In this paper, we propose a mathematical model to simulate internal human migration in the Colombian Pacific region using causal diagrams. This tool allows simulating and making projections about migrational behavior; also, it uses numerical optimization and real data about population projection done by the National Administrative Department of Statics. The optimization strategy, in a first stage, uses genetic algorithms to perform a good exploration of the search space and then, uses a method based on gradient to achieve a good convergence. Finally, the results show a good fit for the proposed model.