A Review of Fundamentals and Applications of Sediment Connectivity Index in Soil Erosion Studies

Identification of sediment production areas, patterns of its delivery from sources to the transport network and the location of deposition sinks are necessary to manage soil erosion. The term connectivity describes the relationship between the sources of runoff and sediment production in the upstream of the watershed and the corresponding sedimentation areas in the downstream. Based on the approach used, there are two types of structural connectivity and functional connectivity. Connectivity index (IC) is one of the most widely used indices to quantify sediment connectivity. The selection of an appropriate weighting factor is one of the challenging issues in IC calculation and it is chosen according to the conditions of each region, the characteristics of the soil surface and available data as well. Therefore, this study was conducted with the aim of reviewing, analysis and collecting past studies so far in order to have a comprehensive look at the methods of quantification of IC and introducing more appropriate approaches for future research in this field. This study reviewed 90 studies related to different dimensions of IC. The review of 25 studies on IC weighting factor published between 2008 to 2022 showed that the two frequently used variables are the C factor of USLE and surface roughness (31% and 25% respectively).It is also suggested that sediment connectivity can be investigated at different time scales, taking into account both structural and functional connectivity. As a result, with better understanding of sediment connectivity, it can be used as a tool for sustainable management of watersheds.