was considered from preliminary design stage, in order to manage surface water at source in accordance with best SuDS practice and to provide flood resilience.


The proposed solution included managing surface water runoff to eliminate discharge to an overloaded combined sewer system, and significantly reducing discharges to the surface water system. This included the construction of localised porous surfaces, filter drains with 'engineered’ filtration zones and tree pits to drain
water from hardstanding areas (Figures 1 and 2). This resulted in the removal of surface water during normal rainfall events from the conventional piped system, through direct discharge to ground and for use by trees/vegetated areas. Excess flows in extreme events are drained to the conventional piped system
through catch pits/silt traps and a filter drain system that provide improved water quality and attenuation.

This sustainable surface water system increased the capacity to deal with extreme rainfall events in an urban setting, whilst achieving greater flood resilience by removing surface water discharges from the combined system that ultimately would discharge to Ringsend Treatment Plant.

The use of SuDS has led to a significant decrease in surface water discharges, thereby creating capacity in the existing network, improving water quality, and enhancing the amenity value for the area through the use of localised permeable surfacing, vegetated areas, filter drains and tree pits, while implementing a design that
aligns with the vision for the area.

Figure 1: Green engineered flood defences – Crumlin Village.

Benefits of Solution

The approach to provide a nature-based, ’engineered’ solution to manage surface water runoff from the preliminary design stage, has produced a cost-effective and climate-resilient design for this scheme. This development at Crumlin village provides better flood management, climate resilience, biodiversity and enhanced landscaped areas, thereby enhancing the area for residents and visitors.

The approach taken for management of surface water runoff for the scheme has removed the need to discharge surface water to the existing combined network through the implementation of this sustainable ‘engineered’ solution. The solution encompassed several sustainable and climate action policies currently being
implemented by Dublin City Council. The benefits from implementing the nature-based solution to
manage surface water runoff include:

- removal of surface water discharges from the public combined system and significantly reducing therequirement to discharge to the surface water system;
- Improved resilience to flooding during extreme rainfall events through use of an ‘engineered’ sustainable response to surface water management;
- improvements to water quality through filtering out pollutants, prior to discharge to ground or to conventional piped systems during extreme rainfall events (and ultimately to rivers and the Ringsend Treatment Plant); and,
- the introduction of tree pits to manage surface water runoff has also enhanced biodiversity and increased the tree canopy for the area, providing shade in times of increased temperatures.

The total catchment area of the scheme was 2,400m². The overall cost for the Environmental Improvement Scheme was €693,663 of which 9% of the costs can be attributed to the implementation of SuDS, thereby providing value for money for this flood resilient solution for managing surface water.

Through public engagement with Dublin City Council Area Office, local councillors and public displays, the scheme had ‘buy in’ from design stage. Feedback from the local community has been positive and indicated that a greater sense of place has been created. The creation of green spaces and benches has enhanced
the ‘sense of place’ for residents and visitors while delivering on the aims of the scheme.

Figure 2: Tree pits for draining surface water.

Project Details:

The construction phase was nine months.
Local authority project contact
Céline Reilly
Executive Manager
Dublin City Council