Wireless sensor networks have become a promising method for disaster monitoring such as real-time forest fire detection, radiological monitoring, earthquake detection, and more. In this thesis, we propose to apply the wireless sensor network technology to monitoring and alerting flooding incident in association with dam discharge. Using a wireless sensor network, adaptive query, and cell broadcasting service, the public alert system for dam discharge can provide the right alert information to the right person at the right time, and we can obtain abundant information by real-time sampling the environmental situations for decision-making in an emergency situation. As proof of this concept, we have developed a prototype dam discharge alert system that employs the adaptive querying technique on top of a wireless sensor network. We have identified that the new cutting-edge technology would provide new services producing a high-quality information service for both the service provider and mobile users. This work will further demonstrate how such ubiquitous computing techniques could be used for environmental issues.