Abstract

Roadside bio-retention (RBR) facilities are low impact development practices, which control urban runoff primarily from road pavements. Using hydrologic models, such as the US EPA Storm Water Management Model (SWMM), RBR are typically designed with some fundamental assumptions, including where runoff completely enters the facilities and fully utilizes the whole surface area for percolation, detention, filtration, and infiltration to the surrounding soils. This paper highlights the importance of inlet hydraulics and the spatial distribution of inflow along a RBR, and proposes an integrated hydraulic and hydrologic modelling approach to simulate its overall runoff control performance. The integrated hydraulic/hydrologic modelling approach consists of three components: (1) A dual drainage hydrologic model to simulate runoff generation, runoff hydrographs entering and bypassing a storm inlet, and the outflow hydrograph from a fully utilized RBR; (2) a computational fluid dynamic model to determine the inflow distribution along a RBR; and (3) an overall runoff control performance analysis of RBR by considering the inlet efficiency, and the partially and fully utilized RBR during a storm event. A case study of an underground RBR in the City of Toronto was used to demonstrate the integrated modelling approach. It is concluded that; (1) inlet efficiency of a RBR will determine the overall runoff control performance; and (2) the inflow distribution will dictate the effective length of a RBR, which may affect the overall runoff control performance.

Highlights

  • In order to control runoff problems associated with urban development, low impact development (LID) aims at restoration of pre-development hydrology by utilizing spatially distributed LID practices throughout a drainage catchment [1]

  • This paper focuses on this research gap and further investigates the captured inflow distribution, along an underground Roadside bio-retention (RBR) using laboratory experiments, computational fluid dynamic (CFD) simulations, and hydrological modelling

  • It consists of three consecutive components: (1) Development of a dual drainage hydrologic model, which simulates runoff hydrographs entering and bypassing a RBR and the runoff control performance of a fully utilized RBR; (2) hydraulic simulations of the inflow distribution along a RBR; and (3) determination of the overall runoff control performance of a RBR with outflow adjustments for partially utilization of the RBR during a storm event

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Summary

Introduction

In order to control runoff problems (e.g., increased flooding, deterioration of water quality, receiving channel erosion) associated with urban development, low impact development (LID) aims at restoration of pre-development hydrology by utilizing spatially distributed LID practices throughout a drainage catchment [1]. Area-based LID practices, known as multi-lot LIDs, are located on large pieces of land such as parks. Among all these different types of LIDs, ROW-based LIDs are the most difficult facilities to implement, due to lack of space and the layout of the road drainage and surrounding utility system. Several innovative structural techniques to control ROW runoff include bio-retentions, porous pavement, catch basin filters, sewer trench exfiltration systems, perforated

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