Morphological change indicators in a semi-arid braided system, the Fiumara Amendolea (Calabria, Italy): multi-temporal evaluation and analysis

Braided rivers constitute fluvial systems of high morphological complexity and significant geomorphological
dynamism. This study analyses the morphological dynamics and braiding intensity of the San Carlo reach
of the Fiumara Amendolea for the period 2022–2024. The Fiumara presents optimal characteristics for the
development of the braiding model: it is a short, steep, ephemeral and torrential watercourse with scarce riparian
vegetation. The analysis of braided systems, such as the one studied here, is key in the context of climate
change, where an increase in the frequency of extreme precipitation events is expected. For the analysed period,
a simplification of the network is observed, a phenomenon that can be attributed to torrential precipitation
episodes recorded during the study period. The methodology integrates photogrammetric processing using
Structure from Motion (SfM) of multispectral UAV/RPAS surveys, GIS-based spatial analysis, and automated
channel network extraction using RivGraph. To measure braiding intensity, four braiding indices (BI) —Brice,
Germanoski-Schumm, Mosley, and the Entropic Braiding Index (eBI; Tejedor et al., 2022)— were computed
for each sub-reach of both the full channel and the most active reach. Additionally, a series of morphological
indices and variables were calculated to establish correlation relationships with the BIs, in order to determine
which of these is most representative of the spatial reality of the Fiumara Amendolea. The results reveal a
generalised reduction pattern in braiding intensity over the analysed period, with alternation of the dominant
geomorphological process; in the headward sector of the San Carlo reach, sedimentation prevails, whereas
incision dominates downstream.
Keywords: braided channels, BI, eBI, Amendolea Fiumara, fluvial geomorphology, SfM photogrammetry,
multitemporal analysis.