With regard to the hidden security and reliability problems of dam monitoring data, this study proposes a system architecture composed of sensor cloud and the Unmanned Aerial Vehicle (UAV) cloud based on BlockChain (BC) technology for monitoring dams to ensure the security and reliability of data. The sensor cloud provides various sensing data, while the UAV cloud collects these data and transmits them to the Dam Monitoring Center (DMC), and the BC technology is applied to ensuring integrity, authenticity, security and traceability of data. The analysis shows that the proposed system has good scalability, which can effectively guarantee the reliable sources of monitoring data and the security of data transmission and prevent potential data attacks. Finally, this study assesses the work performance by evaluating the delay rate of data transfer. The simulation results reveal that the delay rate of the designed system is positively correlated with the probability of generating events and revisit time, but negatively correlated with the alarm interval time, and it presents a higher payment success rate.