Sediment Morphology and the Flow Velocity Field in a Gully Pot: An Experimental Study

Abstract

Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and combined sewer overflows (CSOs) of solids and associated pollutants. To reduce these impacts, gully pots, the entry points of the drainage system, are typically equipped with a sand trap, which acts as a small settling tank to remove suspended solids. This study presents data obtained using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurements in a scale 1:1 gully to quantify the relation between parameters such as the gully pot geometry, discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes. The results show that the dynamics of the morphology of the sediment bed influences the flow pattern and the removal efficiency in a significant manner, prohibiting the conceptualization of a gully pot as a completely mixed reactor. Resuspension is initiated by the combination of both high turbulent fluctuations and high mean flow, which is present when a substantial bed level is present. In case of low bed levels, the overlaying water protects the sediment bed from erosion.

Editorial—Physical Modelling in Hydraulics Engineering

“…Furthermore, contributions in the field of coastal structures and port engineering [14,15], offshore structures [16], and the environmental design of brine discharges [17] are presented in the Special Issue. Other topics covered in the Special Issue are related with pressurized pipe distribution [18][19][20] and urban drainage [21][22][23] systems. Selected highlights from each contribution are summarized as follows:…”

“…In the paper "Sediment Morphology and the Flow Velocity Field in a Gully Pot: An Experimental Study" [22], particle image velocimetry (PIV) and laser doppler anemometry (LDA) measurements in a scale 1:1 gully were acquired to quantify the effects of gully pot geometry, flow discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes of sediments beds. The article highlights that the morphology dynamics of the sediment bed significantly influences the flow pattern and the removal efficiency, prohibiting the conceptualization of a gully pot as a completely mixed reactor.…”