Magnitude and Occurrence Probability of Soil Loss: a Risk Analytical Approach for the Plot Scale for Two Sites in Lower Austria

Long-term contribution of soil loss events depends on both – the magnitude and the occurrence probability – but oftentimes, a limited observation period impedes the assessment of the temporal soil loss distribution. In this research, the event-based soil loss from two plot locations in Lower Austria (Mistelbach and Pixendorf) was linked with the event-based rainfall erosivity (EI30) to assess the temporal soil loss distribution using long-term rainfall data from two meteorological stations in Lower Austria. For both plot locations, a risk analysis was performed to (i) assess the long-term average annual soil loss and to (ii) evaluate the contribution of incremental erosion events according to different event return periods. The risk analysis showed that in Pixendorf the events <20 years return period dominatingly contribute to long-term soil loss, because the contribution of the events >20 years return period is progressively reduced through the low occurrence probability. On the contrary, in Mistelbach the soil loss magnitudes of the extreme events overcome the effect of the low occurrence probability, and consequently, the contribution of the extreme events (>20 years return period) is dominant. The spatially variable contribution of the erosion events reveals the need for spatially customized soil conservation strategies. A risk analytical approach may help to allocate the driving events and thus to define proper event design magnitudes for local soil conservation planning.