In these days, damages from localized heavy rain or typhoon are increase and people are making constant effort to work out countermeasures. Especially, by apply GIS with prompt extraction of information and objective analysis, we could demonstrate more effectively. For that reason, in this research we make the connection between rainfall-runoff model and HEC-RAS which calculate automatically and inquire out the dangerous zone easier way by describing the result with the connection between the Map Object and MFC. Most of all, this research will be very useful to forecast and prepare the disaster because it could plot plane figures, longitudinal sections and cross sections at the same time to help understand the damaged situation.