Solids dynamics in gully pots

Abstract

Runoff entering urban drainage systems contains suspended solids, which carry pollutants and may cause blockages in downstream parts of the system (for example infiltration facilities). Suspended solids inflow should, therefore, preferably be controlled by solids removal at gully pots. This paper presents the results of lab experiments on the solids accumulation in gully pots in a scale 1:1 setup. The accumulation process is initially dominated by settling in the gully pot. When a substantial sediment bed is created, the bed starts to interact with the flow, the removal efficiency of solids decreases, and the bed eventually reaches an equilibrium level. The effects of the discharge, sediment size, and geometry on these processes are assessed. The accumulation rate and equilibrium bed level are strongly affected by the flow pattern which is influenced by the combination of the position the jets impinge on the water and the gully pot’s outlet position.