The aim of this study is to investigate and demonstrate the use of remote sensing and geographic information system (GIS) techniques to create athematic assessment in order to locate a best dam site in Al-Tharthar basin northern Iraq. Automated derivation of multi thematic layers to describe the characteristics of the catchment was performedwith aid of several softwares (Erdas 9.1, Arc GIS 9.3, Global Mapper 11 and Surfer 9). Gathering all these data has to construct database of the catchment area to decide the locations of the proposed dams. Three locationswere chosen.Dam site one was chosen to be the best site since it is provide lesser length with more lake storage and has substantial of foundation material for dam construction.Furthermore, various calculation regarding the design of the dam, its parameters was investigated.

Keywords:Remote sensing, GIS, DEM,Dams sites selection.