199-9 Global Occurrences, Processes, and Implications of Natural Fluvial Connections across Watersheds

Session: Advances in Fluvial Processes and Sediment Transport, Part II

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Natural fluvial connection across watersheds challenges the ingrained perception that drainage divides strictly define watershed boundaries and prevent surface runoff from flowing across them. Once dismissed as geographic errors or overlooked entirely, these connections are globally distributed in difference environments. In this study, we compiled and analyzed 31 documented cases worldwide, categorizing them into three primary types: incision‑dominated, avulsion‑dominated, and headwater connections. We quantified drainage and channel properties, using global hydrography datasets (MERIT Hydro and MERIT Hydro‑Vector) and remote sensing, to characterize their morphologic and hydrologic characteristics. Despite their relative rarity, these connections are not random phenomena; instead, they emerge in diverse settings, including the intermediate stage of river piracy, superimposed alluvial fans, inland deltas, anabranching rivers, sand-silt bed rivers, and glacially influenced headwater divides, and are formed and shaped by established hydrogeomorphic theories and understanding. They enable the transfers of water, sediment, nutrients, and species across watershed boundaries, reshaping downstream hydrology, ecology, and sediment budgets. Our synthesis highlights that natural inter‑watershed connections are critical to understanding drainage reorganization, biogeographic dispersal, and river management, and calls for the inclusion of them in future models and assessments of Earth’s surface dynamics.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9593

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