ROAD GEOHAZARDRISK MANAGEMENTHANDBOOK© 2019 International Bank for Reconstruction and Development / International Development Association or The World Bank
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2 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

ROAD GEOHAZARDRISK MANAGEMENTHANDBOOK

THE WORLD BANK/GFDRR | 3

CO N T E N TS
Contents.. ..................................................................................................................................................................... 4
List of Figures............................................................................................................................................................. 7
List of Photos/Maps/Tables..................................................................................................................................... 8-9
Acronyms & Glossary................................................................................................................................................. 9
Preface .. ....................................................................................................................................................................... 10
Acknowledgments ..................................................................................................................................................... 12
1 PART 1: Framework for Road Geohazard Risk Management........................................................................... 14
1.1

Introduction to Road Geohazard Risk Management............................................................................... 15

1.2

Correlation between Road Construction Activities and Increased Geohazard Risk.......................... 16

1.3Road Geohazard Risk Management Handbook Structure...................................................................... 16

1.4

Definition and Classification of Road Geohazards................................................................................. 17

1.5Road Geohazard Risk Management Strategies........................................................................................ 22

1.6Standard Approach to Risk Management................................................................................................. 22

1.7

Opportunities for Enhancing Road Geohazard Risk Management....................................................... 25

2 PART II: Institutional Capacity and Coordination............................................................................................. 27
2.1

Overview........................................................................................................................................................ 28

2.2

Geohazard Management as Part of Asset Management......................................................................... 28

2.3

Institutional Arrangements.. ....................................................................................................................... 30

2.3.1

Institutional Framework....................................................................................................................... 30

2.3.2

Funding Mechanisms. . ........................................................................................................................... 35

2.3.3

Human Capacity: Expertise Required for Road Geohazard Risk Management............................ 35

2.3.4

Effective Implementation. . ................................................................................................................... 36

2.4

Institutional Capacity Review. . ................................................................................................................... 37

2.4.1

Objective of the Review........................................................................................................................ 37

2.4.2

Procedure. . .............................................................................................................................................. 37

2.4.3

Scope of the Institutional Capacity Review....................................................................................... 38

2.4.4

Target Setting......................................................................................................................................... 38

2.4.5

Improvement Plan................................................................................................................................. 38

3 PART III: Systems Planning................................................................................................................................... 43
3.1

What Is Systems Planning?......................................................................................................................... 45

3.2Road Criticality............................................................................................................................................. 46

3.3

Integrated Information Database.............................................................................................................. 46

3.4

Risk Identification and Assessment.......................................................................................................... 47

3.5

Risk Evaluation............................................................................................................................................. 47

3.5.1

Risk Evaluation Responsibilities......................................................................................................... 47

3.5.2

Information Resources for Risk Evaluation....................................................................................... 47

3.5.3

How to Undertake Geohazard Risk Evaluation................................................................................. 47

3.5.4

Step 1: Definition of the Study’s Geographic Scope......................................................................... 48

4 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

3.5.5

Step 2: Identification and Mapping of Geohazards.......................................................................... 48

3.5.6

Step 3: Preliminary Assessment of Geohazards................................................................................ 52

3.5.7

Step 4: Detailed Assessment of Geohazards..................................................................................... 53

3.5.8

Step 5: Evaluation of Wider Impacts of Geohazards........................................................................ 56

3.6

Network-Level Analysis, or Decision Making under Deep Uncertainty (DMDU)................................. 57

3.6.1

What Is DMDU?....................................................................................................................................... 57

3.6.2

Application of DMDU to Geohazard Risk Management.................................................................... 58

3.6.3

DMDU Methodology............................................................................................................................... 58

3.7

Project-Level Option Selection.................................................................................................................. 61

3.7.1

Option Development............................................................................................................................. 61

3.7.2

Evaluation Approach............................................................................................................................. 64

3.7.3

Benefit-Cost Analysis (BCA)................................................................................................................. 66

3.7.4

Life-Cycle Cost Assessment. . ................................................................................................................ 66

3.7.5

Multicriteria Analysis (MCA)................................................................................................................. 67

3.8

Outcome of the Risk Evaluation Process.................................................................................................. 67

3.9

Selected Resources...................................................................................................................................... 68

4 PART IV: Engineering and Design......................................................................................................................... 71
4.1

Overview of Engineering and Design Solutions...................................................................................... 73

4.2

Definition of Engineered Measures........................................................................................................... 73

4.3

Engineering Investigation and Study for Engineered Measures........................................................... 74

4.4

Types of Structural Measures and Design Considerations.................................................................... 75

4.4.1

Structural Measures for Mountainside Fall or Collapse.................................................................. 75

4.4.2

Structural Measures for Valley-Side Collapse or River Erosion..................................................... 79

4.4.3

Structural Measures for Slide-Type Geohazards.............................................................................. 83

4.4.4

Structural Measures for Flow-Type Geohazards............................................................................... 87

4.5

Selected Resources...................................................................................................................................... 91

5 PART V: Operations and Maintenance................................................................................................................. 95
5.1

Overview of Operations and Maintenance Measures for Geohazards................................................. 97

5.2

Definition of Nonstructural Measures...................................................................................................... 97

5.3

Road Disaster Awareness............................................................................................................................ 97

5.3.1

Control of Road Disasters Caused by Human Activities.................................................................. 97

5.3.2

Traffic Signs to Raise Awareness......................................................................................................... 98

5.3.3

Awareness Raising and Training for Road Stakeholder Engagement............................................ 98

5.4

Maintenance of Structural Measures........................................................................................................ 98

5.5

Early Anomaly Detection and Emergency Information Collection....................................................... 99

5.5.1

Visual Inspection and Hazard Monitoring for Early Anomaly Detection...................................... 99

5.5.2

Emergency Information Collection System........................................................................................ 100

5.5.3

Road Emergency Information System Including Early Warning or Precautionary
Road Closure.......................................................................................................................................... 100

5.6Roles of Volunteers, Local Communities, and Institutional Partnerships in
Geohazard Risk Management..................................................................................................................... 102

5.7

Asset Management as a Response to Disasters...................................................................................... 102

5.8

Selected Resources...................................................................................................................................... 103

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6 PART VI: Contingency Programming.................................................................................................................... 107
6.1

Introduction.................................................................................................................................................. 109

6.2

Emergency Preparedness. . .......................................................................................................................... 109

6.2.1

Development of an Emergency Preparedness and Response Plan............................................... 109

6.2.2

Preparedness Training.......................................................................................................................... 110

6.2.3

Funding. . .................................................................................................................................................. 111

6.3

Emergency Response................................................................................................................................... 112

6.3.1

Emergency Inspection or Postdisaster Needs Assessment............................................................ 112

6.3.2

Emergency Traffic Regulation and Public Notice.............................................................................. 113

6.3.3

Emergency Works. . ................................................................................................................................. 113

6.4

Recovery........................................................................................................................................................ 114

6.4.1

Management of the Recovery.............................................................................................................. 114

6.4.2

Repair...................................................................................................................................................... 115

6.4.3

Rehabilitation and Reconstruction..................................................................................................... 115

6.5

Recovery........................................................................................................................................................ 116

7 Part VII: Reference and Resource Materials....................................................................................................... 119
7.1

References..................................................................................................................................................... 120

7.2

Web Resources. . ............................................................................................................................................ 121

6 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKLIST OF FIGURES
Figure 1.1:

World Bank Disaster-Resilient Infrastructure Life Cycle Approach......................................... 15

Figure 1.2:

Nomenclature of Cuts and Fills..................................................................................................... 18

Figure 1.3:

Road Geohazard Types.................................................................................................................... 19

Figure 1.4:

Generic Risk Management Process............................................................................................... 23

Figure 1.5:

Generic Risk Matrix. . ........................................................................................................................ 23

Figure 2.1:

Asset Management Process. ........................................................................................................... 29

Figure 2.2:

Structure of Institutions and Stakeholders in Coordination Mechanisms for Road
Geohazard Risk Management......................................................................................................... 34

Figure 3.1:

Workflow for Potential Economic Loss Estimation of a Road Location.................................. 56

Figure 3.2:

Potential Uncertainties in Infrastructure Planning Regarding Climate Impacts................... 57

Figure 3.3:

Sample Detailed Hazard Map for a New Road............................................................................. 63

Figure 3.4:

Determining the Appropriate Evaluation Approach to Option Selection............................... 64

Figure 3.5:

Process for Selecting Preferred Option ...................................................................................... 65

Figure 4.1:

Slope Cutting or Removal for Mountainside Fall or Collapse................................................... 77

Figure 4.2:

Rock Bolting and Shotcrete for Slope Reinforcement for Mountainside Fall or Collapse... 78

Figure 4.3:

Slope Framework (Grid Beam) for Slope Reinforcement for Mountainside
Fall or Collapse.. ............................................................................................................................... 78

Figure 4.4:

Examples of Resistance or Absorption against Shock from Mountainside
Fall or Collapse.. ............................................................................................................................... 79

Figure 4.5:

Sample Shelter for Roads Endangered by Mountainside Fall or Collapse............................. 79

Figure 4.6:

Example of Riverbank Protection for Road Riverside Erosion................................................. 81

Figure 4.7:

Examples of Riverbank Protection for Road Riverside Erosion................................................ 81

Figure 4.8:

Catchment-Based Sediment Management Facilities to Mitigate Road Riverside Erosion
and Flow-Type Geohazards. . ........................................................................................................... 82

Figure 4.9:

Ground Surface Drainage for Slide-Type Geohazard.................................................................. 84

Figure 4.10:

Surface-Groundwater Collecting Conduit with Ground Surface Drainage.............................. 85

Figure 4.11:

Subsurface Drainage Drilling......................................................................................................... 86

Figure 4.12:

Ground Anchors as External Resisting Force for Slide-Type Geohazard................................. 87

Figure 4.13:

Sample Ford River Crossing............................................................................................................ 89-90

Figure 4.14:

Protection Structures against Flow-Type Geohazards............................................................... 91

Figure 5.1:

Flows of Early Warning or Precautionary Road Closure under Highly Susceptible
Road Damage Situation due to Geohazards................................................................................ 101

THE WORLD BANK/GFDRR | 7

L I S T O F P H OTO S
Photo 1.1:

Example of Mountainside Rockfall or Rock Collapse................................................................. 20

Photo 1.2:

Example of Mountainside Soil Collapse....................................................................................... 20

Photo 1.3:

Example of Valley-Side Collapse or Erosion from Mountainside and Roadside
Rainfall Inflow.................................................................................................................................. 20

Photo 1.4:

Example of Valley-Side Collapse from River Erosion................................................................. 20

Photo 1.5:

Example of Slide-Type Geohazard................................................................................................. 21

Photo 1.6:

Example of Flow-Type Geohazard (Debris).................................................................................. 21

Photo 1.7:

Example of Flow-Type Geohazard (Flash Flood)......................................................................... 21

Photo 1.8:

Example of Flow-Type Geohazard (Inundation).......................................................................... 21

Photo 3.1:

Example of Combining Aerial Photography with LiDAR Data.................................................... 49

Photo 3.2:

Example of Road Alignment Plan Avoiding Geohazards............................................................ 64

Photo 4.1:

Vegetation at a Road Mountainside Slope ................................................................................... 77

Photo 4.2:

Surface-Groundwater Collecting Conduit with Ground Surface Drainage at Catch Pit................. 85

Photo 4.3:

Drained Subsurface Water at a Sliding Road Mountainside Slope.......................................... 86

Photo 4.4:

Examples of Ford River-Crossing Solutions................................................................................. 89

Photo 5.1:

Management of Auckland Motorway Flooding............................................................................ 105

LIST OF MAPS
Map 3.1:

Sample Detailed Hazard Map for an Existing Road in Nepal.................................................... 51

L I S T O F TA B L E S
Table 1.1:

Framework and Workflow for Road Geohazard Risk Management........................................... 4

Table 1.2:

Road Geohazards, by Location, Movement, and Material Type................................................ 4

Table 1.3:

Opportunities for Enhancing Road Geohazard Risk Management,
by Life-Cycle Stage.. ......................................................................................................................... 12

Table 2.1:

Typical Allocation of Tasks for Road Geohazard Risk Mangement, by Levelof Road Management Authority..................................................................................................... 18

Table 2.2:

Institutional Framework for Road Geohazard Risk Management with
Stepwise Approach.......................................................................................................................... 23

Table 2.3:

Step-Up Targets for Strengthening Road Geohazard Risk Management................................. 24

Table 3.1:

Methods for Identification of Geohazard-Prone Road Locations, by Risk Level................... 33

Table 3.2:

Default Risk Matrix.......................................................................................................................... 35

Table 3.3:

Sample Rating of Likelihood and Magnitude of Geohazard Damage to a
Road Location. . ................................................................................................................................. 37

Table 3.4:

Proposed Road Criticality Components, New Zealand Transport Agency............................... 41

Table 3.5:

Determining Priority Rating under DMDU Approach.................................................................. 43

Table 4.1:

Studies or Investigation Methods to Support the Design of Structural Measures............... 55

Table 4.2:

Typical Structural Measures for Mountainside Fall or Collapse............................................... 57

8 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Table 4.3:

Typical Structural Measures for Road Riverside Erosion.......................................................... 61

Table 4.4:

Typical Structural Measures for Slide-Type Geohazards........................................................... 64

Table 4.5:

Typical Structural Measures for Flow-Type Geohazards............................................................ 68

Table 5.1:

Geohazard Monitoring Types and Equipment Used................................................................... 76

Table 5.2:

Recommendations for Integrating Geohazard Management into Asset Management......... 79

Table 6.1:

Postdisaster Funding Approaches, by Disaster Magnitude....................................................... 86

AC R O N YM S & G L O S SA RY
AMIS

asset management information system(s)BCRbenefit-to-cost ratio

DMDU

decision making under deep uncertainty

EIRR

economic internal rate of return

Geohazard-prone road subsection

Particular part of a road section with a concentration of endangered road 		
locations due to the presence of geohazards

GIS

geographic information system

Hazard-indicating map

A hazard-indicating map is not too detailed, is provided at a large scale 		(1:10,000 to 1:50,000), and identifies all historical and susceptible hazard 		
areas in the vicinity of the proposed new route options.

Hazard maps

Hazard maps are different from hazard-indicating maps, which display a 		specific hazard or several hazards for an identified endangered road location.
They are very detailed and provided at a scale smaller than 1:5,000, which is 		the scale used during the structural measures design stage.

ICT

information and communication technology

IDF

intensity-duration-frequency

ISO

International Organization for Standardization

LCC

life-cycle cost

LiDAR

Light Detection and Ranging, referring to a remote sensing method for 		
locating an object. It is similar in operation to radar but emits pulsed laser 		
light instead of microwaves

NPV

net present value

OM

operation manual

Road section

Length of a road between main intersections or between starting and end 		points, which can extend for several tens of kilometers or even for several 		hundred kilometers

ToR

terms of reference

VOC

vehicle operation cost

THE WORLD BANK/GFDRR | 9

P R E FAC E
Geohazards can be defined as “events caused by geological, geomorphological, and climaticconditions or processes which represent serious threats to human lives, property, and the natural andbuilt environment” (Solheim et al. 2005). They cover almost all hazards affecting road infrastructure,such as slope slides, slope collapses, earth flows, debris flows, floods, and erosion.
Geohazards may result in the loss of human life, extensively damaged infrastructure, and suspended
or disturbed traffic and services such as water and energy supply. Generally speaking, roads should
be robust (able to withstand the geohazard) and resilient (able to quickly restore function following
an event) to provide reliable access to emergency services and to be used as evacuation routes; theyshould also contribute to an efficient local recovery process after a geohazard event.
Most geohazards are linked to climate activity such as rainfall and thawing of ice and snow
or associated with earthquakes that cause large-scale ground movement independent of any
underlying climatic conditions. For many locations around the world, climatic changes haveincreased the intensity of rainfall and raised the mean temperature, in turn increasing flowtype geohazard events such as debris or earth flows and floods. This has resulted in a long-term
increasing rate of geohazard impacts and associated road damage.
Road geohazard risk management has the following principal aims:•	To minimize the risks and effects of geohazards on roads, road users, and the people living
within the wider zone of influence of the geohazard•	To support decisions on the alignment of new roads, or the realignment of and preventive
actions on existing roads, to ensure that the full life-cycle costs (construction costs, risk-based
maintenance costs, and associated impact on traffic disturbances) associated with differinglevels of geohazards are accounted for•	To help protect road users through precautions such as early warning and precautionary roadclosures•	To contribute to the speedy recovery and reconstruction of roads after geohazard events andto the mitigation of future geohazard events.
Road geohazard risk mitigation is technically challenging, typically involving structural measures or

10 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

road realignments that are costly. This handbook considers a stepwise approach that begins with
the institutional setup:•	For low-budget, low-capacity countries, the focus is on retaining the usability of critical roads(often the all-weather road network) to the maximum extent possible, while accepting that
noncritical roads can be closed during certain times of the year. This split approach, along withefficient postdisaster activities as short-term targets, forms the basis of the geohazard risk
management approach.
•	For low-budget, moderate-capacity countries, medium-term targets should focus on
nonstructural measures such as emergency road information and low-cost structural measures
such as rock support at the toe of slips.
•	For moderate-budget, moderate-capacity countries, long-term targets can focus on structural
measures for the management of all-weather roads.
•	Long-term targets include the mainstreaming of road geohazard risk management. Suchmanagement contributes to local geohazard mitigation—as in the case of dike embankments
for flood mitigation, which can function as roads for emergency transportation duringcatastrophic disasters.
The handbook reflects the World Bank’s disaster-resilient infrastructure life cycle (Figure P.1). Eachpart is devoted to a stage of the life cycle, including the underlying institutional capacity andcoordination aspects.

Systems
Planning

Engineering& Design

Operations& MaintenanceContingency
Programming

Institutional Capacity & Coordination

THE WORLD BANK/GFDRR | 11

AC K N OW L E D G M E N TS
Production of the report was led by Akiko Toya, program officer, Global Facility for Disaster Reduction
and Recovery (GFDRR), with valuable guidance from Yuka Makino, senior natural resource management
specialist of the Social, Urban, Rural, and Resilience Global Practice (GSURR), and Kazushige Endo,
director of the United Nations Centre for Regional Development (UNCRD).
This report was prepared by Ian Greenwood, consultant to the World Bank’s Transport and ICT Global
Practice (T&I GP), based on substantive draft documents prepared by a consulting team led by Mikihiro
Mori from Nippon Koei Co. The Nippon Koei Co. team was composed of Yutaka Inagaki, Kenichi Tanaka,Toshiaki Hosoda, Hiroaki Tauchi, Saúl Antonio Castelar, and adviser Shinjuro Komata. The report
greatly benefited from insights and guidance from the Japanese experts, including the Ministry ofLand, Infrastructure, Transport and Tourism, Government of Japan; the Japan International Cooperation
Agency (JICA); Daisuke Higaki of the Japan Landslide Society; Hidetomi Oi of the International Sabo
Network, Tokyo; and Masaki Hiruma of Sabo & Landslide Technical Center, Tokyo.
The team extends thanks to internal peer reviewers, namely Shomik Raj Mehndiratta, practicemanager for South Asia, T&I GP; Fiona Collin, lead transport specialist, T&I GP; Ashok Kumar, seniorhighway engineer, T&I GP; and Masatsugu Takamatsu, disaster risk management (DRM) specialist,
GSURR. The team is also grateful for support from Luis Tineo, lead operations officer, and Julie Dana,
practice manager, of GFDRR.
Special acknowledgments go to the following World Bank staff (and consultants): James Newman,
DRM specialist, GFDRR, and DRM specialists Keiko Sakoda and Naho Shibuya of GSURR. In addition,
we thank Satoshi Ogita, senior transport specialist, T&I GP; Grégoire Gauthier, senior transport
specialist, T&I GP; Frederico Pedroso, DRM specialist, GSURR; Javier Escudero Marroquin, consultant,
T&I GP; Deepak Malik, consultant, GSURR; Liljana Sekerinska, senior transport specialist, T&I GP;
Senad Sacic, program assistant, T&I GP; Svetlana Vukanovic, senior transport specialist, T&I GP;
Darko Milutin, DRM specialist, GSURR; consultants Biljana Abolmasov and Marinos Skempas, T&I GP,
and consultants Yoganath Adhikari and Mohammad Dehghani, GSURR.
The report greatly benefited from professional editorial work by Mary A. Anderson and professionalgraphic design by Carlos Plaza Design Studio.

12 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

THE WORLD BANK/GFDRR | 13

1
F R A M E WO R K F O R
ROA D G E O H A Z A R D
R I S K M A N AG E M E N T

14 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

1.1

1.1 INTRODUCTION TO ROAD GEOHAZARD RISK MANAGEMENT
This handbook outlines an approach to proactively manage the risks of geohazards on roads, road
users, and the people living near and affected by roads through• Improving understanding of the risks of geohazards throughout the road infrastructure cycle;•	Promoting risk avoidance on the alignment of new roads or the realignment of existing roads
to manage construction costs, maintenance costs, and losses from geohazard-induced traffic
disruptions;•	Protecting road users through preparedness, including measures for early warning,
precautionary road closures, and access to emergency services and evacuation routes; and•	Contributing to the speedy recovery and reconstruction of roads after geohazard events and tothe mitigation of future geohazard events.
The World Bank disaster-resilient infrastructure life cycle (Figure 1.1) represents the overall
approach of the guidelines presented in this handbook.
Figure 1.1: World Bank Disaster-Resilient Infrastructure Life Cycle Approach

Systems
Planning

Engineering& Design

Operations& MaintenanceContingency
Programming

Institutional Capacity & Coordination
Source: ©World Bank. Further permission required for reuse.

In Part I, the handbook• Introduces the overall framework;• Defines and classifies the geohazards addressed in this handbook;• Proposes a series of strategies to manage the risks posed by these hazards;•	Describes the opportunities to better integrate geohazard risk management into roadengineering and administration; and•	Explains how the handbook is structured to support road geohazard risk management,
including the standard terms of reference and operations manual in this work.
The classification does not include the effects of certain lower-probability, higher-impact triggers or
inducing events such as large earthquakes, extreme storms, and so on. The handbook focuses mostly
on geohazard events with a much higher likelihood (probability) but with lower impact magnitudes,
such as those triggered by relatively common storm events—wherein engineered solutions or localizedroute realignments can significantly mitigate or eliminate the hazards. However, the overall framework ofgeohazard management and mitigation presented in this handbook is equally applicable to all geohazards.

PART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT| 15

1.2 CORRELATION BETWEEN ROAD CONSTRUCTION ACTIVITIES AND INCREASEDGEOHAZARD RISK

1.2

In addition to what is mentioned in this handbook, there is a clear link between road construction andmaintenance activities and the adjoining areas’ susceptibility to geohazard. Road construction often
worsens the landslide problem in hilly areas by altering the landscape, slopes, and drainages and bychanging and channeling runoff, thereby increasing the potential for landslides. These slides and otherforms of ground failure also have adverse environmental consequences, such as increased soil erosion,siltation of streams, blockage of stream drainages, and loss of valuable watershed and grazing lands.
Road development often also results in an adverse impact on the ecological balance. The cutting forroadwork results in destabilizing of the hill slopes and also loss of vegetation. The road construction
activity releases greenhouse gases and other pollutants because of the deployment of machineryfor various construction stages and for the arrangement of required materials. These activities affectenvironmental sustainability at a time of global warming and climate change—although these effects
can often be offset by reducing the emissions on existing, less-efficient routes. The net result is alikely increase in geohazard risk in the vicinity of the roads constructed or under construction, either
in the short term or permanently.

1.3

1.3 ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK STRUCTURE
This handbook is structured to support road geohazard risk management sequentially and systematically:•	Part I, Framework for Road Geohazard Risk Management, helps users understand the framework forroad geohazard risk management, introduces some basic concepts, and provides context to the overall
handbook.
•	Part II, Institutional Capacity and Coordination, covers the institutional arrangements that are necessary
for the successful implementation of geohazard management.
•	Part III, Systems Planning, covers the systems planning aspects, pertaining to the identification,assessment, and evaluation of risks, along with raising awareness of disasters.
•	Part IV, Engineering and Design, deals with the engineered solutions to address geohazard risks, giving
examples of different solutions to particular risk types.
•	Part V, Operations and Maintenance, focuses on the operations and maintenance aspects of geohazard
management—whether the maintenance of previously engineered solutions or the nonengineered
solutions available to mitigate the impacts of geohazard risks.
•	Part VI, Contingency Planning, addresses contingency programming issues, such as postdisaster
response and recovery, and the important issue of funding arrangements.
•	Part VII, References and Resource Materials, contains the reference list and additional online resources.
Additionally, this handbook includes standard templates for terms of reference (ToRs) that can beadapted for technical assistance projects for road geohazard risk management (see Appendix A) andan operation manual (OM) for the practitioners involved with road geohazard risk management (seeAppendix B). Table 1.1 shows the framework and workflow for project activities of road geohazard risk
management, incorporating references to the corresponding ToRs and OM.

16 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Table 1.1: Framework and Workflow for Road Geohazard Risk Management
PART OF HANDBOOKKEY CONCEPTS

Part II: Institutional
Capacity and
Coordination

Institutional setup• Laws, regulations, andtechnical standards• National or subnational
plans or strategies• Mechanisms for
implementation
Risk identification, assessment, and evaluationof geohazard

Part III: Systems
Planning

Disaster awarenessPart IV: Engineeringand DesignPart V:
Operations
and Maintenance

1.4

Part VI: Contingency
ProgrammingGeohazard risk management planning• For new roads• For existing roads
Operations and maintenance of engineered
solutions

TERMS OF REFERENCE (TOR)(REFER TO APPENDIX A)

OPERATION MANUAL (OM)
(REFER TO APPENDIX B)

ToR 1: Institutional Capacity Review andTarget Setting

ToR 2: Systems Planning: Risk Identification,
Assessment, and Evaluation
ToR 3: Development of Manual for Promotionof Road Disaster Awareness and Partnership

OM 1: Economic Risk
Estimation and CostBenefit Analysis

ToR 4: Design of Structural Measures

Nonengineered solutions

ToR 5: Development of Manual for Operationand Maintenance for Road Geotechnical
Assets, and Implementation of a Road
Geotechnical Asset Management Information
System (AMIS)

Asset management as a
response

ToR 6: Development of Emergency
Information System

Postdisaster response
and recovery

ToR 7: Development of Manual for Postdisaster Response and Recovery

1.4 DEFINITION AND CLASSIFICATION OF ROAD GEOHAZARDSThis handbook defines road geohazards as “events caused by geological, geomorphological, andclimatic conditions or processes that represent serious threats to human lives, property, and thenatural and built environment” (Solheim et al. 2005).
The handbook addresses the typical types of geohazard that adversely affect roads, classifying thembased on their combination of location, movement, and the materials involved in the movement(Table 1.2). The typical risk management method is different for each type of movement, location, andmaterial involved in a geohazard affecting a slope or landscape ecosystem.
Table 1.2: Road Geohazards, by Location, Movement, and Material Type
MATERIAL FACTORSLOCATION AND MOVEMENT TYPEBEDROCKSOIL
DEBRIS

EARTH

WATER

Mountainside fall or collapsea

Mountainside rock fall or collapse

Mountainsidedebris collapse

Mountainside
earth collapse

n.a.

