Development and application of a sediment connectivity index to small fluvial catchments: a case study in Arenoso stream, Córdoba, Argentina

Abstract

Sedimentological connectivity is associated with the degree of linkage between sediment sources and downslope areas. In this study, a connectivity index is proposed to estimate the contribution of different parts of a basin as sources of sediments and to assess the pathway of sediment flux. A small granitic basin located on the eastern slope of the Comechingones Ranges (Cordoba Province, Argentina), was selected as a case study. The semi-quantitative connectivity index is defined by the equation CI = T + Dd + C–B, in which T is the variable toposequences that represents the types of storage and lateral links; Dd is the drainage density and it is used to evaluate the longitudinal links; C corresponds to the number of connections between channels of different order in a basin and it complements Dd in the longitudinal links analysis; and B connotes barriers associated with the number and type of disconnections in the drainage network, thus its sign is negative. From cartographic and field data, a detailed lithological–geomorphological survey was carried out; storage and toposequence types were described, and the barriers were classified according to the type, size, and position in the basin. The CI was determined for each secondary and main sub-basin of the Arenoso stream. Therefore, five connectivity classes were defined from the CI values obtained. This methodology allows arising acceptable results in research associated with the spatial heterogeneity of basin connectivity. The CI developed, in this first approach, showed satisfactory results and is applicable to analysis of small mountain basins, being based mainly on geological–geomorphological–hydrographic maps coupled with detailed fieldwork.