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Natural Hazards & Disasters:Basic Concepts

(5th Edition 2004)

Neil Ericksen


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Table of ContentsPage

List of Tables ....................................................... ................. iiList of Figures ...................................................... ............... iii

Summary: Key Ideas about Natural Hazards .................... 1A Common Language ......................................................... 2 Natural Hazard Concepts .................................................... 2

Interactive........................................................................... 3Dynamic ................................................... .......................... 4Funct ional .......................................................................... 7Feedback. ........................................................................... 9Risk..................................................................................... 10

Are They 'Natural' Hazards? ............................................... 10Reducing Natural Hazards and Losses .............................. 10Altering Losses..................... .............................................. 11Altering Natural Events..................................................... 12Altering Human Uses ........................................................ 12Integrated Approach......................................... .................. 13

Flood Hazard Mitigation ............................................... ....... 13Why This Pattern? ............................................................. 17The Consequences............................................................. 17Resource Management Act 1991...................................... 17

Appendix 1: Glossary.......................................................... 19References Cited ................................................................ .. 20


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Summary of Key Ideas About Natural Hazards

Natural hazards are not the natural events

Natural hazards are not the actual disasters. Natural hazards indicate potential disasters.

People help create natural hazards and disasters bylocating (settling) in areas where extreme natural events

may or do occur.

Natural hazards consist of the interaction betweenpossible human use of an area and possible extreme

natural events

Natural disasters consist of the interaction between actualhuman use of an area and actual extreme natural events.

People often take action to reduce losses or the threat oflosses from extreme natural events.

The most popular actions (relief and rehabilitation andcontrolling the natural event) reduce some losses, but

increase disaster potential (the natural hazard) because

they encourage people to settle in hazardous areas.

Land use planning is not popular even though it doesreduce disaster potential (ihe natural hazard) by directing

people to settle hazardous areas more wisely.

Because natural hazards and disasters are humancreations, land use planning is the most effective way to

reduce both losses and hazards caused by extreme natural

events.

Preventing disasters requires aiming our efforts not somuch at controlling nature and relieving losses, but at the

natural hazards that people are responsible for creating.

Peoples' attitudes and behaviours towards natural events,natural hazards and disasters, and adjustments to them,

need to change for our environment to become less

hazardous.


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Interactive Concept

The interactive notion of a natural hazard can be illustrated by use of a Venn diagram (Figure 1). If it helpsyour thinking, substitute any type of event for the word 'natural' on the diagram, e.g., flood, earthquake, coastalerosion or severe wind.

If the hazard is the interaction between thepotentialnatural event and human use (actual or potential)of thearea in question, then any change of scale in either natural event or human use will alter the effect of the hazard.Thus, the hazard is both dynamic and functional.


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1aNATURAL HAZARDS

Are the possibility of:

Eg.

Avalanche

Tsunami

Flood

Drought

Earthquake

hurricane

Eg

Ski resort

Town farm

Building

crops

IN DIFFERENT PLACES AND OVER TIME

1bNATURAL DISASTERS

Are the ACTUAL occurrence of:

Eg.

Avalanche

Flood

Earthquake

Eg

Village

Farm

Buildings

etc

IN DIFFERENT PLACES AND OVER TIME

Fig 1: The distinction between Natural Hazard and Natural Disaster. The rectangle at the top (Fig 1a)represents all possibilities of resource development in a given area. The circle on the left represents thepotential or actual human use of the area. The right hand circle represents potential for extreme naturalevent. The intersection of the overlapping circles represents the Natural Hazards. The rectangle and circlesat the bottom (Fig 1b) define the actual disaster, it being the impact of an actual event on existing human

uses of an area.

Dynamic Concept


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The 'dynamic' nature of a hazard can be illustrated by adding further information to the Venn diagram, asillustrated in Figure 2. Imagine the natural event is afloodthat could affect a city and Its people (human use ofthe floodplain). The small circle on the left of the diagram represents the scale of urban development in the

past; the intermediate circle, current development; and the large circle suggests future development.

These circles (in Figure 2) are overlapped by others representing small, medium, and large flood events.The scale of hazard varies according to size of the circle on the left and right of the diagram: the humanuse and flood event, respectively.

Fig 2: The creation of flood hazard or disaster potential. In this model thehazard in the community varies with the size of flood event and the extent ofurban development on the flood plain. The model depicts increasingencroachment on to the flood plain, so that for any flood of a given size,future disasters will be larger than past disasters (Ericksen, 1986).

