One of the principal problems faced by countries in tropical region is the high risk of natural related disaster due to the high precipitation level, which can cause floods and provoke landslide. The damaging impact on human beings and public facilities is often worsened in developing countries by the lack appropriate infrastructure for flood control and landslide protection, unchecked deforestation, and high dense of population in urban areas. In this paper we describe the design of environmental monitoring system by using wireless sensor networks (WSN) as platform, as well as the implementation of a prototype system, which could be beneficial to a developing country like Indonesia.