The present research evaluated the impact of management scenarios based on land suitability in prioritizing subwatersheds within the Galazchai Watershed, Iran, on changes in the output hydrograph and sediment graph. As a result, the time-area histogram was developed as the synchronized concentration curve of the watershed for each study scenario, using a distributed spatial travel-time method. The Clark time-area model was then applied to route and simulate the hydrograph and sediment graph of the flow, accounting for the type and extent of each land-use, along with the flow from design rainfall as a model input. The findings revealed that six sub-watersheds were ecologically stressed, accounting for 36% of the total watershed area. Three land suitability-based management scenarios were developed for the priority sub-watersheds to address this. In the next phase, concentration-time isochrons for the watershed were extracted under different scenarios, and the hydrograph and sediment graph components were subsequently analyzed. The results indicated an increase in the area of orchards (from 0.26% to 5.85%) and forests (by approximately 3%) in all scenarios, while the regions of rainfed and irrigated farming decreased by 1% to 2%. These land-use changes reduced the peak and time-to-peak of the hydrograph by up to 7%. However, the management scenarios did not result in a significant reduction in runoff volume. Conversely, approximately 23%, 14%, and 17% reductions were observed in the peak suspended sediment concentration, the mean suspended sediment concentration, and total suspended sediment, respectively. The findings provide a valuable management model for planners and policymakers to focus efforts on high-priority areas. Based on the outcomes, the land capability approach, which emphasizes the restoration of poor and moderate rangelands, was identified as the optimal scenario for the study watershed. Despite the limited expansion of treated areas, this scenario substantially impacts the hydrograph and sediment graph components.