A method for evaluating the evolution of clogging: application to the Pampulha Campus infiltration system (Brazil)

In order to evaluate the hydraulic performance of stormwater infiltration trenches, a study was undertaken to assess clogging and its distribution between the bottom and the sides. The method used was based on the calibration of the hydraulic resistance event by event according to Bouwer's model and applied to a demonstration trench in Belo-Horizonte monitored in the framework of the European Project Switch. The calibration was performed by minimizing the distance between measured and modeled infiltration flow rates and by using continuous measurements of rainfall, inflow, water temperature and depth in the trench. The study showed that the methodology and particularly Bouwer's model was able to produce satisfactory results. It revealed a significant clogging evolution within a year, with global resistance increasing by a factor of 9. A significant difference between the bottom and the sides was observed; the bottom being more rapidly prone to clogging. Sudden fluctuations of the hydraulic resistance of the bottom were found that could be explained by very high concentrations of total suspended solids from inflows (about 2,000 mg/L). Clogging of the sides evolves over the time but with a very low rate.