Valley-side collapse or river erosion

Valley-side rock collapse or rivererosionValley-side
debris collapse
or river erosion

Valley-side
earth collapse
or river erosion

n.a.

SlideaRock slide

Debris slide

Earth slide

n.a.

Flow

n.a.

Debris flow

Earth flow

Flash flood orinundation

Notes:
n.a. = not applicable. The classification boundaries of hazard movement and material types are transitional. Some disasters involve complex hazard types. For example, a ‘debris
slide’ on a mountain slope can change into an ‘earth flow’ after meeting with a torrent.
a. Geohazard movements also include topple and spread (Cruden and Varnes 1996). Here, topple is considered a type of collapse, and spread is considered a special case of slide.

PART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT| 17

Although Table 1.2 focuses on the impact of the geohazard on the road network, the cause (or trigger)of the geohazard can be from a range of natural and man-made factors. These include earthquakes,
initiating landslides; changes in climate, altering soil moisture levels; volcanic activity, creating debris
flows (lahars); removal of vegetation as part of land-use changes; altered river alignments; and thelike. This handbook initiates the investigation from the point of view of the geohazard that manifests
itself on the road network (as per Table 1.2) and then requires the investigations to determine
the cause of those geohazards. The handbook does not, therefore, contain a specific section onearthquakes, volcanoes, or the like—because, in their own right, these may not result in a geohazard to
the road network.
The role of water is quite predominant; it adds weight to the slope by replacing the air voids in the soil
or rock, thereby leading to slope instability; reduces the friction along a sliding surface; and changes
the angle of repose. If there is loose sediment, it becomes oversaturated during heavy rain, causing
individual grains to lose grain-to-grain contact with one another as the water gets between them,
resulting in slide, and liquefaction may occur through vibrations in a soil saturated with water. Water
has a contributory role in most landslides. For a granular flow, the percentage of water may vary from0 percent to around 20 percent, and for slurry flow, it could be 20–40 percent. If the water exceeds 40
percent, the slurry flow would convert into a stream.
A mountainside slope or valley-side slope refers to either an engineered slope (cutting slope orembankment slope) or a natural slope above or below the road surface (Figure 1.2). A “crossing stream
or river” is another type of location (not included in Table 1.2) where flooding, debris flows, and similar
events need to be carefully considered in the design, construction, and maintenance of the crossing
infrastructure. River crossings can be broadly grouped into the three categories: (a) fords (where theroad is designed to have water flow over it, either occasionally or permanently); (b) culverts; and (c)bridges. In worst-case scenarios, the river crossing may block, then release as a flash flood, resulting
in a devasting inundation of downstream communities and infrastructure (including other roads andriver crossings farther down the valley).
Figure 1.2: Nomenclature of Cuts and Fills
Natural Slope

Cut
Fill / embarkment
Embarkment slope
Cut Slope

18 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKThe material factors affecting road geohazards include the following (as also illustrated in Photos 1.1–1.8):•

Bedrock: hard or firm rock that was intact and in its natural place before the movement began•

Soil: any loose, unconsolidated, or poorly cemented aggregate of solid particles—generally ofnatural mineral, rock, or inorganic composition and either transported or residual—together withany interstitial gas or liquid• ebris: soil that contains a weight proportion of more than 20 percent of coarse material greaterDthan 2 millimeters in size (pebble, cobble, and boulder stones)•

 arth: soil that contains a weight proportion of more than 80 percent of fragments smaller than 2Emillimeters in size (sand, silt, and clay)•	
Water: material that is more than 50 percent water by volume, with the remaining volume
composed of soil or other materials.
The handbook further defines five general movement types as follows:•	
Fall: a rapid downward movement of a mass of rock or soil that travels mostly through the air by
free fall, leaping, bounding, or rolling, with little or no interaction between one moving unit andanother (Figure 1.3, panel a)•	Collapse: a gradual or rapid downslope movement of soil or rock under gravitational stress, often
because of artificial factors, such as removal of material from the foot of a slope (Figure 1.3,
panels b and c)•	
Slide: a mass movement of earth, snow, or rock under shear mode along one or several sliding
surfaces (Figure 1.3, panel d)•F low: a movement that exhibits a continuity of motion and a plastic or semifluid behavior, usuallyrequiring considerable amounts of water (Figure 1.3, panel e)•	Erosion: a movement of rock fragments or soil particles from one place to another, mostly bywater flow (Figure 1.3, panel f).
Figure 1.3: Road Geohazard Types(a) Fall (rockfall)(b) Collapse (rock)(c) Collapse (soil)(d) Slide(e) Flow(f ) Erosion (river erosion)

Source: ©World Bank. Further permission required for reuse.

PART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT| 19

Photo 1.1 Example of Mountainside Rockfall or Rock Collapse
A heavy monsoon rainfall of 446 millimeters in 24 hours wasrecorded on July 30, 2003, in southern central Nepal.
The collapsed rock slope blocked the main access road to
Kathmandu from India.
Source: ©Department of Water Induced Disaster Prevention (DWIDP), Ministry of Irrigation, Governmentof Nepal. Reproduced, with permission, from DWIDP; further permission required for reuse.

Photo 1.2 Example of Mountainside Soil Collapse
In the second half of November 2008, the recorded rainfall totaled
600 millimeters in five days in the mid-downstream area of the
Itajaí River basin, Santa Catarina State, Brazil.
The soil on a steep slope collapsed at the boundary of the bedrockon State Road SC-470. This common phenomenon occurs as a
failure at the boundary with bedrock because the water content
of the boundary soil increases and deteriorates easily with theinfiltrated stormwater.
Source: ©Civil Defense, Gaspar Municipality, Santa Catarina State, Brazil. Reproduced, with permission,from Civil Defense, Gaspar Municipality, Santa Catarina State, Brazil; further permission required for reuse.

Photo 1.3 Example of Valley-Side Collapse or Erosion from
Mountainside and Roadside Rainfall Inflow
Extreme rainfall of 1,800 millimeters in seven days during the firsthalf of October 2009 (historically, the biggest seven-day rainfall in
the past 10 years) closed vehicle traffic to Baguio City, Philippines,
completely for three days.
The collapse cut a section of road that was 65 meters long by 65
meters high, closing the main access. The cause of the soil collapse
was inflow and infiltration of stormwater from the roadside to thevalley side of the road.
Source: © World Bank. Further permission required for reuse.

Photo 1.4 Example of Valley-Side Collapse from River Erosion
In the second half of November 2008, the recorded rainfall recorded
totaled 600 millimeters in five days in the mid-downstream area of
the Itajaí River basin, Santa Catarina State, Brazil.
This riverside road collapse, on a federal road, occurred in twostages that form a general pattern for riverside road collapses:• F irst stage: primal collapse from river water infiltration andsaturation of the road foundation and erosion of the roadriverside by floodwater•S econd stage: secondary collapse from rapid drawdown of riverwater, residual water pressure of the roadside ground, andseepage failure of the soil foundation.
Source: ©National Department of Infrastructure and Transport (DNIT), office of Rio do Sul, Santa Catarina
State, Brazil. Reproduced, with permission, from DNIT; further permission required for reuse.

20 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKPhoto 1.5 Example of Slide-Type Geohazard
In January 2009, a slide-type geohazard occurred on a bypassof the Pan-American Highway in the metropolitan area of San
Salvador, El Salvador.
The road was closed because of sliding earth for about threemonths after the rainfall season ended. The sliding surface(bottom of the sliding mass) was 11 meters deep and consistedof deeply weathered paleosol (fossil soil), overlaid by a new
pyroclastic flow deposit (fragmentation from volcanic or otherigneous action). A slide-type geohazard of deep sliding surface cansometimes lag heavy rainfall by several months.
Source: ©Ministry of Public Works, Transport, Housing, and Urban Development (MOPTVDU), El Salvador.
Reproduced, with permission, from MOPTVDU; further permission required for reuse.

Photo 1.6 Example of Flow-Type Geohazard (Debris)
A heavy monsoon rainfall of 446 millimeters in 24 hours wasrecorded on July 30, 2003, in southern central Nepal.
Debris flow blocked roads affecting the main access to Kathmandu
from India.
Source: ©Department of Water-Induced Disaster Prevention (DWIDP), Ministry of Irrigation, Nepal.
Reproduced, with permission, from DWIDP; further permission required for reuse.

Photo 1.7 Example of Flow-Type Geohazard (Flash Flood)
In a flash flood event on July 3, 2008, in the metropolitan area of San
Salvador, El Salvador, floodwater completely covered this bus anddragged it into a flooding urban river, killing all 31 people aboard,
including the driver and the man shown on the roof of the bus.
The rapid urbanization or deforestation of a landscape ecosystemarea may increase stormwater runoff and flash flood hazard.
Source: ©El Diario de Hoy, El Salvador. Reproduced, with permission, from El Diario de Hoy; further
permission required for reuse.

Photo 1.8 Example of Flow-Type Geohazard (Inundation)
A November 2008 storm inundated the high-traffic Federal Road BR101 in the downstream area of the Itajaí River basin, Santa Catarina
State, Brazil.
The road inundation interrupted traffic completely, generating
great economic losses. The submergence of the road caused great
deterioration.
Source: ©Archive Secom, Santa Catarina State, Brazil. Reproduced, with permission, from Santa Catarina
State; further permission required for reuse.

PART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT

| 21

1.5

1.5 ROAD GEOHAZARD RISK MANAGEMENT STRATEGIESRoad geohazard mitigation measures fall into two broad categories: (a) proactive, applied before adisaster; and (b) response and recovery, applied after a geohazard event to manage secondary damage
and recovery.
Road geohazard risk management entails three main elements covered by this handbook: (a)institutional setup, (b) road geohazard risk management for new roads, and (c) road geohazard risk
management for existing roads.
An adequate institutional framework is a necessary condition to guarantee proper road geohazard
risk management, whose activities typically follow road project management stages of preconcept,
concept, design, construction, and operations and maintenance. However, depending upon thecontractual models in use, two or more of these stages may be combined into a single contractual
arrangement. This, in turn, will necessitate that the institution have access to a multidisciplinary team(either employed or engaged as consultants).
The road geohazard risk management processes for new and existing roads differ only in the risk
assessment and geohazard risk management planning stages. The measures common to both new andexisting roads include (a) proactive structural measures (retaining walls and so on, as discussed in PartIV); (b) proactive nonstructural measures (operations and maintenance activities including monitoringof geohazards, as discussed in Part V); (c) postdisaster response; and (d) recovery.
This handbook is designed for application across all road types and road hierarchies. Although theprecise categorization of roads varies from country to country, roads are generally subdivided into
urban, interurban, and rural roads; primary, secondary, and tertiary roads; paved and unpaved roads;
and high (traffic)-volume and low-volume roads. The importance of this categorization of roads within
the context of this handbook is that the recommended road geohazard risk management strategy
varies by road type. For the more-critical road types, the approach is to ensure the road remains
functional and open at all times; for the less-critical road types, the approach is to minimize closuresand ensure rapid recovery after the event. There is, of course, a range of road types and recommended
strategies between these two extremes, but the main point is that geohazard risk management is notpredicated on 100 percent of the road network being available 100 percent of the time.

1.6

1.6 STANDARD APPROACH TO RISK MANAGEMENT

This handbook is based on standard risk management approaches and aligns with the practices in theInternational Organization for Standardization (ISO) 31000 standard (“Risk Management—Guidelines”). 1
Risk management is generally considered to involve a process aligned with the stages in Figure
1.4, with each risk assessed against the probability (or likelihood) and consequence (or impact) of
occurrence (Figure 1.5).

1

See ISO 31000:2018, “Risk Management—Guidelines”: https://www.iso.org/standard/65694.html.

22 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 1.4: Generic Risk Management Stages

IDENTIFYASSESSANALYZERISKMANAGEMENTREDUCECONTROL

TRANSFER

Source: ©World Bank. Further permission required for reuse.

Figure 1.5: Generic Risk Matrix

CONSEQUENCE(impact) if risk occurs

PROBABILITY (likelihood) of risk occurrence
LOW

MEDIUM

HIGH

HIGH

MediumHigh

High

MEDIUM

Low

Medium

High

LOW

Low

Low

MediumPART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT| 23

It is further noted that the ISO/AWI 214992 Security and Resilience group is working on the following(Gasiorowski-Denis 2016):[The] community-based landslide early warning system will serve to empower individuals andcommunities who are vulnerable to landslides to act in sufficient time in appropriate ways to reduce
the possibility of injuries, loss of life, and damage to property and the environment. It is designed toencourage communities to play a much more active role in their own protection.
The guidelines will be used by communities vulnerable to landslide, government agencies, and nongovernmental organizations at central, provincial, municipality/district, sub-district, and village levels.
Its recommendations will include the following:• Risk assessment• Dissemination and communication• Establishment of disaster preparedness and response team
• Development of evacuation route and map• Development of standard operating procedures• Monitoring, early warning, and evacuation drill•	Commitment of the local government and community on the operations and maintenance of thewhole system.
Such a standard aligns well with Part III (Systems Planning), Part V (Operations and Maintenance),
and Part VI (Contingency Planning) of this handbook. The proposed ISO document is focused on theways communities are exposed to landslides and covers a spectrum of soft and hard infrastructure
responses, whereas this manual focuses on a broader range of geohazard risks but confined to roadinfrastructure only.

ISO/AWI (approved work item) 21499, “Security and Resilience—Community-Based Landslide Early Warning System,” is to be developed by the ISO/TC (ISO TechnicalCommittee) 292 on Security and Resilience. For more information, see the ISO/TC 292 home page: http://www.isotc292online.org/.

2

24 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

1.7

1.7 INDICATORS OF NEED TO ENHANCE ROAD GEOHAZARD RISK MANAGEMENT
For most countries, there are significant opportunities to enhance the existing means ofgeohazard management, covering all stages of the life cycle, as outlined in Figure 1.1 and further
expanded in Table 1.3.
Table 1.3: Opportunities for Enhancing Road Geohazard Risk Management, by Life-Cycle Stage
STAGE
Systems Planning(institutional setup)

INSTITUTIONAL ASPECTTECHNICAL ASPECTNo or insufficient laws,
regulations, or technicalstandards, including assignmentof responsible organizations

No or insufficient expertise, or lack ofessential data, for road geohazard risk
management (such as historical weather
data and disaster records)

No or insufficient national or
subnational government plans or
strategies

No or insufficient risk evaluation
practices

No or insufficient mechanisms,
fundingEngineering and Design

No or insufficient mechanisms
or funding for proper design andconstruction

No or inappropriate highway and risk
management planning
No or insufficient engineering
investigation for design
Lack of proper design and construction

Operations and Maintenance

No or insufficient mechanisms or
funding for proper nonstructural
measures or for operations andmaintenance responses

No or insufficient mechanism andsystem (staff, machinery, equipment,
asset management information system[AMIS], information gathering andcommunication systems, guidance
manuals, training, coordination, andpartnership system) for nonstructural
measures
Weak or nonexistent domestic roadmaintenance contracting industry

Contingency Programming

No or insufficient mechanisms or
funding for proper postdisaster
response and recovery

No or insufficient contingency planningfor both technical and physical responseto events, including intelligent transportsystems (ITS) and related AMIS

PART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT| 25

26 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

2
I N S T I T U T I O N A L C A PAC I T Y
A N D CO O R D I N AT I O NPART I: FRAMEWORK FOR ROAD GEOHAZARD RISK MANAGEMENT

| 27

2.1

2.1 OVERVIEW
Without an appropriate institutional framework within which to implement the geohazard risk
management tasks, there is little chance of a successful outcome. The institutional framework covers
two primary aspects:•	The appropriate laws, regulations, and technical standards to enable (or, in some cases,
require) geohazard management•	The appropriate capacity and capability of human resources to deliver an appropriate
geohazard risk management program.
While the underlying laws, regulations, and technical standards may be largely similar from country
to country regarding the need to manage the road network in a safe and efficient manner, the amountof human capital expended on geohazard management will reflect the relative risk exposure in eachcountry (or part of a country). For instance, a road authority managing a road in a mountainous
country with high rainfall will reasonably be more concerned about geohazards and hence invest moretime and effort in their management than will a road authority operating in an area of dry plains. The
guidance below should be considered appropriate for a country with a moderate to high exposure toroad geohazards.

2.2

2.2 GEOHAZARD MANAGEMENT AS PART OF ASSET MANAGEMENT
Although this handbook focuses specifically on geohazard management, it is necessary to also
understand the larger, overarching asset management process that should be in place within any
road authority. Asset management is the all-encompassing framework within which geohazard risk
management occurs, as defined by the American Association of State Highway and Transportation
Officials (AASHTO).

Transportation Asset Management is a strategic and systematic process ofoperating, maintaining, upgrading, and expanding physical assets effectively
throughout their lifecycle. It focuses on business and engineering practices
for resource allocation and utilization, with the objective of better decision
making based upon quality information and well defined objectives.
Source: AASHTO Subcommittee on Asset Management, January 200628 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKA typical asset management process spans all aspects of a road authority’s activities (Figure 2.1).
Different road authorities will have variations on this process in place, but most competent asset
management authorities will have the various steps in the process identified as part of their
management processes (especially those that have ISO 55000 certification in place or intending toachieve it).3
Figure 2.1: Asset Management Process
Understand and Define
Requirements

Develop Asset Life-Cycle Strategies

Asset Management Enablers

2. How will it be paid for?
Develop the Asset Management Policy

Financial and Funding Strategies

Define Levels of Service
and Performance

Understand the Asset Base(the asset register)

Assess Asset Condition“Life Cycle” Decision-Making Techniques

Forecast Future Demand

Capital Works
Strategies and Plans

Asset Management Teams

Asset Management Plans

Information Systems and Tools
Maintenance
Strategies and Plans

Operational
Strategies and Plans

Asset Management
Service Delivery
1. How will it be done?

1. What has to be done?
Quality Management

Continuous Improvement

Identify Asset and Business Risk

Source: NAMS 2011. ©World Bank. Further permission required for reuse.

It is important that geohazard management activities fit within the road authority’s overarchingasset management framework. For instance, risk-rating methodologies should be consistentacross all aspects of the road authority; the information systems used to manage geohazards
should ideally be part of the organization-wide asset management information system (AMIS),
and improvement plans for geohazard management should be prioritized and managed within theoverall improvement plan processes.
The aim of this handbook is not to place geohazard management above asset management but rather
to explain how the key aspects of geohazard risk management should occur—such that these can thenbe incorporated into the overarching asset management processes.
See ISO 55500:2014, “Asset Management—Overview Principles and Terminology”: https://www.iso.org/standard/55088.html.

3

PART II: INSTITUTIONAL CAPACITY AND COORDINATION | 29

2.3

2.3 INSTITUTIONAL ARRANGEMENTS
Part II of the handbook• Defines an institutional framework for road geohazard risk management; and•	Explains a process for conducting an institutional capacity review and target-setting exercise
based on this framework.

The reader is also advised to refer to the following reference document:•	Terms of Reference 1 (ToR 1): Institutional Capacity Review and Target Setting (in Appendix
A) is a standard terms of reference (ToR) to determine the existing institutional capacity to
implement road geohazard risk management, assess the gaps, and establish the step-up target
to strengthen the capacity.
The achievements after using this Part II are• To understand the institutional processes associated with road geohazard management; and•	To assess the current institutional capability for road geohazard management and to set atarget institutional capability.
2.3.1 INSTITUTIONAL FRAMEWORKAn integrated and effective institutional setup may promote a systematic and efficient approach
to road geohazard risk management. The institutional framework comprises (a) laws, regulations,and technical standards; (b) national and subnational government plans and strategies; and (c)mechanisms for implementation.
2.3.1.1 LAWS, REGULATIONS, AND TECHNICAL STANDARDS
Governments may or may not have laws, regulations, and technical standards that govern roadgeohazard risk management.4 If they exist, the laws and regulations stipulate the responsibility
and authority of the actors involved (such as road management authorities, traffic police, andrescue agencies) to ensure the implementation of road geohazard risk management. Moreover, thevarious laws and regulations related to roads and disasters ideally define disaster risk management,
geohazard risk management, and road geohazard risk management consistently.
The main actor involved in road geohazard risk management is the road management authority5—
the government office responsible for managing road transport assets, including planning, setting
road standards, road design, road construction, operations, maintenance, road safety management,
and traffic management. The road management authority develops the road management policies
and strategies that dictate how (among other things) road geohazard management will occur within
its jurisdiction. Other actors or stakeholders include the traffic police, emergency response units,
road users, communities and roadside residents, public transport operators, logistics providers,business personnel, volunteers, insurance providers, and bus and taxi management organizations
and associations.
The laws and regulations also define the road management authority’s roles, its scope of liability
for road geohazard risk management, and its power and authority to protect road users and roadinfrastructure from geohazard damage. The role of the road management authority regarding
geohazards, as defined in this handbook, involves the administration of risk evaluations, risk
management planning, the implementation of structural and nonstructural measures, and postdisaster
response and recovery (that is, prevention and mitigation of secondary damage and recovery).
This chapter draws on the experience noted in the case studies—in particular those of Japan and Serbia (see Appendix C)—combined with the authors’ own experience.
National and subnational road management authorities are mostly government entities, but sometimes they are public or private organizations established as roadmanagement foundations or companies with concession contracts with the government.

4
5

30 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKThe national road management authority develops technical standards regarding road geohazard
risk management, and sometimes the subnational governments modify them to meet the
subnational conditions and restrictions. These technical standards support an appropriate process
on road geohazard risk management. The development of technical standards requires a specificminimum level of technical capacity. Therefore, this handbook considers the development oftechnical standards to be an intermediate target.
Whether at a national or regional level, laws and regulations surrounding forestry, horticulture, soil
conservation, farming, and related activities all have the potential to dramatically influence (for the
better or worse) the risk of geohazards.
2.3.1.2 NATIONAL AND SUBNATIONAL PLANS AND STRATEGIESThe development of national and subnational plans and strategies is essential to promote
proper road geohazard risk management, and therefore this handbook considers suchdevelopment to be an essential target of the national and subnational governments. Whennational governments formulate development plans and strategies, the management plan forroad geohazards must be incorporated as well. Conversely, plans and strategies focusing onroad geohazard risk management should ideally be formulated and subsequently integrated
into the overall national development plans and strategies. It is acceptable to incorporate or
integrate the road geohazard risk management plans and strategies into the higher-level plans
and strategies for disaster risk management, geohazard risk management, road management, ortransport sector management.
The road geohazard risk management plans and strategies should include the following
assessments: (a) the current state of road geohazards, (b) the details of prior failures, (c)risk evaluation results, and (d) mitigation targets for specific probability levels of potential
damages. The government or road management authorities also formulate specific investment
programs and projects to support geohazard risk management.
Some of the national and regional planning activities pertain to the evaluation of the criticalityof roads. It may be that a relatively low-traffic-volume road is of high importance to society
if that road serves the local water treatment plant or the like. Hospitals, emergency services,and evacuation facilities (schools or other public buildings) may well be located off the busiest
roads and are equally critical. Many bridges around the world not only provide vehicle crossing
on top of the bridge but also attach core utilities (water, power, gas, and so on) under thebridge. The planning tasks seek to establish what is often referred to as “lifeline routes” that are
the highest priority for providing both a high degree of protection from hazards and a high levelof resilience for their opening after a disaster.
2.3.1.3 MECHANISMS FOR IMPLEMENTATION
Because geohazard management is part of the road authority’s overall road network management
activities, the organizational structure will not be determined solely by geohazard management
risk requirements. There are good and bad examples (often within the same country) of geohazard
risk management, and these different outcomes are often unrelated to any specific organizational
structure or approach toward the outsourcing of professional and physical works. In other words,
the organizational structure should be seen as neither a hindrance nor a beneficial factor in
addressing geohazard risk management; rather, it is a factor to be worked into the management
processes and practices.

PART II: INSTITUTIONAL CAPACITY AND COORDINATION | 31

The recommended practice is that geohazard risk management be fully integrated into every practiceof the organization and that it does not result in a separate functional arrangement and duplicationof staff roles. Geohazard risks are just one among the many types of risks to keeping a road network
open and operational. Responses to road closures, for instance, should be largely consistent whether
the closure is caused by a geohazard, a vehicle crash, or a structural failure of a bridge—they all
require information to be communicated to road users and stakeholders, road closures to be put inplace, and actions to be taken to secure and reopen the road as soon as practical.
That being said, for the purpose of this manual, three layers of an organization are referred to as follows:•	National office: Nationwide administration that is responsible for nationwide policy making,target setting, planning, and coordination of road management including road geohazard risk
management•	Regional offices: Responsible for national or local government roads, with jurisdiction over asignificant portion of the road network (typically a greater length than can be delivered througha single maintenance yard or maintenance contractor); implementation of the national policies;
and achievement of the targets set•	Local offices: Responsible for national or local government roads, with jurisdiction over roads
that form a maintenance yard or maintenance contractor responsibility. The local offices(potentially delivered by a consultant or contractor engaged by the regional office) manage
and deploy patrols and maintenance staff, assess and monitor the geohazards within theirroad networks, and complete the physical works. The district office is important for timely
postdisaster activities to ensure recovery, including reopening of damaged or closed roads. To
achieve prompt recovery or reopening, it is important to ensure that preparedness measures forroad geohazard events are in place, including arrangements for the availability of machinery andequipment, staff training, and a framework for standby contracts (indefinite delivery contracts).
In large countries and states such as Japan (see the Japan case study in Appendix C), these three levels(and possibly more) can be readily identified owing to different physical locations of the teams andclear role definitions. In smaller countries, the three levels may all be delivered from within one team,with staff sharing their time between the different roles—for example, developing policy one day, andapplying it the next.
It is worth noting that, at the “local office” level, many countries fully outsource the physical works(and many of the management tasks) to the private sector. The management and response togeohazards are not restricted by the service delivery model in use (Table 2.1). For instance, a country
may maintain a fleet of equipment for use in response to geohazards, or it may have contracts in placewith the private sector that can be called upon if a geohazard occurs. What is important is to recognizethat there are distinct levels, each with different roles ranging from governance, to strategy, and on
to operational activities—and that these different levels must be working for a common purpose. To
achieve efficient recovery and reopening, it is important to ensure that preparedness includes having
preexisting arrangements to expeditiously access personnel, plant, and materials. Such arrangements
may include ensuring that in-house staff (in particular, a nodal officer for coordination) are available
and properly trained or ensuring that contractual arrangements are in place that can be activatedquickly when geohazard events occur.

