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Global climate change coupled with an increasing world population, provide a sufficient

rationale for the continued research of natural hazards. As the magnitude and frequency

of hazards increase, there are correspondingly more people placed in harms way. In

order to ensure adequate management practices, it is important to understand both the

physical and perceived risks that are associated with these hazards. I have conducted a

review of geomorphology literature to evaluate the role geomorphologists have in the

management of natural hazards. It is obvious that geomorphology contributes useful

research to the physical processes that cause natural hazards. Attributes such as

magnitude, frequency, and spatial scale of hazards are important elements in their

prediction. Some of the most useful geomorphologic contributions include a

multidisciplinary approach, the establishment of physical risk, prediction methods, and an

international area of focus on developing countries. Through such contributions, it is

hopeful that the urgency of research for both the physical and social aspects of natural

hazards will be fulfilled for the benefit of future management.

Introduction

In a valedictory address given in 1989, H.T. Verstappen stresses the importance

of focusing scientific efforts on global climate change and the study of natural hazards.

Dr. Verstappen is a geomorphologist at the Institute for Aerial Survey and Earth Sciences

in Enschede, Netherlands. He states, “large numbers of people in all parts of the world

are in imminent danger of falling victim to natural disaster, and the pace of global change

is such that we probably have only a few decades to respond adequately and to survive”

(Verstappen, 1989, p.162). Although this is an extreme statement, in 1989 his urgency

for new focus on this research is warranted (Verstappen, 1989).

The shifting global climate contributes to an increase in the magnitude and

frequency of natural hazards. In the same respect, the growing world population allows

for an increase of human lives and development to be placed in harms way. With this

increase comes greater devastation from such hazards as earthquakes, landslides, and

flooding. In order to diminish financial and human loss, it is important to understand

both the physical and perceived risks that are associated with natural hazards.

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I plan to conduct my thesis work on the risk perception of natural hazards in the

Bay Area of San Francisco. This study will be conducted by surveying homeowners in

the Bay Area on their awareness of hazard risks. It will include mapping the predicted

physical risk for the surveyed areas. By linking geomorphology to this study I hope to

gain a better understanding of how geomorphic research can contribute to the study of

natural hazards management.

Risk perception, or risk management, is a tool used to assess and mitigate all risk

presented by natural hazards. It involves a blend of policy-based and science-based

issues. The policy-based issues involve mitigation measures and management strategies

that deal with and help prevent the human and financial loss from hazards. The science-

based issues concern the physical processes of hazards and how they are predicted.

Specifically they include such items as prediction, spatial distribution, and magnitude and

frequency of hazards, all of which can be found within the field of geomorphology. I

chose to conduct a literature review on the role geomorphology plays in natural hazards

research to see where it can contribute to the science issues present in risk management.

The Role of Geomorphologists

“Between 1990 and 1999, 2808 disasters were recorded worldwide. Eighty-four

percent of them were related to geomorphology” (Alcántara-Ayala, 2002 p. 117). Figure

1 indicates that the large majority of hazards present today are geomorphologically

related. According to Alcántara-Ayala, geomorphological disasters include slides,

floods, earthquakes, volcanoes, windstorms, droughts, and wild fires (Alcántara-Ayala,

2002 p. 117). The science-based issues involved in risk analysis relate to such physical

processes. The remaining natural disasters mentioned include extreme temperatures and

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epidemics. This figure demonstrates the obvious role that geomorphologists play in

studying physical processes associated with natural hazards.

Figure 1. X-axis: year, Y-axis: number of occurrences. Alcántara-Ayala, 2002, p.116

Although studies of the physical system were incorporated into natural hazards

research during the fields’ inception, eventually the focus shifted to the social sciences.

Gares feels that at its current state, the field of natural hazards has a social science bias.

It is now the role of geomorphologists to provide in depth studies on the physical

processes of natural hazards, and incorporate them back into the natural hazards field

(Gares, 1994).

