Modelamiento del control topográfico sobre los flujos

This paper presents the numerical model of the behavior of a possible lahar coming from the Mijitayo stream. This lahar is sourced by the gathering of material found inthat place. According to INGEOMINAS, this zone is rated as the limited point where the piroclastic flows coming from the Galeras volcano occur. The threshold conditionswere determined through known theoretical data, assuming that the flow is both constant and unvarying. The numerical model was done through the energy principles andmomentum, and through the continuity equation, the energy equation and the density change.

The model shows the topographical control which makes this work differentfrom other models previously applied to possible flows occurring in the Mijitayo stream, where there is only a wide buffer for the whole stream riverbed. In order toconsider the topography of the stream, the riverbed was broken down into sections and a database including the area, the wet perimeter, the wide surface and the hydraulicradio was done in relation to each section and the different heights of the riverbed.

The respective stages were analyzed by two different volumes which were obtainedthrough the lahar-energy lines. In this way an area of possible affectation for each stage and the respective flow speed were established, as well as the hydraulic depthin each stage during its path. The obtained values of the creased coefficient from both The Manning and The Chezy quite approximate the empirical values for naturalcanals. The results that were obtained from the model entail the flow diffuse, therefore, the density shift is considered throughout its path if the concentrations are low.