This study analyzed changes in cold-air formation and diffusion functions resulting from ridge disruption and compared differences across case areas. The Kaltluftabflussmodell (KALM) model, developed in Germany, was applied to two disrupted ridge sections: the Sacheon Floodway section of the Naknam Ridge and the Gyeongin Ara Waterway section of the Hannam Ridge to evaluate their cold-air formation functions. Simulation results revealed that after disruption, the height of the cold-air layer generally decreased, and the spatial extent of cold-air diffusion narrowed. In the Sacheon Floodway section, the removal of forest and the expansion of impervious surfaces markedly reduced the capacity to generate cold air. Meanwhile, in the Ara Waterway area, terrain modification altered the cold-air flow paths and weakened the diffusion function. These results indicate that ridge disruption can affect the overall microclimatic processes of the formation, flow, and diffusion of cold air. Furthermore, the effects vary depending on the type of disruption and surrounding topographic and land-use conditions, highlighting the need for differentiated impact assessments and restoration strategies. This study contributes to understanding the climatic regulation function of urban-adjacent ridges and provides a scientific basis for future cold-air corridor planning and ridge restoration policies.