A method implemented by computer for the modeling of channels, on the basis of a model comprising at least: - a space of points, said points having coordinates in said space, - an entry constraint comprising at least one first point of said space, - at least one trajectory constraint (103, 105, 104) comprising at least one second point in said space not included in the entry constraint, and - a local directional component (102a, 102b) being dependent on the coordinates in the space, said directional component taking into account the differences in height of the real terrain; in which the method comprises the steps of: - determining a third point from among the at least one first point of the entry constraint, said third point being taken as current point, - initializing a trigonometric component and an iteration number, said trigonometric component being at least dependent on said iteration number, - determining at least one trajectory (707, 708, 709) in said space, said determination is carried out by iteration of the following sub-steps: a/ drawing of a random number and incrementation of the iteration number; b/ determination of a deviation as a function of the trigonometric component and of the random number drawn; c/ determination of a fourth point of the space as a function of said deviation, of the directional component, and of the coordinates of the current point; d/ addition of said fourth point to said trajectory; e/ iteration of the sub-steps a/ to e/ while taking the fourth determined point as current point as long as an end criterion is not complied with; - if the at least one determined trajectory does not comprise at least the second point of the trajectory constraint, recommencing the steps of said method, otherwise providing the at least one determined trajectory. - a space of points, said points having coordinates in said space, - an entry constraint comprising at least one first point of said space, - at least one trajectory constraint (103, 105, 104) comprising at least one second point in said space not included in the entry constraint, and - a local directional component (102a, 102b) being dependent on the coordinates in the space, said directional component taking into account the differences in height of the real terrain; - determining a third point from among the at least one first point of the entry constraint, said third point being taken as current point, - initializing a trigonometric component and an iteration number, said trigonometric component being at least dependent on said iteration number, - determining at least one trajectory (707, 708, 709) in said space, said determination is carried out by iteration of the following sub-steps: a/ drawing of a random number and incrementation of the iteration number; b/ determination of a deviation as a function of the trigonometric component and of the random number drawn; c/ determination of a fourth point of the space as a function of said deviation, of the directional component, and of the coordinates of the current point; d/ addition of said fourth point to said trajectory; e/ iteration of the sub-steps a/ to e/ while taking the fourth determined point as current point as long as an end criterion is not complied with; a/ drawing of a random number and incrementation of the iteration number; b/ determination of a deviation as a function of the trigonometric component and of the random number drawn; c/ determination of a fourth point of the space as a function of said deviation, of the directional component, and of the coordinates of the current point; d/ addition of said fourth point to said trajectory; e/ iteration of the sub-steps a/ to e/ while taking the fourth determined point as current point as long as an end criterion is not complied with; - if the at least one determined trajectory does not comprise at least the second point of the trajectory constraint, recommencing the steps of said method, otherwise providing the at least one determined trajectory.