Rosenfeld states that the global damage from natural disasters “has increased

three-fold from the 1960’s through the 1980’s, leaving more than three million dead and

causing the displacement of more than 800 million persons during that period”

(Rosenfeld, 1994, p. 27). Due to this recent increase in human and economic loss from

natural disasters, the international science community has taken action to predict and

mitigate future disasters. This effort includes incorporating sciences such as

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geomorphology into management and mitigation tasks. Geomorphologists are

researchers capable of understanding the extreme weather hazards that result from

continued global climate change. They are familiar with magnitude and frequency

concepts, which are critical when establishing a threshold of extreme events (Rosenfeld,

1994).

Disaster mitigation studies are inherently multidisciplinary, and geomorphologists

can contribute greatly to most areas of this research. Such studies include past changes of

landforms and processes, current geomorphic processes and their relationship to soils and

hydrology, anthropogenic changes made to the environment, and local land-use planning,

monitoring, and warning systems (Verstappen, 1989).

Although geomorphologists have done little work on risk studies thus far

(Slaymaker, 1996), they can contribute to the risk assessment process by “designing

hazard mitigation strategies in balance with the dynamics of processes within the region”

(Rosenfeld, 1994, p.35). They can also assess risk through their advanced knowledge of

geomorphology by developing prediction models, and through applied geomorphology

that helps manage for future events (Alcántara-Ayala, 2002).

Natural and Geomorphic Hazards

Defining Natural Hazards

Within geomorphology literature, natural hazards are defined in many ways. A

general definition given is that “the term natural hazard implies the occurrence of a

natural condition or phenomenon, which threatens or acts hazardously in a defined space

and time” (Alcántara-Ayala, 2002, p. 108). Such phenomena have been taking place

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since the earth was first formed. It was not until the presence of humans that such

occurrences transformed into natural “disasters” or “hazards”.

Humans play an important role in defining natural hazards. Alcántara-Ayala

defines natural hazards in relation to a state of disequilibrium. He considers this

occurrence to be a sudden disequilibrium between natural forces and the forces of the

social system. “The severity of such disequilibrium depends on the relation between the

magnitude of the natural event and the tolerance of human settlements to such an event

(Albala-Bertrand, 1993)” (Alcántara-Ayala, 2002, p.112). Clague chooses to neglect

hazards that are explicitly due to anthropogenic causes, such as forest fires. Instead he

defines natural hazards as being either geologically or geomorphologically controlled,

and threatening to communities, roads, and major developments (Clague, 1982).

Although he does not include human induced hazards, he does note the importance of

impacts to the human environment.

Distinguishing Natural Hazards From Geomorphic Hazards

Gares argues that unlike natural hazards, geomorphic hazards do not have a direct

affect on human life and usually occur over long temporal scales. Although most authors

do not make the distinction, Gares attempts to differentiate geomorphic hazards from

natural hazards. He defines geomorphic hazards as occurring due to the “instability of

the surface features of the earth” (Gares, 1994, p. 5). According to Gares, hazards do not

become geomorphic until they actually change the landscape (Gares, 1994).

Gares uses the example that earthquakes are a natural hazard and slope failure is a

geomorphic hazard, even if an earthquake causes it. Other specific examples of

geomorphic hazards include coastal erosion, soil erosion, mass movements, and fluvial

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erosion. When compared to natural hazards, Gares feels that geomorphic hazards tend to

have lower magnitude, higher frequency, slower onset rates, more widespread areal

extent, more diffuse spatial dispersion, more regular temporal spacing, and occur over a

longer temporal scale. This may provide difficulty in studies that incorporate both

natural hazards and geomorphic hazards (Gares, 1994).

Although this is an interesting perspective, Gares is the only author to make such

a distinction. Alcántara-Ayala does not distinguish differences between natural hazards

and geomorphic hazards. Instead he terms such events as earthquakes, landslides,

volcanic activity, and flooding as both natural hazards and geophysical events. The true

distinction between the two comes from the presence of vulnerability. Natural disasters

will occur only when both natural vulnerability and human vulnerability are present in

the same space and time. If human vulnerability is not present then the process is simply

a geophysical event (Alcántara-Ayala, 2002). So although he does not choose to make a

definitive distinction between the two, he does define natural hazards as processes having

direct impacts on humans.

