Limited flood disaster information causes insufficient justification for public awareness, therefore, improving flood practice management is needed. This paper applies the flood forecasting model and atmospheric model to identify rainfall distribution and to investigate the threshold values for alert system. The entire system aims to improve flood monitoring, information distribution and an alert system. The geospatial web based system is established to facilitate public awareness by allocating information in timely manner without cumbersome software installation. The process to obtain rainfall and river discharge data, input and transfer data, through the database can be launched after other parameters i.e. elevation, soil, land cover, and basin boundary are set. The entire process takes approximately 15 minutes. The flood warning system and the geospatial web based system are connected to the database and promptly alert in the case of emergency. The yields prove promising results, based on the amount of time and viable function. The existing rainfall spatial based pattern, received from the atmospheric model, takes about 72 minutes to achieve one hourly image. It is a suitable model for observing regional rainfall distribution. It does not serve immediate alert purpose in the emergency situation due to it is too time consuming.