32 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Table 2.1: Typical Allocation of Tasks for Road Geohazard Risk Management, by Level of RoadManagement Authority
NATIONAL TASKS
Establishment of policy
and protocols for resiliencemeasures and geohazard
responses
National road management
planning, including roads underlocal government management
Budget planning and allocation
Administration of postdisaster
activities and reactive measures
for roads in the event ofwidespread disasters
Establishment (if not alreadydone) of the parameters for
dividing the country into logicallocal regions, and setup of local
or regional road bureaus
Establishment of theheadquarters for disaster control
administration for abnormal
conditions and disaster events(including preparedness) for
roads

REGIONAL TASKSLOCAL TASKSRoad management and budget
planning

Management and deploymentof patrol and maintenanceresources for vulnerability
assessment, monitoring, andemergency response

Implementation of conditionassessments, road inventory
collection, and vulnerability
assessments—as required toestablish road information
management systems
Risk evaluation andmanagement planning regarding
road geohazards
Design, cost estimation, andconstruction management forstructural measures

Contribution to implementing or
constructing measures that may
prevent or mitigate the impactsof geohazard events
Establishment of the task teamwith jurisdiction over roaddisaster control for abnormal
conditions and disaster events(including preparedness)

Operation of nonstructural
measures for road geohazard
disasters
Establishment of the regional
office for disaster control
administration for abnormal
conditions and disaster events(including preparedness) forroads

The national road management authorities formulate mechanisms for information communicationand coordination with road users and the other public institutions (local government, community,
meteorological agency, police, disaster prevention or rescue agency, school, and so on); privateorganizations (such as bus operators); and roadside business establishments. The agreements for roadgeohazard risk management should include a clear information communication chart. In turn, bothnational and local road authorities formulate the mechanisms for the efficient implementation of roadgeohazard risk management. These mechanisms are divided into institutional, technical coordination,and funding mechanisms.
The national road authority formulates the road geohazard risk management mechanisms at thenational level, including the national and local coordination mechanisms. These mechanisms are
sometimes expressed as operation guidelines for road geohazard risk management. The local
government road management authority formulates the local road geohazard risk management
mechanisms.

PART II: INSTITUTIONAL CAPACITY AND COORDINATION | 33

Institutional and technical coordination mechanisms require coordination between the roadmanagement authorities and several public and private organizations (Figure 2.2). These organizations
may include the following (noting that different arrangements exist in different countries):
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

Local road management authorities
Disaster risk management authorities
Technical institutions for roads or geohazard risk management
Police, emergency services, and trauma care services
Rescue agencies
Meteorological agencies
River (landscape ecosystem) management authorities
Executives of national and local governments
Environmental organizations
Urban and rural development organizations
Road users
Residents, business establishments, and other persons along the roads
Public transport companies, freight companies, and relevant associations
Utility providers: water, power, telecommunications, and the like
Consultants and contractors involved in the management and maintenance of the road network.

Figure 2.2: Structure of Institutions and Stakeholders in Coordination Mechanisms for Road Geohazard
Risk Management
RELATED AUTHORITIES• River or catchment-based
sediment management
authorities (including waterinduced geohazard risk
management)• Environmental authorities(environmental management
including roads)• Disaster risk management
authorities (overall disasterrisk management including
road geohazards)

SUPPORTERS OF ROAD USERS
AND ROADSIDE STAKEHOLDERS• Police departments (traffic
regulation, traffic accident
inspection)• Rescue agencies (rescue of
geohazard victims)• Health organizations (medicalcare of geohazard victims)

EXECUTIVES OF NATIONAL AND
SUBNATIONAL GOVERNMENTS(usually lead the roadmanagement authorities)

NATIONAL AND SUBNATIONAL
DEVELOPMENT AUTHORITIES(lead agency over roadmanagement)

TECHNICAL SUPPORTERS• Technical institutions for roads orgeohazard risk management (research andtechnical development for road geohazard
risk management)• Meteorological agencies (meteorological
data collection and weather forecasting,early warning for geohazard risk underabnormal weather forecasts)

ROAD MANAGEMENTAUTHORITIES(road administration
including road geohazard risk
management)
ROAD USERS AND ROADSIDE STAKEHOLDERS•R oad users: all modes of travel; public, private, and commercial users•R esidents, business establishments, and other persons along the roads•P ublic transport companies and associations
SERVICE AGENCIES OR BUSINESSES USING ROAD SPACE(water supply, drainage, electricity, communication, fuel, and other companies that
install facilities on the roadside or road subsurface)

34 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

2.3.2 FUNDING MECHANISMS
National road management authorities usually define the funding mechanisms for the whole country.
The national governments coordinate the budget allocation for road geohazard risk management
based on the available national budget and international grants or loans. The funding arrangements
need to cover the following four areas (although separate line items in the budget may not be
explicitly specified and may be included within more-general budget allocations for emergency
response, emergency road maintenance, capital works budget, and routine road maintenance):• Funding for risk evaluations for road geohazards• Funding for road geohazard risk management planning• Funding for proactive measures• Funding contingencies for postdisaster activities and reactive measures.
Of significance is that funds need to be available for the management and preventive activities ofgeohazard management, not just for the remedial postdisaster and reactive measures.
The coordination agreements (which define the purpose of road geohazard risk management
activities and roles of each organization) are recorded as memorandums of understanding or
similar other documents. A council, committee, or similar organization sometimes manages thecoordination mechanism. The main institutions and stakeholders involved are shown in Figure 2.2.
All the major institutions will typically have both national and local structures, and these should be
duly accounted for.
When a geohazard event does occur that requires funding beyond that of the road authority’s dayto-day activities, contingency funds will need to be accessed. Common approaches to contingency
funding include•	Contingent projects: Having some capital projects that are not commenced until near the endof the financial year and that can be deferred should a major event occur;•	Disaster recovery fund: A central (or regional) fund, increased continuously, that can then be
drawn down in the event of a disaster;• Insurance: Used as applicable for significant structures such as bridges and tunnels; and•	Budget reallocation: Moving money from other budget items (potentially from outside the road
sector) to cover the necessary repairs.
The case studies (Appendix C) provide examples of the funding models used in Brazil, Japan, andSerbia to address geohazard risks.
2.3.3 HUMAN CAPACITY: EXPERTISE REQUIRED FOR ROAD GEOHAZARD RISK MANAGEMENT
The expertise required for road geohazard risk management, the logic behind these requirements, andthe necessary activities from each expert field are as follows:•	Rural and urban planning and traffic engineering experts evaluate geohazard risk, especiallythe estimation of the damage due to traffic interruption and the evaluation of road geohazard
impacts on the local and social economy.
•	Economic modelers and disaster risk management experts conduct risk evaluations andcost-benefit analyses for the existing or planned alignment and the investment in required
measures as well as damage estimates for postdisaster activities.

PART II: INSTITUTIONAL CAPACITY AND COORDINATION | 35•	Information and communication technology experts set up emergency road information
systems for collecting and providing geohazard information to road users and otherstakeholders.
•	Engineering geotechnical experts identify and evaluate hazard-prone road locations, evaluate
the geohazard mechanisms, and suggest and provide proactive measures as well as otherdesign conditions for the ground or soil.
•	Hydrological specialists identify both current and future weather events and ensure thatengineered structures have the appropriate capacity.
• Civil engineers plan and design proactive measures and recovery.
•	Social and environmental assessment experts assess the social and environmental aspects of
the required or suggested measures for the geohazard, study the social and environmental
considerations, and monitor the actual impact.
The need for these areas of expertise in full-time roles within a road authority will largely depend on
the country’s geohazard risk exposure. Where road networks have significant exposure to geohazards,
then having geotechnical experts on staff or prearranging accessibility to them from the private
sector may be prudent. Road networks with much less exposure may just engage consultants as
required (although a basic level of skill will need to be retained in-house to enable procurementof the specialists and understanding of their outputs). The main point is that road geohazard risk
management requires a multidisciplinary approach if it is to deliver the maximum benefit to road
users and the community at large.
2.3.4 EFFECTIVE IMPLEMENTATION
Effective road geohazard risk management relies on the institutional capacity to execute each of thefollowing activities:• Disaster risk management• Geohazard identification and evaluation• Design and construction of structural measures and ongoing maintenance• Implementation and operation of nonstructural measures• Postdisaster activities immediately after (or during) the geohazard event• Recovery tasks to return the facilities to full function.
Geohazard management will often require the formulation of new technical standards for roadgeohazard risk management—covering everything from engineering design to the economic
evaluation of risk-based costs.6 If human resource development is needed, for example, the design
and implementation of technical assistance projects or human resource management programs
are considered. Also, equipment, software for geohazard investigation, and analysis are required
for the training for and implementation of proactive measures and recovery. During the initialstage, training experts, equipment, and software are considered to support international technicalassistant programs. An adequate information and communication technology (ICT) infrastructure isalso a requirement for nonstructural measures enabling early anomaly detection; for road condition
emergency information systems (including an early warning or precautionary road closure); and forprompt implementation of postdisaster response and recovery for road geohazards.
The inclusion of operations and maintenance costs in life-cycle cost evaluations is standard practice in many countries, but the means of addressing low-frequency (and
often unpredictable) yet high-cost scenarios into economic evaluations is less commonly practiced.

6

36 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Underpinning all aspects of the activities listed above is the central role that asset management
information systems (AMIS) play in (a) the management of geohazard risks, including holding historical
data on hazards and investments made to mitigate them; (b) the performance of maintenance tominimize risks and ensure that structural measures perform as designed; and (c) the development
and management of emergency response plans and information distribution to response teams andthe general public. AMIS and ICT infrastructure is a common requirement not only for road geohazard
risk management but also for overall road infrastructure asset management and traffic management.
If the ICT infrastructure is insufficient, technical assistance from international donors to improvepolicies and procedures is an excellent target to help in the evolution of a more sophisticated roadmanagement system, including nonstructural measures for road geohazard risk management.
The following systems are vital for effective AMIS: geographic information systems (GIS) incorporating
mapping of geohazard locations along with inventory data and mapping of vulnerable infrastructureor services; closed-circuit television (CCTV) at critical nodes; two-way communication systems (radio,
mobile, data, and systems); public communication systems (VMS, intelligent transport system [ITS]
gantry messages, mobile phone messages, websites, and media announcements); and links to existing
ITS infrastructure (for example, through tolling, weigh-in-motion infrastructure, or traffic management
centers that can be used to ensure the public is notified of events). The systems can also be used
for maintenance decision making, prioritizing structural interventions, maintenance scheduling,
and monitoring of expenditures (useful when justifying structural interventions on a life-cycle-costbasis). Further discussion on ICT is covered under Part III (Systems Planning), Part V (Operations andMaintenance), and Part VI (Contingency Programming).

2.4

2.4 INSTITUTIONAL CAPACITY REVIEW
2.4.1 OBJECTIVE OF THE REVIEWThe objective of the institutional capacity review is to measure how the road authority addresses
geohazard risk and risk mitigation at the national and subnational levels, considering the following
aspects:• Existence and level of maturity of the legal framework, institutions, and plans or strategies•	Review of institutional capacity and capability in relation to human resource needs andsupporting the AMIS and ICT infrastructure• Implementation level of plans or strategies•	Situation and effectiveness of implemented projects on road geohazard risk management,
projects under implementation, and planned projects.
Results of an institutional capacity review reach official consensus on weaknesses, targets for
institutional strengthening, and definition of investment priorities and their financing strategy.
2.4.2 PROCEDURE
The country capacity review may be conducted based on ToR 1: Institutional Capacity Review andTarget Setting and its checklists, included in Appendix A of this handbook. The general procedure
for the review is as follows, requiring access to supporting evidence and interviews to complete theassessment:
1. Understanding and confirmation of review items
2. Collection of necessary data for the review

PART II: INSTITUTIONAL CAPACITY AND COORDINATION | 37

3. Review of the country capacity using checklists
4. Sharing of review results between the people concerned
5. Discussion, evaluation, and finalization of the country capacity review
6. Definition of challenges for the country.
2.4.3 SCOPE OF THE INSTITUTIONAL CAPACITY REVIEWThe scope of the institutional capacity review is classified into three main categories (Table 2.2):•	Review of the institutional framework: To review the laws and regulations, plans and strategies,
standards and manuals, institutional-technical coordination, and financial mechanism for roadgeohazard risk management•	Review of practice on road geohazard risk management: To review the activity for roadgeohazard risk management by road management authorities or relevant organizations•	Review of organizational capacity: To review the authority’s capacity for road geohazard risk
management in terms of human skills, equipment, and related aspects that are required to bein place to deliver on the relevant laws, regulations, and guidelines.
Specific items are shown in the checklists of ToR 1: Institutional Capacity Review and Target Setting(see Appendix A).
2.4.4 TARGET SETTING
This handbook proposes three step-up targets on road geohazard management:•	Essential targets are the initial requirements for instituting road geohazard risk management
and setting up of road geohazard management. They focus on the existence of fundamental
laws, regulations, and high-level plans to support institutions to carry out this function.
Definition of responsibilities in laws and regulations, along with establishing proactive
measures for ad hoc recovery, are important to achieve at this initial target stage.
•	Intermediate targets are the next level of requirements to operationalize road geohazard risk
management. They generate more detailed and upgraded inputs required to make specific risk
management investments.
•	Advanced targets enhance road geohazard risk management through more rigorous review,elaboration, and enhancement using advanced technologies.
These steps conform to the requirement, and the difficulty level also increases as the steps advance.
Each government reviews its institutional capacity and budget constraints and sets a target step as afirst step. The items and activities of each target step shown in this section are intended as an outline
and are subject to be modified and detailed by each government to meet its situation as shown in
Table 2.3 and below.
2.4.5 IMPROVEMENT PLAN
Having completed the capacity review, an improvement plan can be implemented that sets time-based
initiatives to close the gap between current and desired levels of capability. The target (essential,
intermediate, or advanced) along with the time to achieve the target will naturally vary from road authority
to road authority, based on the level of geohazard exposure and other competing demands for funding.

38 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Table 2.2: Institutional Framework for Road Geohazard Risk Management with Stepwise Approach
FRAMEWORKCATEGORYRECOMMENDED PRACTICES
Laws for disaster risk management, geohazard risk management, and roadgeohazard risk management exist and are consistent and comprehensive.

ORGANIZATIONAL CAPACITY

ROAD GEOHAZARD RISK MANAGEMENT PRACTICE

INSTITUTIONAL FRAMEWORK

Laws and regulations

The responsibilities of government authorities and the regulations
regarding disaster risk and hazard management—including the penalties
for illegal geohazard-inducing activities (such as burning agriculture,irrigation watering on roadside slopes, litter on road drainage, dumping
or throwing away of soils, and excavation or filling without authority
approval)—are defined.

National and subnational
high-level plans or strategies

National and subnational government development plans and strategies
include disaster risk management, geohazard risk management, androad geohazard risk management. Such plans and strategies exist at all
government levels.

Technical standards, guidelines, and manuals

Elaborated technical standards include disaster risk management, roadgeohazard risk management, risk assessment, structural measures for roadgeohazard risk management, and road operations and maintenance forroad geohazard risk management (nonstructural measures).

Institutional and technicalcoordination mechanisms

Institutional and technological coordination mechanisms include
consultation from meteorological and hydrological organizations;coordination between national and subnational governments; andparticipation of road users, residents, and private sectors.

Funding mechanisms

Funding mechanisms include budgets for risk assessment, planning onroad geohazard risk management, proactive measures, and contingencies
for postdisaster response and recovery.

Risk evaluation
Geohazard risk management
planning of roads
Structural and nonstructural
measures for roadgeohazards
Road geohazard risk management activities are conducted and deliver
outputs of sufficient quality to drive the geohazard risk management
process as outlined within this guideline.
Postdisaster response andrecovery

Human resources

The necessary human resources (both capability and capacity) are in place
to deliver on all required aspects of geohazard risk management, including
road authority staff, wider government staff, and relevant private sector
participants.

Equipment

Is the equipment available in the right quantity and in the right locations
to address geohazards? Considering that, in many cases, geohazard events
may occur at multiple locations across the network at the same time,equipment needs to be appropriately dispersed to enable an efficient
response.

Facilities

Are the facilities of an appropriate size and in appropriate locations toenable responses? Do they have the necessary emergency power andcommunication systems to be of use in emergencies?

PART II: INSTITUTIONAL CAPACITY AND COORDINATION | 39

Table 2.3: Step-Up Targets for Strengthening Road Geohazard Risk Management
GEOHAZARD
LIFE-CYCLEPHASEASPECT OF ROAD
GEOHAZARD RISKMANAGEMENT

Laws, regulations,and technical standards

Institutional
Setup

STEP-UP TARGETESSENTIAL
Formulation of key laws
and regulations pertaining
to responsibilities for roadgeohazard management andresponse (note that these
are likely to be part of larger
civil defense-type laws andregulations and not specificto geohazards)

INTERMEDIATE

Review and updating of laws
and regulations
Formulation of technicalstandards and guidelines

Review and updating of plansor strategies

ADVANCED
Further review andupdating of laws andregulations, including
the contribution of theroad function subnational geohazard management (for example,
extreme-emergency
management laws)
Further review andupdating of plans or
strategies (for example,
business continuity plan
for road operations)

National or subnational plans andstrategies

Formulation of national or
subnational plans

Mechanisms for
implementation

Formulation of fundamental
mechanisms of funding andof institutional and technicalcoordination

Review and upgrading of
mechanisms (for example,
formulation of operational
procedure of subsidy or coordination committee)

Further review and upgrading of mechanisms(for example, standby
contracts for emergencies)

Risk evaluation

Starting with basic methodof risk evaluation (such as
simple risk qualitative evaluation, using multiple criteria)

Review and upgrading tointermediate method of risk
evaluation (for example,
risk-level rating)

Further review andupgrading to advanced
method of risk evaluation (for example, economic risk evaluation as
potential annual loss)

Formulation of detailed plansor strategies (for example,
comprehensive investment
schemes)

Risk management
planning

Setting up of the frameworkand starting

Review and upgrading of theframework and practices

Further review andupgrading of the framework and practices (forexample, road risk management, which contributes to local geohazard
risk management)

Engineeringand Design

Structural measures

Construction of fundamental structural measures (forexample, earthworks, surface
drainage, and vegetation andbioengineering)

Construction of common
structural measures (forexample, standard retaining
walls)

Adaptation of advanced
structural measures forhigher-magnitude geohazards (for example,
high-energy rockfall
protection)

Operations andMaintenance

Nonstructural measures

Establishment of fundamental measures (for example,
routine patrol and monitoring, and an abnormality
information system)

Enhancement of nonstructural measures (for example,
precautional road closure
arrangements)

Further enhancement(for example, a roadgeohazard early warning
system using advanced
ICT)

Postdisaster response and recovery

Preparation and fundamental practice for postdisaster
response, including preidentification of responsibilities
and budgets to address
geohazard events

Enhancement of postdisaster
response, including formalized plans to address specificgeohazard events, such ascommunication of roadclosures

Further enhancement of
postdisaster response
and recovery (for example, formation and training of special task force
for wide-area severe
geohazard event)Contingency
Programming

Note: ICT = information and communication technology.

40 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKPART II: INSTITUTIONAL CAPACITY AND COORDINATION | 41

42 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

3
SYS T E M S P L A N N I N GPART III: SYSTEMS PLANNING | 43

Systems
Planning

44 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

3.1

3.1 WHAT IS SYSTEMS PLANNING?
The systems planning stage of the life cycle covers those activities that are often referred to as theinstitutional arrangements that are necessary to support the overall geohazard risk management
process. This handbook addresses three main aspects of systems planning:• Risk identification and assessment• Risk evaluation• Risk management planning.
For more detailed information on risk management practices, see ISO 31000.7
The achievements after using Part III are• To understand road geohazard risk identification, assessment, and evaluation; and• To understand the practice of disaster awareness.
Reference documents for Part III of the handbook include the following:• Terms of Reference 2 (ToR 2), Risk Evaluation and Risk Management Planning (in Appendix A) isa standard ToR to either evaluate geohazard risks on an existing road alignment (or whole road
network) or to identify geohazards on a potential new-road alignment. It includes a ToR templatefor consultancy service for risk evaluation and risk management planning of road geohazards.
• Terms of Reference 3 (ToR 3), Development of Manual for Promotion of Road Disaster Awarenessand Partnership (in Appendix A)• Operations Manual 1 (OM 1), Economic Risk Estimation and Cost-Benefit Analysis (in AppendixB) presents the procedures of risk estimation as a potential annual economic loss and provides
model spreadsheets for analysis.
• Case Study of Japan’s Road Geohazard Risk Management (in Appendix C) presents in detail the risk
evaluation procedure in Japan.

3.2 ROAD CRITICALITY

3.2

As is covered later (Section 3.6.3.1, under “DMDU Methodology”), it is critical to all aspects of roadgeohazard risk management to understand the fundamental importance (or criticality) of a road link
within the overall road network. Regardless of the funds available to investigate, monitor, or repair(proactive or reactive) geohazards, it makes sense that the focus should be on the most critical roadlinks first. Criticality in this context extends beyond geohazard risk management because a single
criticality should apply to a road—regardless of the different risks that would affect that road.
Road criticality should be based on national or regional standards and may include items such as
high-priority designation being given to routes that are key to trade; access to social and politicalservices; emergency evacuation and access routes, and so on. Without this, any response (be it
predisaster or postdisaster) runs the risk of being uninformed and not focused on the identified
priority access needs. It is important to note that the criticality of a road may have little to do withthe road from a transport perspective and more to do with the other services that the road serves.
For example, a low-trafficked road may lead to a city’s water treatment plant, making it a highpriority to be protected from risks. Similarly, there may be minor roads that have key gas, power,
telecommunication, or similar utilities buried within the embankment.
See ISO 31000:2018, “Risk Management—Guidelines”: https://www.iso.org/standard/65694.html.

7

PART III: SYSTEMS PLANNING | 45

The determination of a road criticality is therefore best done by a cross-government working group,
which can examine a road from all points of view and assign a criticality index. Such a working group is
the New Zealand Lifelines Council (NZLC) (box 3.1).

Box 3.1 Purpose and Functions of the New Zealand Lifelines Council (NZLC)The NZLC was established in 1999 and focuses on “enhancing the connectivity of lifeline
utility organizations across agency and sector boundaries in order to improve infrastructure
resilience.”
The NZLC specifies three needs for framing its work on infrastructure resilience:• Robust assets or satisfactory alternative service continuity arrangements• Effective coordination, pre- and post-event, at the national and local levels• Realistic end-user expectations, so that users are risk-aware and better able to consider
options.
The principal functions of the NZLC are as follows:• Advising Lifelines Groups on best practices across a range of activities, including
encouraging new projects and supporting them by offering information on methodology
and other learnings from projects in other regions• Providing a link between Lifelines activities and the government, including relevant
government programs such as Lifelines work within the Ministry of Civil Defense &Emergency Management (MCDEM) and national infrastructure planning within Treasury• Promoting and promulgating resilience-related research• Organizing the annual National Lifelines Forum, which updates representatives from
Lifelines Groups and national utilities on the latest developments and provides anopportunity to develop positions on common resilience-related issues.
The NZLC includes the following:• Spark NZ Ltd. (communications company)• Transpower New Zealand Ltd. (national power grid manager)• New Zealand Transport Agency (state highway road authority and 50 percent funder of
local road authorities)• Vector Limited (power and gas distributor)• First Gas Limited (gas transmission and distribution)• Water New Zealand• Ministry of Civil Defense & Emergency Management (MCDEM)• Ministry of Business Innovation and Employment• Earthquake Commission• GNS Science (an earth, geoscience, and isotope research entity).
Source: “Overview of the New Zealand Lifelines Council (NZLC),” Lifeline Utilities, Ministry of Civil Defense & Emergency Management, New Zealand
Government: https://www.civildefence.govt.nz/cdem-sector/lifeline-utilities/new-zealand-lifelines-council/.

46 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

3.3

3.3 INTEGRATED INFORMATION DATABASE
One aspect of geohazard management that needs to be considered is how to integrate all the many
data sets to enable the analysis to occur. For instance, it may be that hydrological information iscollected and held in one government department, land use in another, road information in another,and key social service information (on hospitals, schools, and so on) in their own government
department records. Furthermore, there may be central government, regional government, and local(municipal) government levels involved in each of these different areas—meaning that integrating
information to enable more efficient and effective management of geohazards to occur is a key
enabler of geohazard risk management.

3.4

3.4 RISK IDENTIFICATION AND ASSESSMENT
Risk identification and assessment is the first stage in the risk management process and consists of
two steps:• Step 1: Identifying hazards

3.5• Step 2: Identifying the likely consequences should the hazard occur.

These two steps will then enable the selection of those geohazards that warrant a more detailed
evaluation process (as further discussed below) and associated mitigation measures (see Part IV).

3.5 RISK EVALUATION
3.5.1 RISK EVALUATION RESPONSIBILITIESIn general, road management authorities are responsible for evaluating related risks to their roadsystems. Therefore, these authorities are normally the lead agencies for (a) developing technicalmanuals or guidelines for risk evaluation, and (b) setting rules and time frames for conducting ondemand or periodic risk evaluation inspections on existing roads. The risk evaluation inspections arenormally conducted by staff, experts, or engineers contracted by the road management authorities.
3.5.2 INFORMATION RESOURCES FOR RISK EVALUATION
Bureaus, agency, or institutes of international, national, and subnational levels are information
resources of risk evaluations. The main information sources for geohazard risk evaluations aregeohazard management (or Sabo, sediment control); river management; geology; disaster risk
management; and universities and colleges; and other resources such as the following:• OpenDRI: Open Data for Resilience Initiative, http://opendri.org/• Open Data for Resilience Initiative Field Guide,
https://www.gfdrr.org/sites/gfdrr/files/publication/opendri_fg_web_20140629b_0.pdf• ThinkHazard! http://thinkhazard.org/.
International online resources are shown under “Web Resources” in Part VII of this handbook.
3.5.3 HOW TO UNDERTAKE GEOHAZARD RISK EVALUATION
Although the geographic scope of any geohazard risk evaluation will inherently be different between
studies on existing roads and those on potential new-road alignments, the underlying methods
are the same. For existing roads, the approach may be constrained to a single site, a single road, or
expanded to the entire network of roads. For new-road alignments, the approach needs to ensure fullcoverage of all potential road alignments.

