Grazing management practices can lower soil loss and the subsequent sediment pollution of surface water bodies. To explore the effect of such practices on soil erosion and loss across the landscape of Samothraki the process-based GIS model SWAT was implemented. The most critical areas (subbasins) of soil loss to waters were identified and grazing management scenarios, including livestock reductions by 50% and 100%, grazing period reduction, and a combination of them, were formulated and applied. The annual reduction results varied between scenarios in the range of 10% to 25% for the entire island, and in wider ranges for its individual subbasins, showing a high potential for reducing the vulnerability of the most pressured ones. However, due to the high importance of the natural factors of rainfall and land slopes, the erosion vulnerability of the island overall could be significantly altered only if grazing management was integrated within a reforestation plan.