Climate change is increasing cities’ exposure to heatwaves, floods and extreme weather events. From stormwater management to cool pavements, this section examines some of the ways in which technologies contribute to resilient and green cities. Cities are rising to the climate change challenge using a combination of engineered solutions and blue-green infrastructure.
Innovation examples
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5. Cities / Urban planning / Innovation examplesFrance’s response to the 2003 European heatwave
Getty Images/© piccayaThe 2003 European heatwave caused more than 15,000 casualties in France. It served as a wake-up call for many cities to take action on reducing climate risks in urban areas. The following year, the country drew up the National Heat Wave Plan built on national forecasting and alert systems. Despite hotter summers since, the death toll has been significantly lowered. In addition to a major effort to issue warning messages in time, the plan includes measures such as cooling rooms at senior centers, replacing tarmac at playgrounds with more heat reflective materials, and mandatory insulation in construction regulation. This reflects a growing awareness of the benefit of an integrated response to risks like heatwaves, compared to stand-alone technologies and projects. Since 2012, French construction standards for new buildings and, to a lesser extent for existing buildings, have included requirements regarding comfort during heatwaves. In Paris, adding parks and green spaces has been another key solution to heatwaves. Urban greening is most effective when green spaces are watered during a heatwave. Doing so increases the cooling effect from evapotranspiration. A simulation was made of the potential effects of some measures introduced in Paris, namely applying new construction standards, behavior change in relation to air-conditioning use, and urban greening. If fully implemented, these measures could potentially reduce night-time temperatures by as much as 4.2°C.[1]
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5. Cities / Urban planning / Innovation examplesThe Qunli stormwater park in China
Getty Images /© chinaface“Sponge City” is a term for green infrastructure approaches that combine methods. Combinations include methods such as permeable paving, bioretention (removing pollutants from stormwater runoff), urban vegetation and rainwater collection. Planned at an urban scale, such nature-based solutions can help mitigate stormwater runoff and flooding, improve water quality and recycle rainwater for on-site use. Many solutions are well suited for low-cost implementation. However, they do require careful coordination, planning and a knowledge of local conditions such as soil status to maximize benefit at the city or community scale. Several cities are experimenting with the “Sponge City” approach. They include San Salvador and a number of cities in China. Notably, the city of Harbin in Northeast China has implemented an integrated urban water management (IUWM) strategy to mitigate serious waterlogging. The strategy included revitalizing a dying wetland in the middle of the city surrounded by roads and large development projects. Ponds and mud flats were created around the wetland. A cost–benefit analysis of the urban construct looked at the likely construction and maintenance fees in relation to air quality improvement, rainwater harvesting and flood-risk reduction. It concluded that, although long-term maintenance of the ponds and mud flats may be costly, the social and environmental impact would be positive due to their flood handling capacity.[1]
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5. Cities / Urban planning / Innovation examplesKuala Lumpur’s Stormwater Management and Road Tunnel (SMART Tunnel)
Getty Images /© olloMalaysia’s SMART Tunnel is a stormwater drainage tunnel built to alleviate flooding in the center of Kuala Lumpur. It stretches for nearly 10 km between two locations where the rivers Klang, Ampang and Gombak meet. This makes it the longest stormwater drainage tunnel in Southeast Asia. The system was built to divert large volumes of water from flood-prone areas via a holding pond, a bypass tunnel and a reservoir to store the water. At the same time, the opportunity was taken to integrate a motorway into the system to relieve traffic congestion at the main city center gateway. To protect drivers, automated flood control gates have been installed at either end of the tunnel, operated by a hydraulic system. Ventilation and escape shafts are also available at 1 km intervals. During the March 3, 2009, Kuala Lumpur flashfloods, the SMART system successfully diverted a total 700,000 m3 of floodwater from the holding pond via the tunnel. This avoided the overflowing of the area around Masjid Jamek LRT station.[1] In 2021, the tunnel claimed a new record by diverting nearly 5 m m3 of floodwater from the Klang River to the reservoir.[2]
Proven technologies
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5. Cities / Urban planning / Proven technologiesBlue-green urban planning framework
Climate-KIC, Imperial College London
Getty Images /© bluejayphotoMany cities lack a holistic approach to nature-based solutions to increase resilience. Instead solutions such as providing shade from the sun are applied in a mono-functional way. The Blue Green System project is a methodology and set of tools developed by researchers at Imperial College London, with the support of Climate KIC. The System helps city planners and developers integrate green space, trees and natural flood management into projects. Researchers now provide expertise through services connected to disseminating the blue-green solutions. Thirteen demo sites have been created in different countries to demonstrate solutions such as urban lakes and bioswales, as well as green roofs equipped with sensors for predicting stormwater collection and thermal insulation benefits. The framework is applicable at building, neighborhood and city-scale and suitable both for new and retrofit developments.