PART III: SYSTEMS PLANNING | 47

For existing roads, the outcome of the geohazard risk evaluation is to develop a prioritized list of sites
for subsequent mitigation. For new-road alignments, the risk evaluation process should ensure that
there is a basis for proper planning to avoid cost overruns, construction delays, and costly operationand maintenance outcomes. It can also help to manage the local negative social and environmental
impacts of new roads and to plan the new road functions in coordination with local geohazard
mitigation objectives.
The risk evaluation of geohazards involves mainly detailed hazard mapping, preferably using
geographic information system (GIS) tools. The workflow for risk evaluation of geohazards consists offive steps, as further clarified in the following sections:
1. Definition of the study’s geographic scope
2. Identification and mapping of geohazards
3. Preliminary assessment of geohazards
4. Detailed assessment of geohazards
5. Evaluation of the wider impacts of geohazards.
In principle, new-road planning aims to ensure that the true long-term costs of the differentalignments are appropriately assessed, which typically results in avoidance of high-risk hazardous
locations. By contrast, for existing roads, the intent of risk evaluation and planning is to ensure thatfunds to mitigate risks are appropriately prioritized and that contingency plans can be put in placeshould the risk arise.
3.5.4 STEP 1: DEFINITION OF THE STUDY’S GEOGRAPHIC SCOPE
Although it may appear obvious, it is important that the scope of the study extend sufficiently beyond
the road corridor (existing or proposed) to ensure full coverage of any large-scale geohazards. The
extent of this may be from a few tens of meters in areas of relatively flat terrain to kilometers where
the road is located in a steep mountain valley and risks may be located well off the road alignment.
Following the definition of the road corridor (existing or new) that is the focus of the study, a quick
scan of the area by an appropriately qualified geotechnical engineer will enable the selection of an
appropriate study area. At this stage, it is important to remember that the focus is on the risks thatthe defined road corridor is exposed to—and not on all the risks that may exist within the study area.
Significant risks may remain in the study area, but if they do not have an impact on the road corridor
under investigation, then they will not necessarily be reported or managed (but ideally they would be
passed along to the appropriate agency).
3.5.5 STEP 2: IDENTIFICATION AND MAPPING OF GEOHAZARDS
Geohazard identification typically involves a combination of field-based observations and desktop
analyses. For geohazards that have a high frequency of occurrence (less than 10 years between
events), there is likely to be significant institutional knowledge on the presence (and potentially themagnitude) of geohazard risk sites. However, for geohazards that may fail much less frequently, it isquite possible that there is no awareness that the hazard exists—let alone the potential magnitude ofany failure event.
It is recommended that all identified geohazards be coded into the road authorities’ GIS system, suchthat the resulting information can be readily integrated with other map layer data (terrain, rainfall,road alignments, population data, and so on). Basic information such as location, notional size, type

48 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

of geohazard, and the like should be collected to enable prioritization of resources for subsequent,more-detailed studies.
The first initiative should be to capture the location of all known geohazards. Interviews ofexperienced road authority staff, consultants, contractors, and adjacent landowners are good sourcesof base information for such data. A search of newspaper records and similar sources may also
provide information on both the occurrence and magnitude of previous events, potentially providing
an estimate as to the frequency of failure. By default, these known hazards tend to be very localizedin scale—with dimensions typically in the sub-100-meter range—and they can often be managed
through routine maintenance of either removal of the material deposited onto the shoulder of theroad (regular material being deposited on the road traffic lanes would warrant further investigation
because the safety impacts are much higher), through top-up of small slump sites, and so on. Although
localized, these hazards still have the ability to cause significant disruption to traffic and pose safety
risks to road users and those tasked with removing the materials.
Upon completion of the initial capture of known geohazards, the next stage will necessitate the useof technical specialists (see Part II, Section 2.3.3 on “Human Capacity”) to examine a range of data
sources to identify and classify unknown geohazards. In this context, geohazards can be man-made,such as cut slopes that are too steep to meet the required factor of safety. It is also necessary toconsider how climate change (in particular, any trend of increasing intensity of rainfall) may resultin previously low-risk geohazards becoming higher-risk over time. These geohazards tend to also bemuch larger in scale than those that are observed to fail on a regular basis—with dimensions greaterthan 100 meters not uncommon. Furthermore, if they did fail, the result is often beyond the routine
maintenance contract to address and may result in road (or lane) closures for a moderate period oftime (in days or weeks, rather than hours).
Aerial photography is particularly useful for identifying geohazards, especially where a time-seriesof photographs is available covering many years (or decades). In more recent times, the use of Light
Detection and Ranging (LiDAR) data in conjunction with aerial photography is providing even further
information for the specialists to examine in identifying geohazards such as faults (either currently
active or dormant); landslides; changes in river patterns; and coastal erosion (Photo 3.1). Much of thisdata is made more valuable through having a time series of it, such that a regular program (say, every
five years) of aerial photography should be considered as part of the data collection process of theroad authority.
Photo 3.1: Example of Combining Aerial Photography with LiDAR Data
The photograph shows the path of the 2007 lahar down
Whangaehu River valley at the Round the Mountain Track(Tongariro National Park), North Island, New Zealand. It
is an example of a digitally enhanced map from a LiDAR
survey draped with a vertical orthophoto (an aerial
photo with distortion removed and related to specificpoints on the ground).

Source: QP 2013. ©Quality Planning (QP). Reproduced, with permission, from QP; further
permission required for reuse.
Note: LiDAR = Light Detection and Ranging. A lahar is a violent, highly destructive type ofmudflow or debris flow from a volcano, typically along a river valley.

PART III: SYSTEMS PLANNING | 49

The required detailed hazard map (preferably in GIS) for the planning of new roads is provided on asmall scale (1:10,000 to 1: 50,000); it displays all old and susceptible hazard areas in the study area.
The purpose of detailed hazard mapping is to show what types of geohazards are present throughout
the study area. The mapping is conducted by experts in geotechnical engineering, hydrology, or
hydraulic engineering—depending upon the nature of hazards in the study area. A detailed hazard
map shows all types of hazard-prone locations, including historical event information as well as
potential geohazards. The mapping is mostly formulated by interpretation of contour maps, aerial
photographs, and satellite images, augmented by available information of historical geohazard events.
Field reconnaissance and field interviews (data collection of historical geohazard events and current
abnormalities due to geohazards) are conducted collaterally.
Hazard-prone road locations are identified to initialize the geohazard risk management planning
process. This process is conducted based on the perceived level of geohazard risk, using the methods
outlined in the remainder of Part III and summarized in Table 3.1. Using higher-level identification
methods may identify additional potentially hazard-prone locations. However, these higher-level
methods may not be practical for budget-deficient countries. Therefore, for these countries, the basic
method is recommended other than for selected highly critical road sections. Detailed hazard mapping(advanced method) may be used by countries that can afford such an investment or be limited toareas where the basic method identifies issues that warrant further investigation.
Table 3.1: Methods for Identification of Geohazard-Prone Road Locations, by Risk Level

Budget capacity

Perceived geohazard risk
Low

Low
Medium to High

Medium to High
Basic method

Intermediate method

Advanced method

The identification of hazard-prone road locations becomes more accurate but also costlier as one
moves from basic to advanced risk identification methods. The following text describes each method
level in further detail.
Basic method: On-site visual inspections and information from road users. The road maintenance staff
identifies any abnormality or deformation of the road by using their maintenance experience, on-sitevisual inspections, and information provided by road users.
Intermediate method: Identification survey. Geotechnical engineering experts conduct an identification
survey of hazard-prone road locations by collecting data of historical geohazard damage events,
screening hazard-prone road locations via on-site observations, and filling out inventory sheets for eachhazard-prone road location. Inventory sheets include (a) location type (such as mountainside slide slope,valley-side slope, or site with crossing river or stream); (b) simple observation results such as landscape,ground surface condition, abnormalities or deformations, and existing structural measures; and (c)sketches and photographs. Because hazard-prone road subsections are usually 1–10 kilometers longand road locations are less than 1 kilometer long, the inventory sheets also include a space to describe
the road section’s strategic importance within the hazard-prone road location. (Strategic importance
may include, for example, its designation as an evacuation and emergency transport route for serious
disasters, its importance as a logistic corridor from a main port to metropolitan areas, or its vital
importance to populated areas without alternative detour roads.)

50 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Advanced method: Detailed hazard mapping. Engineering geology experts conduct the detailed
hazard mapping along with the intermediate method (geohazard identification survey). The detailed
hazard map to identify hazard-prone locations is prepared through the analysis of contour maps,
and interpretation is conducted using either aerial photographs or satellite images. LiDAR data (fromplanes, drones, or other techniques) is becoming increasingly affordable at either a project or network
level and can provide a highly detailed data set that can be used to identify land changes in andaround the road network over a period of time. In the sample, a detailed hazard map for an existingroad (Map 3.1), the mapping data contribute to the accuracy of the risk evaluation.
Map 3.1: Sample Detailed Hazard Map for an Existing Road in Nepal
a. Sample map indicating relevant geological features
LegendPhoto-interpreted lineament streams
Riverbed angle: 0-5 degrees
Riverbed angle: 5-15 degrees
Riverbed angle: 15-90 degrees
Riverbed deposits
Existing slope failure
Landslide potential zone
Village name
Chainage (km post)
Narayangharh - Mugling Highway
Highway, or major road
BridgeTransmission line
River terrace
Major river
Contour lineb. Satellite image used to construct sample map

Source: JICA 2009. ©Japan International Cooperation Agency (JICA). Reproduced with permission from JICA; further permission required for reuse.
Note: For this map—prepared for a disaster risk management study of the Narayangharh-Mugling Highway in Nepal (JICA 2009)—an engineering
geologist group identified unstable slopes and slides where supply sources of debris flows are deposited. The mapping was done by fieldreconnaissance and interpreting satellite images from the riverside to the mountainside landscape ecosystems (including the road).

PART III: SYSTEMS PLANNING | 51

3.5.6 STEP 3: PRELIMINARY ASSESSMENT OF GEOHAZARDS
Before a detailed evaluation, an initial assessment should be undertaken to identify where the limited
investigatory and mitigation resources should best be placed.
For the initial assessment, rather than undertaking a quantitative evaluation of both the likelihoodand consequence of a risk event occurring, a simpler qualitative evaluation may be used. If a roadauthority guideline defines likelihood and consequence, then this should be used as the basis for thegeohazard ratings also. If no guidance document exists, the definitions below may be used based on
the documented case studies and author experience.
Likelihood may be defined in terms of occurrence probability (also called the “return period”), as
follows:• Low: more than 20 years between failure events• Medium: 5–20 years between failure events• High: less than 5 years between failure events.
Consequence may be defined in terms of the duration and magnitude of damage, as follows:• Low: Would result in the closure of a noncritical road for up to 3 months, or of a critical road forless than 2 days. The event would not be expected to cause a loss of human life or have significant
safety issues either during the event or during the postevent rectification period.
• Medium: Would result in a closure of a noncritical road for up to 12 months, or of a critical roadfor less than 1 month. The event may have an impact on human life during the event or othersignificant safety issues.
• High: Would result in a closure of a noncritical road for more than 12 months, or of a criticalroad for more than 1 month. Alternatively, the event could reasonably be expected to have asignificantly negative impact on human life during the event (for example, a landslide over a busy
highway).
When applying the above guidance, the analyst will need to consider the various ways in which
a geohazard may fail. For instance, an unstable slope may have many medium-likelihood, lowconsequence events as well as the potential for a low-likelihood, high-consequence event. In such a
scenario, the combination that yields the highest risk rating (Table 3.2) should be adopted. Furthermore,
the assessment needs to consider the nature of the closure: is it a loss of a shoulder (critical for cyclists
and pedestrians but not necessarily critical for motorists); the loss of a single lane on a multilane road;the loss of a whole carriageway; or complete closure?
Once the likelihood and consequence of each identified geohazard have been assessed, Table 3.2 may be
used to assign a resulting “risk rating.” The importance of the initial qualitative assessment is not to get
overly caught up in the details, but rather to focus on the purpose of the initial qualitative assessment—
which is to identify those risks that warrant the highest priority of a more detailed evaluation.

52 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Table 3.2: Default Risk Matrix

CONSEQUENCE(impact) if risk occurs

LIKELIHOOD (probability) of risk occurring

LOW

MEDIUM

HIGH

HIGH

MediumHigh

High

MEDIUM

Low

Medium

High

LOW

Low

Low

MediumThe output from this initial risk identification and assessment process should be a register (andassociated map) showing the location of all geohazards, along with the assessed likelihood,consequence, and risk rating. The register should also contain a short comment as to how the ratings
were arrived at, such that the more detailed evaluation (which may not be undertaken for some years
into the future for low-risk hazards) has a basis to work from.
At this stage, the road authority will need to determine whether further examination of the geohazardsof each (or any) of the options is warranted. For those risks assessed as being low, and where budgets
are limited, then further investigation may not be a good use of funds; these risks may be best dealt
with under a specific operations and maintenance plan. Conversely, risks assessed as high would
warrant further study—or such options could be eliminated as deal breakers through the selection of
the preferred option process (see Section 3.7).
3.5.7 STEP 4: DETAILED ASSESSMENT OF GEOHAZARDSFor those risks that warrant a more detailed assessment, the specialists will typically need toundertake a range of field studies (potentially laboratory testing, drilling bore logs, installingmonitoring equipment, land surveys, or similar) as well as some form of modeling to determine theactual level of risk that exists at each geohazard site.
The aim of the detailed risk evaluation is to better understand both the probability of an event (orthe likely triggers of the event, such as certain rainfall events) and the consequence of the event(such as the flow path of a landslide outside the road corridor). Once these factors are better
understood, the risk rating can be refined as discussed in Section 3.5.6.
In many cases, those undertaking the detailed risk evaluation will also be able to concurrently
advise on the range of potential options to mitigate the geohazard risk. Therefore, there is astrong connection between this detailed risk evaluation phase and the option development task in
Section 3.7.1.
The risk evaluation must prioritize the identified hazard-prone road locations to generate the maximum
effect from limited budgets. The text below describes basic, intermediate, and advanced methods forthe risk evaluation of hazard-prone road locations. The technical difficulty, the cost, and the accuracy ofthe evaluation all increase with the method level. Should the budget not permit a Level 3 approach tobe applied at a network level, then either a Level 1 or Level 2 approach should be applied to identify thehighest-risk sites—to which a higher (Level 2 or Level 3) approach can then be focused.

PART III: SYSTEMS PLANNING | 53

Level 1: Basic method. As described earlier (Section 3.5.6), Level 1 applies a simple matrix approach to
the risk evaluation.
Level 2: Intermediate method—Risk rating of an endangered road location is assigned (low-budget,
medium-capacity countries). The Level 2 approach builds on the Level 1 approach by evaluating the
likelihood and magnitude of damage on a number of subcategories, with a score assigned to each.
These scores are then multiplied to generate an overall score of risk level as follows:
Score of risk level = Score of likelihood of road damage x Score of magnitude of road damage impact
The score of the likelihood or the magnitude is just the sum of the scores assigned to each categoryof items rated (Table 3.3). The “likelihood” rating items include elements such as geohazard activities(existence and progression of minor damage or deformation on the road and roadside slope),
historical geohazard impacts, and existing countermeasures. The “magnitude” rating items include
elements such as the strategic importance of the road, traffic volumes, and detour distance in caseof a road closure. A relatively high rating score is assigned to a category that would increase thelikelihood or the magnitude of a geohazard impact considerably.
With reference to the example contained within Table 3.3, the following is noted:• The example has been designed for the evaluation of land-movement-type geohazards.
For other types of geohazards (for example, impact of flooding), the tables will need to beappropriately modified to incorporate suitable factors and scoring ranges.
• Factors in Table 3.3 that have higher positive scores are considered to be indicative of a high riskof a future event, while negative scores indicate factors that would lessen the risk of a future
event. For instance, the presence of four or more events in the past 10 years is considered
indicative of further events in the future (score of +6), while the presence of deep-rooted
vegetation to hold an earth embankment (above or below the road) is considered to be a
mitigating factor (score of −1).
• In the case of the mitigation measures, more than one factor may be selected depending on
what mitigation is in place, unless such measures do not appear to have been effective atpreventing previous events. For instance, if the vegetation has moved with the land movement,
then its effectiveness may be neutral (a score of 0).
• When assigning scores for the presence of mitigation measures, smaller negative values (thatis, indicative of being less effective) shall be used if appropriate maintenance of the mitigation
measures are not in place or where there is evidence that they have not been effective (that is,
no change in the frequency of events since the mitigation measure was implemented).
• The challenge with this approach is in assigning the score for each rating category, and for this it
is recommended that a technical committee of experts be involved—noting that a range of skill
sets will be required.
• For the rating of the magnitude of damage, it is necessary to consider (if at all possible) the
presence of foot traffic past the hazard even if vehicle detour routes are much longer. If footpassage is possible and porters could transfer goods (and people) to temporary shuttle buseson each side of the closed portion, the score for the rating “detour distance” or “no detours”
shall be decreased accordingly. (That is, the detour is not assessed on the longer length ofvehicle access—unless a specific vehicle must get through or the goods cannot be transported
short distances by porters—but rather on the additional journey time.)

54 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK• In the example, scores of 6, 3, and −1 were assigned for each of the three likelihood factors, resulting
in an overall likelihood score of 8; while scores of 6, 2, and 1 were assigned for the damage, yielding
a score of 9. These two values then are multiplied to yield an overall risk score of 72.
Table 3.3: Sample Rating of Likelihood and Magnitude of Geohazard Damage to a Road Location

RATING CATEGORY

a. Rating items for likelihood of damage from geohazards
History of damage from geohazards

Minor damages or deformations

Mitigation measures applied
since last failure

Check/description/score

Check/description/score

Check/description/score

Geohazards have caused
road closures more than four 6times in the past 10 years.

Minor damages ordeformations are clearlyand evidently progressing
on road.
Minor damages ordeformations are slightly
progressing on road.

x

Geohazards have caused
road closures one to threetimes in the past 10 years.

3

Geohazards have not caused
any historical road closure,just reduced traffic speeds,in the past 10 years.

x

Minor damages ordeformations arerecognized but dormant
on the road.

1

Score of selected rating category

6

Total score: summing up of scores of
selected rating categories

8

6

Vegetation(bioengineering) works
x to hold earth areplanted on roadsideembankment.

−1

3

Drainage works are
installed to lower
moisture in soil.

−2

1Structural measures aredesigned to prevent orprotect from geohazard
during road service
time.

3

−1

RATING CATEGORY

b. Rating items for magnitude of damage from geohazards
Road strategic importanceRoad traffic volume

Distance of potential detour

Check/description/score

Check/description/score

Check/description/score

All-weather roads aredesignated for emergency
6xtransport or evacuation
during disaster.
All-weather roads are notdesignated for emergency
3transport or evacuation
during disaster.

No all-weather roads
exist.

1

Score of selected rating category

6

Total score: summing up of scoresof selected rating categories

9High traffic volumexModerate traffic volume

Low traffic volume

3

Long-distance detour (morethan 30 percent of average
total journey length for
9those traveling past thegeohazard)

2

Moderate-distance detour(10–30 percent of average
total journey length for
those traveling past thegeohazard)

3

1

Short-distance detour (lessthan 10 percent of average
X total journey length for
those traveling past thegeohazard)

1

2

1

PART III: SYSTEMS PLANNING | 55

The setting of the relevant factors and score for use in tables such as those in Table 3.3 need to be
developed on a case-by-case basis. For instance, the relevance of vegetation or drainage as mitigation
measures in a country where the geohazards are related to mass rockfall from earthquakes will
be minimal compared with the same mitigating factors in an area with high rainfall and soil that
suffers from slips. Similarly, the determination of the damage (or impact) encompasses many types:
social, economic, environmental, political, safety-related, access-related, and connectivity-related.
Determining which factors are important enough to be considered in terms of impacts is part of therisk evaluation. For example, various road alignment options may be vulnerable to embankment
slips that may crush a car, wipe out a sensitive fauna or flora species, prevent access to an important
agricultural area, or restrict access to a politician’s house. In setting the values in the tables, theroad authority needs to determine the relative importance of each of those factors and use that
information to identify a preferred alignment or treatment.
Level 3: Advanced method—Risk estimate is calculated as potential annual economic loss. For a Level 3
analysis, the focus moves on to assess the spectrum of potential risk events and, for each magnitudeof a risk event, to evaluate the likelihood (probability) and economic consequence (impact). It isthen the summation of the spectrum of risk events that yields the resulting overall risk evaluation.
The potential annual economic loss is a risk evaluation index of high accountability—shown as
the monetary loss expected annually—and can be prioritized for endangered road locations(Figure 3.1). The potential annual economic losses calculated can be used to estimate the benefitsof implementing risk mitigation measures when completing the cost-benefit analysis during theconceptual and design stages.8
Figure 3.1: Workflow for Potential Economic Loss Estimation of a Road Location

Step A:
Evaluation of annual
exceedance probability (unit:
percentage per year) of themagnitude of road damage
events on a road location

Step B:
Estimation of potential
economic loss
(unit: currency)
for each magnitude ofdamage on a road location

Step C:
Estimation of potential
annual economic loss
(unit: currency per year)

3.5.8 STEP 5: EVALUATION OF WIDER IMPACTS OF GEOHAZARDSThis aspect of the geohazard risk management process is one where the geohazard process produces
outputs for other specialists (notably environmental and social safeguard specialists and economists)
to then use in their work. It is not the expectation that the engineers and hydrologists—who are
specialists in their own right—would undertake these other assessments.
For the detailed estimation procedure, see “Operations Manual 1: Economic Risk Estimation and Cost-Benefit Analysis of Investments for Road Geohazard Risk Reduction”
in Appendix B.

8

56 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Depending upon the approach to selecting the preferred option (see Section 3.7), other specialists
who may require outputs from the geohazard analysis would include road safety personnel, costestimation experts, structural designers, and economists.

3.6

3.6 NETWORK-LEVEL ANALYSIS, OR DECISION MAKING UNDER DEEP UNCERTAINTY (DMDU)
3.6.1 WHAT IS DMDU?
Decision making under deep uncertainty (DMDU) is a relatively recent analytical approach thatprovides an analysis framework for making decisions when there is a high level of uncertainty. Suchdecisions are described by Espinet (2018) as entailing the following difficulties for decision makers:• Difficulty in understanding the true nature of the problem• Difficulty in defining future standards to adapt infrastructure to the changing climate• Difficulty in choosing the best strategy to withstand future weather events.
Espinet (2018) goes on to illustrate the many uncertainties associated with planning infrastructure withregard to climate impacts (Figure 3.2). Although geohazards are not singularly climate-related, the natureof geohazard risks and associated decision making is closely aligned with the above DMDU description.
He further explains that, under DMDU, the decision-making process is reversed from a normal “predict,then act” methodology (identify a scenario, develop solutions, sensitivity-test the solutions) to one
that must develop a range of strategies, identify the vulnerabilities of each strategy, and finallyidentify strategy adaptations to reduce the vulnerabilities.
Figure 3.2: Potential Uncertainties in Infrastructure Planning Regarding Climate Impacts
Planning
infrastructure
for the future

Future climate
from projections

Emissionsscenarios

HydrologicalmodelsGlobal models
Downscaling
methods
GCM initialconditions
Source: Espinet 2018. ©World Bank. Further permission required for reuse.
Note: GCM = global climate model.

PART III: SYSTEMS PLANNING | 57

3.6.2 APPLICATION OF DMDU TO GEOHAZARD RISK MANAGEMENT
For either a new road where the range of risks may be limited or an existing road network that is
relatively short, the traditional ‘“predict, then act” methodology—with associated option selection
based on cost-benefit analysis (either on road authority costs or incorporating economic loss
considerations, as discussed earlier in Section 3.5.7)—is relatively simple and effective. However, forlonger road sections or road networks that are often tens to hundreds of kilometers in length, for the
purpose of geohazard risk assessment, the cost-benefit approach is much more difficult to apply.
As with the example in Figure 3.2, geohazard risk management at the network level consists of a rangeof uncertainties that make it practically impossible to precisely define a future scenario to design for.
A range of factors (climatic, tectonic, man-made, and so on) all have a distribution of probabilities ofoccurrence and magnitude of events. These events can then trigger a range of geohazards in terms oflocation and magnitude, which in turn will have a distribution of impacts on road users and adjacentlandowners. Such a range of unknowns is ideally suited to the DMDU approach.
3.6.3 DMDU METHODOLOGY
The application of DMDU involves a five-step process (Espinet et al. 2018):
1. Determine the criticality of a road link
2. Determine the exposure of the road link to geohazard events
3. Determine the vulnerability of the road link to geohazard events
4. Determine the risk to the infrastructure (expected annual damage to the infrastructure)
5. Calculate the resultant priority of the road link.
3.6.3.1 STEP 1: DETERMINE THE CRITICALITY OF A ROAD LINKThe first aspect of determining the criticality is to define what the measure of criticality will be. This
could include aspects such as• Change in the total road user costs, calculated from analysis tools such as Highway Development
and Management version 4 (HDM-4);9• Total kilometers traveled;• Total travel time;• Total journey time to the nearest school or hospital;•A ny other network-level metric (or combination of metrics) that the road authority wishes to use
to define criticality.
The approach to determining the criticality is to analyze the network, first with the assumption that allroad links are fully functional, and then one-by-one remove a road link from the analysis and recalculate
the metric assuming that road users will divert to their next best route. In this analysis, a “road link” isany length of road that the analyst wishes to consider. The criticality being determined could be that of asingle road, a subnetwork of roads, or some other combination such as a key route between cities.
For each road link, the resulting difference in the metric between the “fully functional” and “withoutlink” results is used to define whether the impact is very low, low, medium, high, or very high. The
exact definition of these ratings is not that important, because it is more about the relativity than theabsolute value. However, a road authority may have in place an existing definition for criticality, andthis should be used if available.
For more information about HDM-4, see http://www.hdmglobal.com.

9

58 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Alternatively to the above analytical methods to assign criticality, a scoring system may be employedbased on predefined criteria. This may be more applicable to low-volume rural roads or to countries
with limited funds to expend on the traffic modeling-based approaches suggested above. For instance,
the New Zealand Transport Agency has had research completed into the development of a criticality
assessment of roads that it controls (AECOM 2016), with the outcome being a recommendation to
adopt a criticality framework that incorporates three elements:• One Network Road Classification (ONRC)• Access to lifeline utilities or a lifeline evacuation route• Access to essential services.
A scoring system was proposed by AECOM (2016), with each criterion to be equally weighted (Table 3.4).
Table 3.4: Proposed Road Criticality Components, New Zealand Transport Agency
CRITERIONPOTENTIALDATA SOURCECOMMENT OR RATIONALE

SCORINGThe ONRC provides an establishedfunctional classification covering
traffic volumes, economic criteria,
accessibility, connectivity, and so on.

4 – National or high volume
3 – Regional or arterial
2 – Primary or secondary collector
1 – Local or access

ONRC
assessment

For a region to recover from any
natural hazard event, it is important
for the various key utilities suchas water, wastewater, power, andtelecoms to be able to access theirassets to inspect and undertake
repairs. This category includes
Access tophysical utility assets such as
lifeline utilities,
substations that require accessor a lifeline
evacuation route to maintain continuity of service
to the public and also access tocritical transport hubs such as ports
and airports. This also includes
any routes that are consideredthemselves as essential for
evacuation.

Based on the total number ofutilities on a route, and by thecriticality of utility, as follows:
4 – More than five locallysignificant utility assets, morethan three regionally significant
assets, or one or morenationally significant assets
3 – Three or four locally significant
utility assets, one or moreregionally significant assets, oran essential evacuation route2 – One or two locally significant
utility assets
1 – No access for utilities

Utility asset
information

One Network
Road
Classification(ONRC)

Access toessential
services

These are essential services thatwould be required for response andrecovery during a natural hazard
event. Seven priority areas areproposed:• Hospitals and large age-carefacilities• Ambulance, fire, police, andemergency ops centers• Major utility control centers• Welfare centers• Key retail outlets (hardware stores,
construction resources, andsupermarkets)• Schools and sector posts• Major industry.

