Debris Flow

Comprehensive account, treating both theoretical and applied aspects of debris flow. The text begins with a discussion of fundamental mechanical aspects, such as flow characteristics, type classification, mechanics, occurrence and development, fully-developed flow and deposition processes. The second part of the book sheds light on the application of theory in relation to computer-simulated reproductions of real disasters. Attention is paid to debris flow controlling structures, design effectiveness and performance, soft countermeasure problems, such as identification of debris flow prone ravines and the prediction of occurrence by the concept of precipitation threshold. The qualitative and fundamental character of this book makes it an excellent textbook for graduate courses in debris flow and it is recommended reading for professionals in engineering, geosciences and water resources who are concerned with mechanics and countermeasures of debris flow. Keywords: stony debris flow, viscous debris flo, landslide induced debris flow, hazard zone mapping, grid type sabo dam.

Tamotsu Takahashi is Professor Emeritus at the University of Kyoto and at the Department of Sediment Research of the China Institute of Water Resources and Hydropower Research in Beijing. In addition to his academic positions, he is the Director of the Association for Disaster Prevention Research in Kyoto. Professor Takahashi began his career in flood dynamics research, and increasingly focused on debris flow and flood hazards. He has been honoured with several awards from the Japan Society of Civil Engineers and the Japan Society of Erosion Control Engineering. In 1991, an earlier book entitled 'Debris Flow', by Tamotsu Takahashi, in the book series of the International Association of Hydraulic Engineering and Research, was published by Balkema Publishers, now a part of the Taylor & Francis Group.

Preface

Chapter 1 What is debris flow?




Various sediment moving phenomena


Definition of debris flow


Classification and characteristics of debris flows



Stony type debris flow


Turbulent muddy type debris flow


Viscous debris flow


The significance of the mechanical classification of debris flows


Classifications on the other points of view


Chapter 2 Models for mechanics of flow



2.1 Models for solids and fluid mixture as the multi-phase flow
2.2 Single-phase continuum models
2.2.1 Visco-plastic fluid model
2.2.2 Dilatant fluid model
2.3 Two-phase continuum models (Mixture theory)
2.3.1 Stress equilibrium equations
2.3.2 Coulomb mixture theory (Quasi-static debris flows)
2.4 Theory for subaerial rapid granular flows
2.4.1 Particle collision stress
2.4.2 Kinetic stress
2.4.3 Skeletal stresses
2.4.4 Constitutive relations
2.4.5 Application of the theory to dry granular flow
2.4.6 Comparison with other constitutive relations for inertial range
2.5 Role of interstitial fluid in inertial debris flows
2.6 The mechanism of immature and turbulent muddy debris flows
2.6.1 Immature debris flow
2.6.2 Turbulent muddy debris flow
2.7 Generalized theory for inertial debris flows
2.7.1 Theoretical considerations
2.7.2 Verification by experimental data
2.7.3 Approximate solution for solids concentration and resistance to flow
2.8 Newtonian fluid model for viscous debris flow
2.8.1 Theoretical considerations
2.8.2 Verification by experiments

Chapter 3 Initiation and development of debris flow




Initiation and development of debris flow due to gully bed erosion



The formation of incipient debris flow by the effects of surface water runoff


The development of stony debris flow on sediment bed


Verification of the theory by experiments


Landslide-induced debris flow



Model for the transformation into debris flow


Mathematical model for the one-dimensional motion of an earth block


Numerical simulation of earth block and debris flow motions across three-dimensional terrain


Debris flow and flood flow induced by collapse of natural dam



Formative conditions and shapes of natural dam


Failure in entire channel width and the resulting debris flow


Prediction of debris flow/flood flow induced by the overflow in partial width


Chapter 4 Characteristics of fully developed flow




Translation of debris flow surge and the shape of the snout



The case of stony type debris flow


The case of viscous type debris flow


Boulder accumulation at the forefront of stony debris flow



Various concepts for the mechanism


The theory of Takahashi (1980)


Competence to transport large boulders


The cause of intermittency


Debris flow around bend


Routing of debris flow in the transferring reach



Kinematic wave method


Dynamic wave method


Chapter 5 Processes and geomorphology of deposition




One-dimensional stoppage/depositing processes of stony debris flow



The arrival distance at the abrupt change in channel slope


Topography of deposit formed at an abrupt slope change


Numerical simulation of depositing process


One-dimensional depositing process of turbulent muddy debris flow


Formation of debris flow fan



Description of the experimental results for stony debris flow and empirical presentations of the feature of debris flow fan


Numerical simulation of fan formation process and its verification


Numerical simulation of fan formation by turbulent debris flow


Particle size distribution in the fan formed by stony debris flow



General situations found in the field and experimental data


Mathematical model for particle size distributions


Erosion and deformation of debris flow fan



Experiments for the process of erosion


Model and its verification for the fan comprised of uniform material


Model and its verification for the fan comprised of heterogeneous material


Chapter 6 Debris flow disasters and their reproduction by computer simulations




The rain storm disasters at Okuetsu



Outline of the disaster


The natural dam formation and the damages done by backwater


Processes of destruction of the natural dam and damages downstream


Horadani debris flow disasters



Outline of the disaster


Hydrograph estimation of the debris flow


Reproduction of debris flow depositing area on the fan


Collapse of the tailings dam at Stava, Northern Italy



Outline of the disasters


Reproduction of the debris flow in the Stava River and its verification


Disasters caused by the eruption of Nevado del Ruiz Volcano



Outline of the disasters


Reproduction of the phenomena


Sediment disasters in Venezuela



Outline of the disasters


Debris flow routing under an arbitrary rainfall condition


Reproduction of debris flow hydrograph and others in the Camuri Grande River


Reproduction of sediment flooding on the Camuri Grande fan


Debris flow disasters at Atsumari, Hougawachi, Minamata City



Outline of the disasters


Reproduction of the processes of debris flow


Chapter 7 Countermeasures for debris flow disasters




Methods to prevent from debris flow generation



Hillside works


Drainage works


Groundsill and bed girdle


Debris flow control by closed type check dam



Sediment depositing process behind check (sabo) dam


Erosion process of the deposit behind sabo dam


Effects of sediment control by sabo dam to downstream


Debris flow control by open-type sabo dams



Kinds and sediment checking mechanism of open-type sabo dams


Blocking model of grid-type dam


Model for debris flow controlling by grid-type dabo dam


Determination of the optimum spacing and the optimum position to install


Making debris flow harmless by channel works and training walls



Design of countermeasures on the fan of the Camuri Grande River


Management of debris flow by training dike


Design debris flows for the countermeasure planning



Method based on the previous data


Prediction of total sediment runoff by field investigation


Theoretical prediction of debris flow scale


Debris flow prone ravines and hazardous area



Debris flow prone ravine


Hazardous zone by debris flow


Prediction of debris flow occurrence by rainfall


References

Notations

Index