Human impact in the form of reservoir construction and river regulation downstream of reservoirs, is causing irreversible alterations to hillslope and river channel connectivity in river catchments. This disruption in the dynamic equilibrium of the river is attributed to sediment accumulation upstream of the reservoir's dam, limited sediment outflow from the reservoir, and increased downcutting downstream of the dam. Consequently, these alterations necessitate further human interference in natural environmental processes through the construction of various river engineering structures designed to reduce the intensity of downcutting. The purpose of the present study was to assess the impact of a small mountain reservoir and additional river regulation structures on the Wapienica River in southern Poland, focusing on the structural and functional connectivity of the river channel in terms of sediment transfer. This assessment was based on erosion and connectivity modeling, as well as field mapping. A high-resolution digital elevation model (HRDEM) was examined in the study along with survey data on suspended sediment accumulation sites along the river. The study utilized open-source tools, including SedInConnect for connectivity index (IC) calculation, and the Soil and Water Assessment Tool (SWAT) for ArcGIS software. It was found that the Wapienica reservoir permanently retains the floating material, making the likelihood of this material flowing out of the reservoir minimal. Within the reverse delta of the reservoir, the entire load of bottom material (sand) is also retained. Thicker bottom material (gravel, boulders) is deposited in the riverbed within the delta, leading to the shallowing of the bed upstream of the delta. These processes disrupt longitudinal connectivity. Six connectivity zones have been identified within the catchment. The first four are situated in the southern part of the catchment: strong connectivity, reduction, concrete channel, and damage area. The remaining two, situated in the northern part are: artificial channel and drainage channels. Each of the six zones is characterized by different sediments and river processes. It was demonstrated that a more detailed and more probably connectivity pattern for hillslopes and river channels may be obtained through the use of several tools and parameters at the same time (i.e., fieldwork, SWAT, IC).

Soil erosion is an important driver of land and ecological degradation, with hydraulic erosion in particular leading to widespread impacts and damage. As an important concept and indicator for characterizing the potential and pathways of sediment production and transportation within watersheds or on slopes, sediment connectivity has gained global attention and thus been analysed since its proposal in 2003. Sediment connectivity has become an effective metric for analysing the sources, processes, and potentials of soil erosion and sediment yield (SY) in watersheds, and it has been considered a popular research topic in the field of soil erosion over the past decade. Considering the lack of up-to-date systematic reviews of conceptual connotations, characterization indicators for sediment connectivity, and quantitative relationships between these indicators and erosion and SY, a bibliometric analysis of sediment connectivity was conducted via the CiteSpace tool, which is based on the Web of Science (WOS), Scopus (Elsevier) and China National Knowledge Infrastructure (CNKI) databases. In this research, the current state, popular topics, and trends in relevant studies were identified, and the conceptual connotations, influencing factors, and indicator algorithms of sediment connectivity and their quantitative relationships with soil erosion and SY were summarized. Furthermore, the contents and directions to be strengthened and improved in the future were determined. The results indicated that over the past 21 years, sediment connectivity has been analysed in 123 countries or regions. Researches have focused primarily on related concepts, indicators, scales, and influencing factors. This concept has been widely applied in various practices such as soil and water resource regulation, land use optimization, and soil erosion control. In previous studies, several linear (SY = a center dot IC + b) and exponential (SY = a center dot eb center dot IC) increasing relationships between sediment connectivity indicators (such as the index of connectivity (IC)) and SY at the slope or watershed scale have been established, facilitating the development of research on prediction and attribution analysis for the identification of sediment sources and changes. There is a consensus on what sediment connectivity is to date, but a unified and complete system has not been yet formed for sediment connectivity and several of its derived concepts. The Index of Connectivity (IC), as the primary means for quantitatively characterizing the status and distribution of sediment connectivity, has led to the creation of more than 20 different algorithms, whereas the included parameters mainly reflect the internal factors influencing topography and land use/cover. The effects of climatic factors and human activities have not been fully considered in previous studies, which has led to relatively backwards researching on functional connectivity indicators. Hence, the classification systems and theoretical frameworks for a series of concepts must be further refined on the basis of sediment connectivity, such as the objective openness, scale dependence, comprehensive impact, and distribution heterogeneity. Moreover, the amount of research on the influences of external drivers and the coupled effects of different factors on indicators of sediment connectivity should be increased. Nevertheless, it is still necessary to explore certain aspects, such as the parameter combinations and normalization methods of the upslope and downslope components of the IC algorithm, and to continuously improve the explanation of the dynamic changes in sediment while considering both hydrological connections along flow paths and off-site impacts on underlying surface variations. Moreover, there is a need to increase the spatiotemporal scale of research on sediment connectivity, explore its feedback mechanisms and close quantitative relationships with soil erosion and SY, focus on the integrated application of different indicators (methods), and validate and results via multisource information to promote relevant applications. The obtained results provide valuable reference for the refinement of theories and methods for sediment connectivity and enhance its support of studies of soil erosion and SY in watersheds.