The Entropic Braiding Index (eBI): a robust metric to account for the
diversity of channel scales in multi-thread rivers
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 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 superior capabilities of eBI via analysis of synthetic,
numerical and field examples. In addition, we show that interrogating
cross-sections via the ratio BI/eBI has the potential to quantify
channel disparity, differentiate types of multi-thread systems, and
inform about cross-section stability to forcing variability (e.g.,
seasonal flooding).