The Entropic Braiding Index ( eBI ): A Robust Metric to Account for the Diversity of Channel Scales in Multi-Thread Rivers

Alejandro Tejedor, Jon Schwenk, Maarten Kleinhans, Ajay B. Limaye, Lawrence Vulis, Paul Carling, Holger Kantz, Efi Foufoula-Georgiou

Published in ‘Geophysical Research Letters’

Abstract

The Braiding Index (BI), defined as the average count of intercepted channels per cross-section, is a widely used metric for characterizing multi-thread river systems. However, it does not account for the diversity of channels (e.g., in terms of water discharge) within different cross-sections, omitting important information related to system complexity. Here we present a modification of BI, the Entropic Braiding Index (eBI), which augments the information content in BI by using Shannon Entropy to encode the diversity of channels in each cross section. eBI is interpreted as the number of “effective channels” per cross-section, allowing a direct comparison with the traditional BI. We demonstrate the potential of the ratio BI/eBI to quantify channel disparity, differentiate types of multi-thread systems (braided vs. anastomosed), and assess the effect of discharge variability, such as seasonal flooding, on river cross-section stability.