A Small-Scale Comparative Analysis of Traditional Drainage and Sustainable Urban Drainage Systems Under Urban Flooding Conditions

Rapid urbanization and intensifying rainfall increasingly overwhelm conventional stormwater drainage, yet experimental evidence comparing it with Sustainable Urban Drainage Systems (SuDSs) in tropical cities such as Panama City is scarce. This study compared the hydraulic behavior and discharged water quality of a 1:2-scale bioretention prototype and a traditional concrete drainage prototype under controlled laboratory conditions. Each prototype received tap water, sediment-laden water, and fertilizer solution through its representative feeding mode; physical parameters were recorded with an Arduino-based sensor network and nitrates, phosphates, and sulfates with a photometer. Both systems recovered comparable volumes (87.5% traditional, 80% SuDS), but the traditional prototype discharged within about 15 s, whereas the SuDS released water progressively over 30 min, with a peak outflow 54% below the inlet flow. The SuDS reduced turbidity below the sensor detection limit and lowered sulfate and phosphate in most solutions, whereas traditional drainage showed no retention. The SuDS also increased EC and, in some cases, nitrate, indicating ion release from the substrate. Under these conditions, the bioretention prototype delayed outflow and improved particulate removal, supporting its potential as a complement to conventional drainage. However, to support its potential as decentralized green infrastructure for tropical cities, full-scale tests are needed.