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The difficulties of measuring bedload transport in gravel bed rivers have given rise to the morphological method wherein sediment transport is inferred from changes in riverbed elevation and estimates of the distance traveled by sediment, its path length. Because current methods for estimating path length are time and labor intensive, we present a method to estimate path length from repeat digital elevation models (DEMs of difference i.e., DoDs). We propose an automated method to extract the spacing between erosional and depositional sites on the DoD by the application of Variational Mode Decomposition (VMD), a signal processing method, to quantify the spacing as a proxy for path length. We developed this method using flume experiments where bed topography and sediment flux were measured and then applied it to published field data with tracer measurements for validation. Our path length estimates had an error lower than 30 % when compared to the measured mode of the tracer distances in the field and generated sediment transport estimates not significantly different than the measured sediment flux at lower discharges in the lab. However, we observed an underestimation of sediment flux at the higher discharges in the flume study. We explore explanations for the underestimation and how the time between survey acquisitions, the morphological active width relative to the channel width, and DoD thresholding techniques affect the proposed method and the potential issues they pose to the morphological method in general.