Author(s): Ajay Shrinivas Muthukumar; Kerry Anne Mazurek

Linked Author(s): Kerry Anne Mazurek

Keywords: Urban runoff; Stormwater retention ponds; Flow pattern; Residence times

Abstract: Stormwater retention ponds are commonly used in urban areas to mitigate flooding and improve runoff quality before it is discharged into receiving waters. Sediment retention is an important function of these ponds, but sediment accumulation can interfere with their effectiveness, leading to costly and periodic dredging. To attempt to address this problem, vortex-type retention ponds have been introduced over the past decade. These ponds are circular in shape with a tangential inlet and a central outlet that creates a long spiral (vortex) flow pattern to the pond's outlet. It was believed that the vortex would provide a long retention time to allow sediment deposition and concentrate sediment deposition near the pond's outer edge for easy removal. However, vortex ponds have been found to suffer from short-circuiting, which may limit their effectiveness in retaining sediment. This study aimed to investigate the short-circuiting issues in vortex-type ponds and determine the influence of secondary flows. The study utilized three-dimensional velocity and turbulence measurements, as well as tracer studies to determine residence times, in a physical scale model of a vortex pond. The study confirmed the presence of radial secondary currents perpendicular to the main flow direction. To address this undesired behavior, potential retrofits were tested including half walls, inlet energy dissipation baffles, and vanes to reduce short-circuiting. The combined use of vanes and inlet energy dissipation maximized the reduction of short-circuiting and the velocities associated with the secondary motion, and significantly improved the performance the vortex pond.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p1618-cd

Year: 2023