Hydrological modeling often requires long-term and stable runoff data. Due to limitations in hydrological stations, hydrological modeling in small-scale catchments faces the challenge of data scarcity. To overcome the challenge of incomplete hydrological data, an integrated modeling approach that includes a semi-distributed hydrological and a hydrodynamic numerical model was employed in a small-scale catchment located in Isserstedt, upstream of the Leutra River, Germany. The results indicated that this integrated modeling approach effectively leverages the strengths of each model and reasonably predicted peak flows. As a measure for regional runoff management, keyline method contributed to more stable hydrographs and lower peak flows, and played a role in water storage and local climate regulation. The framework proposed in this study provided valuable insights into critical storms, hydrographs, and flood extent in storm runoff extremes.