Localized Sediment Resuspension (LSR) model: An Approach to Address Spatial Source Heterogeneity in TSS Modeling for CSO Discharges

Modelling pollutant dynamics in Combined Sewer Overflows (CSOs) remains challenging due to complex transport processes and limited high-resolution data. Total Suspended Solids (TSS), key water quality indicator, are influenced by localized hydraulic conditions and sediment characteristics. This study presents the LSR model as a solution to the limitations of existing models, which often assume uniform spatial heterogeneity and particle size distributions. By integrating spatial heterogeneity, localized dynamics, and inter-event heterogeneity, the LSR model aims to enhance the accuracy of TSS predictions. Events with resuspension potential were analyzed using three structures of increasing model heterogeneity. Increasing model heterogeneity improves accuracy, but its benefits depend on data quality. The best performance was achieved using hotspot-specific resuspension with well-calibrated hydraulics and uniform sediment characteristics due to less accurate TSS calibration. Additionally, three hotspot contribution approaches were tested. The results showed that uniform activation imposes artificial uniformity and oversimplifies real spatial dynamics, limiting the model’s ability to capture true resuspension behavior. In contrast, selective hotspot activation led to notable improvements. These findings underscore the importance of accounting for spatial and inter-event heterogeneity in improving TSS predictions and highlight the potential of the LSR model to capture these dynamics and support urban drainage management.