This book contains the written versions of invited lectures presented at the Gerhard H. Jirka Memorial Colloquium on Environmental Fluid Mechanics, held June 3-4, 2011, in Karlsruhe, Germany. Professor Jirka was widely known for his outstanding work in Environmental Fluid Mechanics, and 23 eminent world-leading experts in this field contributed to this book in his honour, providing high-quality state-of-the-art scientific information. The contributions cover the following key areas of Environmental Fluid Mechanics: Fluvial Hydraulics, Shallow Flows, Jets and Stratified Flows, Gravity Currents, Mass Transfer and Small-Scale Phenomena, and include experimental, theoretical and numerical studies. In addition, former co-workers of Professor Jirka provide an extensive summary of his scientific achievements in the field.