Rick Engineering Company’s Water Resources Division prepared a Geographic Information System (GIS)-based Master Drainage Plan (MDP) for the City of Vista. The study area includes the 17.2-square mile area within the current corporate boundary of the City of Vista, and the unincorporated areas to the east. The MDP was prepared using Arc/Info GIS to prepare and process data from digital CAD files for hydrologic modeling. The GIS files were integrated with the Advanced Engineering Software (AES) hydrology and with cost estimate modules using software developed by Rick Engineering Company, along with AutoCAD drawing files to produce better, more accurate modeling results. The Rational Method was used for basin areas less than one square mile. Soil Conservation Service Unit Hydrograph Method was used in areas greater than one square mile. Together with the City of Vista staff, we estimated pipe sizes or reinforced concrete box system culverts. Where a natural or open-channel system was directed by the City, an unimproved channel was used in the hydrologic and hydraulic calculations. Cost estimates were then prepared with the computer model and incorporated into GIS. The final product was viewed and can be queried using ArcView software.