Abstract
The volumes, rates and grain size distributions of sediment supplied from hillslopes represent the initial input of sediment delivered from upland areas and propagated through sediment routing systems. Moreover, hillslope sediment supply has a significant impact on landscape response time to tectonic and climatic perturbations. However, there are very few detailed field studies characterizing hillslope sediment supply as a function of lithology and delivery process. Here, we present new empirical data from tectonically-active areas in southern Italy that quantifies how lithology and rock strength control the landslide fluxes and grain size distributions supplied from hillslopes. Landslides are the major source of hillslope sediment supply in this area, and our inventory of ~2800 landslides reveals that landslide sediment flux is dominated by small, shallow landslides. We find that lithology and rock strength modulate the abundance of steep slopes and landslides, and the distribution of landslide sizes. Outcrop-scale rock strength also controls the grain sizes supplied by bedrock weathering, and influences the degree of coarsening of landslide supply with respect to weathering supply. Finally, we show that hillslope sediment supply largely determines the grain sizes of fluvial export, from catchments and that catchments with greater long-term landslide rates deliver coarser material. Therefore, our results demonstrate a dual control of lithology on hillslope sediment supply, by modulating both the sediment fluxes from landslides and the grain sizes supplied by hillslopes to the fluvial system.
Original language | English |
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Pages (from-to) | 956-977 |
Number of pages | 22 |
Journal | Earth Surface Processes and Landforms |
Volume | 43 |
Issue number | 5 |
DOIs | |
Publication status | Published - Apr 2018 |
Externally published | Yes |
Funding
Acknowledgements—DRB and MD were funded by an Imperial College Janet Watson Bursary, awarded by the Department of Earth Science and Engineering of Imperial College London. Field campaigns were generously supported by research grants to DRB from the Geological Society of London, the British Society for Geomorphology (BSG) and the British Sedimentological Research Group (BSRG). JM was supported by Imperial College as part of her MSci programme. The authors would like to thank Leonard Sklar, one anonymous reviewer, and the ESPL associate editor, for their very constructive comments that helped improve the manuscript.
Keywords
- grain size
- hillslopes
- landslides
- lithology
- sediment supply