03 Okt 2017

Urban Trees: Green Infrastructure between microclimate improvement and storm risk

Most people are fond of trees and especially inside dense urban environment, they contribute as a large factor to microclimate improvement. They enhance quality of life and thereby the value of estate inside the urban quarter. In these days, many cities have understood that urban trees form a major economic value that cannot easily be replaced once they are gone. Hence, supporting the planting of new trees and protecting the existing ones should be one of the main goals in urban planning and landscape architecture.

With global climate change and the increase of air temperature, it is likely that the occurrence of severe thunderstorm events will rise in the coming years.

The summer storm ELA in the Ruhr-Area in Germany 2014 gave an impressive example, how the destructive forces of wind and rain cannot only destroy significant parts of the urban green infrastructure, but also can stop the daily urban life for several days. So, in order to provide a sustainable urban green planning, we need to ask ourselves not only where would be the best spots for urban trees, but also if they will survive there or if they might turn into infrastructure and health risks.

There are several ways to approach this potential conflict. The first one is the ENVI_MET TreePass that summarizes all relevant environmental parameters for a given tree location. This includes access to wind,sun, soil and water as well as the analysis of average turbulence loads. The second approach is the new ENVI_MET WindRisk analysis (WRA) that is going to be developed in cooperation with the City of Essen, one of the main victims of the ELA 2014 summer storm. The WRA goes down to the tree skeleton of the tree and analyses the potential forces that sum up on the branches and stems in dependency to the trees geometry and its exact location in the urban environment.