This book presents an overview of current research problems and advances in theoretical and applied aspects of environmental hydraulics. The rapid development of this branch of water studies in recent years has contributed to our fundamental understanding of processes in natural aquatic systems and helped provide solutions for civil engineering and water resources management. The book features comprehensively reviewed versions of invited lectures and regular presentations given at the 38th International School of Hydraulics, held May 21-24, 2019, in Lack, Poland. With papers by leading international experts as well as young researchers from around the globe, it covers recent findings from laboratory and field studies, numerical modeling related to sediment and pollutant transport processes in rivers, fluvial morphodynamics, flow in vegetated channels and hydraulic structures in rivers and estuaries.