Localized Ks Assessment for Bioretention in Thailand: Improving SWMM Accuracy

Urbanization in Thailand has significantly reduced natural infiltration surfaces, intensified stormwater runoff, and increased the demand for effective urban drainage solutions. Bioretention systems, guided by water-sensitive urban design (WSUD) principles, offer a promising approach for enhancing infiltration and mitigating urban flooding. However, the effectiveness of bioretention depends critically on the accurate estimation of saturated hydraulic conductivity (Ks), a key input parameter in hydrological models such as the Storm Water Management Model (SWMM). Despite international guidelines, local Ks values for tropical soils and vegetation remain scarce, limiting model reliability. This study aims to determine its suitability as a filter media layer in bioretention systems developed specifically for the Thai context. Two surface conditions, vegetated and unvegetated, were tested using coarse construction sand as filter media. The results showed a significantly higher Ks (an 18.55% increase, p