Experimental investigation for impacts of rain storms and terrain slopes on low impact development effect in an idealized urban catchment

To quantitatively investigate the LID (Low Impact Development) effects under different storms and terrain conditions, an experimental urban catchment with LID measures is developed in this work. The surface runoff control effects of the experimental LID measures are evaluated by quantifying and comparing the peak runoff reduction rate to a traditional infrastructure with no LID. The experimental results on three cross and longitudinal slopes under three storm intensities show that the measured peak runoff of the traditional infrastructures is higher than that of the LID, indicating that LID reduces the peak runoff considerably. As the storm intensities are increased from 0.47 mm/min to 0.84 mm/min, the peak runoff reduction rates decrease from 14.48% to 4.91%, highlighting that LID effects are more significant for low to moderate intensity of storms. The effect of LID in reducing the peak runoff is more significant for a gentler cross or longitudinal slope, for example, the highest reduction in peak runoff (14.48%) occurs when a gentle longitudinal and cross slope of 1' is incorporated. Moreover, the effect of LID is more sensitive to the longitudinal slope when compared to the cross slope. The findings from this study quantify that the LID measures are more effective for low intensity storm across gentler slopes. While the results help in understanding the mechanism of LID effects for optimizing infrastructure planning, they also provide a systematically measured data for numerical model validation and coefficient calibration.