Resilience of the city thanks to a water-sensitive urban design



The average global temperature last year rose 1.2 degrees Celsius from pre-industrial levels, and experts predict this decade will be the hottest on record.

If this trend continues, it will not only lead to sea level rise, but also more severe and frequent storms.

Mitigating this climate trend to avoid the tipping point of a 1.5 degree temperature rise will require a global, drastic and rapid change in our economic consumption and industrial systems, especially in developed countries, which have been responsible. historical programs. Meanwhile, developing countries, which are most vulnerable to the impacts of climate change, will need to develop adaptation strategies.

Following on from our article last month, we ask architect and environmental planner Mari Arias, and consultant for JLPD, to share her perspective on climate resilience through water-sensitive urban design, on the basis of his postgraduate research. The subject is topical and coincides with the UN summit on climate change COP 26.

Vulnerabilities of disasters, hazards

Recovery and resilience have become a major concern given climate change and the higher frequency of natural and man-made hazards. Flood damage can cause significant development delays that can last for several years.

Urban resilience has become a major consideration in the planning and development of new cities. Urban resilience is “the capacity of an urban system… to maintain or quickly return to the desired functions in the face of a disturbance”. Cities are exposed to accumulated stresses and sudden shocks, which can lead to social disruption, physical collapse or economic deprivation. The need to ensure the capacity of cities to adapt to change and to rapidly transform their urban systems to ensure sufficient adaptive capacity comes into play in urban development.

Stormwater management strategies, opportunities

Water in cities appears in many different forms, such as sewage and gray water, potable water, runoff which must be drained from hard surfaces to minimize flooding, natural water bodies and artificial elements in the public sphere.

However, it is remarkable that the built state of urban areas does not recognize the natural water cycle: precipitation, infiltration, surface runoff and evaporation. The constant increase in population and built-up areas, especially in urbanized cities, often results in an increase in impermeable surfaces leaving less room for water to seep into the ground.

Water Sensitive Urban Design (WSUD) combines water management, urban design and landscape planning to achieve sustainable and resilient stormwater management in cities. Its main objectives are to protect water quality through filtration and retention methods; reduce stormwater runoff and peak flows by reducing impervious surfaces, as well as local retention and retention measures; and integrate stormwater management into landscaping using multiple corridors, which contribute to visual and recreational enjoyment.


It also aims to consider the water cycle throughout the design and planning of these water management solutions to further improve local character, community and quality of life.

WSUD methodologies and strategies are grouped according to their function: water use, treatment, retention and infiltration, transport and evapotranspiration. These strategies aim to conserve water resources by recycling rainwater, recharging groundwater and facilitating the reduction of flooding and stormwater runoff to downstream areas by increasing the permeable surfaces where water can be. temporarily stored, and possibly routed to drains and canals.

WSUD has been used as an emerging urban development approach for some Asian cities.

A notable example is the Cheonggyecheon Stream in Seoul, South Korea, a restored 11 km stream in the middle of the city that was once topped by a highway. The project has shown an improvement in its recreational value by providing publicly accessible equipment for residents and tourists. By using the presence and natural process of water, it has reduced the heat island effect, with the stream acting as a cooling mechanism facilitating thermal comfort while managing stormwater runoff. .

A similar concept was adopted in the design of Tianjin Culture Park in China. Designed by Ramboll Studio Dreiseitl, the landscaping concept of the 90 ha open urban space aims to provide stormwater mitigation strategies and increase outdoor comfort for pedestrians. Solutions include the creation of a rainwater harvesting system across the 10 ha lake, which can accommodate a 100-year flood. Retention trenches have been built in the park, making it possible to gradually feed rainwater into the lake thanks to cleaning biotopes that treat runoff water.

The Philippines, for its part, has yet to fully integrate water-sensitive urban design into the overall design of their cities. There are attempts to incorporate such concepts into plans and translate them into reality, but with the ever increasing price of real estate and the clamor for space in cities, public amenities and open spaces are often lacking. neglected.

The recent storm surges in the country testify to the critical importance of stormwater management in the overall function of cities. There is a need to reassess the way we plan and design our cities to ensure the resilience and continued functioning of our urban systems.

The columnist is the founder and director of JLPD, a real estate planning and development consulting firm.

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