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Water Today Title December 5, 2022

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Update 2022/7/12
climate Change

From Sponge City to Micro Water Management On Rooftops

Amsterdam Start-Up RESILIO addresses critical urban challenges related to flooding, heat and water supply, energy consumption and biodiversity

By Suzanne Forcese

RESILIO applied an interdisciplinary approach with public and private stakeholders to repurpose 10,000 sq meters in different neighbourhoods in Amsterdam. The roofs contain smart valves to optimize the water management of the city. In doing so climate risks to biodiversity are reduced.

In The Netherlands, people have always lived with water and are used to getting rid of it as soon as it falls. However, due to climate change, Amsterdam is increasingly facing lengthy periods of heat and drought, causing wood rot and structural building damage as well as heat stress.

Additional space for water is needed so that it can be stored and reused.

In a city that can be “squeezed” when necessary, like a sponge, the blue-green (BG) roof solution is based on this Sponge City concept.

To increase urban resilience to climate change, RESILIO, a Blue-Green Roof infrastructure solution was tested in Amsterdam. The solution reduces runoff after rainfall by retaining precipitation and mitigating heat stress, caused by increased evapotranspiration (the sum of evaporation from the surface and transpiration from plants) and a higher albedo effect (the ability of surfaces to reflect sunlight).

And...in case of drought ...the blue layer protects and aids the survival of the top plant layer.

These ingenious smart roofs in Amsterdam catch rainwater

WATERTODAY learned more about the rooftop revolution from RESILIO’s communications director, Roseanne Nieuwesteeg.

WT: What does RESILIO mean? What is the challenge in Amsterdam that inspired this concept? How much R& D led up to this project.

Nieuwesteeg: RESILIO is an acronym for “Resilience nEtwork of Smart Innovative cLImate-adaptive rOoftops.’

In the last couple of decades, Amsterdam has dealt with larger amounts of rainwater, severe heat stress and decreased biodiversity.

With RESILIO, a project which lasted from November 2018 to April 2022, Amsterdam created a living laboratory of 10,000 square meters of smart-blue-green roofs on existing social housing and privately owned real estate.

WT: Please describe the technology.

Nieuwesteeg: The smart blue-green roofs are equipped with smart sensors and valves. As the sensors measure the water level, the valves respond to the weather forecast and open and close at the right time. To control the valves an ingenious system called Decision Support System (DSS) is used. The system knows exactly how much water a roof can or should store. This is useful when there is going to be heavy rainfall or in times of drought.

WT: How does a Blue-Green Roof Work?

Nieuwesteeg: Different types of vegetation can grow on the roof, such as mosses, sedums, herbs, grasses, ferns, shrubs or a combination. There is a difference between extensive (sedum) and intensive (vegetation) green roofs.

The Roof System, (roof construction) bears the weight of the roof and provides thermal insulation

The planting is rooted in the substrate layer, similar to soil. This layer provides support and nutrition to the plants.

The filter layer prevents particles from the substrate from ending up in the water storage layer and clogging it up. It also ensures an even distribution of the water, which can be absorbed by the plants.

The water retention is an extra drainage layer. This layer consists of a lightweight crate system in which rainwater is stored. Here, an integrated fibre technology has been incorporated, which makes water transportation from the storage to the plants possible.

The water-and root-proof layer protects the underlying roof construction from invading plant roots and prevents leaks.

Seeds from bird droppings, which could grow into roots cannot have that effect with the layer of root-resistant bitumen. 

Then there is also a waterproof bitumen that ensures the water remains on the roof.

10,000 sq m of smart blue-green roofs are realized in Amsterdam. A blue-green roof stores rainwater underneath the layer of plants by using a smart valve. The rainwater is retained during dry periods and discharged when it starts raining

WT: Now that RESILIO has completed this first living lab project, what’s next?

Nieuwesteeg: Smart BG roofs offer a climate adaptation solution which aims to address the impact of extreme rainfall and heat, while simultaneously increasing urban greenery and biodiversity.

However, BG roofs are still at the innovation stage of technical development. More research is needed into the performance of BG roofs on buildings and upscaled to entire neighbourhoods and cities.

WT: A large part of what RESILIO’s next steps is dependent on financing which is dependent on awareness. How are you bringing rooftops down to street level?

Nieuwesteeg: We are involved in numerous participation activities such as information meetings, face-to-face communication, and participation in local events with a BG "Roof Bike” where a working model of the system was installed on a Dutch cargo bike.

We also do creative workshops with children at bookstores.

WT: in the past three years, RESILIO has built up considerable experience in implementing a network of roofs, what conclusions have you come to?

Nieuwesteeg: The RESILIO research yielded important insights into the performance of smart BG roofs. Based on this research and practical insights, we can conclude that a smart grid of BG Roofs can be a meaningful component of a city-wide climate adaptation strategy.

Bring your roof to life!

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