Effect of kinetic energy-intensity relationships and 0.5-h maximum intensity estimation methods on rainfall erosivity

Gabriel Lobo, Carlos Bonilla

Wednesday 1 july 2015

11:00 - 11:15h at Oceania Foyer (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 9H. Water resources - Catchment

This paper computes and compares rainfall erosivity values derived from five kinetic energy-intensity (KE-I) relationships using estimated 0.5-h and measured 1-h maximum rainfall intensities (I30 and I60, respectively). Three exponential, a logarithmic and a linear KE-I relationship were used to compute rainfall erosivity from 1-h pluviographic records corresponding to 30 sites in Central Chile; a total of 415 years of data were analyzed with more than 18,000 storms. The erosivity results were compared using a statistical test and by comparing the mean erosivity values. Two of the three exponential equations yielded statistically equal erosivity results for every site. The third one underestimated the erosivity values of the other exponential equations in an average of 25%, showing that the exponential equation is sensitive to changes in its regression parameters and is therefore site-specific. The logarithmic equation yielded the maximum erosivity estimates, which were statistically equal to the erosivity results of two of the exponential equations. The linear relationship yielded statistically different erosivity results that were up to three times smaller than those of the other equations. Computing erosivity using I60 provided erosivity results that where 10% smaller than the results obtained using I30, regardless of the KE-I relationship and the site. The I60 is, in average, 10% smaller than I30 in the study sites, which shows that I30 is directly proportional to erosivity. Thus, the differences in erosivity reported among the KE-I relationships are independent of the I30 estimation method. Because large differences in erosivity were reported between the KE-I relationships, selecting a KE-I relationship that adapts to local conditions is crucial for accurate erosivity estimations. On the other hand, accurately estimating I30 is critical when large differences exist between different estimation methods because erosivity is directly proportional to I30.