Sa Huynh and Champa: Riverine and Coastal Geomorphology Shaping Ancient Social Landscapes in the Thu Bon Basin

FUNABIKI Ayako1*, YAMAGATA Mariko2, KUBO Sumiko3, NGUYEN Van Tho4, NGUYEN Huu Manh5, and NGUYEN Thi Mai Huong6

The central coastal region of Vietnam, especially the Thu Bon River basin, contains numerous archaeological sites and cultural assets, and interaction via river networks originating in the Truong Son Mountains has been noted. Archaeologists regard the Champa Kingdom (2nd-19th centuries) as a federation of multiple riverine polities that developed within individual basins (Trần, 1988). In the Thu Bon basin three key centres – sacred temples (My Son), the royal capital (Tra Kieu), and the port town (Hoi An) – are located, and archaeological survey and site database compilation are ongoing. Examination using geomorphological classification maps shows that site locations reflect local landform characteristics. My Son lies in a mountainous basin; Tra Kieu occupies a relatively flood-free area at the southern margin of the floodplain; and Hoi An is situated near the river mouth in a transitional zone where coastal dunes and fluvial deposits overlap. Upstream, Sa Huynh culture (Iron Age, 4th-3rd  centuries BCE to ca. 100 CE) remains occur along rivers. Around Tra Kieu, scattered Pleistocene terraces overlain by dune sand are present, and evidence there displays continuity from Sa Huynh Iron Age contexts to later Sinicized and Indianized influences. Sa Huynh- and Champa-period sites near Hoi An lie on geomorphologically stable ground where coastal dunes and upstream-derived alluvium coincide. In the Da Nang area to the north, Champa sites are distributed along small rivers across lowlands between terraces. These spatial patterns indicate a close relationship between river/coastal geomorphology and the organization of ancient social landscapes.