A specific example will be used to substantiate these ideas. The map in Figure 3 shows the change in built-uparea of the northern part of Invercargill in decades since 1953. Superimposed on the pattern of city growthis the areal spread of the flood that occurred in January 1984. If that flood event is accepted as a constant,then the growth in flood hazard (the potential for disaster) in Invercargill over the last 30 years was a direct

consequence of increased settlement in flood-prone areas Of the City. The consequence of this human creationof flood hazard was the disaster in 1984, which is illustrated in the photograph in Figure 4 (Ericksen, 1986).


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Fig. 3. The creation of flood hazard or disaster potential in northern Invercargill, 1953-1984. In this map,the flood event is that which occurred in January 1984. Two-thirds of the built-up area in the flooded areawas created after 1953. Over one-quarter of the built-up area was created in the last decade. Thehazard or disaster potential became a reality when $55 million in insured property was lost in 1984(Ericksen, 1986).

Fig. 4. An oblique aerial photograph of the flood disaster in northern Invercargill, 31 January - 2February 1984, showing flooded suburbs of Collingwood and Grasmere looking up North Rd over theWaihopai River bridge. Photo covers the left of centre of the map in Figure 3. looking north-north-westtowards an area flooded by Waikiwi Stream (top left corner). (Courtesy: Soufhland Calchment Board).


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Fig. 5. Types of flood losses: property losses, including direct primary and secondary losses; primary andsecondary social disruptions; and human casualties (Ericksen, 1986

Functional Concept

That natural hazards are functional1 is apparent from the fact that the scale and nature of the hazarddepends, in part, on the type and intensity of the humanuse of an area. If an area is in rough grazing thenthe hazard is low and the losses that result from a flood event quite small. If exactly the same flood eventwas foreseen as affecting dense housing in the area hen the hazard would be high and losses would be largeif the event occurred (See Figure 9 later in booklet). Similarly, trellised kiwi fruit will suffer more in anextreme wind than grass.

Hazards, and the disasters that result when extreme events occur, are not 'Acts of God' or 'freaks of nature'.They are human creations. They stem from human efforts to use the resources in an environment. What isa hazard to one group may, however, be a resource to another. For example, if an area is experiencing a

drought and there is a sudden deluge, the resulting runoff may fill long-depleted reservoirs. This wouldimprove city water-supplies and/or water-based recreational resources. The same rains may, however, causedisastrous flooding of parched farmlands and low-lying areas of urban settlements. A disaster results inlosses to property, social disruption and human casualties. Various forms of loss- direct and indirect- areshown in the chart in Figure 5. Newspapers highlight these losses.

TangiblePROPERTY

LOSSESe.g, buildings, contents,

roads, power poles,

vehicles

TangibleSOCIAL

DISRUPTIONeg, lost production, cut

social services like

Water, power, etc.

IntangibleHUMAN

CASUALITIESeg, loss of life,

Physical and mental

injuries

DirectPRIMARYLOSSESeg. Flooddamagedbuildings,vehicles,

bridges,raillines

DirectSECONDARY

LOSSESe.g., flood-causes,

fire damage toproperty

IndirectPRIMARYDISRUPTIONSe.g., lost businessdue to floodedpremises; cost ofevacuations

IndirectSECONDARYDISRUPTIONSe.g., lost familyincome due toflooded work-place

FLOOD LOSSES


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Fig. 6. A simple systems model of natural hazards showing the interrelationships between natural event,human use, and hazard effects that results from resource development (Adapted from Kates. 1970;1971).

HAZARDEventUse

Response

LOSSES

PropertyDisruptionCasualties

ALTERLOSSES

DECIDING WHATTHIINGS CAN BEDONE TO ALTER

LOSSES ANDHAZARDEFFECTS

ALTERNATURAL

NATURALEVENT

HUMANUSE

ALTERHUMAN

EXTREMENATURAL

EVENT

RESOURCES

HUMANUSE

HAZARDS

EFFECTS

Fig 7. A simple systems model of natural hazards showing the influence ofeasures aimed at reducing losses. Some measures aim to directly alter the

atural event; some directly alter the human use of an area; and others aim tolter the actual losses. Thus, the hazard is a function of event, use, andctions taken to reduce losses. The feedback arrows suggest that alteration tone part of the system affects all other parts. Careful consideration of theseteractions can reveal counterintuitive consequences of some actions (Adaptedom Kates, 1970; 1971).