Based on the total “priority score”
calculated based on all the priority
services accessed by a given route(refer to body of the main report for details):

4 – Score of more than 5
3 – Score of 3–4
2 – Score of 1–2
1 – Score of less than 1

Essential
service asset
information

Source: AECOM 2016.

PART III: SYSTEMS PLANNING | 59

3.6.3.2 STEP 2: DETERMINE THE EXPOSURE OF THE ROAD LINKThe next stage is to assess the impact of a range of different-magnitude events on the road network.
Exposure could be related to rainfall, earthquakes, or any other trigger of a geohazard event. A typicalanalysis should consider 5–10 different exposure levels for each geohazard risk category underconsideration (such as rainfall, earthquake, and so on). The more exposure levels analyzed, the morereliable the results will be when subsequently determining the risk rating of a road link.
Ideally, the lowest exposure level should yield little, if any, damage to the road network. If thecalculation of the vulnerability (Step 3 in the DMDU process) for the lowest exposure levels indicatesotherwise, then a new lower level of exposure should be considered until such a scenario is found.
Alternatively, it may be possible to assume that a high-exposure event such as a 1-in-1-year rainfall
will have zero impact (low vulnerability) on infrastructure for the purpose of this analysis.
For instance, it may be that the exposure is being assessed on the impact of a range of return-period
rainfall events—from 1-in-5-year events to 1-in-1,000-year events. Under each exposure scenario,
each road link is assessed as to what impact such an event would have on that particular road link,measured in terms of water depth across the road. As with the criticality analysis, the water depths arethen grouped into bands ranging from very low, low, medium, high, or very high levels of exposure.
3.6.3.3 STEP 3: DETERMINE THE VULNERABILITY OF THE ROAD LINK
Having identified the range of exposure levels that each road link could be exposed to, thevulnerability is then assessed on the basis of the assumed financial cost to the road authority to repair
the damage. As with the exposure analysis, there will be a vulnerability for each return period being
analyzed. For practical application, it may be necessary to make assumptions about the likely impact
of different exposure levels that can be readily applied across the road network.
For instance, a rainfall exposure event of “very low” impact may be assumed to cause only minimal
damage to the unpaved portions of a road, while a “very high” exposure may also result in the loss of
paved surfacing, among other things.
Because the analysis is on the basis of a road link, and because roads will be affected differently
at different locations along the road, the vulnerability assessment is the arithmetic sum of thevulnerabilities along each road link. For instance, using the aforementioned rainfall example, thevulnerability of a road link can be estimated based on the length of road with “very low” impact
multiplied by the unit rate to undertake minor repairs, plus the length of road with “low” impact
multiplied by its unit rate, and so on.
3.6.3.4 STEP 4: DETERMINE THE RISK TO THE INFRASTRUCTURE
The risk to any given road link is then the expected annual loss (EAL) based on the combination of
the exposure level and the vulnerability costing (Espenit et al. 2018). This is calculated using thetrapezoidal rule, where the probability of an event is the inverse of its return period. The formula for
EAL for each road link is therefore as follows:

Where n is the number of exposure events under analysis;
i is an integer between 1 and n−1, corresponding to the exposure event analyzed;
Ti is the ith return period; andDi is the damage to the infrastructure corresponding to Ti.

60 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Based on the resultant EAL, the risk of the road link is categorized as very low, low, medium, high orvery high. Again, the exact definitions of these categories are not so important, because it is more
about determining the relative risk levels between road links.
3.6.3.5 STEP 5: CALCULATE THE PRIORITY OF THE ROAD LINKThe final step is to combine the criticality with the risk ratings to calculate the priority of each roadlink. This is undertaken using a matrix (Table 3.5).
Table 3.5: Determining Priority Rating under DMDU Approach

CRITICALITYRISK RATINGVERY LOWLOW

MEDIUM

HIGH

VERY HIGH

VERY LOW

Very Low

Very Low

Very Low

Very Low

Low

LOW

Very Low

Low

Low

Low

MediumMEDIUM

Low

Low

MediumMediumHigh

HIGH

MediumMediumHigh

High

Very HighVERY HIGH

MediumHigh

High

Very HighVery High

Note: DMDU = decision making under deep uncertainty.

Once the priority rating of each road link is determined, the highest-rated links are then subjected
to further detailed analysis. If the initial definition of a road link was a relatively long length of road(or even a subnetwork of roads), it may be appropriate to rerun the DMDU analysis on the highpriority road links, with each road link split into a number of small links. This will then provide further
guidance as to the best portion of the network on which to focus subsequent efforts.
At some stage, the DMDU approach will lead to the need to examine specific solutions at specificlocations—as addressed in Section 3.7.

3.7

3.7 PROJECT-LEVEL OPTION SELECTION
Although a road in poor condition can be readily repaired, a road in a poor location cannot
be so readily modified. Most of the investment in a road in poor condition can be salvaged,
but excessive maintenance costs follow when it is in a poor location and can even lead to theabandonment of such a road. Hence, there is a need for proper investment of time and money infinalization of road alignment.
3.7.1 OPTION DEVELOPMENT
Road geohazard risk management sometimes has negative effects or causes trade-off impacts to road
users and local stakeholders, as in the following typical cases:• Roadside river erosion measures sometimes increase the flooding risk on the opposite side ofa riverbank because of the change in river flow; they can also increase a flow rate caused by anarrowed river watercourse because of the erosion protection structures installed on the roadside.
• Precautionary road closures have the trade-off between saving road users’ lives and generating
traffic-related losses (detour, waiting, and trip cancellation) and can cause inconvenience or evenisolation in local areas.

PART III: SYSTEMS PLANNING | 61

A balance must be struck between (a) road safety and reliability, and (b) the cost of improving roadsafety and reliability. Such issues and other important items should be decided while accommodating
stakeholders’ opinions—recognizing that geohazards are but one input to an overall road project
evaluation process. Even relatively high geohazard risks may well be acceptable where the alternativeroutes are significantly costlier or are otherwise undesirable relative to a less reliable route throughthe hazardous area.
The geohazard risk management policy should consider the road type, as noted in Part I, Section 1.5.
The basic idea is that for low traffic volumes, the investment in road geohazard risk management may
be relatively low, considering a balance between the investment level and the expected level of safety
and reliability of the road against geohazards. Conversely, for high-traffic-volume roads or roads
serving key strategic destinations, a high degree of road resilience is desired with an associated higher
level of investment in risk mitigation measures. In Part IV, Photo 4.4 provides a comparison of rivercrossing solutions that illustrate different levels of resilience to geohazard events.
A road geohazard risk management approach for non-all-weather rural and low-traffic-volume roads ispractical but should allow for temporary road closure under abnormal weather conditions. An example
is to build a low-cost ford river crossing that is designed to allow water with soil to pass over the road
carriageway during floods. The road is submerged and may not be used during flooding; however, thisloss in accessibility for the infrequent nature of the geohazard and the low number of users affected
can save significant construction costs compared with a bridge. Further details on the design of fords
are covered in Part IV, Section 4.4.4. The strategies are determined by cost-benefit analysis of bridge
construction cost, potential annual economic loss, and maintenance cost considering temporary roadclosure and sand and debris removable after flooding.
An adequate operations and maintenance system and a flooding system to alert users and prevent
loss of life are required, the complexity of which will vary from country to country. It is important tohave in place standby machinery and staff during heavy rains to clear the debris accumulated on thefords just after the flooding.
Geohazard risk management strategies for low-volume roads in low-budget countries also should
consider a low initial investment to allow geohazard damage control to be completed in several years.
For example, a mountainside slope can be intervened by making a small cutting operation, insteadof a full cut operation, and waiting for several years for it to become stable with a gentle gradient by
natural collapsing.
For low-capacity countries, geohazard identification and evaluation is difficult and may lead to either
underevaluation or overevaluation of different endangered road locations. Misevaluation can result incost-consuming geohazard risk management. It is a practical strategy to keep initial investments small
for structural measures. For several years after the new road construction, endangered road locations
can be identified by visual inspection, and earlier remedial measures (such as works for minor damage
portions conducted without the need for designs, such as sealing of cracks) can be applied to preventthe development of more serious damages.
Proper new-road alignment planning by avoidance of moderate and high geohazard risk locations cansave significant life-cycle costs, avoiding cost overruns, costly delays of construction, and subsequent
maintenance costs (as illustrated in Photo 3.2). Planning of alternative alignment for the geohazards
should consider the terrain present on both sides of the road (that is, slopes above and below the road).
It is important to pay attention to inundation risks, especially when the route passes through flat areas.

62 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 3.3 shows a detailed hazard map prepared for a new-road alignment, with the preferredalignment (orange line) being selected to avoid the sliding slope and the slope susceptible to rivererosion. This example is significant because it illustrates that, in many cases, the selection of a newroute can be made so as to reduce the geohazard risk, but often it is not possible to eliminate all
geohazard risks. In such a situation, the evaluation of options can be thought of as picking the “least
bad” outcome.
Figure 3.3: Sample Detailed Hazard Map for a New RoadAVOID THE SLIDING SLOPEAVOID THE UNDERCUT SLOPESUSCEPTIBLE TO RIVER EROSION

0SLIDING SLOPEFALLING SCRAPE

GULLY
TALUS
ROAD ALIGNMENT PLANNED TO AVOID
HAZARDOUS LOCATIONSLOW LANDALTERNATIVE ROAD ALIGNMENT HAVING HIGHGEOHAZARD DANGER

Source: ©World Bank. Further permission required for reuse.
Note: Map is a hypothetical example.

PART III: SYSTEMS PLANNING | 63

Photo 3.2: Example of Road Alignment Plan Avoiding Geohazards

FINALIZED ALIGNMENTORIGINAL ALIGNMENT PLAN

The Sindhuli road alignment in Nepal was shifted up the mountain to avoid an area of unstable
collapse-type geohazard and the undercut slope susceptible to river erosion. Although the total lengthof the road is longer, significant life-cycle costs can be saved.
Source: ©Department of Roads (DOR), Ministry of Physical Infrastructure & Transport, Government of Nepal. Reproduced, with permission, from DOR;
further permission required for reuse.

ea

3.7.2 EVALUATION APPROACH
The first stage in selecting the preferred option is to define the evaluation approach, with Figure
3.4 providing an overview of how to determine the appropriate methodology to apply. Typically,for existing roads, the different options can be compared using life-cycle cost analysis on thepresumption that each option will broadly offer the same benefits to road users, and the decision is
primarily a technical one as to which solution can be delivered for the lowest cost.
For new-road alignments, the decision will typically involve multiple factors, including many
nongeohazard factors such as cost (initial construction and ongoing maintenance); safety, social andenvironmental impacts; property impacts; cultural issues; vehicle operating costs; and so on. For
such scenarios, road authorities will often revert to the use of multicriteria analyses (MCAs) or similar
techniques.10 Then, having decided the basis upon which the preferred option will be selected, a threestep evaluation process can be implemented (Figure 3.5).
Figure 3.4: Determining the Appropriate Evaluation Approach to Option Selection
Do the options have
similar impacts onsocial, environmental,
and cultural outcomes?

No

Do the options havesignificant and long-term(>30 years)
costs and benefits?

No

Can nonfinancial
outcomes be readily
quantified?

Yes

Yes

Yes

Life-cycle cost analysis(section 3.7.4)

Multicriteria analysis(section 3.7.5)

Benefit-cost analysis(section 3.7.3)

Source: NAMS 2004. ©National Asset Management (NAMS) Steering Group. Reproduced, with permission, from NAMS Steering Group; further permission required for reuse.
For further guidance on making decisions involving infrastructure, see NAMS (2004).

10 

64 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKNo

Figure 3.5: Process for Selecting Preferred Option

OPTIONOPTIONA

B

OPTIONC

Apply deal breakers to eliminate unacceptable options

Use pair-wise comparison to eliminate suboptimal options

as.

Complete analysis of remaining options
Source: NAMS 2004. ©National Asset Management (NAMS) Steering Group. Reproduced, with permission, from NAMS Steering Group; further
permission required for reuse.

Initial screening of the options with the assessed risks, costs, benefits, and other factors will often
identify solutions that are unacceptable in one or more category (often referred to as deal breakers).
This will involve a multidisciplinary team because, often, avoiding one negative factor—such as
avoiding a moderate geohazard risk adjacent to a river—will result in higher social disbenefits throughthe location of a road on, say, valuable farmland.
In applying deal breakers, it is important to not eliminate an option just because it is undesirable fromone specialist’s viewpoint, and it is also important to use only absolute deal breakers. For instance,
an alignment that goes through a United Nations Educational, Scientific, and Cultural Organization(UNESCO)-protected area could well be considered a deal breaker, whereas an alignment that has aslightly higher geohazard risk could still be acceptable if the other factors are strongly in favor of it.
In general, the analysis will compare the existing situation of “no new road” with each of the proposedalignments. For each component of the project, the specialists should undertake sufficient analysis
to enable them to justify why a given option should not be considered further. These nonacceptableoptions can then be eliminated from further consideration. This deal-breaker stage may eliminate
options for any factor under consideration, including those of a non-geohazard-risk nature.
Subsequent pair-wise comparison of any two acceptable options may reveal further options thatcan be eliminated because an existing alternative is better across all factors under consideration.
For instance, if alignment A is cheaper to construct and maintain and has a lower geohazard risk
along with lower social and environmental impacts, yet also delivers better economic outcomesPART III: SYSTEMS PLANNING | 65

than alignment B—then alignment B can be eliminated from further analysis, regardless of whetheralignment B has yet been compared with alignments C, D, and E.
The remaining alignments will then need to be developed, consulted upon, and otherwise subjected
to option evaluation according to the country’s normal decision-making practice. Geohazard
considerations are then considered as part of the overall costs, reliability of routes (and associatedbenefits), and wider social and environmental impacts.
3.7.3 BENEFIT-COST ANALYSIS (BCA)
The BCA approach converts both benefits and costs over the analysis period into monetary terms,
providing the ability to calculate the following indicators:• Net present value (NPV) = present value of the benefits – present value of the costs— I f the NPV is greater than $0, then the investment is worthwhile, with larger positive values
indicating a greater return on the investment. The NPV tends to favor large-scale investments,
where large benefits can be realized.
• Benefit-to-cost ratio (BCR) = present value of the benefits / present value of the costs— I f the BCR is greater than 1, then the investment is worthwhile. The BCR is better suited tocomparing investments of significantly different costs.
• Internal rate of return (IRR): The discount rate at which the present value of the benefits equals thepresent value of the costs. A higher IRR indicates a better project, because it will “pay itself off” ina shorter period of time.
To determine the benefits, it is necessary to consider the wider economic benefits of the options.
Because the calculation of economic loss from geohazards is a relatively complex analysis, it isaddressed separately in Operations Manual 1 (in Appendix B).
Although these approaches can be used at a network level, they are more appropriately applied
to discrete project-level analyses where the different investment options provide different benefit
streams. For many geohazard solutions, the benefit streams are very similar and it is only the costsof the solutions that vary significantly—thereby enabling the use of a simplified life-cycle cost (LCC)
assessment comparison, as discussed below.
3.7.4 LIFE-CYCLE COST (LCC) ASSESSMENT
At a minimum, all options should be compared on an LCC basis (NAMS 2004). The LCCs include theinitial investment costs of each option, along with the corresponding annual maintenance cost. The
evaluation period for determining the LCC should align with established practices within the roadauthority, which typically range between 15 and 50 years. Where no guidance is provided within acountry on the period to analyze, a good approach is to consider the life expectancy of the longest-life
option.
To determine the LCC assessments, the following input data are required:• Investment cost for the option• Annual maintenance cost for the option• Periodic renewal cost for the option if that is required within the evaluation period• Discount rate for cost-benefit analysis.

66 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKThe LCC of each option is then the sum of the discounted costs, and it is this value that is used whencomparing option costs. The LCC is calculated using the following formula (assuming that investment
costs occur in the first year)11 (NAMS 2004):

Where

LCC is the present value (or discounted) life-cycle cost for the option;
InvCost is the initial investment cost of the option;n is the analysis year;
P is the analysis period;
AMC is the annual maintenance cost in year n;
PRC is the periodic renewal cost in year n; andDR is the discount rate as a decimal (for example, 6 percent = 0.06).

Having calculated the LCC for each option, then under the assumption that the benefits are largely
similar, the option with the lowest LCC is the preferable solution for implementation. The purpose of
the LCC approach is to enable the trade-off between different solutions that may have substantiallydifferent initial investment costs and ongoing maintenance costs.
Sensitivity analysis should also be conducted by varying each input parameter within an appropriate
range and noting any change in the determination of the least-cost option. Projects are consideredrobust if, after each factor change, the same option remains preferable. If the impact of the sensitivity
analysis results in a change to the option that is the least cost, then further analysis may be warranted
to enable a lowering of the sensitivity test ranges of the variables.
3.7.5 MULTICRITERIA ANALYSIS (MCA)
Where the benefits or disbenefits between solutions are not broadly similar, then comparison on abasis other than just costs will be required. MCA enables such a comparison to be made, wherein theoptions are ranked across a range of user-defined factors, in much the same way that the decision on
how to define the criticality of a road is undertaken (see Section 3.6.3.1).
The challenge in applying MCA is to determine the relative weighting between the different factors
being assessed (NAMS 2004). Once the rating criteria have been set, each option is then scored acrossthe criteria and the sum (often weighted) of the criteria added up. The LCC will typically be included asa criterion, although this may be separated into the discrete components noted earlier in Section 3.7.4:
investment, annual maintenance, and periodic costs.
Because MCA is not expected to be used often for the evaluation of project-level geohazard risks, it is
not discussed further in this handbook.

3.8

3.8 OUTCOME OF THE RISK EVALUATION PROCESS
Whether it be a network-level analysis or a project-level analysis, the purpose of the risk evaluation
process is to prioritize hazard-prone road locations for the subsequent application of risk mitigation
measures (refer to Parts IV, V, and VI). The evaluation results are used in the initial decision-making
process for optional next steps such as
Where different options have vastly different construction periods or construction is likely to span more than one year, then discounting of the investment costs as per
the periodic renewal costs should be undertaken, with the investment cost split across the different years based on expected expenditure of funds.

11 PART III: SYSTEMS PLANNING | 67• Remedial measures (works for minor damage portions conducted without the need for design,
such as sealing of cracks);• Engineering studies for proactive risk management measures;12• Routine visual inspections only; or

3.9• No further action, in the case of low-priority risks.

3.9 SELECTED RESOURCES
The following annotated list provides resources pertaining specifically to the topics covered in Part III.
AECOM. 2016. “Review of Methods to Determine Criticality of Roading Networks.” Report prepared for
the New Zealand Transport Agency by AECOM New Zealand Ltd., Tauranga, New Zealand.
Deoja, B., M. Dhital, B. Thapa, and A. Wagner, eds. 1991. Mountain Risk Engineering Handbook.
Kathmandu, Nepal: International Centre for Integrated Mountain Development (ICIMOD). Provides
the procedure of road geohazard risk evaluation, including rating procedures for geohazard risk inchapters 20, 22, and 23.
Espinet, X. 2018. “Prioritization of Road Interventions in Nampula and Zambezia, Mozambique
under Changing Flood Risk and Other Deep Uncertainties.” PowerPoint presentation, World Bank,
Washington, DC.
Espinet, X., J. Rozenberg, K. S. Rao, and S. Ogita. 2018. “Piloting the Use of Network Analysis andDecision-Making under Uncertainty in Transport Operations: Preparation and Appraisal of a Rural
Roads Project in Mozambique under Changing Flood Risk and Other Deep Uncertainties.” Policy
Research Working Paper 8490, World Bank, Washington, DC.
GESU-DOR (Geo-Environment and Social Unit, Ministry of Physical Planning and Works, Governmentof Nepal). 2007. “Roadside Geotechnical Problems: A Practical Guide to Their Solution.” Guidelines
document, GESU-DOR, Kathmandu, Nepal. Provides simple multicriteria risk evaluation procedures forroads.
Highland, Lynn M., and Peter Bobrowsky. 2008. “The Landslide Handbook—A Guide to Understanding
Landslides.” Circular 1325, U.S. Geological Survey, Reston, VA. Provides landslide evaluation tools
including mapping in its Appendix B.
Hughes, J. F., and K. Healy. 2014. “Measuring the Resilience of Transport Infrastructure.” Research
Report 546, AECOM New Zealand Ltd. Report prepared for the New Zealand Transport Agency by AECOM
New Zealand Ltd., Tauranga, New Zealand.
NAMS (National Asset Management Support). 2009. Optimised Decision Making Guidelines. Thames,
New Zealand: National Asset Management Steering Group.
OAS (Organization of American States). 1991. “Primer on Natural Hazard Management in Integrated
Regional Development Planning.” Reference document, Department of Regional Development andEnvironment Executive Secretariat for Economic and Social Affairs, OAS, Washington, DC. Provides a
general explanation of risk assessment.
Winter, M. G., F. Macgregor, and L. Shackman, eds. 2005. Scottish Road Network Landslides Study.
Edinburgh: Scottish Executive. Provides detailed risk assessment procedures, especially for debris flow.
Proactive risk management measures include structural and nonstructural measures for geohazard-prone road locations. In contrast, reactive measures are introduced
after the road damage due to geohazard has already occurred and are intended to prevent future damage.

12 

68 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKPART III: SYSTEMS PLANNING | 69

70 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

4
ENGINEERING AND DESIGNPART IV: ENGINEERING AND DESIGN | 71

Engineering& Design

72 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

4.1

4.1 OVERVIEW OF ENGINEERING AND DESIGN SOLUTIONSPart IV describes the process of road geohazard risk management using engineered (or structural)measures. It presents their definition, the general flow of road construction and structural measures,the engineering investigation of structural measures, the structural measures to consider based on
geohazard types, and the construction management process. It explains the following aspects ofengineered or structural measures:• Engineered measures, implementation stage, and engineering investigation and study;• Types of structural measures and design consideration, by geohazard type.
The achievements after using Part IV are• To understand the implementation stage of investigation and study for structural measures; and• To understand basic and common structural measures and their design considerations, bygeohazard type, and the application of geosynthetics as recently developed materials forstructural measures.
Reference documents for Part IV of the handbook include the following:• Terms of Reference 4 (ToR 4), Design of Structural Measures (in Appendix A) is a standard termsof reference of structural measures design of engineering investigation and study, preliminary
design, and detailed design.
• Case Study of Japan’s Road Geohazard Management (in Appendix C) shows examples of structural
measures in Japan.

4.2

4.2 DEFINITION OF ENGINEERED MEASURESEngineered (or structural) measures are engineering solutions to prevent or protect road damage due
to geohazards. They include measures implemented as• Preventive (proactive) measures implemented to lower the risk of geohazard failure;• Emergency works, in highly susceptible areas or during geohazard events, that are subject toengineering design; and• Recovery conducted as secondary damage protection or recovery works in a postdisaster stage
that are subject to engineering design.
Although the trigger to implement an engineered measure may vary—and the budget and time
constraints might also vary significantly—the fundamental approach is often similar, particularly
when the solution to be implemented is a long-lived one, such as a concrete retaining wall. A wellengineered road with a functionally efficient geohazard-proof system will have more or less negligible
vulnerability. The same road, if badly designed and constructed, may be 100 percent vulnerable. In
other words, vulnerability depends on level of exposure, susceptibility, and degree of preparedness.
In this handbook, structural measures include structures made of concrete or mortar, steel, wood,asphalt, geosynthetics, earth, and vegetation or bioengineering as well as their composites.
“Geosynthetics” refers to any synthetic material—typically polymeric products used to reinforce
earth against collapse or erosion, such as geotextiles (permeable material) and geomembranes(impermeable material). Earth structures include engineered slopes (cutting slope or embankment
slope)—or just a cutting process undertaken as a weight removal of a sliding slope head—andembankments used as a counterweight of a sliding slope toe.

PART IV: ENGINEERING AND DESIGN | 73

Engineered measures can increase the robustness of roads. They are usually implemented during
the stages of road construction and operations and maintenance, based on the priority of thecountermeasures required on road hazard-prone locations. They are measures for geohazard risk
management, but they can also be implemented as postdisaster recovery measures. An environmental
and social impact assessment (ESIA) is typically required (and should be undertaken even if not
required) during the concept design phase of new road construction or for the planning of engineered
measures for existing roads.

4.3

4.3 ENGINEERING INVESTIGATION AND STUDY FOR ENGINEERED MEASURESThe design of structural measures requires investigation and analysis of the relevant geographical,
geological, geotechnical, hydrological, and hydraulic conditions of a particular location. The
investigation methods depend on the geohazard types and the planned structural measures. Several
types of studies or investigation methods are usually conducted to support the design of structural
measures (Table 4.1).
Table 4.1: Studies or Investigation Methods to Support the Design of Structural Measures
TYPE OF STUDY OR INVESTIGATIONPROCEDURES AND OUTPUT

Topographic or contour mapping

A base map is created at a scale of 1:100 to 1:5,000 depending on thescale of the hazard area.

Detailed engineering mappingor section profiling

The map or section profile (scale of 1:100 to 1:5,000) shows the outlinesof geohazards, soil and rock types, geological structures, springs andseepages, drainages, structures, historical flood area and elevation, andslope brake (changing line of slope gradient).

Engineering evaluation of soil
and rock mass

Field reconnaissance, subsurface drilling with core samples, trial pits
and trenches, geophysics surveys, in situ tests, and laboratory tests areused. Evaluation is conducted using classifications of soil types and rockcrack density and weathering. The engineering properties of strengthand durability for seepage are evaluated. The density and directionality
pattern of the plane of discontinuities (such as joints) of a rock mass
are evaluated.

Slope stability calculation forslide-type geohazards

Limit equilibrium methods are predominantly applied in the world forroad slopes because of their simplicity compared with more realistic,
yet more complex, analytical procedures. The safety factor is the resultof dividing the resistance force against instability by the instabilitycausing force. A safety factor greater than 1.0 indicates that the slope isstable.

Hydrological calculations

The outputs of hydrological calculations are the volume of floods ordebris or earth flow at the road-crossing points of rivers or streams—or
the depth of submergence on a road location—obtained by inputting
several return periods (occurrence probability in years) of rainfall andthawing water.

Flow rate calculation

The flow rate of a riverside road bank, bridge abutments, or piers arecalculated by inputting several return periods (occurrence probability inyears) of rainfall and thawing water.

Scouring prediction calculation

Scouring prediction depths of a road riverside bank foot, bridge
abutments, or piers are calculated by inputting several return periods(occurrence probability in years) of rainfall and thawing water.

