Assessing temporal variability and controlling factors on the hydrosedimentary response in mediterranean catchments

Résumé

- Introduction: Assessing the hydrological response and suspended sediment transport in rivers is fundamental to improve the knowledge and management of water resources, floods, droughts, transmission of pollutants and soil erosion at catchment scale. The Mediterranean regions received special attention due to the seasonality of their climate, which promotes large differences in water resources availability between years and seasons. Furthermore, the land cover of most Mediterranean catchments have been strongly modified by humans over millennia creating a complex landscape causing a significant influence on the hydrosedimentary behaviour of fluvial systems. - Research content: This thesis aims to determine the effects of basin lithology, land uses and temporal scales on runoff generation and suspended sediment transport dynamics in representative Mediterranean catchments. Continuous measurements in hydrometric stations were used over a five-year period at: a) Small Mediterranean catchments (i.e. < 10 km2) characterised by contrasting land uses and lithology, where rainfall-runoff relationships were carried out at multiple temporal scales to achieve a better understanding of the hydrological response. b) A representative small mid-mountainous Mediterranean catchment (i.e. Es Fangar, 3.4 km2), where the role of soil moisture in water and suspended sediment fluxes were investigated during five hydrological years. c) Two medium size Mediterranean catchments (i.e. Búger in Mallorca, 68.2 km2; Carapelle, in Southern Italy, 506 km2) selected to analyse the most relevant driven factors affecting the flow regime and to quantify the runoff and suspended sediment yields at different temporal scales. - Conclusions: The results of this thesis confirmed that physical driving factors (lithology and land cover) and the conservation state of human structures (terraces and check dams) exerts a strong control in the hydrological response and suspended sediment transport. The spatial distribution, patchiness and interaction between these driving factors explained water and sediment yields of the study catchments. The analysis of the runoff response and suspended sediment transport from the annual to the event scale allowed to identify the hydro-meteorological driving factors and how these are related to the physical and human features of the catchments. The XV characterization of catchment features from a science-based approach has demonstrated to be essential for understanding the hydrosedimentary response to move towards an integrated management catchment process useful to simulate multiple future scenarios of land use and climate change.