Water sensitive urban and building design

Water in cities is increasingly recognised as a valuable resource. About 30% of EU territory and 33% of Europe’s population is affected by water stress during an average year (EEA, 2025). The situation is expected to worsen as climate change is increasing the frequency, magnitude, and impacts of extreme events, including droughts. Managing wastewater, flooding, rain and surface run-off waters should therefore be based on integrated solutions taking the multiple uses and the value of water into account. Water Sensitive Urban Design (WSUD) integrates water cycle management (including rainfall, runoff, drought and evaporation) into the design and planning of cities. Central to WSUD is the integration of natural water systems into urban environments, promoting sustainability and well-being (Tasnia et al., 2025).

WSUD aims to manage urban water as a valuable resource, protecting water quality and ecosystems of receiving waterways and water bodies, and managing the risk of stormwater and flooding. WSUD can be implemented at multiple scales, from single building to neighbourhood up to the whole city level. Two key principles are essential when implementing WSUD: (1) All elements of the water cycle and their interconnections are considered concurrently to achieve an outcome that sustains a healthy natural environment while meeting human needs; (2) consideration of the water cycle is made from the outset, and throughout the design and planning process.  

A comprehensive strategy for WSUD should consider the following technical aspects:

(i) planning for water conservation (optimise water distribution amongst various uses, minimise water demand, investigate wastewater re-use and storm water harvesting opportunities, see also related adaptation options of Water reuse and Water Restrictions and Rationing);

(ii) improving the chemical quality of storm water (including stormwater treatment measures to reduce pollutants);

(iii) integrating water sensitive elements and strategies into urban design, for example through practices such as green roofs, permeable pavements and constructed wetlands.

Institutional aspects such as collaboration with watershed authorities, alternative approaches to community involvement, and ways to drive innovation are equally important and should frame the whole process of WSUD implementation. 

Sustainable Urban Drainage Systems (SUDS) are part of WSUD and refer to structures built to manage surface water runoff, in a way that mimic natural drainage. SUDS often incorporate soil and vegetation in structures that are otherwise usually impermeable (e.g. green rooftops); the uptake and passage through soil and vegetation reduces runoff velocity and improves water quality. Surface permeability in urban areas can be increased by using permeable paving where appropriate (e.g. footpaths, car-parking areas, access roads). Infiltration devices, such as “soakaways”, allow water to be drained directly into the ground, while basins, ponds, and even urban public spaces such as children’s playgrounds can be designed to hold (excess) water when it rains. All these solutions are able to reduce surface run-off, attenuate flood impacts and increase groundwater recharge. Moreover, if these solutions are complemented with the harvesting and use of rainwater for non-potable uses, pressure on drinking water resources can be reduced, meeting water efficiency targets. The WSDU paradigm and SUDS have clear linkages with the concept of nature-based solutions (NbS), Urban Green Infrastructure (see the adaptation option Urban green and blue infrastructure), and Sponge cities, which have recently been highlighted as important adaptation measures in many EU policies and strategies as well as exhaustively studied in EU funded projects.

The local context and type of WSUD planned or implemented defines the key stakeholders to engage. If the design is more focused on a block or at building level, key stakeholders to be involved  are property owners, investors and property managers. If the main issue is about stormwater management solutions as a part of urban planning, collaboration between different organisations from policy sectors (land use, environment, and transportation), experts (e.g. researcherlandowners is needed. The selection of stakeholders also depends on the spatial scalability of the planned system (e.g. biofilter at the street level vs. large-scale stormwater pond). Broader flood risk management initiatives at city level require long-term collaboration among local and regional authorities, and with those stakeholders who implement the plan, as also including land or property owners. On top of that, to enhance public acceptance of different WSUD solutions, the general public, citizens and local residents should be engaged at the early stage of planning and design. Novel funding models such as public-private partnerships require close collaboration with the private sector, especially if they are part of implementation process.

The importance of institutional frameworks (governance and management) for successful and widespread implementation of these measures is considered central. Planning processes require earlier and more intense consultation with different planning authorities.  

An important success factor for the implementation of WSUD by private households is the availability of financial support. Governments can also subsidize investments to improve water management and use in cities. For example, the domestic use of rainwater for non-potable uses in Bremen (Germany) was encouraged by a Federal state investment subsidy.

The New European Bauhaus Facility is a new funding tool that aims to revitalise neighbourhoods by promoting solutions that “are not only sustainable, but also inclusive and beautiful”. Funding opportunities to re-think and re-design urban spaces, also including green elements and water circular models, can be found on the dedicated funding webpage.

