In this study, the effects on freshwater fish of flood control studies were investigated in Ilıca and Kömürcü streams where upper basin of Koçköprü Dam Lake in Van-Erciş. Ilıca Stream, Kömürcü Stream and Zilan Stream are running water in which formed Koçköprü Dam Lake. The flood control studies were carried out for prevent of agricultural land around the İşbaşı village and avoidance of sedimentation of the dam lake in Ilıca and Kömürcü streams by DSİ. In this context, the bed of streams is channelized and, riparian zone is cover with big stones as sloppy. The transversal barriers were made into the stream bed for avoiding of flood scouring in Ilıca and Kömürcü streams. The effects on freshwater fish of flood control studies in Ilıca and Kömürcü streams were carried out before and after the flood control studies by sampling program. During the study, 3 taxon endemic for total 5 taxon freshwater fish have been identified in Ilıca and Kömürcü streams. These 5 taxon of freshwater fish as Alburnus tarichi, Barbus ercisianus, Alburnus mossulensis, Capoeta kosswigi and Oxynoemacheilus ercisianus is affected by flood control studies into streams have been determined. Particularly, this fish taxon were captured in all sampling station before the flood control studies in Ilıca Stream, fish was not sampled after the flood control studies upper sampling point cause of high transversal barrier into the stream and, it was distributed only near the stream mouth have been identified. In this study, suggested solutions have been developed for continue to old natural habitat with their lives of 3 endemic taxon of total 5 taxon freshwater fish.