This study has been executed aiming at identifying, classifying and investigating the environmental effects of Lorestan’s Roodbaar Dam during its exploitation phase through utilizing MIKE11 software and LINMAP technique. Lorestan’s Roodbaar Dam is located in Lorestan Province, 100 kilometers to the South of Alugoodarz Town on Roodbaar River (from branches of Eastern Dez River), within the area of Zagros Mountains in the West of Iran. It is crucial not to consider merely one parameter when using the evaluation methods, on the contrary, the mutual effects of all parameters and their consequent effects must be taken into account. The immediately- affected area was located through collecting data from the environmental conditions of the area and from the technical information on Roodbaar Dam using MIKE 11 software. The positive and negative effects of the dam were eventually prioritized using LINMAP mathematical model. Prioritizing the positive effects of the project indicated that (income) ranked 0.0507, following that (services, industry, commercial) ranked 0.0480 and was placed in the second place. Two villages will go under water with the construction of this dam. This will lead to the mentioned villagers moving and their resettlement. Therefore (moving) ranked 0.3452 and it earned first place among the negative effects of the dam and (erosion) (sedimentation within the dam’s container), (the endangered plant species within the area) all ranked 0.2959 and were placed second within the prioritization. At the end proper approaches were presented for the exploitation stage of Lorestan’s Roodbar Dam taking into consideration the results obtained from prioritizing the effects.