Thesis: Digital twin cities would help sustainably manage public spaces
Currently, many of the mistakes made during the planning and design stages of urban landscaping have to be corrected later through maintenance. However, it would be possible to create a resilient urban space — rich in biodiversity and suitable for people of all ages — from the outset by making greater use of historical data and digital twins of cities, according to a doctoral dissertation defended at TalTech.
"We can't just do poor planning, try to make up for it with good design and construction and then somehow manage the longest phase — maintenance," says landscape architect and newly minted doctoral graduate from Tallinn University of Technology, Kristiina Kupper. Instead, she argues, urban space should be designed to last from the very beginning. In her master's thesis, Kupper introduced the concept of the "green space lifecycle" to support this idea. The term, which encompasses planning, design, construction, maintenance and the management of all these phases, has since been incorporated into the Estonian capital's "Tallinn 2035" strategy.
In her recently defended doctoral dissertation, Kupper further developed this concept. Specifically, she examined how data-driven approaches and digital twin technologies can contribute to the sustainable planning and management of urban public spaces. Kupper says her more than 30 years of experience as Pärnu's city gardener and a landscape architect in Tallinn inspired her to write about her work in the context of an industrial PhD. "There's constant talk about the need to improve public spaces and raise their quality and eventually I came up with an idea of how to actually do that," she explains.
How will the city look in November five years from now?
The challenges facing both Tallinn specifically and Estonia more broadly have been outlined in various strategies. In short, according to Kupper, they include urbanization in Estonia, public health and an aging population and adapting to climate change. "Green areas and habitats are also fragmented, meaning they are not connected into a functioning network," she notes. In Kupper's view, good urban planning should address all these shortcomings, but the decisions must be more rooted in science than they currently are. "I came to the conclusion that data is the key to solving all of these problems more effectively," she says.
Kupper offers a simple example: a tree planned for an urban space. If the planning phase fails to allocate sufficient space for the tree to grow — free from underground utility lines — there's little flexibility left once the project reaches the design stage. "If we want to provide good conditions for a tree, we face a choice: either plant it in inadequate conditions or leave it out altogether. The quality of public space can only be improved if we make an effort at every stage," the landscape architect emphasizes.
On one hand, her dissertation recommends that landscape planning make greater use of longitudinal historical data. As a case study, she examined 150 years' worth of data related to Kaarli puiestee.
Although the boulevard has been widely studied, the data, according to Kupper, is often either descriptive or anecdotal, focusing, for example, on the impact of tunnel construction or the condition of a single tree. "Static tree data, like species and location, doesn't change. But when it comes to deciding whether an avenue needs maintenance or a full renewal, dynamic data is what really matters: how the tree's health has changed over the years," she explains.
On the other hand, Kupper believes city planning should make greater use of future scenarios. This could be achieved through a digital twin of the city — a computer model that includes the entire urban environment, complete with its landscape elements. "You can't experiment with nature in real life, but in a digital twin, we can test out scenarios and make informed decisions," the landscape architect explains. While creating digital twins of buildings is relatively straightforward, modeling trees and the ever-changing natural environment is far more complex.
Even so, digital twins would still improve urban planning, as they allow for better public engagement, Kupper says. People would have a much clearer understanding of how proposed changes might affect their experience of urban space. "When looking at drawings, everyone envisions the city differently. In 3D models, trees are often static too. But with digital twins and dynamic models, we can use virtual reality to show what a space will look like in, say, five years in November or ten years in June," she notes.
According to Kupper, the inanimate elements, like buildings, are now well represented in Tallinn's citywide digital twin. As part of the GreenTwins project, Tallinn also took part in developing dynamic models for trees. The ongoing follow-up project, TreeCity, in which Tallinn is also a partner, aims to develop dynamic models of tree root systems. "This will help preserve existing trees in the future, since the above-ground part depends heavily on the roots. Tallinn is making great strides toward incorporating dynamic greenery into its digital models," Kupper says.
Urban centers for everyone
In her dissertation, Kristiina Kupper examined not only the past and future of urban space but also its present-day design. To do so, she and her co-authors of a related academic article analyzed ten Estonian town centers that were revamped under the "Great Public Space" program: Elva, Kuressaare, Kärdla, Põlva, Rakvere, Rapla, Tõrva, Valga, Viljandi and Võru. According to Kupper, the town center is where people come for services and thus it must be convenient and accessible. "What I found particularly interesting was looking at them through the lens of how well they meet the needs of an aging population," she notes.
Kupper identified strengths and weaknesses in each town center. One key issue she highlighted was paving. "Visually and architecturally, we aim for exciting solutions. But monochrome gray paving isn't a good choice for people with impaired vision," she points out. Older adults also struggle with uneven surfaces, such as cobblestones.
Paving wasn't the only concern. Kupper observed other shortcomings as well, such as a lack of public toilets, too few free outdoor activities for seniors and an insufficient variety of benches. "Benches should be chosen with backrests and armrests to make it easier to get up. We might prefer benches with a simple design, but we need to offer different options," she explains. Directional signage and maps to aid with orientation were also often missing.
In light of her findings, Kupper recommends that urban planners follow the principles of universal design. In other words, city spaces should be designed with the understanding that amenities like benches and toilets are important for people of all ages. She also proposes a solution in her dissertation for maximizing the use of urban space data in the digital realm. "This brings us back to the idea of the green space lifecycle: if we carefully consider our choices during the planning phase and design and build with quality, then maintenance becomes much easier," Kupper says.
Kristiina Kupper defended her dissertation, "Management of Urban Public Spaces: Challenges and Future Directions from a Municipal Perspective," on January 15 at Tallinn University of Technology's Tartu College. Her supervisors were Nele Nutt, senior lecturer at TalTech, and affiliated professor Zenia Kotval. The opponents were Professor Maria Ignatieva from the University of Western Australia and Professor Pat Crawford from South Dakota State University.
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Editor: Marcus Turovski
