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Sustainable Urban Drainage Systems (SuDS)

Sustainable urban drainage systems (SUDS) are a wide category of water interventions to align modern drainage systems with natural water processes. SUDS comprise “a sequence of management practices, control structures, solutions and strategies designed to efficiently and sustainably drain surface water, while minimising pollution and managing the impact on water quality of local water bodies” [1]. 

SUDS can be considered more sustainable than traditional drainage methods mostly due to the co-benefits they can bring to urban areas such as recreational benefits, biodiversity and habitat creation, and carbon storage and sequestration. SUDS are also environmentally beneficial because they cause minimal or no long-term damage. 


The main types of SUDS are the following: 


Hard-drainage flood prevention can be considered as a hybrid nature-based solution (NBS) that focuses on the delivery of additional permeability with respect to traditional engineered approach to water management. It supports water infiltration thus reducing pluvial flood risk in urban areas and improving the quality of water within sewerage systems [2]. 


Grassed swales are shallow, flat bottomed, vegetated open channels designed to convey, treat and often attenuate surface water runoff (Urban GreenUP).  

Grassed swales in Izmir, Turkey. URBAN GreenUP. Source: https://www.urbangreenup.eu/cities/front-runners/izmir.kl#lg=1&slide=17. 


Water retention ponds provide additional capacity to retain storm water continuously. In dry periods, they hold water, providing a water source that can be accessed. They can improve the water quality (e.g., with downstream infiltration). For example, in UNaLab, a retention pond has been built in Vuores, Finland to enable the treatment (retention and sedimentation) of urban runoff from a new housing estate. It complements the existing measures in the Vuores area for enhanced stormwater quality and quantity management. 

Retention pond in Vuores, Finland. UNaLab. Source: https://unalab.eu/en/retention-pond. 


Floodable parks can be designed to control flow rates and decrease flow peaks by storing excess floodwater and releasing it slowly once the risk of flooding has passed. This solution can mitigate potential impacts caused by surface run-off water from rain, flash-floods or from small- and medium-sized watercourses. Other potential benefits are reducing the water flow entering the public sewerage system and delivering amenity and biodiversity benefits (Urban GreenUp). 


Water-retentive pavements, including hard drainage pavements and green parking pavements, are permeable pavements that are commonly used on roads, paths and parking lots. These solutions can help control storm water, reduce stagnation of runoff and surface water, and improve water quality via filtration. 


Constructed wetland is a NBS mostly designed to increase water quality and/or support wastewater treatment, which recreates the removal processes developed in natural wetlands, exploiting complex biochemical, physical, and physiological removal processes (ReNature). 


Rain garden is a bio-retention shallow basin designed to collect, store, filter and treat water runoff. To optimise its functions, it must include a porous soil mixture, native vegetation and some hyperaccumulator plants, capable of phytoremediation (cleaning up contaminants). For example, see the rain garden developed in the Gavoglio Urban Park in Genova (part of the UNaLAB project). 


Most SUDS are widely available on the market, with some variation in technology readiness level depending on the technological and innovation components. 

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