Riparian buffer zones have important ecological functions such as sustainability of water quality, reducing sediment accumulation, and preventing erosion. However, it is often very difficult to develop a general rule for these areas since each riparian zone may have different rainfall characteristics and soil properties. In this study, the width of riparian buffer zone was determined around a sample dam lake to achieve sustainable water quality and soil conservation. The research was conducted in Palandöken Dam Lake located in the eastern city of Erzurum in Turkey. For the implementation of the riparian buffer zone, firstly, flood conditions were taken into account based on series of satellite images and then depression zone was calculated using Archydro software based on Digital Elevation Model. Two satellite images of the study area taken in August 2008 and April 2011 were compared to determine the potential flooded areas. Then, potential depression zone, which are around and beyond the flooded areas, were determined based on terrain structure (sink areas). Finally, the width of the riparian buffer zone was determined by including reserve zone and management zone onto the depression zone. The results indicated that depression area was 5,774 ha. The area and perimeter of riparian buffer zone were 6,364 ha and 59 km, respectively. It was found that hydroecological approach using geographical information system technology can be successfully implemented to provide maximum sustainable protection of water and soil resources in riparian zones, especially in the lake basins.