Nowadays, the world faces with lack of electricity access, water scarcity, climate change and global warming. The hydropower industry has a crucial role to deal with these problems as well as to develop projects for sustainable development. However, if social, environmental and economical impacts of a hydroelectric power plant (HEPP) project are not considered, it might lead to irreparable destructions. Nowadays, in Turkey, due to social and environmental problems resulting from hydropower projects, the opponents of HEPP projects are increasing. Whether there are any deficiencies in hydropower project&rsquo / s development procedure causing environmental and social problems is researched in this thesis. The laws and legislations in Turkey related to hydropower project are investigated. The International Hydropower Association (IHA) has developed Hydropower Sustainability Assessment Protocol for hydroelectric power projects. It assesses the projects according to economic, social and environmental measurements. Thus a case study, namely Kayraktepe Dam and HEPP Projects is evaluated to identify social, environmental and economical effects of the project at an early stage by using this Sustainability Assessment Protocol. The effects of large scale dam are compared with the effects of medium dam and five diversion weirs on social, environmental and economical issues.