In 1996, Slaymaker was the first to classify geomorphic hazards into the three

sub-groups: endogenous (processes that occur “within” the Earth), exogenous (occurring

“outside” of the Earth), and those induced by climate and land-use change (Slaymaker,

1996). Eight years later, Alcántara-Ayala uses this same classification for geomorphic

hazards. He states that volcanism and neotechtonics are examples of endogenous

geomorphic hazards, while floods, karst collapse, snow avalanche, channel erosion,

sedimentation, mass movement, tsunamis, and coastal erosion are given as examples of

exogenous geomorphic hazards. Desertification, permafrost, degradation, soil erosion,

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salinization, and floods are given as examples of geomorphic hazards induced by climate

and land-use change (Alcántara-Ayala, 2002).

Other authors choose to ignore the human element and define geomorphic hazards

strictly in relation to prediction and probability. Panizza defines a geomorphological

hazard as “the probability that a certain phenomenon reflecting geomorphological

instability will occur in a certain territory in a given period of time” (Panizza, 1987, p.

225). An instable landform will occur through disequilibrium with the natural

environment, and only through a shift or change can this landform move toward an

equilibrium state (Panizza, 1987). According to Slaymaker, geomorphologists tend to

define a geomorphic hazard as “the probability of a change of a given magnitude

occurring within a specified time period in a given area” (Slaymaker, 1996, p.1).

Magnitude & Frequency of Geomorphic Hazards

Even though numerous definitions for what constitutes a “geomorphic hazard”

can be found, all authors seem to agree that the magnitude and frequency of the hazard is

an important distinction. Gares, Slaymaker, and Alcántara-Ayala feel that magnitude,

frequency, temporal scale, and spatial scale are all key geomorphic concepts correlated to

natural hazards (Gares, 1994; Slaymaker, 1996; Alcántara-Ayala, 2002). Magnitude

covers the characteristics of the hazard and frequency describes how often the event is

likely to occur (Alcántara-Ayala, 2002).

Table 1 is very useful in showing the impact of frequency and magnitude, and

how different geomorphological hazards are broken down. It shows the 3 classes of

geomorphic hazards mentioned earlier: exogenous, endogenous, and climate or land-use

induced, in relation to magnitude and frequency. A downfall of this table is that it does

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not show a distinction between site, local, regional, and national hazards. However, it

does show that there can be an important distinction made between high magnitude and

low magnitude hazards (Slaymaker, 1996). It is also interesting to note that many

hazards can be found in both categories.

Table 1. Categories of geomorphic hazards. Slaymaker, 1996, p.2

Specific physical attributes of hazards can prove useful in future management

practices. The magnitude and frequency of past geomorphic hazards can indicate trends

in geomorphological instability, and potentially help predict when and where hazards will

occur in the future (Panizza, 1987). Traditionally, geomorphologists have concentrated

their efforts on large (regional) scales. However, for proper implementation of mitigation

and risk management, a smaller (local) scale must be examined (Rosenfeld, 1994).

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Specific Contributions

The previous literature has established that geomorphology can indeed benefit the

field of natural hazards. Now it is important to focus on the specific contributions

geomorphology can make to natural hazards management including a multidisciplinary

approach, the establishment of geomorphological risk, prediction methods, and an

international area of focus.

Multidisciplinary Approach

The field of natural hazards “involves conflicts between physical and human

systems” and is an obvious subject of study for geographers (Gares, 1994, p. 1). It is

only through a multidisciplinary approach that hazards research can manage for the

future. “Amongst geoscientists, geomorphologists with a geography background might

be best equipped to undertake research related to the prevention of natural disasters given

the understanding not only of the natural processes, but also of their interactions with the

human system” (Alcántara-Ayala, 2002, p.108). D. Alexander, M. Panizza, and H.T.

Verstappen are all geomorphologists who incorporate their advanced understanding of

geomorphological processes with social issues for a more thorough understanding of

natural hazards (Alcántara-Ayala, 2002).

