The purpose of this paper is to integrate the proactive role of communities and the use of flood modeling in the implementation of a flood early warning system. Manual rain gauges were installed in 20 houses of volunteers living within the Bicol River basin to monitor rainfall. Rain information is sent twice daily via SMS message to a receiving computer. The received data are used to run a basin model that was developed in HEC-HMS, which converts precipitation excess to overland flow and channel run-off. Different watershed models were developed for different rainfall events. Geomorphic analysis using 3?s SRTM Digital Elevation Model (DEM) processed in a GIS platform was also done to refine the overland flow. The derived hydrographs were used in the HEC-RAS hydraulic model which has as main output threshold values for the rain-flood relationship.