Analysis of bioretention cell design elements based on Fourier amplitude sensitivity test(FAST)

Sensitivity analysis of bioretention cell design elements can provide a theoretical basis for the design and construction of a bioretention cell. This study uses the storm management model (SWMM) and the bioretention infiltration RECARGA to generate runoff and outflow time series for calculation of hydrologic performance metrics. The hydrologic performance metrics include: the overflow ratio, groundwater recharge ratio, ponding time and underdrain flow ratio. The FAST method is chose to analyze sensitivity of design elements for two types of bioretention cell, one without underdrain and the other with underdrain. The results show that the surface area is the most sensitivity to most the hydrologic metrics for both types of bioretention, while the planting soil depth and the gravel depth are the two least sensitive elements. The saturated infiltration rates of planting soil and native soil are another two sensitive elements for bioretention cells without underdrain, but the saturated infiltration rate of planting soil and underdrain size are another two sensitive design elements for bioretention cells with underdrain.