The emerging field of socio-hydrology is a special case of social-ecological systems research that focuses on coupled human-water systems, exploring how the hydrologic cycle and human cultural traits coevolve and how such coevolutions lead to phenomena of relevance to water security and sustainability. As such, most problems tackled by socio-hydrology involve some aspects of engineering design, such as large-scale water infrastructure, and self-organization in a broad context, such as cultural change at the population level and the hydrologic shift at the river basin or aquifer level. However, within the field of socio-hydrology, it has been difficult to find general theories that assist our understanding of the dynamics emerging from the interplay between design and self-organization, hindering generalization of phenomena between cases. We address this gap by developing insights on how the theoretical frameworks of robustness-fragility trade-off and cultural multilevel selection can inform our understanding in this regard. We apply the two theories to two cases in the Ganges Brahmaputra Delta in Bangladesh and the Kissimmee River Basin in Florida, illustrating how the two theories may provide general insights into causal mechanisms shaping the socio-hydrological phenomena observed in the two cases. Specifically, we use the two theories to address (1) the transference of system fragility across different domains due to design choices and (2) the multilevel social processes in the nested organizational hierarchy that lead to the formation or collapse of shared cultural traits. We show that these two theories, separately or taken together, can provide richer theoretical grounding for understanding socio-hydrological phenomena.