Thanks daverave and oxygenfish for your responses. It is the section titled mud at the bottom of the node layout. I have two image textures connected to a ramp one for the muddy river bed and one for the sides of the river bank. The whole landscape is textured with the layered texture connected to a lambert named ground.

In the image below i have marked in red the current direction of the ramp texture but i want it changing up the slope of the bank marked in green and I am usure how to go about this. Will update later.