74 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKA good reference for studies or investigation methods to support the design study of engineering measures isthe Mountain Risk Engineering Handbook (Deoja et al. 1991), specifically concerning (a) engineering evaluation ofsoil and rock mass in Chapter 9 (“Soil Mechanics”), Chapter 10 (“Rock Mechanics”), and Chapter 11 (“Geophysics”);and (b) slope stability calculation for slide-type geohazards in Chapter 13 (“Stability Analysis of Slopes”).
From both a geohazard risk and a climate change adaptation perspective, understanding hydrology
is important for the design of drainage and structural measures. For example, Table 4.1 presents
the types of hydrological and hydraulic rate calculations that should be conducted as part ofengineering investigation, such as depth of submergence on a road location with different return
periods. A simple hydrological calculation can be done by many engineers to size drainage andculverts based on standard return-period rainfall events and simple formulae. Under somecircumstances, however, detailed hydrological and hydraulic calculations have to be conducted using
modeling software that requires calibration and validation using past data. Such circumstances
may include road crossing of flood-prone streams and rivers; major structural investments (bridges,
large culverts, river bank protection, or retaining walls where water is a concern); or cases where
the consequence of failure would be significant to either road users or adjacent land users. Suchdetailed analysis should be undertaken by relevant trained professionals.13

4.4

4.4 TYPES OF STRUCTURAL MEASURES AND DESIGN CONSIDERATIONS
The types of structural measures are selected depending on the type of geohazards on the road.
Earthwork with surface drainage and vegetation (bioengineering) is always the basic countermeasure
to consider for each type of geohazard.
Depending on the method of construction and materials, it is necessary to account for economic
efficiency, availability of construction materials and machines, social or environmental negative
impacts, and the difficulty of maintenance.
Fundamental structural measures for essential targets are mainly earthworks, surface drainage,
and vegetation. Common structural measures for intermediate targets are all shown in this section.
Advanced structural measures are high-specification measures that can manage larger-magnitude
geohazards (for example, high-energy rockfall protection).
4.4.1 STRUCTURAL MEASURES FOR MOUNTAINSIDE FALL OR COLLAPSE
Structural measures for a fall or collapse are classified into slope stabilization measures andprotection measures (Table 4.2). In the case of mountainside falls or collapses, the cutting process
or removal process of unstable rock and soil is essential (Figure 4.1). The slope drainage should
prevent rivers or streams from causing slope instability on the road or nearby properties.
The slope cutting gradient (vertical to horizontal) ranges from 1:0.3 to 1:1.5 depending upon thegeotechnical properties of the material. The design guidelines for road construction or slopeengineering of each country or organization of local countries (such as those in Central America)
or of high-income countries are used as references. These guidelines—which define recommended
cutting gradients depending on the soil rock types and their characteristics—should be used as thebasis for any works.
Vegetation has considerable effectiveness for slope stability because it mitigates slope surface
erosion and water infiltration into the slope ground. Drainage and vegetation are most effective on
slopes with a gentle gradient because rainfall effects are diminished relative to those on a steep
slope. Intermediate slope benches (a “berm” on a cutting slope, as shown in Figure 4.1 , panel a)14 also
Good references for hydrological, flow rate, and scouring prediction calculations include AASHTO (2007) and FHWA (2012).

13 

PART IV: ENGINEERING AND DESIGN | 75

contribute to slope stability, serve as rockfall collectors or to absorb falling energy, and provide a
working space for the installation of ditches or a passage for inspection or maintenance of the slope.
Table 4.2: Typical Structural Measures for Mountainside Fall or Collapse
PRIMARY CATEGORYSECONDARY CATEGORYTERTIARY CATEGORY
Slope cutting (Figure
4.1, panel a)

Cutting or removal of
unstable rock and soil
(Figure 4.1)

Slope stabilization
measures

Prevention of erosion
or slope surface
instabilities

Trimming (Figure 4.1,
panel b)

Scaling (Figure 4.1,
panel b)Slope drainage
Vegetation or bioengineering
Rock bolting (Figure
4.2, panel a) or soil
nailing
Shotcrete (Figure 4.2,
panel b)Slope reinforcement

Pitching work
Slope framework(grid beam) (Figure
4.3)

PROCEDURE FOR CONCEPTDESIGN LAYOUT
Unstable rock or soil on the slope isidentified through visual inspection andshown in the plan and profile. Estimate
the volume for cutting or removal as wellas the land acquisition requirement of
the mountainside slope.
Note that the action of cutting, trimming,or scaling a slope may in itself trigger a
geohazard event and should be undertaken under the guidance of an appropriately qualified geotechnical engineer.
Lay out slope drainage and vegetation
for soil slope. For the spring portion or
identified erosion phenomena, drainage
shall be laid out to drain such spring or
surface water safely during heavy rain.

Area of unstable soil or rock on theslope is identified through visualinspection and shown in the plan andprofile. Estimate the volume of theslope reinforcement area.

Buttress walls (cavity
filling)
Retaining and breast
walls
Catch ditches

Protection measures for endangered road

Resistance or absorption against the shock

Barrier (catch fence,wall) (Figure 4.4,
panel a)Slope intermediate
bench (berm) as rockor soil collector (Figure 4.1, panel a)
Wire netting (rockfallnet) (Figure 4.4, panelb)Guide fall or collapse
direction to the outsideof the endangered road

Guide wall

Determine the possibility of hitting theroad directly or by several bouncesby simple distance from slope to toe
experimentation.
Determine the possible maximum
rockfall size and calculate the energyof hitting. The protection measures areplanned to be durable from the shock
energy through energy absorption or by
guiding the fall or collapse to the direction outside of the endangered road.

Shelters (Figure 4.5)
Tunnels

While many of the figures in this manual illustrate instability or vulnerability above the road (in the cut batter), often instability occurs below the formation level (that is, inearth mass that is supporting the road formation). Potential slips below the road formation can sometimes be harder to identify because they are less visible from the roadsurface but also can be harder to address owing to challenging access conditions, although the same techniques are equally applicable both above and below the road.

14 

76 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 4.1: Slope Cutting or Removal for Mountainside Fall or Collapse
a. Slope cuttingb. Unstable portion removal

Removed (soil)
Trimming/Scaling

Cutting
Road

Ditch
Berm

Unstable
PortionRoad

Source: © World Bank. Permission required for reuse.

Vegetation and vegetation foundation works (bioengineering) are effective in (a) reducing surface
erosion caused by water and rainfall impact; (b) reducing infiltration of rainwater; (c) binding
subsurface soil with its root systems (Photo 4.1); and (d) improving the landscape of the cut slope.
Vegetation is often adopted as a method of slope stabilization in conjunction with structural solutions.
In selecting the type of vegetation to be planted or seeded, factors such as rainfall, temperature,slope gradient, and soil properties should be given full consideration. If the slope is prone to erosion,foundation works for vegetation are provided to support the fertilized soil. Then the vegetation
foundation is finalized when the soil’s supporting role results in the young plant or seedling plant
having grown up, the root system having bound the subsurface soil, and the vegetation supporting
materials (either natural materials or geosynthetics) having decayed.
Photo 4.1: Vegetation at a Road Mountainside Slope
A road mountainside slope in El Salvador,
August 2016, displays vetiver glass after 11months of planting. Its long roots have awell-known soil-binding effect.

Source: © World Bank. Permission required for reuse.

For rock slopes, rock bolting and shotcrete are typical procedures used (Figure 4.2)—solutions thatare equally applicable both above and below the road. Rock bolting is applied to unstable boulders
detaching from stable rock mass. Shotcrete or framing work (grid beam) is applied to the fractured
rock slope. Shotcrete is less durable than framing works and difficult to apply to a slope with water
seeping from the rock face. Weep holes for drainage from behind the shotcrete area are required so as
not to destroy the shotcrete from the generated water pressure.

PART IV: ENGINEERING AND DESIGN | 77

Figure 4.2: Rock Bolting and Shotcrete for Slope Reinforcement for Mountainside Fall or Collapsea. Rock bolting

b. Shotcrete (spraying)

Road

Rock bolt
Shotcrete
Stable rock mass

Unstable rocks

Fissured rocks

Rock
Road
Source: © World Bank. Permission required for reuse

A slope framework (grid beam) or the construction of a grid beam of mortar or concrete on a slope isa method to reinforce the stability of the slope. It can be installed on weak rock or a highly fractured
rock with some water springs, where shotcrete cannot be used. Its objective is to prevent a surface
collapse, and it can be used as a counterforce structure for the anchor lock bolts; the open spaces of
the grid can be covered with vegetation (Figure 4.3).
Figure 4.3: Slope Framework (Grid Beam) for Slope Reinforcement for Mountainside Fall or Collapse

Armored concrete

Shotcrete

Vegetation

Source: © World Bank. Permission required for reuse.

Framework (grid beam)

There are several protection measures for roads endangered by mountainside falls or collapses. They
are subdivided into “resistance or absorption against shock” and “guide fall or collapse direction
toward the outside of the endangered road.” Barriers are resistance measures against impact,
describing walls, fences, or a combination of walls and fences (Figure 4.4, panel a). Wire netting(rockfall net) alternatives are installed to absorb the rockfall shock and are divided into covering types(Figure 4.4, panel b) and catching types that work like a pocket.

78 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 4.4: Examples of Resistance or Absorption against Shock from Mountainside Fall or Collapse
a. Barriers

b. Wire netting (rockfall net)
Falling rock

(Frontal view)

AnchorRockfallRockfall net
Concrete
Road

Road

Fissured rocks

Source: © World Bank. Permission required for reuse

The typical practice of guiding the fall or collapse direction toward the outside of the endangered roadconsists of using shelters (Figure 4.5). The fall or collapse from the mountainside is captured by the
shelter roof and directed into the valley-side slope of the road. This approach is commonly used forvery loose material and in mountain passes where avalanches may be a hazard.
Figure 4.5: Sample Shelter for Roads Endangered by Mountainside Fall or Collapse

Inpact-absortion material
Deposited material

Shelter

Road
Source: © World Bank. Permission required for reuse

4.4.2 STRUCTURAL MEASURES FOR VALLEY-SIDE COLLAPSE OR RIVER EROSION
A valley-side collapse or river erosion can cause a collapse of the road foundation, with the recovery
time for full restoration of functionality often taking many days or even months to recover. Slopestabilization measures for a collapse are usually the same as those for a mountainside fall or collapse.
In many cases, the entry or infiltration of stormwater or snow-melting water into the valley-side
slope of the road induces the road foundation collapse. Therefore, a designer should design a proper
drainage system based on hydrological calculations using a formula or curve for rainfall intensityduration-frequency (IDF).
Road riverside erosion also induces valley-side collapses and road foundation collapses. Countermeasures
for river erosion require not only protection from roadside erosion at the riverbank side but also theconsideration of the negative impact on the opposite side of the road. Flooding or erosion risks increase
because of flow direction change, flow rate increase owing to the narrowing of channels, or higher floodlevels from the roadside erosion protection works at the riverbank side—all of which can be unintended
consequences of riverside protection works. Riverbed degradation and aggradation may increase the riskof road riverside collapse, which requires measures to prevent these phenomena (Table 4.3).

PART IV: ENGINEERING AND DESIGN | 79

Table 4.3: Typical Structural Measures for Road Riverside Erosion
PRIMARY CATEGORYSECONDARY CATEGORYTERTIARY CATEGORY
Revetment (Figure 4.6)
Revetment foot protection (apron)(Figure 4.7)

Riverbank protection

Spurs or groins (Figure 4.7)
Guide wall for river flow (Figure 4.7)
Riverbed girdle (Figure 4.8)

Catchment-based
sediment management
facilities

Measures for riverbed
degradation, which
induces road riverside
erosion (groundsill)

Measures for riverbed
aggradation, which
induces road riverside
erosionPROCEDURE FOR LAYOUT OF
CONCEPT DESIGN
Determine the protection
range for minor damaged
portions. The structure typeis determined by considering
the estimated flow rate.
Lay out for protection fromscoring and riverbed degradation, which may induce
roadside river erosion.

Falling works (Figure 4.8)

Lay out for protection from scoring and riverbed degradation,
which may induce roadside rivererosion, or lay out the portion
where the river current collides
with the road valley-side slope
at the river bend.

Slope stabilization works of upstream
water in a landscape ecosystem orreforestation (vegetation, foundation
works for vegetation) (Figure 4.8)

Lay out the slope stabilization works in the landscapeecosystem, where riverbed
degradation may induce roadriverside erosion.

When designing structural solutions for valleys or to address river erosion, there is often the need
to use large volumes of river shingle and boulders, fallen rocks, slope wastes, and landslide debris
in pavement layers, embankment construction, and protection works instead of simply dumping the
excavated material on the valley side. Such approaches both prevent damage to the valley side androad embankment and minimize the change in the normal flow of the river, which can adversely affectthe riverbanks.
River revetments are the most common riverbank protection measures against riverside road erosion(Figure 4.6).15 Although Figure 4.6 illustrates the use of gabion baskets to hold the rocks in place, inmany situations a rock revetment without the gabion baskets may be practical—especially where river
flow rates are not sufficient to dislodge the rocks. Check dams in gullies to dissipate the energy ofwater, as well as scour checks in ditches in areas of steep grade, are often companion measures tothose riverbank protection measures.
Alternative solutions that may be used instead of, or with, revetments include installation of• Reno mattresses, consisting of small rocks bound in a wire mattress, with a thickness of about 200
millimeters, more commonly used as aprons at culvert outlets or in table or side drains;• Rock gabion walls (small rocks placed in wire gabion baskets, generally measuring 1 meter x 1
meter x 2 meters) as a form of retaining wall at the riverbank; and• Gabion aprons, which are flexible (can be inclined downward toward the river center) and serve asfooting for the revetment without destroying or making a scouring hole underneath it.
A revetment is a facing of stone, concrete, fascines, or other material to sustain an embankment.

15 

80 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 4.6: Example of Riverbank Protection for Road Riverside Erosion (Revetment)
Road

Highest flood level
Revetment or
Reno mattressExitingGabion apron

Maximum scour

Geotextile
Launched position
Source: GESU-DOR 2007. ©Department of Roads (DOR), Ministry of Physical Planning and Works, Government of Nepal. Adapted, with permission, from
DOR; further permission required for reuse.

If an active flow is attacking a riverbank portion, a river flow guide wall and spurs or groins may beinstalled to guide or absorb the energy from the water flow (Figure 4.7). Most examples use the gabion
because it is a low-cost engineering measure for areas where stone materials are easily available,
and its workability and construction efficiency are good.16 However, gabions are less durable and not
ideally suitable for water-flow protection because of the scouring of their structural bottom. Gabion
foundations for riverbanks should consolidate the foundation and their apron using methods such as
soil cementing.
Figure 4.7: Examples of Riverbank Protection for Road Riverside Erosion

River

Narrow

River

Guide wall

Roadside
Guide wall

Wide

Spacing between spur or groinshould be smaller than 2.5
times of each spur/length (L)

River

River

River width

Spur or groin
Roadside

Roadside
L
Soil cement

GabionSpur or groin length
Concrete

Bank protection
Source: Adapted from GESU-DOR 2007. ©Department of Roads (DOR), Ministry of Physical Planning and Works,
Government of Nepal. Adapted, with permission, from DOR; further permission required for reuse.
A gabion is (a) a hollow cylinder of wickerwork or strap iron, like a basket, that is filled with stones or earth and used in building fieldworks as revetments; or (b) a gabionlike contrivance filled with stones, to assist in forming an earth retaining wall, dike, or similar structure.

16 PART IV: ENGINEERING AND DESIGN | 81

Catchment-based sediment management facilities are also adequate to mitigate riverside road erosion
in mild erosion situations. Landscape ecosystem management not only affects the road section itself
but also mitigates river erosion risk for other nearby properties through the slowing of water flows.
Catchment-based sediment management is subdivided into measures for riverbed degradation or
aggradation. The riverbed degradation measures include groundsill works, which are divided intoriverbed girdles and falling works (Figure 4.8). A riverbed girdle is a structure whose crown (the highest
surface of the structure) is at the same level as the riverbed; it is the least expensive way to protect
the riverbed. In contrast, falling works have the crown higher than the riverbed to reduce flow speed.
The measures for riverbed aggradation aim to mitigate flow-type geohazards such as debris flows andflooding by maintaining the flow capacity of the waterway. Bioengineering in the landscape ecosystemcomprises vegetation and foundation works, which decrease rainfall runoffs. These decrease flow-type
geohazard or erosion volumes (sediment yields) and riverbed aggradation.
Figure 4.8: Catchment-Based Sediment Management Facilities to Mitigate Road Riverside Erosion andFlow-Type Geohazards
Debris flow

Impermeable check dam

Foundation works for vegetation

Vegetation

Permeable
check dam
Groin

Groundsill
works

Driftwood

Riverbed
girdleBridgeFalling works

Road

Road

82 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Road

4.4.3 STRUCTURAL MEASURES FOR SLIDE-TYPE GEOHAZARDS
The countermeasures for slide-type geohazards are subdivided into three main types of risk mitigation(Table 4.4):• Avoidance of the area
• Reduction of the slide’s driving force• Increase of the resisting force against the slide.
The slide’s driving force can be reduced by removing the head top portion of the slide-prone terrain(earthworks). Strengthening of the resisting force against slides can be done using counterweight fills(earthworks), along with ensuring that water drainage or infiltration prevention is in place to increaseinternal friction strength.
Table 4.4: Typical Structural Measures for Slide-Type Geohazards
TERTIARY CATEGORYPROCEDURE OF CONCEPT DESIGN LAYOUTPRIMARY CATEGORYSECONDARY CATEGORY

Sliding area avoidanceRoad alignment selection or realignment toavoid endangerment by slides

Reduction of slide’s
driving force

Earthworks

Removal of rock or soil
Planning the layout of the earthworks inof slide head to reduce
the available land use is a priority.
weightEarthworks

Counterweight fills on
sliding footLay out the alignment if land acquisition
is realistic.

Planning the layout of the earthworks inthe available land use is a priority.

Ground surface drainage (Figure 4.9)

Water drainage orinfiltration prevention
to increase internal
friction strength
Strengthening of resisting force against
slides

Surface-groundwatercollecting conduit
with ground surface
drainage (French drain)(Figure 4.10 and Photo
4.2)

Subsurface drainage(drainage drilling) (Figure 4.11 and Photo 4.3)

Reduce the water pressure affecting thesliding surface to increase the resident
force of the slide. The drilling layout
covers all sliding mass horizontally(generally 5–10 degrees upward) withthe length of drilling at generally 20–50
meters.

Vegetation or bioengineering (Figure 4.9)

Reducing the infiltration of rainfall is
supplementary work.

Ground anchors (Figure 4.12)

Ground anchors and piles are planned
additionally if the other works cannot
meet the slope stability requirement
sufficiently.

Piles
Installment of external
resisting force

Lay out to drain the surface water and/or surface groundwater so as not to infiltrate deeper ground or increase waterpressure on the sliding surface.

Retaining structures
such as crib walls orreinforced earth
Installation of geosynthetic protection orslope mesh

PART IV: ENGINEERING AND DESIGN | 83

Ground surface drainage is illustrated in Figure 4.9. The left-side figure (panel a) shows ground surface
drainage to prevent surface water inflow from the outside to the inside of the sliding area. The rightside figure (panel b) shows how to drain surface water from inside of the sliding area to the outside.
The practicality of subsurface drainage needs to be examined by a skilled specialist because there is arisk that further land movement could result in a blockage of the drains, requiring further drilling.
Figure 4.9: Ground Surface Drainage for Slide-Type Geohazard
a. Surface drainage(outside of sliding mass)b. Surface drainage(inside of sliding mass)

Crown of slide
Moist soil within
sliding mass

Moving mass
Road

Moving mass
Road

Source: © World Bank. Permission required for reuse.

Although not affecting transport infrastructure, the Cairnmuir Landslide in New Zealand—50 meters
above the surface of Lake Dunstan and held back by the Clyde Dam—provides an excellent example ofboth of these surface drainage approaches. The Cairnmuir Landslide is a slow-moving (less than 300
millimeters per year) landslide that was considered a risk of giving way into the lake and overtopping
the Clyde Dam (a 100-meter-high concrete hydroelectric dam). To reduce the risk, the ground surfaceof the landslide was covered with a waterproof coating and surface drainage over an area of some
14,000 square meters. Within the landslide itself, some 18 kilometers of drainage tunnels were bored
to lower the water table and further stabilize the slope. The total cost of stabilizing the landslide
would be close to US$1 billion in today’s terms (in 2019).
A surface-groundwater collecting conduit with ground surface drainage also called a French drain
is standard practice to control the sensitive groundwater level rising in response to rainfall andactivation of sliding by intense rainfall (Figure 4.10).17 Surface groundwater is collected into a conduit
section made of crushed stone through a perforated drainage pipe, which is a perforated pipe covered
with permeable textile (geotextile). The bottom and sides of the conduit portion are enclosed by
an impervious sheet (geomembrane) to avoid the leakage into lower ground. The collected surface
groundwater is flowed down the drainage pipe for several tens of meters and flows out into open
space at the catch pit, where it is drained into an open ditch (Photo 4.2).
A French drain or weeping tile (also blind drain, rubble drain, rock drain, drain tile, perimeter drain, land drain, French ditch, subsurface drain, subsoil drain, or agriculturaldrain) is a trench filled with gravel or rock or containing a perforated pipe that redirects surface water and groundwater away from an area. A French drain can have
perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock.

17 

84 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 4.10: Surface-Groundwater Collecting Conduit with Ground Surface Drainage
Surface concrete

Groundwater table

Backfilling soil
Drain ditch

Stone base

Natural ground surface
Water
Permeable textile orgeotextile (green)

Water

Natural ground

Crushed stone
Impermeable sheet or
geomembrane (red)Drainage hole
Drain ditch
Catch pit

Stone
Backfilling soil
Crushed stone
Drainage hole
Natural groundBackfill soil

Drain ditch

Base concrete
Drainage hole
Source: © World Bank. Permission required for reuse.

Photo 4.2: Surface-Groundwater Collecting Conduit with Ground Surface Drainage at Catch Pit
The site is a section of the Sindhuli-Bardiabas
Road in Nepal, August 2014.
The image displays drained, collected surface
groundwater from a conduit drainage pipe.

Source: Mikihiro Mori / Japan International Cooperation Agency (JICA). ©JICA.
Reproduced, with permission, from JICA; further permission required for reuse.

PART IV: ENGINEERING AND DESIGN | 85

Subsurface drainage drilling is also a common practice to lower the groundwater surface more
drastically, decrease pore water pressure at the sliding surface, and increase the internal friction
strength at the sliding surface on the subsurface. The most common practice is horizontal drillingdrainage from roadside to mountainside with a 5- to 10-degree elevation angle (Figure 4.11). The
longest practical length is 100 meters in most situations. It is important that the drainage of collected
groundwater from the outlet of the pipe extends to the outside of the sliding mass or to an area notaffected by geohazards. The installation of the drainage requires specialized skills and equipment todetermine the correct spacing and length of each drilled hole, both to ensure its effectiveness andto avoid exacerbating the risk of a landslide. Once the hole is drilled, a perforated pipe (wrappedin geotextile fabric) is typically installed to collect water and transport it to the surface. As noted
earlier, in the Cairnmuir Landside in New Zealand, more than 18 kilometers of subsurface drainage wasinstalled. A further example is shown in Photo 4.3.
Figure 4.11: Subsurface Drainage Drilling

Moving mass
Groundwater table
GabionRoad
Drilling hole

Source: © World Bank. Permission required for reuse.

Photo 4.3: Drained Subsurface Water at a Sliding Road Mountainside Slope
This drilling operation, in El Salvador, was managed
by the JICA Technical Cooperation Project team,April 2013.

Source: Edenilson Quintanilla / Japan International Cooperation Agency (JICA). ©JICA.
Reproduced, with permission, from JICA; further permission requiredå for reuse.

86 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Use of ground anchors is another popular practice on road slopes to apply external resistance force
against slide-type geohazards. Such external resistance force works are called “restraining works,” andtheir implementation depends on the requirements defined after “control works” (earthworks anddrainage works) are completed.
A ground anchor (as shown in Figure 4.12) is a device designed to apply external resistance force to thesliding surface. It is divided into three parts: a fixed anchor (fixed using grouting to the stable ground),a free anchor (to transmit the tensile force), and an anchor head with a concrete plate (which takes thereaction at the surface part).
Figure 4.12: Ground Anchors as External Resisting Force for Slide-Type Geohazard
Crown of Slide
Free anchor
Anchor HeadConcrete plate
Road

Fixed anchor

Ground anchor
Source: © World Bank. Permission required for reuse.

For many years, geosynthetics have been applied to enhance the performance of structural measures.
Geosynthetics have been used to support geohazard measures as follows:• Reinforcement of embankment slope soils with reticulated geogrid• Prevention of soil draw-out for the sand and fine-grained soil from cut slopes and for drainage ofwater-permeable ground with nonpermeable, cloth-like geotextile• Prevention of infiltration of surface water and rainwater under the ground with nonpermeable,
cloth-formed geomembrane• Drainage of materials in the back of the vegetation foundation of cut slopes with thegeocomposite drain• Coverage of perforated pipe with geotextile.
Given the diverse range of geosynthetics available in the marketplace and their diverse range ofuses, installation requirements, and functionality, further details on these are not contained within
this manual.
4.4.4 STRUCTURAL MEASURES FOR FLOW-TYPE GEOHAZARDS
The planner or designer shall conduct the hydrological and hydraulic calculation using the intensityduration-frequency (IDF) of rainfall for the selection of countermeasure types and design for flow-type

PART IV: ENGINEERING AND DESIGN | 87

geohazards (debris flows, earth flows, and flash floods). Properties of the flow, such as the component
ratio of the flow (contents of stone, soil, and water) are also important to consider when designing thestructural measures to ensure that flow paths are not readily blocked, resulting in the overtopping ofdrainage structures and subsequent erosion of the road or diversion of floodwaters into adjacent land.
The countermeasures for flow-type geohazards are subdivided into three main types: adequate flow
structures for road-crossing waterways, retarding or protection structures, and landscape ecosystemconservation (Table 4.5).
Table 4.5: Typical Structural Measures for Flow-Type Geohazards
PRIMARY CATEGORYSECONDARY CATEGORYPROCEDURE OF CONCEPT DESIGN LAYOUT

Road bridge
Adequate flow
structure ofroad-crossing
waterways

Retarding structure
Protection structure
Landscapeecosystem
conservation

Road-crossing culvert

Lay out waterway structure with adequate
Ford river crossing: (a kind of bridge orcapacity against flow-type geohazards.
culvert that allows flood and soil or rockflows to cross, passing over the road surface(Figure 4.13)
Sand pockets
Stormwater storage, retarding basin
Debris flow check dam (Figure 4.14)
Flood control dam
Hillside works or reforestation to reduce
stormwater runoff (Figure 4.8)
Groundsill (Figure 4.8)

Regarding the protection structure forlandscape ecosystem conservation, it isconceptually designed so that, to reduce
the peak flow rate, land for temporary
water retardation upstream of the stream
or river crossing is available. This isnormally planned for regional flow-type
geohazard control (not only for a specificroad location).