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Feedback Concept

If it is agreed that alteration of human use of an area leads to changes in the nature ot hazard (or disasterpotential), then what we do to 'reduce' the potential for disasters, by definition also alter the hazard. This mayseem circular and obvious, but the point is extremely important. Many people who have had responsibility

for reducing losses from extreme natural events have failed to recognize this distinction between hazard

and disaster and their actions have often aggravated both.

People do not usually become concerned about hazards, until a disaster occurs. When a disaster happens people, and communities of people, often decide to do things that will reduce future losses. The thingsthey do also affect the hazard. Thus, our definition of a natural hazard must include not only 'natural event'and 'human use', but also the 'things we do to reduce losses.' (The things we do are often called adjustmentsor measures or actions.) Why should it be important to include this third component? Because some things

people do to reduce losses, actually make the hazard worse. This idea will be explored further in the finalsection on Flood Hazard Mitigation

It is perhaps helpful to think about this paradoxical situation, by modeling the natural hazard as a simplesystem (Figure 6), Once this has been done we can deal directly with the things (adjustments) we do toreduce losses and the implications these actions have (or hazards or potential disasters.

The event, use, and hazard identified in the Venn diagrams in Figures 1 and 2, and depicted for Invercargillin Figure 3, are restated in the systems model in Figure 6, together with the potential effects of the hazard.

The many measures that can be taken to reduce potential losses may be classified into those that influence:the natural event; human use of an area; and disaster effects or tosses. They are listed in Table 2 (later in this

booklet). These three main influences are shown in Figure 7 as feedback arrows. Each arrow flows back tothe hazard box and onto disaster effects. The model therefore stresses the interactive and dynamic nature ofnatural hazards.

Risk Concept

The risk is a measure of the vulnerability of a particular area to natural events of a given size or magnitude.The evaluation of risk is based on records of past events. The longer and more detailed the record, the betterthe estimation of risk. The risk is expressed in terms of the likelihood (chance or probability) of an event ofgiven size occurring. The larger the event the less likely it will occur. If the probability of a large event is 1

percent (or 1 chance in 100) in any year, then the fact that the event happened this year does not lessen thechance of it happening next year. (Think of it as tossing a coin. There is a 50:50 chance of heads or tails oneach toss. Turning up heads on one throw does not affect or reduce the 50 percent chance of getting heads onthe next throw.)

Obviously, the size of an event and the frequency with which it recurs relate to other dimensions of the event.A large, rare flood, for example, will be deeper and more widespread over the floodplain than a small flood.

Rare droughts last longer and often affect larger areas than moderate droughts, and so on. Thus, variousparameters of the event are interrelated and the overall phenomenon (or natural event) may be thought of asfunctioning parts of a complex physical system. It is important for people who have responsibility forreducing hazards and losses to know the physical dimensions of the natural event. These include parametersshown in the table below. These physical dimensions must be related to human use patterns in the area at riskfor the nature of the hazard to be properly detailed. Only then can effective action be taken. For example,

people may use land use planning, insurance, and emergency actions to reduce losses, but in order to beeffective, these actions require information on the levels of risk for different areas. That is, for example,the size and frequency of the event and the area affected by it.


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size (e.g., the volume of flood water or volume of land

frequency (e.g., how often on average do events of given size recur).

Speed of onset (e.g., earthquakes approach suddenly while droughtsapproach slowly).

duration (e.g., earthquakes approach suddenly while droughts

approach slowly).areal extent (e.g., landslides occur over small areas; droughts over large

areas).

Are They 'Natural' Hazards?

When describing the functional nature of natural hazards it was stressed that hazards are 'human creations'.Nevertheless, the discussion thus far shows that the causal agents of 'natural' hazards are both natural and

human. This, then, raises doubts over the appropriateness of the term 'natural hazard' as a label tor the phenomena we are interested in. The hazards we are interested in ('natural hazards') are in part humancreations, and that it is in some ways misleading to label them 'natural' hazards. On the other hand, it would

be equally misleading to label them 'social' hazards because they are in part created by natural events. Thus,a natural hazard that leads to a natural disaster when an extreme natural event occurs is not usefully labeled a'social hazard' or 'social disaster'. To do so would confuse it with such 'social' disasters as the alcoholinduced vehicular accidents.

