Climate is changing. It is widely accepted that irrespective of the emission reductions efforts, adaptation to the already committed climate change is a must in the coming decades. Flooding is one of the most devastating climate-induced hazards, calling for adaptation across scales: from government-led adaptation (e.g. dikes), to personal household-led adaptation. There are numerous private adaptation measures, both structural and non-structural, that households can autonomously take to reduce damages and speed up own recovery, in case of the adverse event does occur. Worldwide household surveys provide the empirical evidence suggesting that the appraisal of fear, perceptions of own coping abilities and social influences affect individual decision to adapt. Especially the latter appear as a strong determinant of household-led adaptation. Yet, the role of social networks has not been studied systematically, let alone the exploration of the interplay between private households' adaptation and public policies in the presence of social influences. To increase the understanding of social networks' impact on private flood adaptation under various public policies, an empirical agent-based model is built. In addition to empirical flood maps, I employ Protection Motivation Theory and households' survey data from Houston (Texas, USA) to capture the household’s adaptation decisions, which are subject to social influence. To represent a range of social networks, I explore the effect of three random networks - Erdös-Renyi random network, Barabasi-Albert scale-free network, Watts-Strogatz small-world network -- on the diffusion of flood preparedness. These three networks could serve as a proxy of diverse types of social relationships that vary across cultures, with some being hierarchical and others egalitarian. Furthermore, I test how the diffusion of private adaptation among households evolves under four generic public policy strategies: protection by publicly-funded infrastructure, market-based policy such as subsidy, information policy and regulatory policy.
The thesis findings reveal that the type of social networks influence success of private adaptation decisions significantly. Notably, the effect of social norms depends on the network configuration, where more homogeneous networks lead to higher private adaptation uptake. Furthermore, the thesis quantifies the interaction effects between social networks and policies designed to support private climate change adaptation, for example communication campaigns affecting individual risk perceptions that in turn drive household-led adaptation. Therefore, information policies can be very effective in steering public opinions and, hence, the uptake of households' adaptation measures. Moreover, I find that in the presence of social networks, public adaptation policies interact with each other: a combination of subsidies with communication exhibit synergistic effects on the flood damage reduction from private adaptation. Policies that do not interact with households' perceptions, like infrastructure projects or laws, can be considered more robust - less sensitive to social networks. To conclude, networks can shape the success of climate change adaptation policies and should be accounted for in their design. Further research should focus on the endogenous evolution of social networks and the model behavior under changing flooding conditions and what this complex adaptive system's dynamics means for future cross-scale adaptation efforts.