A Novel Approach to Quantify Sediment Transfer and Storage in Rivers—Testing Feldspar Single-Grain pIRIR Analysis and Numerical Simulations

Summary

Quantifying sediment transport and storage in fluvial systems is fundamental for understanding the transfer of eroded materials from source to sink. Here, we investigated the potential of a combined approach using a luminescence measured in modern fluvial sediments and numerical simulations to quantify transport and storage in rivers. We acquired luminescence data at the single-grain scale on feldspar sediments of Waimakariri and Rakaia braided rivers (New Zealand) using a post infra-red infra-red stimulated luminescence protocol. We considered three metrics from the analysis of luminescence equivalent dose (D_e) distribution: the percentage of bleached and the percentage of saturated grains, and the mean D_e. All three metrics show similar longitudinal trends along both rivers. To derive quantitative information on sediment transfer from these data, we developed a numerical model that simulates the longitudinal evolution of D_e distribution of a population of grains during transport and storage in floodplains. The model considers four main parameters: the transport length of grains during floods, their resting time between successive transport events, the bleaching probability (probability of the luminescence signal to be reset due to sunlight exposure during transport or rest), and the likelihood of partial bleaching. Identification of model parameters that best reproduce natural observations allowed estimating transit time of sediments between 2.1 and 10.3 Kyr (mean of 6.9 (Formula presented.) 2.9 Kyr), corresponding to mean virtual transit velocity of 20–95 m.yr⁻¹ (mean of 46 (Formula presented.) 28 m.yr⁻¹). Our study illustrates the potential of the combined single-grain luminescence and modeling approach to quantify sediment transfer in fluvial systems.