Prior to 1960, natural hazards were approached from an almost strictly physical

perspective. It was not until the 1960s and 1970s that social and economic characteristics

were implemented. Many of the geomorphology articles mentioned in this review

promote the inclusion of more social, political, and economic characteristics into

geomorphology research. This will allow for an easier collaboration with other fields of

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study. It will also cause management and the general public to show more interest in

geomorphic hazards (Gares, 1994).

Establishing Geomorphological Risk

By including both social and physical elements in hazards research,

geomorphological risk can be established. The field of geomorphology plays an

important role in establishing this risk. “The risk approach to geomorphic hazards

enables a fuller incorporation of both expert analysis and societal synthesis in the solution

of the natural hazards problem” (Slaymaker, 1996, p.6). The risk approach mentioned

here transcends past the simplicity of previous geomorphic hazard studies that mostly

focus on physical processes.

Throughout the 1990s, the studies have extended even further to include

perceptions of hazards, which is an important factor in developing risk management

approaches. Alcántara-Ayala stresses the importance for researchers to involve

themselves not only in the science of natural hazards, but also in the risk assessment and

management programs (Alcántara-Ayala, 2002). Those dealing with geomorphological

risk and especially those trying to mitigate this risk must also deal with the organizational

problems of a social, economic, and political nature, that contribute to this risk (Panizza,

1987).

A geomorphic hazard multiplied by the social and economic vulnerability of a

region produces the geomorphological risk present there (Panizza, 1987). It is the

probability that the social and economic structures of an area can withstand the

geomorphological instabilities present. It is important to note that geomorphological risk

is impossible to predict without knowing the social and economic make-up of a particular

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location. A fantastic example of this is that “erosion is a hazard that may not involve any

risk in a desert area, whereas in a densely populated or highly industrialized area, it could

represent a high risk” (Alcántara-Ayala, 2002, p.228).

It is important in hazards management to weigh options and focus research based

on the severity of risk. Slaymaker specifically defines how geomorphologists can

establish this risk. He mentions three main steps geomorphologists can take when

determining geomorphological risk. The first is the mapping of geomorphic hazard

domains, which can also be ranked according to degree of instability. The second step is

to assess the vulnerability present. This is where human and economic loss is evaluated.

The final step is to prioritize georesources, which would place the highest priority on

urban land since this is where human life is most consolidated (Slaymaker, 1996).

Methods for Prediction

Methods for predicting hazards are probably where geomorphologists can

contribute the greatest to management efforts. Although these methods are not

guaranteed to predict the next big disaster, they can help with making emergency

decisions, aide in mitigation measures, and reduce future risk in an area. Some basic

methods used to predict hazards include geographic information systems (GIS), remote

sensing, modeling, and statistical techniques.

The mapping of landforms coupled with land-use and infrastructure, emergency

services, risk management, public awareness, training, regulation, and social insurance is

now possible due to the advent of GIS. It allows for the mapping, modeling, and

decision-making tools to handle all of these elements. When this technology is paired

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with the Global Positioning System (GPS) and satellite remote sensing, geographic data

collection is greatly improved (Rosenfeld, 1994).

Geomorphological hazards prediction also benefits from the technology of remote

sensing. Such techniques can “delineate geomorphic zones with distinctive origins,

surficial materials, and erosional sensitivities” (Rosenfeld, 1994, p.33). Remote sensing

has a great influence upon monitoring events and therefore has increased in the frequency

of its use. Remote sensing techniques are most useful with large-scale hazards and can

provide useful hazard zoning maps and assist in structural mitigation (Rosenfeld, 1994).

Along with the methods mentioned above, there are an abundance of methods for

predicting individual hazards such as flooding and landslides. Flood prediction can be

accomplished by using measured properties from past small floods to predict future large

floods. Theoretical models based on assumed principles of flooding can be created.

Assumptions about the sediments, landforms, and erosional scars of past floods to predict

future occurrences can also be accomplished for flood prediction (Baker, 1994).

Landslide prediction can occur through evaluating spatial patterns of environmental

factors such as rainfall intensity (Zhou, 2002). Soil wetness modeling and topographic

attributes can also be used when predicting landslides (Gritzner, 2001).

