Invited perspectives: reframing transboundary flood vulnerability through “Hydrosocial Connectivity” for just and adaptive governance

Transboundary flood risks are intensifying across South Asia due to climate change, land-use change, and rapid development in shared river basins. However, governance responses remain dominated by hydrological control and infrastructure-heavy strategies, overlooking the deeper social, institutional, and political drivers of vulnerability. We define transboundary flood vulnerability as the heightened and unequal exposure of downstream and marginalised communities to flood risk, shaped by systemic governance disconnections between hydrological flows, governance fragmentation, and inequalities across borders. To address this gap, this paper advances “hydrosocial connectivity” as a diagnostic and relational lens for revealing how disconnections across hydrological, social and governance systems produce transboundary flood vulnerability, with implications for governance. Adopting a hydrosocial systems perspective, it conceptualises the Ganges–Brahmaputra basin as an interdependent socio-environmental system where hazards and vulnerabilities are co-produced through feedback between environmental dynamics and governance structures. Within this framing, hydrosocial connectivity captures the dynamic and uneven interlinkages between water flows, social relations, and governance processes across scales and borders. Through a focused critical review of the India–Nepal–Bangladesh floodplain (a low-lying, flat depositional plians and delta region of the Ganges-Brahmaputra basin), the analysis shows how the absence of basin-wide agreements, limited data-sharing, and the exclusion of local knowledge are not isolated governance gaps but symptoms of disconnections (also a blind spot) those reinforce vulnerability and undermine resilience. This framing highlights how risk and resilience are shaped not just by physical flows but by power, politics, and participation. By centring justice, equity, and collaboration, a hydrosocial connectivity approach offers a pathway for rethinking transboundary flood governance beyond borders, beyond hydrology, and toward more coordinated adaptive and inclusive outcomes.