Linking landslide susceptibility to sediment yield at regional scale: application to Romania

• Landslide susceptibility is an important predictor of sediment yield in Romania.
• Lithology and seismicity are important factors to explain SY in Romania.
• Topography is not a good predictor of regional differences in SY in Romania.
• Landslide location is not important to explain regional patterns of SY in Romania.
• Sheet and rill erosion explains little of the observed variance in SY.

It is generally accepted that catchment sediment yield (SY, t km− 2 y− 1) can be strongly influenced by landsliding. Nevertheless, due to data requirements, only few studies investigated this effect at a regional scale. The objective of this study is therefore to explore the potential of a landslide susceptibility map for explaining the spatial variation of SY in Romania. We selected 133 catchments in Romania for which SY was measured during a period of at least 10 years. For each catchment, we derived a variety of proxies that potentially explain SY, including several indicators of landslide occurrence. The latter were derived from a published landslide susceptibility map. Results show that SY is significantly correlated with mean landslide susceptibility (r2 = 0.30). Estimates of average sheet and rill erosion rates showed a much weaker correlation with SY (r2 = 0.06). Further analyses showed that the strong correlation between SY and landslide susceptibility is mainly attributed to regional variations in lithology and seismicity. Especially the latter may play a crucial role in understanding denudation rates at regional scales, e.g. by facilitating the occurrence of landslides. Using landslide proxies that also account for sediment connectivity did not result in stronger correlations. Overall, our results show that landslide susceptibility maps can be a highly useful tool to predict SY at regional scales, provided that they incorporate all relevant factors.