Landslides have some effects on the Earth's natural environment. A landslide may change the forest and vegetation borders by releasing downward sediments, forest cover and vegetation. Moreover the diversity of life living in these border areas is adversely affected because of this boundary changing. In addition to the mass movement, heavy rainfall and seismic activity have the important roles to trigger probable landslides prone areas which are to take action. The generation of the current digital elevation model (DEM) is very important immediately after the landslides in order to determine movement direction, character and impacts of the landslide. High resolution DEMs are increasingly generated from photographs acquired with consumer cameras from the unmanned aerial systems (UASs). In this study, we generate DEM reflecting the most current topography of the landslide area on the forestry area, to compare of DEMs from different flight dates and finally with the RTK-GNSS surveys at the landslide borders. In the Biga Peninsula-Turkey, the vegatation is inherently affected by each gravitational mass movement that is one of the major problems endangering the forests. The results showed that the UAS-based DEM generation is higher-accurate in centimeter level, more efficient, faster and lower cost technique with respect to the terrestrial surveys. As a final result, this procedure could be used as a tool for quick determination of vegetation and forestry border changes in landslide areas.