Surface runoff occurs when excess rainfall cannot infiltrate the soil quickly enough, potentially increasing flood risk. Several factors affect runoff, including meteorological conditions and physical landscape properties. Generating global runoff data previously required extensive processing and storage, but tools like Google Earth Engine now enable this type of analysis using available global datasets on precipitation, soils, land cover, and topography. The methodology uses the Curve Number method to produce runoff maps by combining hydrologic soil group, land cover, and slope data to assign curve numbers, then calculates runoff based on these numbers and precipitation data. Limitations include the empirical nature of the Curve Number method and its restricted applicability to certain regions and land uses.