Satellite views of Earth’s major river systems reveal their familiar treelike drainage patterns. The pattern – called dendritic – and its prevalence suggests that it may be the optimal state in which rivers exist. Challenged by the knowledge that numerical models of drainage evolution have yet to substantiate this assumption, researchers are now thinking of rivers as existing in a persistent reorganizational state instead of being in a set, stable configuration. Understanding this has implications for land use and infrastructure management decisions.