Changes in land cover within urban areas can reduce infiltration capacity and increase surface runoff. This study aims to evaluate infiltration rates, surface runoff, and the sensitivity of land cover changes within the core area of the Widya Mandira Catholic University (UNWIRA) Kupang campus using the Horton Model. Field measurements were conducted using a double-ring infiltrometer at three observation points representing vegetated land, semi-permeable surfaces, and impervious/built-up areas. The Horton parameters were calibrated through nonlinear optimization by minimizing the Root Mean Square Error (RMSE), after which they were applied to estimate cumulative infiltration over a 60-minute period. Surface runoff was estimated based on design rainfall with return periods of 2, 5, and 10 years, while sensitivity analysis was performed through scenarios involving a 1–5% reduction in permeable land area. The calibration results produced RMSE values ranging from 0.894 to 2.001 cm/hour. Zone 2 exhibited the greatest infiltration capacity, reaching 2,405.42 m³, whereas Zone 3 had the lowest infiltration capacity, 618.33 m³, and generated the highest R₁₀ runoff volume of 1,090.07 m³. Under the scenario involving a 5% reduction in permeable area, runoff in Zone 1, Zone 2, and Zone 3 increased by 8.28%, 18.87%, and 2.84%, respectively. These findings indicate that Zone 2 is the most sensitive in relative terms, whereas Zone 3 is the most vulnerable based on its actual runoff volume. Overall, the results underscore the importance of preserving permeable areas and enhancing infiltration facilities in future campus development.
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