Structures for waterway crossings should be designed using appropriate target return periods offloods, with appropriate consideration of the impact of soil, rocks, and other debris in the water. As a
low-cost measure for low-volume roads or roads that are not required to deliver all-weather access,ford river crossings are designed. A ford river crossing is a kind of bridge or culvert that allows flowtype geohazard elements (flooding and soil or rock flows) to cross and pass over a road surface. An
adequate flow structure for fords will not overflow into the neighboring carriageway outside of theford structure or waterway and will not be destroyed by the flow-type geohazard crossing over theford. Floods and soil or rock will flow transversally to the concrete road surface, and the road is closed
during periods of flooding.
A ford river-crossing structure (Photo 4.4 and Figure 4.13) is made of reinforced concrete to be robust
against the shock of colliding stones and to prevent erosion during periods of high flow. Protection
walls are placed on the upstream side of the ordinary road sections to prevent water with soil orstones from reaching the road pavement (outside of the ford structure). Depending on the volume ofwater in the river, ford crossing culvert pipes may be installed with sufficient capacity to handle theriver flow under normal weather conditions, with the alternative being a permanent flow of water ofless than 200 millimeters in depth18 across the ford at all times.

Above this level, crossing on foot, bicycle, or motorcycle becomes difficult, and water can enter the footwell of motor vehicles with low ground clearance.

18 

88 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKPhoto 4.4: Examples of Ford River-Crossing Solutions
a. Ford river crossing without culvert
This type of crossing is for a river whose waterlevel presents a problem only during flooding.
The ford river crossing is a type of bridge thatallows the flow of flooding water to cross overthe carriageway. It is used on rivers whoseriverbeds have a gentle gradient.

b. Ford river crossing with culvert
This type of ford river crossing is for a river
where water flows not just during flooding but
also during normal times.

c. Ford river crossing of continuous box type
Although not technically a ford, this type ofcrossing is applied to large-flow-rate rivers. It
is designed to allow flooding water over the
carriageway.

Source: ©Department of Roads (DOR), Ministry of Physical Infrastructure & Transport, Government of Nepal. Reproduced, with permission, from DOR; further permission
required for reuse.

Figure 4.13: Sample Ford River Crossing

Flow
Direction

Wall

Wall
Road
Surface

Guard
BlocksFord

Concrete
Apron

Structure

Culvert
Section Pipes
B

Road
Surface

Section A

Wall

PART IV: ENGINEERING AND DESIGN | 89

Figure 4.13: Sample Ford River Crossing (cont.)
SECTION A
Road
Pavement

FORD STRUCTURE(REINFORCED CONCRETE)WATER / DEBRISON TOP OF FORDGROUND

Culvert Pipes
SECTION B
FORD STRUCTURE(REINFORCED CONCRETE)DOWNSTREAM

UPSTREAM

Guard Blocks

GROUNDGROUND

Apron Structure

Culvert Pipes

Reinforced Concrete Bed

Source: © World Bank. Permission required for reuse.
Note: A “ford river crossing” refers to a kind of bridge that allows flow-type geohazard elements to pass over the road surface.

Check dams (Figure 4.14) provide protection to roads and other infrastructure against flow-type
geohazards. Concrete-type check dams with outlet conduits are typically used for flood control (Figure
4.14, panel b). Gabion-type check dams are a lower-cost option to the concrete solution and requirea foundation treatment such as soil cementing to protect the foundation against scouring (Figure
4.14, panel a). Permeable check dams, such as those made from gabions, have the advantage of not
disturbing the natural water and sediment flow; they protect only against large boulder stones ordriftwoods during a flooding event (Figure 4.14, panel c). Check dams are commonly used to control
erosion and sedimentation in roadside drains. They slow down water flow (reduce erosion of the drain)
and allow for sediments to fall out into the dam area behind each check wall. It is important that thesystem be kept well maintained or it loses its effectiveness.

90 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 4.14: Protection Structures against Flow-Type Geohazards
a. Gabion check dam

b. Concrete check dam

Debris flow

Debris flow
GabionGabionRoad

Roadc. Road-crossing culvert and permeable check dam
Planned debris flow heightRoad

Debris flow
Front apron
Permeable check dam

Box culvert
Source: © World Bank. Permission required for reuse.

PART IV: ENGINEERING AND DESIGN | 91

4.5

4.5 SELECTED RESOURCES
The following annotated list provides resources pertaining specifically to the topics covered in Part IV.
AASHTO (American Association of State Highway and Transportation Officials). 2007. Highway Drainage
Guidelines, 4th ed. Washington, DC: AASHTO. Provides hydrologic and hydraulic calculation procedureand road drainage design.
Cruden, D. M., and D. J. Varnes. 1996. “Landslide Types and Processes.” In Landslides: Investigation and
Mitigation, edited by A. Keith Turner and Robert L. Schuster, 20–47. Washington, DC: Transportation
Research Board. Provides investigation and mitigation procedures.
Deoja, B., M. Dhital, B. Thapa, and A. Wagner, eds. 1991. Mountain Risk Engineering Handbook.
Kathmandu, Nepal: International Centre for Integrated Mountain Development (ICIMOD). Provides thestability analysis of slope (chapter 13), construction materials (chapter 15), retaining walls (chapter 17),drainage (chapter 19), detailed survey and design (chapter 24), and construction (chapter 25).
FHWA (Federal Highway Administration). 2012. “Hydraulic Design of Highway Culverts, Third Edition.”
Publication No. FHWA-HIF-12-026, FHWA, U.S. Department of Transportation, Washington, DC. Provides
hydrologic and hydraulic calculation procedures and road-crossing culverts design.
GESU-DOR (Geo-Environment and Social Unit, Ministry of Physical Planning and Works, Governmentof Nepal). 2007. “Roadside Geotechnical Problems: A Practical Guide to Their Solution.” Guidelines
document, GESU-DOR, Kathmandu, Nepal. Appendix provides examples of different structural
measures.
Highland, Lynn M., and Peter Bobrowsky. 2008. “The Landslide Handbook: A Guide to Understanding
Landslides.” Circular 1325, U.S. Geological Survey, Reston, VA. Provides landslide mitigation concepts
and approaches in its Section III.
Howell, J. 1999. Roadside Bio-Engineering: Site Handbook. Kathmandu, Nepal: Department of Roads, His
Majesty’s Government of Nepal. Provides details on roadside vegetation works.
IGS (International Geosynthetics Society) website, http://www.geosyntheticssociety.org/, provides
instruction for the use of geosynthetics in geohazard risk management measures.
JLS (Japan Landslide Society). 2012. “Landslides in Japan (The Seventh Revision).” Periodic report, JLS,Tokyo. Provides investigation procedures and examples of structural measures.
Keller, Gordon, and James Sherar. 2003. “Low-Volume Roads Engineering: Best Management Practices
Field Guide.” Report prepared for the U.S. Agency for International Development, Washington, DC.
Provides many low-cost structural measure techniques.
Winter, M. G., F. Macgregor, and L. Shackman, eds. 2005. Scottish Road Network Landslides Study.
Edinburgh: Scottish Executive. Provides structural measure techniques for debris flow in section 8.4(“Mitigation Techniques”).
World Bank. 2012. “Field Guide on Soil Bioengineering for Slope Stabilization in Timor-Leste.” Working
Paper No. 73666, World Bank, Dili, Timor-Leste. Provides vegetation technique for slope protection.

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5O P E R AT I O N S A N D M A I N T E N A N C EPART V: OPERATIONS AND MAINTENANCE | 95

Operations& Maintenance

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5.1

5.1 OVERVIEW OF OPERATIONS AND MAINTENANCE MEASURES FOR GEOHAZARDSPart V provides procedures to enhance road geohazard risk management through preparedness orother nonstructural measures in the operations and maintenance stage.
Part V of the handbook• Defines and explains the activities of nonstructural measures and important practices to increase
positive effects; and• Explains the procedures and operational considerations regarding the nonstructural measures.
The reader is also advised to see the following reference documents pertaining to Part V:• Terms of Reference 5 (ToR 5), Development of Manual for Operation and Maintenance for Road
Geotechnical Assets (in Appendix A), is a standard terms of reference (ToR) to formulate manuals
in the maintenance of structural measures, early anomaly detection and emergency informationcollection, and emergency preparedness and response.
• Terms of Reference 6 (ToR 6), Development of Emergency Information System (in Appendix A)
is a standard ToR to develop a road emergency information system, including early warning or
precautional road closure.
• Road Geohazard Risk Management: Case Study of Japan (in Appendix C) shows examples ofnonstructural measures in Japan.
The achievements after using Part V are• To understand the purpose and procedures of nonstructural measures;• To understand the planning and operational consideration of nonstructural measures; and5.2• To understand the importance of good communication with key stakeholders and their
participation for effective nonstructural measures.

5.2 DEFINITION OF NONSTRUCTURAL MEASURESIn contrast to structural measures, nonstructural measures for road geohazards are any measures not
involving physical construction. They are less expensive than structural measures and include• Routine maintenance of previously constructed measures;• Monitoring of geohazards (potentially using automatic measuring devices, linked to automatedwarning systems); and• Road closures to prevent injury before (or during) a geohazard event.
Nonstructural measures include risk avoidance methods (such as advanced warning or closing roads)
to prevent vehicle damage and loss of human life even if a geohazard event occurs, and they seek toensure efficient maintenance of the structural measures for geohazard risk management.

5.3

5.3 ROAD DISASTER AWARENESS
5.3.1 CONTROL OF ROAD DISASTERS CAUSED BY HUMAN ACTIVITIESHuman activities often trigger road geohazard disasters. For example, garbage and accumulated
sediment (including the deliberate infilling of side drains for property access) in roadside drainage
makes the drainage less effective and could activate a road geohazard. Water use, such as irrigation
or deforestation, and banking of the potential sliding slope head or cutting the slope foot may cause
geohazard activities as well.
PART V: OPERATIONS AND MAINTENANCE | 97

Raising public awareness is a first step toward stopping harmful human activities that could induce
geohazards on roads. Laws and regulations that control land use are also necessary to prohibit
harmful human activities that may cause geohazards.
5.3.2 TRAFFIC SIGNS TO RAISE AWARENESS
The road management authority installs traffic signs and uses intelligent transport systems (ITS),
mobile phone warnings, social media, websites, or other channels to inform road users of endangeredroad locations, hazard-prone road subsections, and road subsections selected for the precautionary
road closure to protect road users from disasters and accidents.
5.3.3 AWARENESS RAISING AND TRAINING FOR ROAD STAKEHOLDER ENGAGEMENTEngagement of the primary road stakeholders (road users and residents near the road) requiresthat they receive information on any abnormality (as described below in section 5.5.3) as well as on
the control of road disasters caused by human activities (as noted above). Toward those ends, anawareness-raising campaign or training is preferably conducted.
Holding a campaign or training along with a road safety campaign or a community disaster evacuation
drill (if in an urban area or if the geohazard event would isolate a community) are practical steps. It isalso practical that any such awareness campaign, training, or drill involve the various and institutional
partnerships as described in section 5.6.

5.4

5.4 MAINTENANCE OF STRUCTURAL MEASURES
Appropriate maintenance of structural measures guarantees the measures’ proper effect. This handbook
includes the maintenance of structural measures among the nonstructural measures because such
maintenance is work conducted without the need for a specific design. Proper maintenance requires
preparation of an inspection schedule, maintenance procedures, materials, and machinery.
Maintenance includes the removal of sediments in debris flow protection dams or sand traps andthe preservation of slope vegetation. Maintenance costs and their availability are considered during
the planning stage. A feasibility assessment of the structural measures is commonly included in themaintenance costs.
The maintenance of structural-measure methods established in roads or adjacent to them is unified
with the maintenance of roads such as pavements and carried out by road management offices,branch offices, and commissioned private companies and workers. The road management authorities
develop the maintenance plans (such as yearly maintenance plans) of structural-measure methods(systems, schedules of patrol or checking, materials, and preparations of machine parts), and theymeasure the budget as a part of the maintenance plans of roads.
The maintenance and management of structural-measure methods are often not limited to theoperation of roads maintenance entities. Such methods (for example, removal of earth and debris
from a dam or a sedimentary sand place and maintenance of seeding and planting works in a basin)
are established in road crossings outside the road management sites or valley streams and rivers
to the side against flow-type disasters such as earth and debris flows, floods, and flash floods.
Therefore, the road management authorities adjust their plans and budgets with disaster management
authorities as well as with the organizations, local governments, communities, and other entities
that manage maintenance entities such as water utilization and conservation of mountains, river
improvement, erosion control, and irrigation.

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5.5

5.5 EARLY ANOMALY DETECTION AND EMERGENCY INFORMATION COLLECTION
5.5.1 VISUAL INSPECTION AND HAZARD MONITORING FOR EARLY ANOMALY DETECTION
The early detection of anomalies is important to prevent disasters and avoid damages for road users.
Both visual inspections and specific geohazard monitoring have their place in this effort.
The visual inspections are conducted using a range of tools and techniques and are carried out either
by vehicle or on foot. Based on their frequency, they are subdivided into the following:• Routine patrol: Visual observation conducted from vehicles daily, weekly, or at some other timeinterval. These are typically undertaken by staff with limited geohazard technical expertise but
who often have significant experience on the road network and are aware of how the network
performs and where high-risk locations are.
• Inspection patrol: Inspection of endangered road locations before and after the rainy season,
earthquakes, or other potentially hazardous events. It is performed with the aid of the hazard
inspection record format and past records including photos or sketches.
• Emergency patrol: Inspections during highly disaster-susceptible situations or in response tocomplaints of abnormalities from road users or other observers. The initial emergency patrol may
then generate the need for a specialist’s inspection.
• Automated geohazard monitoring: Monitoring of failing (falling, collapsing, or sliding) slope groundmovement and geohazard triggers such as heavy rainfall or the rise of groundwater tables (Table 5.1).
The monitoring is conducted at prioritized endangered road locations where structural measures
have not been implemented owing to budgetary or technical difficulties. The monitoring results areused as criteria for early warning and precautionary traffic closures to avoid damages to road users.
Table 5.1: Geohazard Monitoring Types and Equipment Used
GEOHAZARD PHENOMENAHARDWARE SUPPORTSurface movement

Monitoring CCTV camera
Rockfall detector
Extensometers
Crack gauge
Surface tilt meterGPS devices
LiDAR

Subsurface movement

Borehole inclinometers
Pipe strain gauge meters

Groundwater fluctuation

Groundwater meter
Piezometer

RainfallRain gauge
Automatic weather station

Note: CCTV = closed-circuit television. GPS = global positioning system. LiDAR = Light Detection and Ranging. For useful references about informationand communication technology (ICT) for geohazard risk management, see the Japan Bosai Platform’s Solution Map, https://bosai-jp.org/pc/
solutionmap. In addition, Highland and Brobowski (2008) provide landslide monitoring procedures (in appendix B) and sample safety information forlandslides or debris flows (in appendix D). JLS (2012) provides examples of slope movement measurement.

PART V: OPERATIONS AND MAINTENANCE | 99

Routine geohazard patrols can be combined with other functions such as road operation maintenance.
Trained patrol staff should be assigned to the geohazard-prone road subsections to look for geohazard
abnormalities. The ideal solution uses the monitoring equipment shown in Table 5.1; however, should
funding not permit, there are simple equivalent monitoring techniques that don’t require expensive
machinery and materials. Instead of a fully automated weather station, for example, a manual rain
gauge will also provide key inputs to the monitoring of geohazard risk profiles.
Light Detection and Ranging (LiDAR) systems are becoming ever more affordable and are part of manyroad authorities’ standard equipment sets—especially when combined with a drone to capture video
and photographic data. For high-risk sites, drones can be flown at regular intervals and the resultant
three-dimensional (3-D) land models compared within geographic information systems (GIS) to
identify the area and scale of land movement. Not only is this often more affordable than installing
sensors into a geohazard; it can also cover many more geohazards for the same cost.
5.5.2 EMERGENCY INFORMATION COLLECTION SYSTEM
Emergency information can be obtained from road users and stakeholders and through geohazard
monitoring. Road users and residents near the road can contact road management authorities toinform them of road abnormalities via telephone, the internet, or face-to-face communications.
Usually, a specific telephone number is assigned for such emergency communication, although it isseldom confined to a single type of emergency (such as geohazards). To guarantee the stakeholders’engagement, road disaster awareness efforts are also required (see Section 5.3).
When a road management authority receives the information from road users or residents, it checks
for abnormalities and takes emergency actions if necessary.
5.5.3 ROAD EMERGENCY INFORMATION SYSTEM INCLUDING EARLY WARNING OR PRECAUTIONARY ROAD
CLOSUREA road condition emergency information system is effective in providing road users with information
about geohazard damage occurrences, situations highly susceptible to geohazards, and traffic
conditions including road closures. Such early warnings and precautionary information give road users
the ability to minimize their losses in adverse conditions by enabling alternative route choices—and, in
extreme cases, can avoid loss of life.
Geohazards are often triggered by heavy rainfall. Therefore, a rainfall index often provides an early
warning and be used as criteria for a precautionary road closure. The information can be disseminated
via road information boards, road operations and maintenance staff, traffic police, mass media,
websites, mobile phone alerts, and roadside facilities such as fuel stations. Because the disseminationof information is highly important for geohazard risk reduction, collaboration must be strong between
the road management authority, the local or highway police, and the mass media.
The flows of early warning or precautionary road closure information due to geohazards (Figure 5.1)
reflect the multifaceted challenges involved in terms of both collecting and dispersing information.

100 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Figure 5.1: Flows of Early Warning or Precautionary Road Closure under Highly Susceptible Road
Damage Situation due to Geohazards
INFORMATION FROM OUTSIDE THE
ROAD MANAGEMENT AUTHORITY

INFORMATION FROM INSIDE THE ROAD
MANAGEMENT AUTHORITY

Police, meteorological agency, road
users, residents, communities, businessestablishments along the roads, mass
media, local government organizations, roadinformation centers, disaster information
centers

Routine, inspection, or abnormal patrol bystaff, contractor, or delegated personnel

Information

Order of patrol

Information

ADMINISTRATIVE STAFF OF ROAD MANAGEMENT AUTHORITY
Execution and cancellation of the early warning
OUTSIDE OF ROAD MANAGEMENT AUTHORITY
Communication by telephone or email with
police, road information center, disaster
information center
Communication with website and roadinformation board: road users, mass media,
and others

STAFF, CONTRACTOR, OR DELEGATEDPERSONNEL OF ROAD MANAGEMENTAUTHORITY
Emergency patrol, preparedness of
postdisaster activities, traffic control (placingof barricades for precautionary road closure
ordered, guide or control of transportation at
the site)

The geohazard warning system should be part of the overall road authorities’ early warning systemthat covers any situation that is highly susceptible to disasters and traffic accidents, such as dense
fog and strong wind. The early warning is just a warning without any physical measures, but the
precautionary road closure is the decisive ordering of a road closure. The decisions to issue warnings
and order road closures should be carefully determined based on the level of danger and adherenceto established procedures. The road management authority selects the road sections for early
warnings or precautionary road closure—the disaster-prone or accident-prone road sections during
abnormal weather or other conditions such as river floods or flood tides—and then uses establishedprocedures as follows:• Preparation of criteria for early warning or precautionary road closure. The road management
authority uses an index of hazard-trigger condition or geohazard activation (for example, theamount of rainfall or thawing, wind speed, increase in the speed of a slow-moving ground mass[measurable using strain gauges or automated survey equipment], volcanic activities, and so on)
to set the criteria for early warning or precautionary road closure for each of the selected roadsections.

PART V: OPERATIONS AND MAINTENANCE | 101• Execution of the early warning or precautionary road closure. When the early warning or the
precautionary road closure starts, the road management authority announces the possibility ofa geohazard damage event or dangerous conditions that could cause traffic accidents, as wellas the dangerous road sections, using road information sign boards or other types of notices.
During the ordering of precautionary road closure, the road management authority also places
barricades to stop traffic at the start and end points of each of the dangerous road sections. A
precautionary road closure has difficult operational aspects because it causes losses to road users
due to detours, time spent waiting for traffic opening, or trip cancellations. It is thus necessary tominimize the period of road closure. The first practical step should be an early warning that is notaccompanied by any road closures. The precautionary road closure needs to be supported by the
traffic police using all applicable laws.
• Cancellation of the early warning or the precautionary road closure. To cancel the early warning or
the precautionary road closure, the road management authority sends a patrol to the dangerous
road sections and confirms that no abnormalities remain in the aftermath of the abnormal climate
situation or other dangerous situations.

5.6

5.6 ROLES OF VOLUNTEERS, LOCAL COMMUNITIES, AND INSTITUTIONAL PARTNERSHIPSIN GEOHAZARD RISK MANAGEMENT
The partnership between the road sector, local stakeholders, and the private sector, including
residents, can enhance information sharing, help prevent road disasters, and improve road geohazard
risk management. The following actions can help to form good partnerships:• I nformation sharing (as described earlier in Sections 5.3 and 5.5) and integration of the disasteremergency information systems of the community or municipality with the road emergency
information system•M eetings of subnational governments, bus and taxi transport organizations, and the national roadadministration•V olunteer support programs for road disaster management (for example, road drainage
maintenance including garbage clearance, snow clearance, and maintenance of roadside trees androad slope vegetation)•C reation of incentives for volunteer support, such as the installation of roadside billboards topromote the supporting organizations or private companies.

5.7

5.7 ASSET MANAGEMENT AS A RESPONSE TO DISASTERS
As noted in Part II, Section 2.2, geohazard management is part of the overall asset management
practice within a road authority, with Figure 2.1 providing an example of an overall asset management
process. Although climate change is not the same as geohazard management, there are significant
overlaps between the two subjects, and it is worth reflecting on the specific actions proposed byHenning, Tighe, and Greenwood (2017), who reviewed the asset management process and proposed
specific additional activities that should be incorporated into each stage of the process to ensure
climate change was appropriately addressed. Their proposed approach includes a series of specificinitiatives that should be implemented to ensure that geohazard management is considered at eachstage of the asset management process (Table 5.2).

102 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

Table 5.2: Recommendations for Integrating Geohazard Management into Asset Management
PHASE

STEP IN AM PROCESS(REFER TO FIGURE 2.1)
Develop the AM policy

KEY ADDITIONAL ACTIONS•UNDERSTAND AND DEFINE REQUIREMENTS•
Define levels of service andperformance•

Forecast future demand•••
Understand the asset base

•
•
•
•

DEVELOP ASSET LIFE-CYCLE STRATEGIES

Ensure that network resilience measures (for example, restore all major roads within 12 hours of theend of a 1-in-100-year flood) are included into the level-of-service framework.
Revise design guides to take into account the changing frequency of climatic events, and ensure thatdesign standards are in place for geohazards.
Future demand forecast such as demographic changes and traffic-loading increases should be
integrated with geohazard impacts on the expected performance of infrastructure.
Providing for future growth in high-risk areas should be avoided (or at least fully understood aheadof growth being permitted).
Ensure that data on highway assets and their vulnerabilities or deficiencies are complete and upto-date.
All data collection processes should be geospatially referenced.
Road data and information should highlight interdependencies with other infrastructure.
Link lifelines and critical interactions between asset groups in the base data.

Assess asset condition•

Data collection should include measuring and recording of specific geohazard risk effects on road
networks.

Identify asset and business
risks

•
•

Ensure that geohazard risks are recognized as risks to the asset and delivery of services.
Risk and vulnerability assessments—already commonly used for geohazard management—should
be integrated with risk management from an organizational risk perspective.
The integration with AM risk promises significant efficiency gains.

•

LEVERAGE ASSET MANAGEMENT ENABLERS

Specifically address geohazard risk management within the AM policy statement, including whathorizon is to be planned for.
Have agreements in place on how the damage from major events will be funded and who will beentitled to financial support.

Life-cycle decision-making
techniques•

Operational strategies and
plans

•

Maintenance strategies and
plans

•

Capital works strategies and
plans

•

Updating of current design criteria is needed to address the full range of geohazards.

Financial and funding strategies•

Financial and funding strategies should investigate the impacts of different investment scenarios
on geohazard mitigation.
Financial and funding strategies should be in place for responding to potential disaster events.

Asset management team

•

•

•
•
•

•

•

•

Current analytical processes need to incorporate multiobjective capabilities and often needrefinement to include risk-based costs.
More emphasis on community involvement in decision making is required when bringing geohazard
management into the AM decision making, as often the solution is to reduce the reliability of access.
Operational plans should include specific allowances for identifying and addressing deficient
adaptation measures, such as making sure drainage structure are cleaned and without blockages.
Include retrofitting of infrastructure that is found to be significantly deficient.
Trial new designs that may offer better life-cycle solutions to common geohazards.
Operational procedures should include policies and processes identified for responding to disasters.
Maintenance strategies and plans should include specific allowance and focus on addressing items
that limit the impact from geohazards.
Ensure that there is an accurate record of materials removed from geohazards, as these data areneeded for the calibration of many geohazard simulation models.

Effective integration of geohazard management and AM must be driven from executive managementlevels within organizations.
Appoint someone as the geohazard management champion to drive all these actions through theorganization.

Asset management plans•

Ensure that the AM plan specifically addresses geohazards.

Information management
systems and tools••

Information management systems should include the recording of specific geohazard data forplanning purposes.
A data residence plan should be in place to respond to disaster planning needs.

AM service delivery andprocurement•

Legislation and procurement processes should allow for the response to shock events.

Quality management•

Quality management of geohazard measures needs to ensure their sufficient functioning.

Continuous improvement•

Identify improvements necessary for geohazard management, and integrate these into the overall
improvement plan for the road authority.

Source: Base table from Henning, Tighe, and Greenwood 2017.
Note: Table adapts the asset management (AM) process from NAMS 2011 (shown in Part II, Figure 2.1, of this handbook) to focus on geohazard management.

PART V: OPERATIONS AND MAINTENANCE | 103

Experience has shown that it is extremely difficult to develop good emergency response policies
during an emergency. It is, therefore, necessary to have policies in place before the risk event,addressing issues such as the following:• Priority of roads to be reopened-	Prioritization includes the concept of “lifeline” routes that recognize that traffic volume alone
does not represent the importance of a road. Low- to medium-trafficked roads may lead to key
nonroad infrastructure such as water treatment plants, hospitals, or civil defense sites—andshould be appropriately prioritized for maintenance and restoration.
• Pre-event maintenance- If the geohazard is caused by a climatic event such as predicted heavy rainfall, predeterminedsites should be checked before the rainfall event to ensure that the drainage infrastructure willfunction as designed during the event.
• Communication- Who is going to communicate what, and to whom?
- Who has what authority to talk to the media?
• Emergency repairs that can be undertaken without design- The road often contains many other services, some of which may be private utilities. There is aneed to ensure that policies don’t result in overinvestment in temporary repairs.
• Mix of public and private sector response to a geohazard event- The private sector may be equally as capable as public works of responding in emergencies.
- Ensure that contracts are in place that cover all roads if using the private sector.
-C ontracts can require the private sector to supply equipment and labor that will be directed aspart of a public works response.
Although the natural process is toward the elimination of any significant geohazard risks, a review ofapproaches applied to climate change risks shows that the need for investment in physical works canoften be offset through non-asset solutions. For example, parts of the northern motorway in Auckland,
New Zealand, are submerged during king tides and storm surges (Photo 5.1). Although an investment ofmany hundreds of millions of dollars would raise the road, currently an approach of communication,
operational lane closures, and maintenance to remove debris enables the network to be operated
without such investment.