The Venn diagrams in Figures 2 and 3 and the systems diagrams in Figures 6 and 7 usefully stress theinteractive nature of the hazards and disasters we are interested in. Calling them 'natural hazards' and'natural disasters' is a convenient short-hand for classifying the various types of hazards and disasterscaused (in part) by extreme natural events. This in turn enables us to refer to the different types of hazards

by theprincipal causal agent in nature- flood, earthquake, hurricane, etc. If the 'social' causal agent wasused as the means for labeling these sorts of hazards, the resulting classification would be very confusing, ifnot meaningless.

Reducing Natural Hazards and Losses

Acting in ways that reduce the natural hazard in a community lessens the scale of disaster when an extremeevent occurs. In other words, reducing the hazard lessens the potential for losses. (Equivalent terms to the

word 'reduction' used in the literature on natural hazards are 'amelioration' and 'mitigation'.)

There are numerous actions (measures or adjustments or coping mechanisms) that people can take to eitherindividually or collectively reduce losses from natural events. Not all measures taken, however, reduce thenatural hazard. The reasons for this are given in the sections below.

The range of measures that can be taken to reduce losses varies depending on the type of event and thecultural group in question. A study in Sri Lanka uncovered 264 different kinds of actions people takecollectively to reduce the flood problem (Burton, Kates, and White, 197S, 40). In New Zealand, the listwould not reach 50 (Ericksen, 1971; 1976b; 1986). These differences in part reflect the differences in types of

hazard, but are mostly due to the character of the societies in question.

Modern technological or industrial societies (e.g., United States of America and New Zealand) employactions that: emphasize the control of nature; are inflexible and hard to change once the approach is


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established; are capital intensive in their requirements (like flood control works); involve complexgovernmental structures to implement them; and tend to be fairly uniform in application cover large areas(White, ed., 1974; Burton, et al., 1978).

Because we are dealing with basic concepts it would not help to detail the many actions here (See Burton, etal., 1978). More useful is a classificationof potential actions into three broad approaches: altering actuallosses, altering the natural event, and altering human use in hazardous areas (Table 2). An indication of theirinfluence on the hazard system appears in Figure 7

Altering Losses

A major approach to dealing with the actualeffects of disasters is to relieve losses after they have occurred.This can be done through public relief and rehabilitation of an area. For example, government grants and

public donations provide cash for people who have lost essential possessions. The declaration of adisaster by authority of the Civil Defence Act in New Zealand, for example, enables the personnel,organizations, and materials of central, regional and local government agencies to be used to help localcommunities to rebuild essential services, like sewerage and water supplies, after a disaster has struck.

The main approach for dealing with thepotentiallosses from an individuals perspective is through insurancetaken out in anticipation of such losses. People pay premiums to insurance companies in recognition of thechance that they may be affected by a future disaster.

These measures obviously relieve the burden of loss for individuals affected by a disaster. They spread thecosts in time and space beyond affected individuals onto others in the wider community, and from theaffected to community to the nation at large. However, the money and material that flows into an area is


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generally used to reinstate property and people in the same areas affected by the disaster. These actions bythemselves do nothing to reduce the hazard and, consequently, do nothing to reduce losses from futureevents.

Altering Natural Events

A popular approach to dealing with hazards, or the potential effects of disasters, is to try and alter or otherwise

contain or prevent the natural event. For example, barriers can be built to contain floods within river channels,divert avalanches away from villages, or prevent storm surges encroaching beyond sand-dunes. Clouds have

been seeded to induce rain and break droughts or to dissipate the energy of a hurricane, although suchattempts are more experimental than practical. Attempts to release tectonic strain and therefore prevent severeearthquakes have been made in USA,

The main problem with this approach is that the measures are far from reliable. For example, embankments(stop-banks) in New Zealand may prevent floods of moderate size and frequency, but sooner or later they are

breached and/or overtopped when a major flood occurs, as at Paeroa, 1981; Mataura 1978; Opotiki, 1964;Whakatane 2004, Manawatu 2004; and many other places. In the meantime, stopbanks encourageintensification of human settlement in the path of the eventual flood.

This problem is illustrated in Figure 8 for the area in Palmerston North affected by flooding from theMangaone Stream. The cross-section through Mangaone Stream shows the way in which stop-banks haveenlarged and the stream artificially deepened in response to each major flood starting in the 192O's.

