The natural and human structuring of rivers and other geomorphological systems: A tribute to William L. Graf

This special issue honors the contributions of William L. Graf to geomorphology and river science. A hallmark of Will's work over the course of his career has been a focus on the natural and human structuring of river systems. More broadly, Will has been an innovator and leader who has shaped the way in which geomorphologists conduct research. Through his work, he has made fundamental contributions to basic fluvial theory, to the understanding of human impacts on river systems, and to policy-relevant science. He has demonstrated by example how to pursue policy-relevant science and to participate in science-based policy formulation. His contributions to river science can be classified into several themes: (1) the hydrology and geomorphology of suburban drainage systems, (2) riparian vegetation and river systems, (3) the spatial structure and dynamics of incised channels, (4) the dynamics of dryland river systems, (5) heavy metals in river systems, (6) dams and dam removal, and (7) water and public policy. The papers in this special issue reflect many aspects of these themes and address topics related to (1) the understanding of rivers and other geomorphic systems in the midst of dynamic physical change, (2) human influences on geomorphic processes, (3) the intersection of geomorphology and public policy, and (4) the fusion of geomorphic analysis and GIScience.