By Georgios Anastasiou (Greece)
In an urban environment, the existence of trees is crucial. The green factor created by trees presence in a city provides a better and healthier environment for people. Trees are present above the earth's surface, but they do exist in the underground too with their roots. Meanwhile, in a city’s underground environment an infrastructure including gas, sewer, electricity and telephone pipes and lines are also present. The coexistence of tree-roots and the city’s underground infrastructure can be in some cases problematic.
In this research, it is studied the possible ways of interaction between tree roots and urban underground infrastructure. The urban underground infrastructure is an obstacle to the tree roots growth when they go looking for a more nutrient or moisture-rich part of the soil. The roots either anchor on smaller obstacles using them to stabilise themselves (winds, snow etc.) or they find even the smallest crack to penetrate them. There are three main types of tree root-systems: (i) the tap-root, (ii) the heart-root and (iii) the flat-root system. After studying existing non-invasive methods, an original method is proposed as a conceptual representation of the tree root-systems. The conceptual representation brings some of the basic parameters that affect the growth of a tree/root. Then this method is implemented in the CityEngine software which is the 3D GIS environment of choice. In this way, the models will be ready to use in Geo-Information Science’s applications. Combining the knowledge of the available literature with original ideas, three tree-root models were designed in CityEngine. The models simulate the main tree root volume and have a growth function that can change each model’s size relatively to the given age value of the tree. The models are then validated to assess their use for the specific tree species found in the Dutch cities. Lastly, a collision detection operation is implemented to the models, so that an intersection with another object is registered. The case study takes place in a Dutch city, thus the trees to be studied are Elm, Oak, Horse Chestnut, Ash, and Plane.
This study is the first step for a discussion, and gives some initial feedback, on how to consider the damage risk of underground infrastructure from the root in the urban environment. This application can potentially be interesting for policy makers, surveyors, and researchers.