Using ground penetrating radar to locate and categorise tree roots under urban pavements

Street trees are commonly associated with pavement cracking and lifting, resulting in costly repair of the pavement and/or removal of the affected tree/s. This study used Ground Penetrating Radar (GPR) to evaluate the effectiveness of three different prototype permeable pavement designs in reducing pavement damage caused by street tree roots (Melaleuca quinquenervia). Initial tests conducted in a simulated test environment were then replicated in the field to examine the performance of the GPR. The initial test results were positive and indicated that this technique could be used to reliably determine tree root size and depth under pavements with minimal error. Positive root identification results were recorded for all three prototype pavements. The accuracy of the GPR results was found to vary according to soil type, depth of aggregate sub-base, and water mass contained within both the soil, and the buried objects during the calibration process. The three-dimensional nature (overlapping) of genuine tree roots also affected the detection accuracy of the GPR in the field. The study has shown that GPR may play an important role in tree root identification in future, and improve pre-emptive trip hazard reduction management. Increasing permeable pavement sub-base depths may also lead to less pavement damage by tree roots thereby preventing future trip hazards and avoiding costly repairs.