European collaboration initiatives like the Partnership Water Sensitive City, established within the Urban Agenda for the EU, is expected to promote WSUD. It envisions a future where European cities become more resilient, sustainable, and climate-adapted by placing water sensitive design at the heart of urban policies. The Partnership is composed of 23 partners representing national and regional authorities, urban authorities, European umbrella organisations, other stakeholders, and the European Commission.

Main enablers include partnership among stakeholders, effective monitoring and valuation systems for implementation process and benefits, knowledge sharing mechanisms and technologies, economic instruments, plans, legal acts and regulations, education and training, open innovation and experimentation, and appropriate planning and design of sustainable solutions.  

Conversely, there are many uncertainties related to the implementation of WSUD that can limit its implementation. They mainly relate to inadequate financial resources, limited space and time availability, institutional fragmentation, lack of knowledge and inadequate regulations. 

Costs

Investments for WSUD may increase total costs of construction, planning and management work, but on the other hand can reduce negative impacts for citizens, buildings and the entire city, and decrease unexpected costs to repair damages caused by extreme weather conditions such as flooding or stormwater run-off. Implementing WSUD for stormwater management instead of traditional sewage systems can lower rainwater fees (that are generally based on the extension of impervious property surface, which directs rainwater into the public sewage system) of private households or block of houses (Rainwater saving and use in households, Bremen).  

Rainwater storage facilities at building level can cost at least EUR 6,000 (Rainwater saving and use in households, Bremen). They can be higher for larger interventions (EUR 17,500 for rainwater storage facility of a climate proof building block, Amsterdam).  

Cost-effectiveness of investments should be estimated in the local context since they depend on local climate and environmental conditions (e.g. precipitation, proportion of paved soil, density of built environment) and economic factors (e.g. prices of water). Total costs also depend on the size, technical complexity and required intensity of maintenance. Recent studies of costs of different nature-based solutions (e.g. green roofs, biofilters, rain gardens etch) have brought some insights on potential costs of WSUD. For example, in Finland the implementation costs of a stormwater pond (size 10 000 m2) varied between EUR 240 000- 600 000 (CITYWATER project). Construction costs of green roofs can significantly vary across  countries and differ based on the roof type, vegetation planted, technical requirements etc. For example, a cost-benefit assessment made by Alves et al., 2020 considered an investment cost (Capital Expenditure - CAPEX) of about EUR 80 /m² and maintenance cost (Operational Expenditure - OPEX) of about EUR 2.33 /m²/year. In Hamburg, the costs range from EUR 40-58 /m². Inn Basel, initial estimates of approximately EUR 100/m² were subsequently revised downward to around EUR 25/m².

Benefits

WSUD reduces stormwater flood risks (area and people flooded) in urban areas. Other benefits include the reduced stress on water resources by decreasing the likelihood of overexploitation of water and increasing water availability. Nature-based solutions in WSUD usually provide multiple benefits by enhancing recreational opportunities, wellbeing, aesthetic values, and biodiversity.

The most relevant EU policies that can trigger the implementation of WSUD are the Water Framework Directive, the Floods directive, and the revised Urban Wastewater Treatment Directive. The last encourages integrated urban wastewater management aiming  to increase synergies with climate change adaptation and actions to restore urban ecosystems. Member States (article 5) shall ensure that integrated local urban wastewater management plans are established for all agglomerations of 100 000 p.e. (population equivalent) and above by 2033. Furthermore, by 2039, integrated urban wastewater management plans should also be put in place for agglomerations between 10 000 p.e. and 100 000 p.e. where storm water overflows or urban runoff pose a risk for the environment or public health. Urban wastewater management plans are reviewed at least every six years after their establishment and updated where necessary.

The EU Nature Restoration Regulation also aligns with WSUD by encouraging the establishment of more nature in cities.

In addition, the Water Resilience Strategy further commits to restore and protect the water cycle and promotes “sponge cities”, integrated with nature-based solutions to absorb and release water in a controlled way.

WSUD is a broad area of practice that includes very heterogeneous adaptation measures with a wide range of technical solutions. Therefore implementation time varies greatly, mainly depending on the scope and the size of the initiative. Very small scale WSUD practices at a single building level can be implemented in few months while large scale implementation that involve a neighbourhood or even an entire city can take several years. 

Practices implemented regardless of the spatial scale (technical solution in a single building or large integrated solutions at the neighbourhood scale) are generally long lasting (> 10-30 years) but they usually require regular maintenance otherwise their capacity can significantly decrease or the system’s function can fail.