Evaluation of Active, Beautiful, Clean Waters Design Features in Tropical Urban Cities: A Case Study in Singapore

Abstract

In Singapore, active, beautiful, clean waters design features (ABCWDFs), such as rain gardens and vegetated swales, are used as a sustainable approach for stormwater management. Field monitoring studies characterising the performance of these design features in the tropical region are currently limited, hampering the widespread implementation of these systems. This study characterised the performance of individual ABCWDFs in the tropical climate context by monitoring a rain garden (FB7) and a vegetated swale (VS1) that were implemented in a 4-ha urban residential precinct for a period of 15 months. Results showed that total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) concentrations were low in the new residential precinct runoff, leading to poor removal efficiency despite the effluent concentrations of individual ABCWDFs that were within the local stormwater treatment objectives. Average TSS, TP and TN EMCs of four sub-catchment outlets were lower (23.2 mg/L, 0.11 mg/L and 1.00 mg/L, respectively) when compared to the runoff quality of the major catchments in Singapore, potentially demonstrating that the ABCWDFs are effective in improving the catchment runoff quality. Findings from this study can help to better understand the performance of ABCWDFs receiving low influent concentrations and implications for further investigations to improve stormwater runoff management in the tropics.

Scientific Evidence behind the Ecosystem Services Provided by Sustainable Urban Drainage Systems

“…Regulation Services: Water Quality Af. The event mean concentrations of total suspended solids, total phosphorous, and total nitrogen are lower in catchments with green swales than without SUDS [54].…”

“…Af. The discharge quality of the catchments with bioretention ponds is better than those without them [54].…”

“…Regulation Services, Water Quality: SUDS seem to be an ideal technique to improve the quality of runoff [40,54,160], but sometimes, given the high temperatures that characterize it, problems of a lack of oxygen in the waters [159] or eutrophication [212] in the stormwater green infrastructure may appear.…”

A preliminary development of a coupled surface and subsurface flow model for swale system

“…In the momentum equation, is the bed slope, is the friction slope. is estimated using Darcy-Weisbach equation as follows, IOP Publishing doi:10.1088/1755-1315/1238/1/012022 3 (3) is estimated based on whether the flow is laminar, transitional or turbulent [10]. Equation ( 1) and ( 2) are the full dynamic wave equations, with the inclusion of inertial term.…”

“…In Best Management Practice (BMP), swales are recommended as replacement for concrete drain. Research have shown that swales are not only efficient in managing stormwater runoff [1,2,3], but also enhance the aesthetic of the surrounding environment. Swale system is also recommended as one of solution for sustainable urban drainage system [1].…”