Rainfall analysis of debris flows in the Obří důl Valley in the Krkonoše Mts., Czechia

Abstract

Rainfall is the most important triggering factor responsible for the occurrence of debris flows in the Obří důl Valley in the Krkonoše Mts. The critical rainfall conditions for slope failures are not the same for different debris flows, and may be strongly influenced by regional geological and geomorphological conditions. Nevertheless, analysis of hourly intensities, daily rainfall, cumulative data and the antecedent precipitation index (API) revealed that several of the above-mentioned factors are necessary to trigger the debris flow. On the other hand, a significant amount of daily rainfall (e.g. 225 mm) could trigger a debris flow without the support of any other rainfall characteristics in the monitored area and period under review. We used several rain gauges from the study area but the local differences in rainfall were so high that data from more remote stations was difficult to include in the Obří důl Valley. This is why only a limited amount of precise data is available for some years.