Modelling of stormwater detention ponds for water level, flow and velocity under future climate change

Abstract

In equatorial countries, drainage engineers are implementing adaptive measures to bolster infrastructure resilience against climate change, particularly on urban stormwater systems which are among the facilities most vulnerable to increasing rainfall volumes. This paper describes one such effort that proposes the partitioning of a large, single dry pond into two smaller ponds, a rare practice. A case study was conducted using Storm Water Management Model software to model an 80 m long dry pond with orifice plates at the 20, 40, or 60 m points, to produce the 20:60, 40:40, and 60:20 pond designs. The models developed based on the conventional and partitioned ponds were subjected to IPCC 6th Assessment Report’s near-, medium-, and long-term scenarios of the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 events. Simulation results for the conventional pond indicate that future climate scenarios significantly increase peak inflow rates and velocities; however, maximum water levels remain within capacity, with no predicted overflows. The partitioned pond simulation findings are encouraging, which cause the water level, flow rate, and velocity in the second pond to decline by nearly 50% regardless of its design, compared to the first pond. The velocity profiles of the three partitioned designs, along the pond length, were compared. Only the 60:20 pond demonstrated the ability to produce a settling velocity <0.1 m/s near the end of the first pond, which suggests that this pond design can treat suspended sediments.