Numerical modelling of hydro-morphological processes dominated by fine suspended sediment in a stormwater pond

Mingfu Guan,Sangaralingam Ahilan,Dapeng Yu,Yong Peng,Nigel Wright

doi:10.1016/j.jhydrol.2017.11.006

Mingfu Guan, Sangaralingam Ahilan + Show 3 more

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https://doi.org/10.1016/j.jhydrol.2017.11.006

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Abstract

Fine sediment plays crucial and multiple roles in the hydrological, ecological and geomorphological functioning of river systems. This study employs a two-dimensional (2D) numerical model to track the hydro-morphological processes dominated by fine suspended sediment, including the prediction of sediment concentration in flow bodies, and erosion and deposition caused by sediment transport. The model is governed by 2D full shallow water equations with which an advection–diffusion equation for fine sediment is coupled. Bed erosion and sedimentation are updated by a bed deformation model based on local sediment entrainment and settling flux in flow bodies. The model is initially validated with the three laboratory-scale experimental events where suspended load plays a dominant role. Satisfactory simulation results confirm the model’s capability in capturing hydro-morphodynamic processes dominated by fine suspended sediment at laboratory-scale. Applications to sedimentation in a stormwater pond are conducted to develop the process-based understanding of fine sediment dynamics over a variety of flow conditions. Urban flows with 5-year, 30-year and 100-year return period and the extreme flood event in 2012 are simulated. The modelled results deliver a step change in understanding fine sediment dynamics in stormwater ponds. The model is capable of quantitatively simulating and qualitatively assessing the performance of a stormwater pond in managing urban water quantity and quality.

Highlights

In river systems, fine-grained sediment is a natural and essential component and plays a crucial role in the hydrological, ecological and geomorphological functioning of the system
In all three experimental cases, it has been observed that suspended load is the main transport mode, which ensures the applicability of the cases in the model verification
Sediment transport in a trench To verify the capability of the proposed model in predicting bed evolution under the conditions of unsteady flows a simulation was carried out to compare with experiments originally conducted at the Delft Hydraulics Laboratory to investigate the movable bed evolution caused by steady open channel flow

Summary

Introduction

Fine-grained sediment is a natural and essential component and plays a crucial role in the hydrological, ecological and geomorphological functioning of the system. The receiving waters (Saeedi et al, 2004; Jartun et al, 2008; Jones et al, 2008) These urban pollutants attached to sediments have implications on both habitats of downstream receiving waters and human health (Wood and Armitage, 1997; Owens et al, 2005; Crosa et al, 2010). To mitigate these risks, more sustainable features, such as stormwater ponds, are increasingly used in urban catchments as an option to manage fine suspended sediments (Ahilan et al, 2016; Allen et al, 2017) by storing stormwater runoff, trapping fine sediments and improving urban runoff quality.

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