- Contracting type: Service
- Technology level: Medium
- Country of origin: United Kingdom
- Availability: Worldwide
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5. Cities / Urban planning / Proven technologiesStormwater management software
United States Environmental Protection Agency
Getty Images /© Larisa RudenkoThe EPA’s Storm Water Management Model (SWMM) is an open source public software free for use worldwide. It can be used by local, state and national actors for the planning, analysis and design of stormwater and drainage systems. By evaluating gray infrastructure such as pipes and storm drains, this tool can be used to develop stormwater control solutions to reduce urban runoff and discharge. It can also be used to map flood plains and design strategies to avoid sewer overflows. For example, various combinations of green infrastructure (including rain gardens, bioretention cells, green roofs and bioswales) can be modelled to determine their effectiveness in managing runoff.
- Contracting type: Free
- Technology level: Medium
- Country of origin: United States
- Availability: Worldwide
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5. Cities / Urban planning / Proven technologiesUnderground bioretention and water storage
Treebuilders
Photo: © TreeBuildersTreebuilders underground bioretention system serves two functions: bioretention and underground water filtration and water storage. The technology is described as a “submerged rain garden”. It exists of soil-containing modular units to support large tree growth combined with on-site stormwater management through absorption, evapotranspiration, interception and filtration. The underground structure avoids taking up extra space in crowded cities. Instead, enough space is provided underground to allow the tree roots to grow, its absence often preventing urban trees from thriving. The modular units simultaneously treat stormwater runoff at source rather than allowing it to enter sewers untreated.
- Contracting type: Service
- Technology level: Medium
- Country of origin: The Netherlands
- Availability: Worldwide
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5. Cities / Urban planning / Proven technologiesSoakaway crates for stormwater collection
ACO
Getty Images /© CBCK-ChristineSoakaway is a sub-surface drainage technology that manages surface water and stormwater runoff on site. It is essentially a pit with several holes in the ground that collects rainwater before further dispersing into the earth. Filling the holes in the pit with materials such as stones and rubbles slows the infiltration of water into the ground, instead of discharging it immediately to an offsite location such as a sewer. ACO StormBrixx is an example of a plastic geocellular soakaway system for the attenuation and infiltration of water. The design consisting of brick-bonding and cross-bonding is flexible. It can be used across various construction environments either as a standalone solution or part of an integrated sustainable urban drainage (SuDS) scheme.
- Contracting type: For sale
- Technology level: Medium
- Country of origin: United Kingdom
- Availability: Worldwide
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5. Cities / Urban planning / Proven technologiesLarge-scale rainwater catchment system
Aarhus Vand
Getty Images /© San Francisco Chronicle/Hearst Newspapers via Getty Images / ContributorResidents of a new housing estate Nye in Aarhus, Denmark, are using treated rainwater for their washing machines and toilets. The project was carried out by Aarhus Vand, a public utility water company. The technology consists of a system where rainwater collected from roofs is drained into a basin, or artificial lake, together with other rainwater and surface water flows. A water treatment plant located near the basin filters the water to a good standard. From the plant, this water is channeled first into water reservoirs then into homes via a separate piping system for use by washing machines and toilets. By reusing treated rainwater on a larger scale, up to 40 percent of drinking water is saved.