104 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOKPhoto 5.1: Management of Auckland Motorway Flooding
Location: Auckland northern motorway, New
Zealand
Traffic volume: circa 150,000 vehicles per day
Issue: Combination of king tides and storm
surges result in southbound traffic lanes(including dedicated bus lane) going underwater
for a period of one to two hours at high tide.
Response: Processes in place to monitor
predicted tide levels. Advance warning in media
and signage. Traffic management plan enacted.
Maintenance crew ready to sweep road as water
recedes.
Result: Most drivers alter their travel time to
avoid peak tides and are generally unimpacted.
A potential major investment in raising the roadis mitigated through non-asset solutions, with
only a minimal impact on traffic.

5.8

Source: Top image source www.stuff.co.nz, Bottom image source www.
greaterauckland.org.nz ©Reproduced, with permission, from Greater
Auckland; further permission required for reuse.

5.8 SELECTED RESOURCES
The following annotated list provides additional resources pertaining specifically to the topics coveredin Part V.
Deoja, B., M. Dhital, B. Thapa, and A. Wagner, eds. 1991. Mountain Risk Engineering Handbook.
Kathmandu, Nepal: International Centre for Integrated Mountain Development (ICIMOD). Discusses themaintenance procedures (chapter 26) and detailed guidance for nonstructural measures for geohazard
risk management
Highland, Lynn M., and Peter Bobrowsky. 2008. “The Landslide Handbook: A Guide to Understanding
Landslides.” Circular 1325, U.S. Geological Survey, Reston, VA. Provides landslide monitoring procedures(appendix B) and sample safety information for landslide and debris flows (appendix D).
JLS (Japan Landslide Society). 2012. “Landslide in Japan (The Seventh Revision).” Periodic report, JLS,Tokyo. Provides examples of slope movement measurement.

PART V: OPERATIONS AND MAINTENANCE | 105

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6
CO N T I N G E N C Y P R O G R A M M I N GPART VI: CONTINGENCY PROGRAMMING | 107

Contingency
Programming

108 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK

6.1

6.1 INTRODUCTION
Contingency programming consists of three distinct phases:• Emergency preparedness: what happens before a geohazard event• Emergency response: what happens during and in the immediate aftermath of an event• Recovery: what happens following the emergency to restore full functionality to the road network.
The achievements after using Part VI are• To understand forms of emergency preparedness—an overlooked aspect of geohazard risk
management;• To understand the items and procedures needed for emergency inspection or postdisaster needs
assessment;• To understand procedures of emergency traffic regulation and public notice; and• To understand contingency programming activities by type of recovery.
Reference documents for Part VI of the handbook include the following:• Terms of Reference (ToR 7), Development of Manual for Postdisaster Response and Recovery (inAppendix A) is a standard terms of reference (ToR) to formulate manuals in emergency inspection
or postdisaster needs assessment, emergency traffic regulation, and recovery.
• Road Geohazard Risk Management: Case Study of Japan (in Appendix C) discusses the practices of
postdisaster response and recovery in Japan.

6.2

6.2 EMERGENCY PREPAREDNESS
A key outcome from all the prior phases of geohazard risk management described in this handbook
is that of understanding the nature of existing risks across the network. From this information, it
is necessary to develop an emergency response plan covering what actions would be taken, andby whom, if various risks were to occur. Two key activities underpin the successful completion of
emergency preparedness:• Having in place an emergency preparedness and response plan; and• Undertaking preparedness training to ensure that the plan can be deployed.
6.2.1 DEVELOPMENT OF AN EMERGENCY PREPAREDNESS AND RESPONSE PLAN
A well-designed, well-executed emergency preparedness and response plan is a key element of roadgeohazard risk management. The following items are essential to the planning process:• Definition of organizational roles, responsibilities, and responsible authorities• Identification of required materials and equipment, and where they should be located on the
network, to enable an effective and efficient response• Establishment of an emergency control center and emergency response team
• Determination of criteria for prioritizing response measures• Development of response procedures based on (a) classification of emergency levels; (b) advanceagreements or contracts for information communication; and (c) emergency activities (especiallyemergency recovery works for damaged roads) with organizations inside and outside of roadmanagement authorities, including communities and private companies

PART VI: CONTINGENCY PROGRAMMING | 109

• Development of a communication protocol, including the establishment of strong internal andexternal lines of communication (including with local communities) and coordination mechanisms
with other government agencies and private organizations• Execution of emergency response drills and training.
In the case of highly disaster-susceptible situations, the general emergency response procedure
typically proceeds as follows:• Collection of information on weather, road, and traffic conditions• Confirmation and recording of information to a road management log and preparation of asummary report to executives of road management authorities• Call-up of staff for emergency response (after securing the safety of road users and staff, because
the protection of human life is always the priority)• Arrangement of materials (such as temporary barricades, roadblocks around dangerous portions,and sandbags for immediate remedial earthworks)• Issuance of early warning of a disaster-susceptible situation, or the initiation of traffic control
measures, including precautionary road closure• Initiation of emergency disaster protection measures, such as sandbag placement to protect
against temporary soil collapse• Initiation of general postdisaster response and recovery (recovery from geohazard damage), as
described further below.
An often-overlooked aspect of preparation concerns disposal of materials from slips. Geohazards may
well involve a significant volume of material to be disposed of when a major risk event occurs. Prior
agreement on where the disposal of any removed materials will be placed can make the recovery
process more efficient and also avoid creating secondary geohazards through the placement of
excavated materials in inappropriate locations. All necessary consents should be in place permanently
for such disposal sites.
6.2.2 PREPAREDNESS TRAINING
While it is important to have in place all the necessary laws, regulations, processes, and people inplace to deal with geohazard risks when they materialize, it is also necessary to undertake necessary
training through drills to train the many parties involved and to identify gaps in the aforementioned
documents. There are often large gaps between disaster risk management policies and manuals
and the actual needs in emergency response such as equipment mobilization and government
preparedness. It may be that the local office staff have never been trained with (or have access to) theadvanced equipment that the central head office uses and that are required by the guidelines.
For each of the main geohazard risk types and locations within the domain of a road authority,
drills (and follow-up training) should be undertaken annually (or as frequently as deemed relevant
given issues such as changing policies, equipment, or key suppliers of services such as maintenancecontractors and consultants). These drills shall be designed to test all aspects of the geohazard
response and involve all the respective parties to make the drill as “real life” as possible—including
when key individuals cannot be contacted.

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6.2.3 FUNDING
The funding of postdisaster recovery is an essential element of the risk management process.
The approach taken to the funding of disaster recovery should be directly related to the expectedmagnitude of disaster events (Table 6.1). The option of cutting back on maintenance standards (thatis, stopping the maintenance of the rest of the road network to fix up geohazards in one area) is notrecommended, because the long-term consequences of doing so can significantly increase the overall
cost to the nation of the original hazard.
Table 6.1: Postdisaster Funding Approaches, by Disaster Magnitude
EXPECTED MAGNITUDE OF DISASTERAPPROACH

DESCRIPTION

Small relative to average annual
budget of road authority

Contingent projects

Certain capital improvement projects(such as adding capacity to the network) are identified as being contingent on risks not occurring. If the risks
do eventuate, then these projects are
postponed.

Moderate or limited to specificinfrastructure items

Insurance

The road authority takes out insurance
against the risk of geohazards occurring. This is often more practical for
specific road assets such as bridges ortunnels than for the network in totality. If the risks are high, then the cost of
insurance will also be high.

Moderate to large relative to theaverage annual budget of the roadauthority

Road authority budget item

A line item is contained within theroad authority’s budget to cover disaster events. The item may be suitablefor dealing with events of, say, up to a
1-in-10-year probability of occurrence.

Large relative to average annual
budget of the road authority

Central government disaster fundThis could be a centralized fund justfor roads or an overall fund for any assets affected by natural disasters. Thisapproach is one of “self-insurance”
and works on the premise that there
will be a regular flow of funds into andout of the disaster fund. It is suitable
for large events, such as those with aprobability of occurrence less frequent
than 1 in 10 years.

A special case of “contingent projects” is available through some international development partners
such as the World Bank, whereby a zero-dollar Contingency Emergency Response Component (CERC)
can be added to a standard loan arrangement. If a disaster does occur, uncommitted funds can bediverted from their original purpose and readily made available for disaster response.
With any funding approach, the question of “how much money will be required?” must be answered.
Even countries with a long history of data collection and ongoing exposure to geohazards may not
get this right all the time. For instance, in New Zealand the 2011 Christchurch earthquake resulted
in damage that exceeded the central government’s National Disaster Fund. To determine the likely
funding needs, an analysis of the range of magnitude and consequence of different geohazard
scenarios will be required.

PART VI: CONTINGENCY PROGRAMMING | 111

6.3

6.3 EMERGENCY RESPONSE
Box 6.1 Overview: Transport Sector Recovery and Reconstruction
In the immediate aftermath of a disaster, during the emergency relief and response phase,the highest priority is to carry out life-saving emergency services, including providing medical
attention, food, water, and shelter. To do this, vital transport and supply routes, including
roads, ports, and airports, need to be cleared of debris so that evacuations can take place andlife-sustaining services can be implemented.
Immediate recovery activities occur in parallel with emergency response activities. Transport
officials need to be well coordinated with relevant response agencies to maximize public
safety, to protect and preserve transport facilities as much as possible, and to reopen thetransport system as quickly as possible. Meanwhile, transport sector recovery planners
undertake the estimation of postdisaster recovery and reconstruction needs by assessing thevalue of destroyed assets and of transport production flows.
Source: World Bank 2018.

Immediately after a significant geohazard risk event, it may be necessary to trigger an emergency
response procedure. The highest priority during the initial emergency response phase is on life-saving
services (Box 6.1). The role of the road network in such life-saving services is critical, whether it be foraccess to sites by emergency responders or for the transport of the injured from sites to hospitals.
The focus of the emergency response phase is therefore about making rapid decisions in the field,
using limited information, to restore key critical routes (see Section 3.2 on road criticality) as quickly
as possible before moving on to the remainder of the network.
For large-scale geohazard events (those caused by major climatic events or earthquakes), it is often
the role of emergency response crews (those of either the road authority or contractors) to both clear
the road and to provide an initial assessment of the scale of works required at sites.
6.3.1 EMERGENCY INSPECTION OR POSTDISASTER NEEDS ASSESSMENT
The emergency inspection or postdisaster needs assessment of a road is conducted to determine thefollowing:• Damages to and abnormalities of the road• Phenomena that had caused the disturbance or road closure and secondary damages (forexample, surface depression of the road or debris fallen from a road mountainside slope)• Road access to logistics, supplies, medical care, and so on• Needs and priorities for the traffic function of the roads.
The postdisaster needs assessment is conducted in connection with the emergency inspection during
abnormal weather conditions. In the emergency inspection, necessary urgent measures are performed
such as the placement of barricades, roadblocks, or sandbags to catch collapses, and so on.
Postdisaster activities are unified with nonstructural measures for geohazard risk management as follows:• Observation patrol and hazard monitoring for early anomaly detection• Emergency information collecting system for disasters and anomalies

112 | ROAD GEOHAZARD RISK MANAGEMENT HANDBOOK• Emergency response for highly disastrous situations• Emergency information system for road conditions including early warnings or precautionary roadclosure.
In most cases, the emergency inspection is conducted by the same staff that performs the routine
maintenance of roads. It is important that good communication exist with local public and privateorganizations such as subnational governments, residents along the road, police, and rescue forces.
In the emergency inspection, necessary urgent measures are performed such as the placementof barricades, roadblocks, or sandbags to catch collapses, and the covering of the ground withimpervious sheets to prevent water infiltration.
6.3.2 EMERGENCY TRAFFIC REGULATION AND PUBLIC NOTICE
If the emergency inspection determines that road traffic circulation is impossible or highly dangerous,
the road management authority sets a detour and starts the traffic regulation until road recovery
is completed. The emergency information is publicized to road users and residents through either
temporary or permanent information boards on roads. A permanent electronic information board islinked with “nonstructural measures.”
An information system for road conditions, including early warnings, is ideal. The information system
can be linked to various media such as television, radio, and car navigation sets, and it can help road
users make decisions related to their trips and transportation activities.
6.3.3 EMERGENCY WORKS
Emergency response consists of simple works aimed at preventing road traffic suspension. If roads
are closed at many locations in a large area owing to a massive disaster such as wide-scale flooding,earthquakes, or the like, then a coordinated and prioritized response is needed. Initial activities
include removal of debris, clearing of drains and waterway areas, safety inspections at bridges, safety
inspections of structures and slopes following active slip situations, and so on.
For the emergency recovery and elimination of road obstacles, it is important to begin the activity ofemergency recovery with preliminary nonstructural-measure activities (including visual inspection
to contribute to early abnormal discovery, observations such as precipitation and the groundmovement, abnormality, and an urgent information system of road traffic conditions). Prior plansand preparations to affect emergency recovery—such as preparations of materials and equipment,
contracts pertaining to private contractors that have local construction machinery and prioremergency recovery experience, and an emergency recovery preliminary budget—are all key elements
to have in place ahead of the emergency occurring. It becomes possible to speed up emergency
recovery by locating a road management district officer close to the center of the disaster response to
expedite decision making and shorten lines of communication.

PART VI: CONTINGENCY PROGRAMMING | 113

6.4

6.4 RECOVERYBox 6.2 Transport Recovery Plan
During the short-term recovery phase, transport sector recovery planners use the results ofthe postdisaster needs assessment to develop a recovery plan, begin to prioritize recovery
needs against limited resources, and mobilize the required financing to rebuild the transport
network and services in a way that better serves community and nationwide needs now and in
the future. Transport officials must work with affected communities to integrate their concerns
and needs into these plans. Consider that short-term recovery decisions have long-term
implications. For instance, decisions about materials and labor procurement affect the local
economy, while locations for debris removal sites can limit longer-term options.
During the medium- to long-term recovery phase, transport officials need to continuallyassess recovery progress against objectives via a monitoring and evaluation framework(established during immediate or short-term recovery) that can incorporate new information
and be adapted accordingly. Transport officials need to begin to think about future land use
planning and investments in preparedness that will make recovery faster and more effective
in future disaster events.
Source: World Bank 2018.

Reactive measures involve recovery of the road asset to reinstate traffic flow, along with the conceptof “build back better,” which is the concept of “recovery with improvements” such that the geohazard
risk is lower after the event than it was beforehand. Reactive measures are subdivided into emergency
recovery (covered earlier), repair, rehabilitation, and reconstruction—as expanded on further below.
Although the emergency response phase is, by definition, undertaken rapidly to restore basic
functionality, it is important that the subsequent phases be undertaken more holistically considering
the long-term costs and benefits of options (Box 6.2). It is quite possible that, under major events,
restoring the existing road is not the best solution and that rather than recovering the existing road,the solution may be to make substantial changes to the alignment to lessen the future exposure of the
network to risk.
For example, in New Zealand, the State Highway 3 through the Manawatu Gorge was subject to ongoingsmall landslides since it was first opened in the 1870s. Each of these on its own was cleared up andthe road reopened. However, following a major event in 2011, the road was closed for an extended
period (opening in August 2012 with parts still one-lane). The road was temporarily closed by further
slips in April 2015. In April 2017, a further large slip closed the road. While clearing that slip, a further
slip of 10,000 cubic meters of rock occurred. Rather than try and remediate the site, the New ZealandTransport Authority determined to close the route permanently and instead invest the funds in thecreation of a new, lower-risk route.19
6.4.1 MANAGEMENT OF THE RECOVERYFor routine geohazards, the rectification of damage will likely be managed and delivered throughstandard business operations. However, for large-scale disasters, a special management structure may
be put in place. In Australia, for instance, following the 2010 Queensland Floods that did widespread
damage to the road network and other critical infrastructure, the Queensland Reconstruction Authority
was formed to coordinate the rebuilding program beyond the initial response and to allocate theSee “Manawatū Tararua Highway,” Projects, New Zealand Transport Agency: https://www.nzta.govt.nz/projects/sh3-manawatu.

19 

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special relief fund that was created. The authority now also has a role to increase the resilience of
critical infrastructure. Furthermore, a separate Commission of Inquiry was established to investigate
all matters related to the floods and to ensure that appropriate lessons were identified and put inplace.
For large-scale events (especially those triggered by earthquakes), it is entirely possible that therecovery of the road network will be managed as part of a larger recovery effort. This larger effort willconsider not just the reinstatement of roads but also the utilities buried within the roads and, at thelargest scale, the very nature of land use served by the roads. An example of this occurred following
the 2011 Canterbury (Christchurch) earthquakes in New Zealand, wherein the Canterbury Earthquake
Recovery Authority (CERA) was formed to deliver the recovery. CERA had wide-ranging powers andcould suspend laws and regulations for the purpose of earthquake recovery. The department operated
for five years, from 2011 until April 2016. Under CERA, large areas of the city were deemed unsuitablefor further use as residential areas, road networks were reconfigured, and key social services wererelocated.
Within New Zealand, the 2016 Kaikoura earthquake caused massive damage to the main state highway
and adjacent rail line, severing both for a period of almost 12 months. To enable coordination of the
response, an alliance was put in place covering both the road and rail authorities, who in turned
worked with industry to restore access.20
6.4.2 REPAIR
Repair refers to simple works after minor disasters, such as the sealing of cracks on a road toprevent further deformation of the road foundation through water infiltration. It also relates to thereinstatement of minor assets that may have been damaged during the event, for which design andbudgetary issues do not apply.
Prior agreement should be in place on the extent or nature of works to be completed as “repairs”
versus those to be undertaken as rehabilitation or reconstruction.
6.4.3 REHABILITATION AND RECONSTRUCTION
Rehabilitation consists of construction works that are typically contracted out, divided into temporary
rehabilitation and full-scale rehabilitation. Temporary rehabilitation is conducted just to secure traffic
reactivation, including partial-width traffic recovery, temporary detour alternatives, and temporary
bridges. Such traffic reactivation is important because long-term suspension of traffic will greatly
affect the lives of adjacent residents (for example, commuting, attending school, going shopping, andreaching medical facilities). When a secondary disaster is also expected, temporary rehabilitation
should include the construction of countermeasures to prevent any secondary consequences.
Full-scale rehabilitation entails the execution of required disaster prevention measures based on
detailed survey and design. It is conducted for improvement of the roads, such as road widening.
Full-scale rehabilitation should prevent any secondary disasters. It includes remedial work on existing
countermeasures based on a detailed survey and the design of new countermeasures. Strengthening
existing countermeasures or constructing new countermeasures can be planned to minimize themaintenance cost of the road functionality.
If the road functionality is interrupted in a complex way such that long-term closure will occur toreinstate traffic flow, reconstruction rather than just rehabilitation should be conducted. For largescale reconstruction, geohazard risk management procedures for new roads can be applied.
See “Kaikōura Earthquake Response,” Projects, New Zealand Transport Agency: https://www.nzta.govt.nz/projects/kaikoura-earthquake-response/.

20 PART VI: CONTINGENCY PROGRAMMING | 115

For example, following the closure of the Manawatu Gorge in New Zealand to a significant landslide,
the New Zealand Transport Agency took the opportunity to investigate alternative routes andultimately determined to abandon the existing route in favor of a new route that was deemed a lower
geohazard risk. Although such as decision may cause a longer loss of traffic access in the short run, thelong-term improved reliability of the new route is considered a worthwhile trade-off.

6.5

6.5 RECOVERYThe following annotated list provides additional resources pertaining specifically to the topics coveredin Part VI.
FEMA (Federal Emergency Management Agency). 1993. “Emergency Management Guide for Business andIndustry: A Step-by-Step Approach to Emergency Planning, Response and Recovery for Companies of
All Sizes.” FEMA 141/October 1993, FEMA, Washington, DC. A recommended guidance document on thesubject of contingency programming.
World Bank. 2018. “Transport Sector Recovery: Opportunities to Build Resilience.” Disaster
Recovery Guidance Series, Global Facility for Disaster Reduction and Recovery (GFDRR), World
Bank, Washington, DC.

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7
REFERENCE AND
R E S O U RC E M AT E R I A L SPART VII: REFERENCE AND RESOURCE MATERIALS | 119

7.1

7.1 REFERENCES
AASHTO (American Association of State Highway and Transportation Officials). 2007. Highway Drainage Guidelines. 4th
ed. Washington, DC: AASHTO.
AECOM. 2016. “Review of Methods to Determine Criticality of Roading Networks.” Report prepared for the New ZealandTransport Agency by AECOM New Zealand Ltd., Tauranga, New Zealand.
Cruden, D. M., and D. J. Varnes. 1996. “Landslides Types and Processes.” In Landslides: Investigation and Mitigation:
Special Report 247, edited by Turner A. Keith and R. L. Schuster, 36–75. Washington, DC: Transportation Research Board.
Deoja, B., M. Dhital, B. Thapa, and A. Wagner, eds. 1991. Mountain Risk Engineering Handbook. Kathmandu, Nepal:
International Centre for Integrated Mountain Development (ICIMOD).
Espinet, X. 2018. “Prioritization of Road Interventions in Nampula and Zambezia, Mozambique under Changing Flood
Risk and Other Deep Uncertainties.” PowerPoint presentation, World Bank, Washington, DC.
Espinet, X., J. Rozenberg, K. S. Rao, and S. Ogita. 2018. “Piloting the Use of Network Analysis and Decision-Making
under Uncertainty in Transport Operations: Preparation and Appraisal of a Rural Roads Project in Mozambique under
Changing Flood Risk and Other Deep Uncertainties.” Policy Research Working Paper 8490, World Bank, Washington, DC.
FHWA (Federal Highway Administration). 2012. “Hydraulics Design of Highway Culverts, Third Edition.” Publication No.
FHWA-HIF-12-026, FHWA, U.S. Department of Transportation, Washington, DC.
Gasiorowski-Denis, Elizabeth. 2016. “ISO Tackles Early Warning System for Landslides.” News archive, July 29.
International Organization for Standardization (ISO), Geneva.
GESU-DOR (Geo-Environment and Social Unit, Department of Roads, Government of Nepal). 2007. “Roadside
Geotechnical Problems: A Practical Guide to Their Solution.” Manual, GESU-DOR, Ministry of Physical Planning andWorks, Government of Nepal, Kathmandu.
Henning, T., S. Tighe, and I. Greenwood. 2017. “Integrating Climate Change into Road Asset Management.” Technical
Report, Working Paper No. 114641, World Bank, Washington DC.
Highland, Lynn M., and Peter Bobrowsky. 2008. “The Landslide Handbook: A Guide to Understanding Landslides.”Circular 1325, U.S. Geological Survey, Reston, VA.
JICA (Japan International Cooperation Agency). 2009. “The Study on Disaster Risk Management for NarayangharhMugling Highway: Final Report.” 2 vols. JICA, Tokyo.
JLS (Japan Landslide Society). 2012. “Landslide in Japan (The Seventh Revision).” Periodic report of JLS, Tokyo.
NAMS (National Asset Management Support). 2004. Optimised Decision Making Guidelines: A Sustainable Approach toManaging Infrastructure. Thames, New Zealand: National Asset Management Steering Group.
———. 2011. International Infrastructure Management Manual (IIMM). 4th ed. Wellington, New Zealand: Institute of Public
Works Engineering Australasia (IPWEA).
QP (Quality Planning). 2018. “Plan Topics 2013: Natural Hazards.” Guidance note, QP website: http://www.
qualityplanning.org.nz/index.php/planning-tools/natural-hazards/risk-based-approach-to-planning-for-naturalhazards.
Solheim, A., R. Bhasin, F. V. D. Blasio, L. H. Blikra, S. Boyle, A. Braathen, J. Dehls, et al. 2005. “International Centre for
Geohazards (ICG): Assessment, Prevention, and Mitigation of Geohazards.” Norwegian Journal of Geology 85: 45–62.
World Bank. 2018. “Transport Sector Recovery: Opportunities to Build Resilience.” Disaster Recovery Guidance Series,
Global Facility for Disaster Reduction and Recovery (GFDRR), World Bank, Washington, DC.

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7.2

7.2 WEB RESOURCES
American Association of State Highway and Transportation Officials (AASHTO)
http://www.transportation.org/
Centre for Research on the Epidemiology of Disasters (CRED)
http://www.cred.be/Federal Highway Administration (FHWA), U.S. Department of Transportation
https://www.fhwa.dot.gov/
International Centre for Geohazards (ICG)
https://www.ngi.no/eng
International Centre for Integrated Mountain Development (ICIMOD)
http://www.icimod.org/
International Centre for Water Hazard and Risk Management (ICHARM)
http://www.icharm.pwri.go.jp/index.html
International Geosynthetics Society (IGS)
http://www.geosyntheticssociety.org/
International Organization of Motor Vehicle Manufacturers
http://www.oica.net/
International Sabo Network
http://www.sabo-int.org/
Japan Bosai Platform (JBP)
https://www.bosai-jp.org/en
Japan Landslide Society
https://japan.landslide-soc.org/?lang=en
Japan Road Association
http://www.road.or.jp/english/
Probabilistic Risk Assessment Platform (CAPRA)
http://www.ecapra.org/
OpenDRI: Open Data for Resilience Initiative
http://opendri.org/

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Open Data for Resilience Initiative Field Guide
https://www.gfdrr.org/sites/gfdrr/files/publication/opendri_fg_web_20140629b_0.pdf
ThinkHazard!
http://thinkhazard.org/
UNESCO: Disaster Risk Management
http://www.unesco.org/new/en/natural-sciences/special-themes/disaster-risk-reduction/geohazardrisk-reduction/
United Nations Office for Disaster Risk Reduction (UNISDR)
https://www.unisdr.org/
U.S. Geological Survey Geologic Hazards Science Center
https://geohazards.usgs.gov/
World Bank: Global Facility for Disaster Reduction and Recovery (GFDRR)
http://www.gfdrr.org
World Bank: Transport
http://www.worldbank.org/en/topic/transport
World Road Association (PIARC)
http://www.piarc.org/en/

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CONTACTThe Global Facility for Disaster Reduction and Recovery (GFDRR)
Email: gfdrr@worldbank.org
Website: https://www.gfdrr.org/
GFDRR is a global partnership that helps developing countries better understand and reduce their vulnerabilities to natural
hazards and adapt to climate change. Working with over 400 sub-national, national, regional, and international partners,
GFDRR provides grant financing, technical assistance, training, and knowledge sharing activities to mainstream disaster andclimate risk management in policies and strategies. Managed by the World Bank, GFDRR is supported by 37 countries and 11
international organizations.
World Bank Disaster Risk Management Hub, Tokyo
Phone: +81-(0)3–3597–1320
Email: drmhubtokyo@worldbank.org
Website: http://www.worldbank.org/drmhubtokyo
The World Bank Tokyo Disaster Risk Management (DRM) Hub supports developing countries to mainstream DRM in national
development planning and investment programs. As part of the Global Facility for Disaster Reduction and Recovery, the DRM
Hub provides technical assistance grants and connects Japanese and global DRM expertise and solutions with World Bank teams
and government officials. The DRM Hub was established in 2014 through the Japan-World Bank Program for Mainstreaming DRM
in Developing Countries – a partnership between Japan’s Ministry of Finance and the World Bank.