Hillslope Hydrology and Stability

Landslides occur when hillslopes become mechanically unstable, because of meteorological and geologic processes, and pose a serious threat to human environments in their proximity. The mechanical balance within hillslopes is governed by two coupled physical processes: hydrologic or subsurface flow and stress. 

Hillslope Hydrology and Stability

The stabilizing strength of hillslope materials depends on effective stress, which is diminished by rainfall, increasing the risk of gravity destabilizing the balance and causing a landslide.

This book presents a cutting-edge quantitative approach to understanding hydro-mechanical processes in hillslopes, and to the study and prediction of rainfall-induced landslides. Combining geomorphology, hydrology, and geomechanics, it provides an inter-disciplinary analysis that integrates the mechanical and hydrologic processes governing landslide occurrences, across variably saturated hillslope environments. 

Topics covered include a historic synthesis of hillslope geomorphology and hydrology, total and effective stress distributions, critical reviews of shear strength of hillslope materials, and different

bases for stability analysis. Exercises and homework problems are provided for students to engage with the theory in practice.

This is an invaluable resource for graduate students and researchers in hydrology, geo-morphology, engineering geology, geotechnical engineering, and geomechanics, and also for professionals in the fields of civil and environmental engineering, and natural hazard analysis.

Foreword

Even a cursory inspection of Hillslope Hydrology and Stability by Lu and Godt will impress most professionals interested in processes at the interface between geotechnical engineering and hydrology. 

This unique textbook represents an attempt to systematically unify concepts from vadose zone hydrology and geotechnical engineering into a new hydro-geo-mechanical approach with special emphasis on quantifying natural mechanisms for the onset of hydrologically induced landslides. 

Professionals will particularly appreciate the comprehensive coverage of concepts ranging from fundamentals of geomechanics and soil properties to the state-of-the-art concepts of hillslope hydrology, with explicit treatment of soil heterogeneity, layering, and vegetation mechanical and hydrologic functions. 

The authors have been able to weave a coherent picture based on the cutting-edge state of knowledge regarding landslides as natural geomorphological processes and as ubiquitous natural hazards in mountainous regions. Students will appreciate the lucid coverage of topics offering a systematic introduction to key ingredients essential for understanding the occurrence of landslides in their broader natural context (often missing in technical textbooks). 

Students are guided through aspects of precipitation with its instantaneous to inter-annual patterns, as well as aspects of soil types and the geomorphological context of landslides. This provides a solid foundation for introduction of more specific technical aspects of infiltration, hillslope hydrology, and hydro-mechanical properties, and assembles the roles of these factors on a hillslope mechanical state. 

Students will find clear explanations of fundamental concepts inspired by numerical examples to help them develop appreciation for the orders of magnitude for the quantities involved. Numerous motivating homework problems further promote self-study.

Hillslope Hydrology and Stability helps chart the boundaries of the emerging interdisciplinary field of soil hydromechanics. The authors offer a rigorous link between hydrology and soil mechanics by providing a unified treatment of effective stress (suction stress) under variably saturated conditions (Chapter 6). 

The authors also provide a fresh look at well-established concepts found in textbooks from hydrology and geotechnical engineering fused together using new crucial aspects typically glossed over in standard texts, thereby providing a unique new perspective. 

For example, the interplay between hillslope subsurface flows and soil layering (forming hydrologic barriers), a critical mechanism for abrupt landslide triggering, has rarely been previously discussed in a quantitative hillslope hydromechanical context as done in Chapter 3. 

The quantitative treatment of root reinforcement and the role of plants in the mechanical picture of natural hillslopes (Chapter 7) is another example of the conceptual integration in the basis of the book. 

The wealth of information on numerical values of key parameters and the instructive use of case studies described in Chapters 9 and 10 make Hillslope Hydrology and Stability an outstanding resource for students, researchers, and practitioners alike. 

No doubt the test of time would add refinement to this labor of love that contains numerous new concepts – I hope students and researchers would be challenged and inspired by the breadth and depth offered in this unique treatise on hydro-mechanical hillslope processes.

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Hillslope Hydrology and Stability