Unveiling Global Hillslope Connectivity: A Comprehensive Analysis Using Cutting-Edge Methodologies

In a recent study on structural hillslope connectivity across the globe, researchers utilized a methodology based on a previous reference to calculate the Index of Connectivity (IC). The IC represents the likelihood of sediment from an upslope point reaching a downslope target, such as streams. The IC is empirically defined as the logarithm of the ratio between the upslope and downslope elements of connectivity.

The upslope component, Dup, is determined by the average weighting factor of the contributing upslope area, the average slope of the area, and the area itself. On the other hand, the downslope component, Ddn, is calculated as the sum of flow path lengths to downstream channels for each cell at the steepest slope direction, weighted by the slope gradient and weighting factor at each cell.

To conduct their analysis, the researchers used Digital Elevation Models (DEMs) with a 90-meter spatial resolution from HydroSHEDS. They defined targets as nearby streams using the HydroRIVERS dataset and excluded certain regions due to data limitations. The study focused on basin-averaged analyses at the HydroBASINS level 5.

To investigate the drivers of connectivity globally and their sensitivity to climate change, the researchers built a regression model based on the Generalized Additive Model for Location, Scale, and Shape (GAMLSS). They considered tectonic and climate drivers from previous studies and examined their correlation using a correlogram.

The study utilized a 4-parameter Skew t type I (ST1) distribution to model the IC values across the globe. The distribution parameters were estimated based on predictors such as elevation, potential evapotranspiration, peak ground acceleration, precipitation, profile length, and slope. The researchers also assessed the impact of climate change by analyzing precipitation and potential evapotranspiration data from climate models.

The study identified limitations related to the model features, such as the dependence on DEM accuracy and the use of a roughness factor for weighting. Future research directions include exploring the influence of land use changes on connectivity, analyzing functional connectivity, and investigating the sensitivity of tectonic parameters on structural connectivity.

Overall, this research provides valuable insights into the factors influencing hillslope connectivity globally and highlights the importance of considering both tectonic and climatic drivers in understanding landscape dynamics.