International Area of Focus

Finally, geomorphology can contribute to the management efforts in developing

countries. This is a topic found throughout geomorphic hazards literature. Many reasons

are provided for this international focus on developing countries. First of all, developing

countries are generally located within close proximity to geomorphological hazard zones

such as severe flooding, or seismic and volcanic activity. Secondly, developing countries

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are usually in a state of poor economic, social, and political conditions, which provide

greater susceptibility to human and financial loss from hazards (Alcántara-Ayala, 2002).

Finally, much of the destruction from natural hazards comes from lack of mitigation in

hazard prone areas. In developing countries, it is usually not the lack of education or

knowledge of the hazard that prevents mitigation, but the “lack of resources or

unwillingness to divert limited national wealth to such causes” (Rosenfeld, 1994, p.27).

Panizza feels that vulnerability to hazards will be high in areas of low social organization,

with a lack of prediction and monitoring techniques, and an inefficient intervening

governing body (Panizza, 1987).

“As the severity of disasters increase, there is an exponential rise in the number of

casualties among the poorer nations” (Rosenfeld, 1994, p.31). Table 2 shows that the

global death toll from natural hazards is highest in developing countries (Alcántara-

Ayala, 2002). The table does show significant impacts from hazards in countries such as

Japan, USA, France, and Switzerland, but it is obvious that the impacts are much greater

in countries such as Bangladesh, India, China, Guatemala, Colombia, and Mexico

(Alcántara-Ayala, 2002).

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Table 2. Some of the major geomorphology related natural disasters of the world form

1990 to 1999. (Data source: EM-DAT and the *Office of US Foreign Disaster

Assistance). Alcántara-Ayala, 2002, p. 111.

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Conclusion

“It is clear that the conceptualization (of natural hazards) has changed from a

perspective of a merely physical or natural event, towards the integration of the human

system” (Alcántara-Ayala, 2002, p.118). I feel that geomorphological hazard research

should also follow in this trend. More recently, geomorphology literature is breaking into

“Applied Geomorphology” which transcends past the physical studies to include human

impacts, mitigation measures, and management implications.

By incorporating geomorphology into my own studies of risk perception I will

greatly enhance the science-based issues involved and have a better understanding of the

methods for predicting hazards. My assessment of the vulnerability present from both

physical and perceived risk will also be improved. Providing more appropriate scientific

methods for prediction and implementing international training programs for increased

education will reduce vulnerability to natural hazards in the future (Alcántara-Ayala,

2002).

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References

Alcántara-Ayala, I. 2002. Geomorphology, natural hazards, vulnerability and prevention

of natural disasters in developing countries. Geomorphology 47(2): 107-124.

Baker, V. 1994. Geomorphological understanding of floods. Geomorphology 10(1): 139-

156.

Clague, J.J. 1982. The role of geomorphology in the identification and evaluation of

natural hazards. pp. 17-43 in R.G. Craig and J.L. Craft (eds), Applied Geomorphology.

Winchester, Mass: Unwin-Hyman.

Gares, P.A, D.J. Sherman, and K.F. Nordstrom. 1994. Geomorphology and natural

hazards. Geomorphology 10: 1-18.

Gritzner, M., W.A. Marcus, R. Aspinall, and S.G. Custer. 2001. Geomorphology 37(1):

149-165.

Panizza, M. 1987. Geomorphological hazard assessment and the analysis of

geomorphological risk. In V. Gardiner (ed.), International Geomorphology 1986, pp.

225-229. Part I. New York: Wiley.

Rosenfeld, C. L. 1994. The geomorphological dimensions of natural disasters.

Geomorphology 10(2): 27-36.

Slaymaker, O. 1996. Introduction. In: Slaymaker, O. (Ed.), Geomorphic Hazards. Wiley,

Chichester, pp. 1-7.

Verstappen, H.T. 1989. Geomorphology, natural disasters and global change.

Symposium on Aerospace Survey and Natural Disasters. International Institute for Geo-

Information Science (ITC) Journal (3-4): 159-164.

Zhou, C.H., C.F. Lee, J. Li, and Z.W. Xu. 2002. On the spatial relationship between

landslides and causative factors on Lantau Island, Hong Kong. Geomorphology 43(3):

197-207.