Observing flows on land surfaces, streams, and rivers is complex, expensive, and time-consuming. Simultaneously, accurate runoff and stream flow data are scarce. Therefore, a simple rainfall-runoff model that mimics the real-world system becomes indispensable. Although wide ranges of rainfall-runoff methods/models have been developed in the past, most have inherent limitations in simulating different hydrological systems. With a thorough evaluation and review of rainfall-runoff methods, a new conceptual model that can simulate alternative runoff generation, infiltration, and saturation excess, has developed. The new model quantifies the stream flow with a multi-layered approach and well separates the contributions of infiltration-excess runoff (IRun), saturation excess runoff (SRun), sub-soil lateral flow or interflow (IFlow), and the base flow (BFlow). The model’s performance has also been proved using the calibration and validation processes of six randomly selected gauged catchments from different river basins in Ethiopia as representative of tropical-monsoon hydrological systems. The ranges of statistical values for R-square, RMSE, NSE, and PBIAS were 0.77- 0.87, 0.47 -1.04, 0.52- 0.93, and 0.0, respectively, confirming that the new model performs well for different hydrological systems. Moreover, the single-user-interface computer programs for the model running also facilitate its use as plugging with various tools, including GIS packages and database catalog systems.