Flash floods pose severe risks to both upstream and downstream communities. They can destroy critical infrastructure, such as hydropower dams and transport corridors, and disrupt livelihoods by damaging farms and isolating villages. Transboundary vulnerabilities are significant, as floods originating in Nepal or Tibet can impact Indian states like Bihar, Arunachal Pradesh, and Sikkim with minimal warning. The long-term effects include riverbed siltation, which exacerbates flooding in downstream plains.