Environmental Adaptation Driven by Dynamic Water–Soil Coupling: Late Neolithic–Early Bronze Age Settlement Patterns on the Chengdu Plain (4500–1200 cal BP)

Abstract Background:Understanding dynamic settlement adaptations under extreme hydrological stress is a central theme in landscape ecology. The Neolithic–Bronze Age settlement cluster of the Chengdu Plain (4500–1200 BP) offers an ideal case for decoding human settlement strategies in a monsoonal flood-basin system. Objectives:To reveal the spatial trajectory of settlement adaptation to hydrological landscapes and to quantify the coupled “landform–soil–hydrology” driving mechanisms. Methods:A 30 m DEM, palaeochannel reconstructions and pedological data were integrated in a GIS-based spatially explicit model to quantify the co-location of twelve representative sites against multiple environmental covariates. Soil mechanical tests (shear strength, plasticity index) and stratigraphic correlations from excavation reports were used for cross-validation. Results: (1) Early phase (Baodun culture): settlements selected secondary fluvial terraces, constructing earthen walls on clay-loam soils (15–25 % clay) but remained within back-swamp zones vulnerable to overbank flooding. (2) Mid phase (Gaoshan/Yandian): relocation to mountain-front cols (>15° slope) enhanced runoff evacuation; col corridors balanced resource access with flood buffering while soil clay contents were maintained at ~25 %. (3) Sanxingdui phase: occupation of high-clay (>28 %) terraces at the margin of the Tuojiang backwater, where a natural clay–gravel aquitard–aquifer sequence, together with a 1.5 km setback from the palaeochannel, substantially reduced hydrological risk. (4) Late phase (Shierqiao): penetration into low-elevation hinterlands, relying on stable minor tributaries (~0.5 km distance) and continuous clay belts while abandoning walled enclosures.The key constraint is the plasticity gradient of soils (15–45 % clay) governing engineering resilience, with col drainage efficiency and backwater-margin positioning jointly constituting a natural buffering system. Conclusions: Through iterative learning, the ancient Shu developed a hierarchical “landform–soil–hydrology” coupled adaptive model. Their resilience strategy—leveraging natural processes such as col barriers, clay engineering and secondary channels—provides a Nature-based Solution (NbS) reference for contemporary flood-plain planning.