The Value of Rigorous Science for Green Infrastructure
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Stormwater retention testing. Photo courtesy Green Roof Diagnostics
“We Don’t Need Data”
“We don’t need data and research. I do it by gut feeling, and that has been enough for the past decades”. I was frankly quite surprised when I kept hearing statements like these when approaching green roof industry members. To me, data is the foundation for everything, the basis upon which sound decisions are made, and something particularly of importance now as our world is changing on so many levels ranging from climate to urbanization.
I was new to green roofs, but I worked for almost a decade with nutrient cycle modeling in aquatic systems. I have a Ph.D., a postdoc, and plenty of field sampling experience on over 35 marine and land expeditions. The data we produced was later used to help guide the Baltic governments towards best practices to deal with Baltic Sea eutrophication and algal blooms.
Interestingly, most people’s prior ‘gut feelings’ about my Ph.D. topic told a diametrically different story to what the data later showed. Gut feelings would have led us down the wrong path, starting with bad political decisions and ending with an ecosystem in even more distress. The data gave us a compass to support political decisions and incite effective action. Good data was key.
Shortly after I began working with green roofs, I also met with some pioneering thinkers such as Charlie Miller and Elizabeth Fassman-Beck and many, many more who inspired me profoundly and excited me about the science that is green roofs. Now, several years later, I could not wish to work in another field. I simply love this work!
The weather station mounted on the roof of the Green Roof Diagnostics rain laboratory. Photo courtesy Green Roof Diagnostics
Working with policymakers in Europe, we often encounter issues with very high groundwater tables that allow for little percolation. This has been a particular problem for several of our warehouse projects where huge roof areas, high groundwater tables, and at-grade space constraints restrict the use of traditional stormwater solutions. For these projects, data-driven green roof design with stormwater models opened up opportunities to manage all stormwater on the roof. Firstly, the best-performing retention capacity was determined through the modeling of a range of green roof profiles. The second step was to model the outflow rates of a 100-year design storm and ensuring that the maximum allowable outflow rate of 10L/s/Ha was met. Data had already given us the information that a traditional green roof profile could not fulfill the requirements of step 2, which is why only detention (delay)-types of green roofs can be considered for acceptable stormwater delay.
Our Future World
Our world is rapidly changing. Currently, about 56 percent of the world’s population lives in urban areas, and this number is expected to increase to 66 percent by 2050. At the same time, our climate is changing bringing with it increasingly extreme weather such as intense storms, hail, drought, and extreme heat.
These changes bring with them significant challenges, especially for urban areas. Many of the challenges result from a reduction in plant cover in favor of materials such as stone or asphalt. Most of us know the details around this, and it is generally a depressing read. However, this article intends not to spread doom and gloom but to celebrate the innovation that is our best chance in managing our urban climate. Just take a look at the Netherlands and the fantastic work on flooding protection and stormwater engineering that stems from this small country. Admittedly, the pressure on The Netherlands to perform well in this area is exceptionally high as 26 percent of its surface is below sea level, and failure would result in disaster. But out of this pressing need comes great innovation, and as our metropolitan areas are increasingly in need, innovation is already sprouting.
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Carefully collected and modeled data on green roofs have led to the development of a range of different types of vegetated roofs that are able to delay (detain) the outflow of water in a similar way to a standard (outdated) concrete stormwater cistern or tank. Suddenly, crowded cities with little at- and below-grade space can manage stormwater fully on the rooftops using green and natural solutions that also bring other benefits such as cooling and biodiversity and much more. Without the data collected and the models made, the solutions would never have achieved the permitting required for stormwater tools needed to meet a set maximum allowable outflow rate during a specified design storm such as 5L/s/Ha during a 60min, 70mm, Type II storm.
We are slowly reaching a point in many countries and cities where doing nothing about climate change is starting to cost more financially than the investment needed for the change. One example from my location, Germany, is the costs due to hail and flooding damage which are increasing all over the country, creating financial challenges to both municipalities and individuals. Insurance companies in some European countries have started to reduce real estate premiums when installing some types of green infrastructure due to the increased protection it can provide the property. One example is the insurance company Interpolis that has set up collective procurement funds to lower the cost of green roofs. The rationale is that green roofs can reduce storm damage, leading to reduced damage claims.
