Changing climate in the Adriatic region coupled with ever increasing coastal urbanization results in the increase of water related ecological issues. Urban areas are characterized by high levels of surface sealing in the form of buildings and other impermeable surfaces such as streets, sidewalks and parking lots. As water is unable to infiltrate the ground, this leads to fast runoff, which is problematic during the heavy rains, storms and flash floods. Under hot weather conditions with low precipitation, even dry unvegetated land can behave as concrete in terms of heat reflection and lack of water absorption, compounding the problem of runoff from sealed surfaces. Water Sensitive Urban Design (WSUD) is an approach to integrate water cycle management with the built environment through planning and design, to minimize the hydrological impacts of urban development on the surrounding environment. The goal is to lessen the impact of the development on the natural hydrological system in terms of water flow and quality. In its broadest context, WSUD encompasses all aspects of the urban water cycle, including stormwater, water supply, and wastewater management.
The objectives of WSUD are to reduce the negative impacts of buildings on the water balance, maintain or even enhance the water quality, encourage water conservation and maintain water-related environmental and recreational opportunities. WSUD responds to a growing focus on sustainability in urban planning, and WSUD systems are widely recognized by researchers, practitioners and policy-makers as a sustainable way to manage urban water systems in the face of global trends, such as increased urbanization and climate change (Kuller et. al. 2017).
A wide set of management practices can be applied under WSUD, including both structural (green infrastructure systems e.g. rain gardens, wetlands) and non-structural measures (i.e. policies aimed at improving efficiency of water use) (Kuller et. al. 2017). The type of measures implemented depends also on the scale of the project, from buildings to parks to neighbourhoods. Despite the scale, a comprehensive WSUD strategy involves planning for water conservation (optimize water distribution amongst various uses, investigate potable water conservation, wastewater re-use and create storm water harvesting opportunities); improving the quality of storm water (including storm water treatment measures to reduce pollutants); and integration with elements of urban design (Climate-ADAPT, 2016).
WSUD technologies are designed to facilitate the natural processes of stormwater flows, including retention, detention, conveyance, infiltration, evapotranspiration, treatment and harvesting (Kuller et. al. 2017). Many different techniques and combinations of techniques can be used. The overall approach is to reduce hardened, impervious surfaces and accurately design the drainage of urban spaces, in combination with the use of pervious streets, penetrable concrete and water passing pavements. Enhancing the infiltration of storm water reduces runoff into sewer systems and urban spaces, attenuating flood peaks, reducing the urban pollution load in run-off, as well as reducing the risk of damages due to drainage system failure by flooding, while at the same time facilitating groundwater recharge (Climate-ADAPT, 2016).
Surface permeability can be increased by using permeable paving for things such as footpaths, car-parking areas and access roads, thus reducing surface run-off and increasing groundwater recharge. Infiltration systems, including devices such as soakaways, allow water to be drained directly into the ground; basins, ponds/lakes, and urban infrastructure such as public parks can be designed to hold excess water when it rains. Bio-retention, oil and sediment separators, sand filters, screens, sediment basins and swales can help remove contaminants and sedimentation from stormwater runoff. Furthermore, measures to harvest rainwater for non-potable uses can also reduce the pressure on drinking water resources (Climate-ADAPT, 2016).
Sustainable Urban Drainage Systems (SUDS) are an important component of WSUD, which include management practices that make modern urban drainage systems more compatible with the components of the natural water cycle, such as storm surge overflows, soil percolation, and bio-filtration. SUDS are made up of one or more structures built to manage surface water runoff and tend to mimic natural drainage. SUDS often incorporate soil and vegetation in structures that are usually impermeable (e.g. see Green roofs, and green/living walls), as the uptake and passage through soil and vegetation reduces runoff velocity and improves water quality. Examples of WSUD at the building level include rainwater saving and use in households in Bremen, Germany (Climate-ADAPT, 2018), and the green roof strategies in Hamburg, Germany (Climate-ADAPT, 2016) and Milan, Italy (Municipality of Milan, 2019). Parks in Alicante (Burgen, 2019) and Madrid (Climate-ADAPT, 2014), Spain exemplify the use of such facilities to store and process excess stormwater. At the neighbourhood level, Clichy-Batignolles, Paris, France (Mairie de Paris, 2015) is an example of promoting the natural water cycle in a larger context.
