Modeling the Effect of High Soil Moisture on the Wind Resistance of Urban Trees

Abstract

In urban areas, typhoons frequently cause the tilting and uprooting of trees, resulting in damage to city infrastructure. During periods of intense rainfall, at shallow soil depths, soil water content is typically high, reducing the anchoring resistance of tree roots in the soil. Tree root systems play an important role in providing anchoring resistance against severe winds during typhoons. In this study, we examined the influence of high soil saturation on the turning resistance of trees by conducting winching tests on three tree species found in urban areas. In highly saturated soils, the maximum resisting moment of camphor trees (Cinnamomum camphora (L.) J. Presl.) is 35–50% lower than in soils with low saturation levels. A tree’s maximum resisting moment (TMmax) exhibits a linearly positive relationship with its diameter at breast height (DBH) in near-saturated soil conditions. The ratio of TMmax values to DBH in near-saturated soils is noticeably lower than in low-moisture soils. Our research establishes a relationship between the DBH of trees and the strength of the wind that they can resist during typhoons, as measured on the Beaufort scale.