Conference Agenda

Tree pits are an essential component of Blue-Green Infrastructure, balancing stormwater management, urban cooling, and biodiversity. However, their design must consider both drainage efficiency and tree health, as excessive water retention can lead to waterlogging, while insufficient retention increases drought stress. Existing models either require complex parameterization or lack the ability to predict both saturated and unsaturated conditions simultaneously. This study presents a conceptual tree pit model integrated into the EPA SWMM framework, enabling long-term simulations of waterlogging and water stress probabilities. The model introduces a four-layer approach, incorporating a surface, soil, tree, and storage layer, and applies a modified groundwater model and water stress response model to predict plant-available water and waterlogging risks. A case study in Melbourne, Australia, using 18 months of water level data from nine tree pits, validates the model’s performance. Nash-Sutcliffe Efficiency (NSE) shows reasonable predictive accuracy. The results suggest that tree presence introduces additional processes not yet included in the model. Despite this, the model provides a valuable tool for optimizing tree pit designs, supporting urban water management strategies, and reducing the frequency of extreme water conditions for urban trees.