- Contracting type: Service
- Technology level: Medium
- Country of origin: Denmark
- Availability: Denmark
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5. Cities / Urban planning / Proven technologiesRetrofit cool pavement coating
EnduraBlend
Getty Images /© Yung GettyEnduraBlend is a retrofit solution for “hot” pavements. It is in the form of a reflective coating that decreases solar absorption. Reflective treatments for paved surfaces like Endurablend can help reduce heatwave duration and severity. The company’s Pavement Surface Coatings contain special infrared solar reflective pigments that reduce asphalt pavement temperature. The result is a lower heat index, lower energy costs (for cooling in nearby buildings) and better air quality. In addition, Endurablend extends pavement life-time by protecting the asphalt surface from petroleum, salt and de-icing materials, as well as UV degradation. Endurablend has an expected lifespan of 10 years in heavy traffic and extreme weather conditions.
- Contracting type: For sale
- Technology level: Low
- Country of origin: United States
- Availability: Worldwide
Frontier technologies
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5. Cities / Urban planning / Frontier technologiesOpen source flood tracking
Cloud to Street
Photo: © CloudtoStreetCloud to Street’s free Global Flood Database offers an overview of flood exposure around the world. The database is the world’s largest collection of flood maps. It combines 15 years of data on 913 floods with human settlement maps across 169 countries to help scientists, governments and financial institutions prepare better and protect against flood-risk. Through the use of satellites and artificial intelligence, floods can be tracked in near real-time anywhere in the world to insure risk and save lives. Maps can be downloaded from 15 public and private satellites, down to 250 m resolution. The company also offers paid services and claims to have provided support to 28 governments worldwide, including to the Republic of Congo, where floods could quickly be identified to relocate at-risk refugees, secure emergency aid and provide targeted relief.
- Contracting type: Service
- Technology level: High
- Country of origin: United States
- Availability: Worldwide
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5. Cities / Urban planning / Frontier technologiesCool pavements
ePAVE
Photo: © ePAVE LCCDark pavements absorb from 80 to 95 percent of heat. They add to global warming by radiating heat into the atmosphere where it is trapped by the greenhouse effect. Cool paving materials reduce urban temperature and make cities more comfortable during hot weather. ePAVE is a cool pavement product with a patented formula. It is engineered to provide asphalt and concrete surfaces with a layer of protection that also has climate adaptation benefits. The technology consists of a two-component polymer cement composite. The first component is a dry ingredient powder, the second a liquid polymer emulsion resin. The reflective coating is said to mitigate the urban heat island effect by reflecting solar radiation. This lowers surface and ambient air temperatures, while improving air quality.
- Contracting type: For sale
- Technology level: Medium
- Country of origin: United States
- Availability: United States
Horizon technologies
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5. Cities / Urban planning / Horizon technologiesAI-driven satellite solution for green space
Husqvarna
Getty Images /© Darryl FonsekaHusqvarna Urban Green Space Index (HUGSI) is an AI-driven satellite solution focusing on urban green space. The tool measures and analyzes urban green space in selected cities worldwide. It does so by applying computer vision and deep learning techniques to satellite imagery. The aim is to provide objective and continuous quantifications of urban green space and allow cities to track their development and benchmark against global standards. To date, over 250 cities in 60 countries have been ranked according to indicators such as health of urban vegetation, tree coverage and urban green space distribution.
- Contracting type: Service
- Technology level: High
- Country of origin: Sweden
- Availability: Worldwide
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5. Cities / Urban planning / Horizon technologiesPedestrian navigation tool for cool streets
Barcelona Regional Urban Development Agency
Getty Images /© Vera TikhonovaSummers in Barcelona are becoming increasingly hot due to climate change. Cool Walks is an app developed by a public agency in Barcelona that allows pedestrians to choose the shadiest path to where they want to go. By picking the starting point and destination for your walk, as well as the time of day, recommended routes are provided. Using LIDAR, high-resolution models of ground elevation (including trees and buildings) were created. Combined with manually-gathered data, this allows the app to model direct sunlight and shade, and guide pedestrians toward shady sidewalks, drinking fountains or places to shelter. Similar digital tools for helping citizens navigate cities through various climate impacts could become commonplace in the future.
- Contracting type: Free
- Technology level: Medium
- Country of origin: Spain
- Availability: Barcelona
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