Currently it is not possible for a River element to be on the edge between two polygon inhomogeneities. An example of a situation where this would be valuable is a canal in an area with various managed phreatic levels, where the managed level on one side of the canal differs from the level on the other side of the canal. A similar feature exists with building pit elements, where the sheet pile wall can exist on the edge of the inhomogeneity.
Currently it is not possible for a River element to be on the edge between two polygon inhomogeneities. An example of a situation where this would be valuable is a canal in an area with various managed phreatic levels, where the managed level on one side of the canal differs from the level on the other side of the canal. A similar feature exists with building pit elements, where the sheet pile wall can exist on the edge of the inhomogeneity.