A climate-resilient old town with the Digital Twin Munich

At the beginning of the year, the heat of summer seems forgotten. But in just a few months ago, it will be so hot in many places, not only in Munich's city center, that people will long for green and cool places. In future, it should be possible to reach cool places to stay in the old town, within 150 meters, despite rising temperatures due to climate change. This is according to a report by mahl-gebhard-konzepte, which was commissioned by the Department of Urban Planning and Building Regulations. The major challenge for the planners: Munich's old town is characterized by numerous historic and listed buildings, squares, and streets. This character and attractiveness need to be preserved and go hand in hand with climate adaptation measures.

But where is it particularly hot? Where is the need pressure for action particularly high? Which cooling measures achieve the desired effect? And how do they fit in with the listed structures of the old town ensemble? To answer these questions, employees of the GeodataService in the Department of Communal Services with the IT Department have used, and further developed, the Digital Twin Munich. This makes it possible to use simulations of Munich's urban climate to visualize the consequences of climate change and to make planning tangible even today. This was funded by the Free State of Bavaria as part of the EU-city-center-funding-initiative, which provides European Union funds from the REACT-EU program.

Measures for a climate-resilient old town must be developed in a targeted and individualized manner so that they are effective and fit into the diverse spatial structures. A key aspect in this context: where is it particularly hot in summer and where is the pressure to act particularly high?

To answer this question, GeodataService Munich connected the newly developed urban climate model PALM-4U to the Digital Twin and simulated the urban climate for Munich's city center. The simulation model determines a wide range of data and parameters for different times of day and night, including information on wind currents, air temperatures and the PET index. This represents the perceived temperature. For technical model assumptions and the correct interpretation of the complex simulation results, close cooperation took place with the Department for Climate and Environmental Protection.

„The urban climate simulation with the Digital Twin illustrates the high cooling effect of
greening and unsealing measures. This allows more tailored solutions to be developed so that
climate adaptation is successful for all Munich residents.”
Christine Kugler, City Councillor and Head of the Department for Climate and Environmental Protection, City of Munich

The key results were visualized in different maps for the stakeholders involved and made
available in an interactive web application. This allowed the identified "hot spots" to be taken
into account when selecting so-called focus areas. The experts developed specific proposals
for adaptation measures for these areas.

For the focus area "Hackenplatz with Hackenstraße", the urban climate simulations were deepened. For this purpose, the two-dimensional concepts for adaptation measures, such as new trees, some planting beds, façade greening or a redesign of Hackenplatz, which were created as part of the report "Integration of climate-resilient green and open space structures in Munich's historic old town", were transferred to the three-dimensional Digital Twin. The urban climate simulation was carried out together with Fraunhofer IBP. The result of the simulation in the Digital Twin shows: The measures increase the comfort level during hot weather in the city by significantly lowering the maximum daytime temperature. Night-time temperatures could also be noticeably reduced. It is also clear that tailored measures should be proposed individually for each location in order to achieve the greatest possible cooling effect.

“The Digital Twin is an excellent tool for illustrating the transformation of the city in convincing scenarios and opens up the possibility of taking a realistic look into the future.”
Prof. Dr. (Univ Florence) Elisabeth Merk City Councillor and Head of the Department of Urban Planning and Building Regulations , City of Munich

The 3D visualization was brought to life in close cooperation between employees of the GeodataService Munich, the IT Department and IT@M using the Unity game engine. An application was created which makes it possible to move freely through the focus area from a pedestrian perspective, as in a computer game, and to experience the future ideas for Hackenstraße, Hackenplatz and Brunnstraße today. With the click of a mouse, you can switch between the current situation and the proposal for the redesign. Visualizations of the urban climate simulation can also be added: Hotter and cooler places become visible as well as the effect of the planned measures.

The application enables all those involved to better evaluate the measures through realistic visualizations. Possible conflicts become visible at an early stage and can also be resolved through suitable approaches in interdisciplinary cooperation.

"The example of the climate-resistant old town shows very clearly how fundamentally important the development and provision of innovative IT solutions is for the future of the City of Munich."
Dr. Laura Dornheim City Councillor and CDO, City of Munich

In the simulations and visualizations presented here, the various components of the digital twin interlock perfectly. An essential basis for the simulations and visualizations is the comprehensive database of the digital twin which contains data including urban aerial mapping, street surveys (“Streetview”), the semantic 3D city model and numerous other urban geodata. Simulations are used not only to supplement information on the current situation, but also to measure changes in the context of "what-if scenarios". All stakeholders involved can then work together - on the basis of a uniform and comprehensive database as well as realistic and comprehensible visualizations - to optimize planning and make even more informed decisions.

"High-quality basic data, new simulation models and modern visualizations interlock like gears in the digital twin. This enables us to support the various departments of the city administration and to make Munich fit for the future."
Kristina Frank, City Councillor and Head of the Department of Communal Services, City of Munich

By identifying heat islands with the urban climate simulation, cooling measures can be prioritized and optimized where they are most necessary and effective. The realistic visualizations also allow them to be optimized in terms of urban design. In this way, the digital twin helps to ensure that Munich's residents can continue to enjoy their historic old town in the future - and that on hot days they are no more than 150 meters from the nearest cool spot.

Alexander Mayr,
GeodataService Munich, City of Munich

Sebastian Freller,
GeodataService Munich, City of Munich