In default vanilla; the Helgen Mud textures use the Ratway dungeon set.  If you use a texture overhaul for the Ratway; this texture will be replaced and potentially lead to seams or poor blending.

T4's Underground included a mesh that re-paths to unique textures for the mud instead of using the Ratway.  I have included these here along with parallax support via the mesh and a new texture.

You do NOT need this mod if using Underground Ratway Parallax

My screen shots without this mod were using WiZkiD's Riften and Ratway + Grass Must Grow Landscape Add On; it had seams and poor blending.   With this mod and still using WiZkiD's Riften and Ratway + Grass Must Grow Landscape Add On you can see a noticeable improvement in blending,  Your mileage may vary depending on your Landscape textures.