A computer-implemented method for determining a karstic region modified by karstification phenomena, comprising: a/ receiving a geological model of the karstic region comprising cells, said model comprising at least one first zone , named seed zone, comprising cells of the model and at least one second zone , named target zone, comprising cells of the model, each cells of the model having coordinates; b/ determining a first cell , named seed cell, in the cells of the at least one seed zone; c/ determining a second cell , named target cell in the cells of the at least one target zone; d/ if a distance between the seed cell and the target cell is above a predetermined distance : d1/ determining a third zone , named bifurcation zone, based on the coordinates of the seed cell, the coordinates of the target cell, a distance distribution, an angular distribution, d2/ determining a third cell, named bifurcation cell in said bifurcation zone; d3/ re-iterating step d/ with a cell based on said bifurcation cell as the seed cell; e/ determining fourth cells, named trajectory cells, in the geological model based on the seed cell, the target cell and bifurcation cells determined in step d/; f/ for each current cell in the trajectory cells, f1/ determining , for the current cell, conduits characteristics based on a predetermined conduit density distribution, a predetermined conduit aperture distribution and trajectory cells connected to said current cell; f2/ determining, for the current cell, cell characteristics based on the conduits characteristics of said current cell. a/ receiving a geological model of the karstic region comprising cells, said model comprising at least one first zone , named seed zone, comprising cells of the model and at least one second zone , named target zone, comprising cells of the model, each cells of the model having coordinates; b/ determining a first cell , named seed cell, in the cells of the at least one seed zone; c/ determining a second cell , named target cell in the cells of the at least one target zone; d/ if a distance between the seed cell and the target cell is above a predetermined distance : d1/ determining a third zone , named bifurcation zone, based on the coordinates of the seed cell, the coordinates of the target cell, a distance distribution, an angular distribution, d2/ determining a third cell, named bifurcation cell in said bifurcation zone; d3/ re-iterating step d/ with a cell based on said bifurcation cell as the seed cell; d1/ determining a third zone , named bifurcation zone, based on the coordinates of the seed cell, the coordinates of the target cell, a distance distribution, an angular distribution, d2/ determining a third cell, named bifurcation cell in said bifurcation zone; d3/ re-iterating step d/ with a cell based on said bifurcation cell as the seed cell; e/ determining fourth cells, named trajectory cells, in the geological model based on the seed cell, the target cell and bifurcation cells determined in step d/; f/ for each current cell in the trajectory cells, f1/ determining , for the current cell, conduits characteristics based on a predetermined conduit density distribution, a predetermined conduit aperture distribution and trajectory cells connected to said current cell; f2/ determining, for the current cell, cell characteristics based on the conduits characteristics of said current cell. f1/ determining , for the current cell, conduits characteristics based on a predetermined conduit density distribution, a predetermined conduit aperture distribution and trajectory cells connected to said current cell; f2/ determining, for the current cell, cell characteristics based on the conduits characteristics of said current cell. <EOS>