Application of Ground Penetrating Radar for mapping tree root system architecture and mass density of street trees

The importance of street trees in the urban environment is widely recognised. Nevertheless, the absence of proper urban planning, combined with lack of resources and methodologies for road maintenance, have made the interaction between trees and the urban environment as a priority task to pursue. The uncontrolled development of tree roots can cause extensive damage, such as the cracking and uplifting of pavement and curbs, that could seriously endanger safety of pedestrians, cyclists and drivers. Within this framework, Ground Penetrating Radar (GPR) has already proven its effectiveness for the non-destructive evaluation and monitoring of road pavements. This research aims to demonstrate the potential of GPR in mapping the root system architecture of street trees. To this purpose, a GPR system equipped with a 700 MHz central frequency antenna was used to survey the area around a street tree (natural soil and flexible pavement structure). A multi-stage data processing methodology is proposed to map the tree root system architecture. Moreover, information on the mass density of roots at different depths is also provided. Results have proven the viability of the proposed method for root detection and mapping under road pavements. Analyses of results have also proven the potential of GPR in identifying safety-related occurrences from the interaction between the root system and the existing pavement structure.