A dimensionless procedure for the design of infiltration trenches

In recent decades, best management practices in stormwater management have been widely adopted in an attempt to mitigate problems connected with the growth in runoff flow rates and volumes; these successful, innovative, and sustainable approaches feature distributed installation of storage, vegetated, and infiltration systems in catchment areas. In particular, infiltration systems, which are generally implemented in soils with medium or high infiltration capacity, where their runoff attenuation performance is significant, encompass infiltration trenches (i.e., linear excavations built to store a certain quantity of the surface runoff volume, and slowly release it into the surrounding subsoil during and after rain events). This article describes a procedure for the design of infiltration trenches in which the upstream catchment area is represented through a kinematic model with a linear area-time curve and the balance of incoming and outgoing flow rates and stored water volumes is used to represent the trench. The outgoing flow rates infiltrating the surrounding soil during a rain event are calculated by means of a constant infiltration capacity equal to the saturation hydraulic conductivity of the soil. The procedure exploits a dimensionless approach, and dimensionless graphs that are thereby obtained can be easily used for the design.