Evaluation of kinetic energy and erosivity potential of simulated rainfall using Laser Precipitation Monitor

Abstract

Rainfall kinetic energy is a widely recognized indicator of a raindrop's ability to detach soil particles in rainsplash erosion. However, it is challenging to estimate the kinetic energy (KE) of a given rain event, because it involves analysis of the terminal velocity and drop size distribution (DSD) of raindrops. A preferred alternative is to relate KE to rainfall intensity. Therefore we sought to characterize simulated rainfall, establish a relationship between kinetic energy and intensity as a function of both time (KEt, Jm−2h−1) and volume (KEvol, Jm−2mm−1), and examine the erosivity potential of each event. A rainfall simulator and Laser Precipitation Monitor (optical disdrometer) were used to characterize raindrop size, terminal velocity and KE at different rainfall intensities (1.5 to 202mmh−1). Values of KEt ranged from 26.67 to 5955Jm−2h−1 and KEvol ranged from 16.10 to 34.85Jm−2mm−1, which is comparable to values determined from natural rain of similar intensity ranges. A power-law function and a polynomial function between KEt and rainfall intensity had coefficients of determination (R2) of 0.99 and 0.98 (P<0.0001), respectively. The best-fitting relationship between KEvol and intensity was a power-law function (R2=0.95; P<0.001). We found that erosivity had a very strong correlation with rainfall depth (R2=0.99; P<0.0001) in power-law function. Furthermore, regardless of rainfall intensity, KE is more strongly correlated with raindrop size than volume of raindrop.