Thus, as for post-disaster relief, pre-disaster measures that try to modify the cause or effects of a naturalevent may reduce some losses from smaller natural events, yet actually increase the natural hazard and with itdisaster potential with respect lo larger more rare events.

EVOLUTION OF PROTECTION FROM MANGAONE STREAM

Stopbanks Channel enlargement

1978 1960s 1945 1930s1920s

1920s Natural condition (estimated)

1930s Protection1941 Flooding1945 Proposed protection1947 Flooding1953 Flooding1960s Protection1976 Flooding1978 Protection19B0's Assumed growth will reduce capacity of existing protection

Fig. 8. The evolution of channel enlargement and raising of stop banks lo protect first rural and thenurban land uses from Mangaone Streams, Palmerston North (Ericksen, 1986

Altering Human Uses


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Since natural disasters are largely human creations, the most effective way to reduce losses and the hazard isthrough altering human use of resources in areas at risk from extreme natural events. The main approach fordoing this is land use planning and management and emergency preparedness.

Zoning ordinances and building codes are the main measures available for planning and managing land uses.They can be applied to areas at risk from natural events. To plan land uses so that they are sensitive to therealities of nature, it is necessary to clearly identify and map areas at risk from natural events. The extent ofhazard can be assessed by relating various sorts of land uses to the risks. For example, an area exposed tomoderate floods may be suitable for parklands or even flood-proofed (water tight) industrial buildings, but itwould seem most unsuited for dense housing where large numbers of people would be at risk. Before openingnew areas for agriculture it would be essential to establish, from past records, the fluctuations in rainfall so thatthe type or types of farming chosen will not be exposed to the threat of drought on the one hand or floods on theother. Planners of new settlement along the front-range of mountains must be mindful of the paths oflandslides and/or avalanches. These various planning measures are long-term in their application. That is, theyneed advanced planning and once applied they operate over time to guide new developments into lesshazardous forms.

Emergency actions can also be prepared for well in advance of actual disasters. They are, however, short-term inapplication. They include such things as evacuation of people and property from the hazard zone. To beeffective they need an appropriate forecasting system to warn people of the on-set of the event and its likelyconsequences.

Altering human uses in hazardous areas is the most effective way of reducing both losses from natural eventsand the natural hazard. Unfortunately, this approach to the problem appears to be least applied. The reasonsfor this are many and complex. Many local politicians see the production of hazard maps and policies for landuse management as affecting growth and development and thereby rateable income, i.e., property taxes.Property owners and developers often feel these measures will affect their property values and profits. However,research in the United States on floods and earthquakes and in New Zealand on floods shows that disclosureof the hazard does not significantly influence property values (Montz, 1994).

However, the fear many local councillors and property owners have that disclosure will affect growth and

development by adversely impacting property values, means that hazard and mitigation information that isimportant for altering human uses in hazard-prone areas is not always made very public by local governments.This is in spite of the fact that legislation required them to do so (Ericksen, 1986; Ericksen, Berke, Crawford, andDixon, 2003).

Integrated Approach

For most problems the solutions to them are often complex. It is likely that the most effective approach toreducing both losses and hazards from extreme natural events will require some combination of measuresfrom the three approaches described above. That is, it will require an integratede and unified approach. Forexample, to reduce losses to existing flood-prone property, stopbanks (embankments) would be useful. Newdevelopment should, however, be directed away from the more hazardous locations or other preparednessmeasures should be taken, like land and/or building elevation and flood-proofing of buildings. Whenthese measures fail, evacuation, relief and rehabilitation, and insurance, if available, should be available tohelp people bear the losses.

Flood Hazard Mitigation

In New Zealand, a wide range of legislation evolved over the years that enabled all of the measures notedabove to be implemented, particularly with regard to flood hazard. However, until the 1990s, the pattern of

response was highly biased towards altering losses (post-disaster relief and rehabilitation) and alteringfloods events (soil erosion and flood control works) (Ericksen, 1986). In other words, only minimalattention was given to altering uses in flood-prone areas through land use management and related

preparedness measures. This pattern of response for flood hazard is summarised in Figure 9. Since the


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Resource Management Actof 1991, the amount of flood control has lessened, primarily because centralgovernment stopped subsidizing local government for their development. Nevertheless, local governmenthas still been slow to adopt integrated community preparedness programmes, as flooding in the Eastern Bayof Plenty in 2004 clearly shows.

