Discordant drainage patterns
A drainage pattern is described as discordant if it does not correlate to the topology and geology of the area. Discordant drainage patterns are classified into two main types: antecedent and superimposed while anteposition drainage patterns combine the two. In antecedent drainage, a river's vertical incision ability matches that of land uplift due to tectonic forces. Superimposed drainage develops differently: initially, a drainage system develops on a surface composed of 'younger' rocks, but due to denudative activities this surface of younger rocks is removed and the river continues to flow over a seemingly new surface, but one in fact made up of rocks of old geological formation.