RAINFALL EROSIVITY IN NORTHEASTERN AUSTRIA

Rainfall erosivity is the main driver for soil detachment and sediment transport, and represents the climatic factor most influencing the risk of soil erosion at a given site. Our objectives were to explore 15 min rainfall breakpoint data from 51 rain gauges in the northeastern part of Austria to (1) calculate rainfall erosivity values for this region, and (2) analyze statistically whether there exists a temporal evolution in rainfall erosivity. Rainfall data (May to October) covered between nine and 53 years. Rain gauges were located at elevations between 150 and 970 m a.s.l., and mean rainfall depths were 514 (+/- 169) mm and 652 (+/- 156) mm for Lower Austria (LA) and Upper Austria (UA), respectively. The calculated rainfall erosivity factor (R factor) ranged from 273 to 1599 with an average of 884 MJ mm ha(-1) h(-1) in LA and from 637 and 1697 with an average of 982 MJ mm ha(-1) h(-1) in UA. Rainfall depths and erosivities showed greater variability in LA than in UA, which can be attributed to the different ranges of topographic regions in LA. For both states, relationships could be established between average rainfall from May to October and the R factor, with correlation coefficients between 0.77 (LA) and 0.85 (UA). Overall, for the same rainfall amounts, rainfall erosivity was lower in UA than in LA. In LA, time series analyses showed a significant temporal increasing trend in rainfall intensity, rainfall erosivity, and storm number and intensity. These positive trends at 90% of the stations with data sets of >25 years indicate possible future R factor increases and increasing erosion risk. In UA, only 25% of the rain gauges showed a significant positive trend in rainfall erosivity, and 40% showed a significant increase in rainfall intensity. Changes in rainfall patterns were more distinct in eastern Austria than in northern Austria, thus impacting runoff, infiltration, and erosion processes in this area in the future.