Modeling spatio-temporal variation of longitudinal connectivity and its relation to meander evolution

Transfer of material inside a river reach is usually explained through connectivity - more specifically, functional connectivity, which refers to the system dynamics and sediment transfer in a geomorphological system at a certain spatio–temporal scale. Connectivity is usually understood as the cause of river forms, such as meander planform types but measuring and quantifying sediment connectivity variation over time still remains as a challenge. Many studies have quantified connectivity through digital elevation models of difference of two time-steps but this approach lacks the temporal variation between the time-steps. In this study we run detailed morphodynamic model of one hydrological year in order to assess weekly spatio-temporal variation of longitudinal functional connectivity over 6-kilometre sub-arctic river reach. Comprehensive field datasets (including sediment sampling, monitoring of morphological change and continuous discharge and water level measurements) were collected multiple times during the year to calibrate and validate the model over various discharge events. The results revealed detailed spatio-temporal morphological changes, the timing and magnitude of sediment cascade and the variation of connectivity inside the reach during the modelled year. We could define connectivity thresholds for certain discharge events and evaluate the interplay between sediment cascade and meander planform types. These threshold values can contribute in evaluating the climate change effect on sediment cascade in sub-arctic areas, and offer further understanding of complex interplay of connectivity and river forms in present and future.