Costs and benefits
The costs and benefits of water-sensitive urban and building design measures range significantly depending on the scale of the intervention, as well as the type of technology used. While benefits of grey measures can unfold immediately, those measures based on ecosystem services (e.g. phytoremediation) may require some time for the (constructed) ecosystem to unfold their full capacity of delivering services.
Benefits of successful application of WSUD include the protection of existing natural features and ecological processes; the maintenance of natural hydrologic behaviour of catchments; the protection of the water quality of surface and ground waters; a reduced pressure on the reticulated water supply system; a reduced wastewater discharge to the natural environment; and the integration of water into the landscape to enhance visual, social, cultural and ecological values (Climate-ADAPT, 2016). The integration of water into the urban landscape also has the potential to lessen the Urban Heat Island effect, and thereby improves life and health conditions for local population and tourists, as well as reduce cooling demand (i.e. energy needed for air conditioning). Most efficient results may be obtained when rain water is used for new horizontal and vertical greenery, which will also contribute to improving thermal comfort in buildings, therefore in energy efficiency and in mitigating the climate change. Careful landscape planning may significantly contribute to urban biodiversity, as well as to the market value of the real estate in the relevant zone. This includes multiple benefits to nature and to people living in such areas where there is, for example, the re-naturalization of watercourses that had been closed over or diverted into channels, often vaulted with concrete.
Implementation time and lifetime
Implementation time depends on the scale of the WSUD intervention. For example, a green roof can be installed in a much shorter time than a larger intervention.
Once made, WSUD features have the potential for a long lifetime; at least as long as the technology utilized lasts.
Source for more detailed information
Burgen, Stephen, 2019, The rain in Spain: how an ancient Arabic technique saves Alicante from floods, The Guardian, 15 August 2019, https://www.theguardian.com/cities/2019/aug/15/the-rain-in-spain-how-an-ancient-arabic-technique-saves-alicante-from-floods
Climate-ADAPT, 2014, Case study: The refurbishment of Gomeznarro park in Madrid focused on storm water retention, https://climate-adapt.eea.europa.eu/metadata/case-studies/the-refurbishment-of-gomeznarro-park-in-madrid-focused-on-storm-water-retention
Climate-ADAPT, 2016, Adaptation option: Water sensitive urban and building design, https://climate-adapt.eea.europa.eu/metadata/adaptation-options/water-sensitive-urban-and-building-design
Climate-ADAPT, 2016, Case study: Four pillars to Hamburg’s Green Roof Strategy: financial incentive, dialogue, regulation and science, https://climate-adapt.eea.europa.eu/metadata/case-studies/four-pillars-to-hamburg2019s-green-roof-strategy-financial-incentive-dialogue-regulation-and-science
Climate-ADAPT, 2018, Case study: Rainwater saving and use in households in Bremen, Germany, https://climate-adapt.eea.europa.eu/metadata/case-studies/rainwater-saving-and-use-in-households-bremen
Kuller, Martijn, Peter M. Bach, Diego Ramirez-Lovering and AnaDeletica, 2017, Framing water sensitive urban design as part of the urban form: A critical review of tools for best planning practice, Environmental Modelling & Software, Vol. 96, pp. 265-282 https://www.sciencedirect.com/science/article/abs/pii/S1364815216310623
Municipality of Milan, 2019 , Environment. New resources for green roofs and for the energy requalification of private buildings, Comune di Milano Press Office 14 August 2019, https://www.comune.milano.it/-/ambiente.-nuove-risorse-per-i-tetti-verdi-e-per-la-riqualificazione-energetica-degli-edifici-privati
Marie de Paris, 2015, The Eco-District Clichy-Batignolles: A Reference In Sustainable Urban Development In Paris, https://archive-clichy-batignolles.parisetmetropole-amenagement.fr/sites/default/files/exe_web_cb_dossierpresse-en_2.pdf
AECOM & Arup, 2013, Water Sensitive Urban Design in the UK – Ideas for built environment practitioners, https://www.susdrain.org/files/resources/ciria_guidance/wsud_ideas_book.pdf