Global scale bedload flux modeling
Bedload flux is an important component of the total fluvial sediment flux. Bedload dynamics can have a substantial effect on rivers and coastal morphology, infrastructure sustainability, aquatic ecology and water availability. Bedload measurements, especially for large rivers, are extremely scarce worldwide, where most global rivers have never been monitored. The paucity of bedload measurements is the result of 1) the nature of the problem (large spatial and temporal uncertainties), and 2) high costs due to the time-consuming nature of the measurement procedures (repeated bedform migration tracking, bedload samplers). Numerical models can help fill measurement gaps and provide a framework for predictions and hypothesis testing. Here, I present a first of its kind global bedload flux model using simplified Bagnold Equation, which considers only two dynamic (discharge and river slope) parameters along with few constant parameters (e.g., gravity, sediment density). Evaluation of model has been done based on observations for 59 river locations, mostly in the U.S. The model parameters, as well as other influential fluvial and basin parameters (e.g., discharge, drainage area, lithology), were evaluated against observed bedload to find their potential influence on bedload prediction. Considering the simplicity in the parameters needed to predict bedload flux through this model, and the capabilities to give first order estimation the model is helpful to give the large-scale overview of dynamic bedload flux universally. Also, the longitudinal dynamics between suspended and bedload sediment fluxes are mapped in three large rivers.