Video: TED Talk by the excellent landscape architect Kotchakorn Voraakhom developed a massive park in Bangkok that can hold a million gallons of rainwater, calling for more climate change solutions that connect cities back to nature.
Economically sound nature-based projects involving multiple forms of green infrastructure are popping up all over the globe. One of them is in Augustenborg in Sweden, a desolate settlement that turned into a prosperous area using green infrastructure already 30 years ago! Another great example is the Chulalongkorn University Centenary Park in Bangkok which literally saved the city from sinking. To create this 12 acre (4.8Ha) park in central Bangkok, thorough stormwater modeling was carried out, taking future climate scenarios into account. This meticulous collection of data and subsequent analysis prevented severe ecologic and economic damage to a city with 10.7 million inhabitants. This is the true power of green nature-based infrastructure and modeling.
Grey to Green Transition
Green Roof Diagnostics (GRD) is an independent research institute that focuses on measuring and modeling green roof retention and detention. It has been a fascinating journey during which we had to reassess many of our assumptions (gut feelings) of what we thought green roofs could deliver and what they could not deliver. In the process, we have discovered a few new capacities. Furthermore, we have also made an effort to make our data accessible for end-users by developing several web-based tools. Thus far, we have changed the perspective of several large international green roof companies by having them look at and understand this new data, which is telling many stories and is revealing many opportunities.
The rain simulator in which anything from a drizzle to downpours can be simulated. Every drop is accounted for including potential sheet flow and overspill. Photo courtesy Green Roof Diagnostics
For the gray-to-green transition to happen, we need decisions based on reliable data and science. This can be demonstrated by the evapotranspiration model (ET-model) Green Roof Diagnostics (GRD) built that showcases huge differences in roof performance between cities within Germany, within the US, and even within the small, but oh, so mighty, Holland (I am a Holland-fan after all!). Many of our clients were surprised and almost shocked when they played around with the data in the modeler.
The ET modeler is based on 20 years of stochastic weather data and collected retention data. It models plant stress, irrigation needs and will also shortly include future climate models to assess how roof maintenance and requirements will change over the lifespan of the roof. The modeler aims to ensure that the most optimum roof profile and plant palette is chosen for a specific climate.
Everyone, and I mean literally, everyone, is depending on that our green infrastructure solutions work and that they will not fail when they are needed the most. Failure can lead to reputation damage and a slowing down of the gray-to-green transition process, which will hurt us on all levels ranging from society to environment and economics. Therefore, thorough and well-conducted research into these critical green technologies is vital. Many green roofs are built the same way today, as they were 20 years ago, and this is a stark contrast to other industries with more data-driven progress. The one-size-fits-all green roof is old news, and the diversification of the green roof sector is promising as a green roof needs to be designed with a specific climate in mind.
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We also need to design green infrastructure with the future volatile climate in mind and make predictions on performance and design in a future world. Published data show that the design storms we are currently using might be outdated as they are based on past years. GRD is updating the evapotranspiration modeler (ET-modeler) to include modeled storms for future scenarios. What does a 100-year storm look like in 10 years? In 50 years? Data indicate that this storm may, in many places, be noticeably different than the currently used one.
In addition, the new data that has been generated on water management indicates that the standards currently used to measure such seemingly simple things as retention and outflow delay (detention) should be re-assessed to make sure they are accurate. It simply is not enough to rely on methods that were, at best, a ballpark estimate 30 years ago.
The green infrastructure industry has an incredible responsibility to provide the best possible green solutions for the 66 percent of the world’s population that will live in urban areas by 2050. We can only get there through excellent research and rigorous science, as well as close collaborations with civil engineers. Much of the resistance in the gray-to-green conversion, at least in the US, is due to a miscommunication between civil engineers and the green roof industry. Civils speak the language of data, and we need to supply that.
We have tremendous opportunities ahead covering all pillars of sustainability: ecology, society, and economy. To capture these, we need reliable data to make better data-based decisions for our rapidly changing future world.
Dr. Anna Zakrisson is a Swedish biologist and VP of European Affairs for Green Roof Diagnostics. She has studied and carried out research in plant sciences and microbial ecology at several renowned international institutions, including Cambridge University, UK, Max-Planck Institute, Germany, and Stockholm University, Sweden. Since 2018, she has worked as a consultant for green infrastructure and is currently based in Berlin, Germany.
View the Green Roof Diagnostics Evapotranspiration Modeler
