Practitioners in water engineering rely on a thorough understanding of shallow water flows in order to safeguard our habitat, while at the same time sustaining the water environment. This book proposes a unified theoretical framework for the different types of shallow flow, providing a coherent approach to interpret the behaviour of such flows, and highlighting the similarities and differences. Every major topic in the book is accompanied by worked examples illustrating the theoretical concepts. Practical examples, showcasing inspiring research and engineering applications from the past and present, provide insight into how the theory developed. The book is also supplemented by a range of online resources, available at www.cambridge.org/battjes, including problem sets and computer codes. A solutions manual is available for instructors. This book is intended for students and professionals working in environmental water systems, in areas such as coasts, rivers, harbours, drainage, and irrigation canals.