Recovering head and flux distributions at the sediment-water interface for arbitrary, transient bedforms by inversion of photographic time series

TL;DR

This paper introduces a noninvasive inversion method to recover head and flux distributions at the sediment-water interface for complex, transient bedforms using photographic time series, validated with new experimental data.

Contribution

It presents a novel regularized inversion technique for arbitrary bedforms, enabling analysis of hyporheic exchange without relying on simplified assumptions or costly simulations.

Findings

Successfully applied to three experimental setups with different flow regimes

Generated the first dataset of head and dye front distributions for natural sand bedforms

Demonstrated the method's ability to handle complex, transient bedform geometries

Abstract

Existing works that predict bedform-induced hyporheic exchange flux (HEF) typically either assume a simplified streambed shape and corresponding sinusoidal head distribution or rely on costly computational fluid dynamics simulations. Experimental data have been lacking for the formulation of a priori prediction rules for hydraulic head and flux distributions induced by spatiotemporally heterogeneous natural bedforms because it has not previously been feasible to determine these in the laboratory. We address this problem, presenting a noninvasive technique for regularized inversion of photographic time series of dye front propagation in the hyporheic zone, compatible with arbitrarily-shaped, generally transient bedforms. We employ the technique to analyze three bench-scale flume experiments performed under different flow regimes, presenting a new data set of digitized bed profiles, corresponding head distributions, and dye fronts. To our knowledge, this is the first such data set collated for naturally-formed sand bedforms.