ADJUSTMENTS FOR REDUCTING FLOOD LOSSES

ADJUST FLOODS TOPEOPLE

MODIFY FLOOD CAUSEAND EFFECT

ADJUST PEOPLE TOFLOODS

MODIFY FLOOD-LOSS

ADJUST FLOOD LOSSESMODIFY

POTENTIALFLOOD-LOSS

EFFECTS

Watershed Treatment

ChannelIm rovements

Stopbanking and

Dams and

Zoning Ordinances

Sub-divisionRe ulations

Building Codes

Public Acquisition

Flood Forecasting

EmergencyPre aredness

Flood Insurance

Subsidies & PublicRelief

PUBLIC INFORMATION AND EDUCATION

MEASURES USED IN NEW ZEALAND

STRONGADOPTION

MODERATEADOPTION

WEAKADOPTION

Fig 9. Pattern of flood adjustments and the extend adopted in New Zealand.The many measures for modifying loss potentials are weekly adopted relativeto those that modify the flood event and flood losses (Ericksen, 1971a;updated 1986).


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Fig 10. Trends in flood protection costs and insured losses, 1953 1980. The fall in protectioncosts in the 1970s due to economic recession and diversion of funds to irrigation works (Ericksen1986)

FLOOD-LOSSES AND PROTECTION COSTS1950 - 1985


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Fig 11. Self-perpetuating protecting of floodplain settlement: a). natural conditionssupporting rough grazing in swampy land adjacent to a channel with 5 year floodcapacity; b) 15 year flood protection of intensive farmlands; c) 50 year projection ofurbanizing floodplain which when flooded leads to; d) 100 year protection. The bags ofmoney indicate the increased actual and/or potential cost of relief and rehabilitation asland use intensifies. Bottom of diagram shows settlement guided over time byjudicious land use management measures


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Why this pattern?

Basically, flood losses are generally seen as problems caused by nature. The best solution is seen ascontrolling the natural event. After setting up catchment boards in the 1940's, large amounts of public moneywas spent on flood control works through the central government scheme of subsidies. The costs for thisapproach escalated steadily in succeeding decades. By the 1980's almost all of the 100 flood-pronecommunities with populations in excess of 1,000 people had "flood protection". Yet in spite of the increasingexpenditure on flood control works, flood losses continued to rise. This protection cost - flood loss trend

appears in the graphs in Figure 10. The cost of protection flattened in the 1970's due to diversion of moneyfrom flood control to publicly funded irrigation works and to an economic recession.

As flood disasters continued to occur in spite of large scale efforts at flood protection, increasing amountsof public money was being spent on relief and rehabilitation, which was reinvested in the same flood-proneareas. The reason for this was the classical case of the solutions becoming the problem. In essence,stopbanking and channelisation are self-perpetuating. As land use in flood-prone communities intensifies

behind ever larger protection works, the disaster potential grows from flood events larger than those forwhich the flood control works were designed. Sooner or later protection is overtopped and/or breached.While individuals and communities affected by floods have their losses reduced through relief andrehabilitation, the cost to the nation as a whole escalates. While many benefits are gained in the process of

floodplain occupation, the cost of doing so lies in infrequent flood disasters. The idea of creating a selfperpetuating system is illustrated schematically in Figure 11.

The Consequence

While many officials in regional catchment boards did try to encourage officials in local councils to useland use management as a means for reducing flood hazard, the latter tended to see the catchment boards asthe solvers of their flood problems. Besides, community officials did not wish to impede growth anddevelopment in their areas by pushing for land use controls.

It is estimated that between 1968 and 1984, 10 major floods, including regional floods, caused about $1.2billion worth of damages. By 1984, the National Water and Soil Conservation Authority had spent about $1billion on soil erosion and flood control works through its catchment boards in local areas.

Getting out of this dilemma requires flood-prone communities to deal with the problem themselves. That is,they have to internalise their costs of locating in flood-prone areas, rather than externalise them to the nationas a whole. This means becoming less reliant on nationally subsidised protection and relief and more relianton altering human uses on the floodplain within their own community. This is done by encouraging peoplewanting to develop on flood-prone land to do so in ways that are compatible with the realities of periodic,

but potentially devastating, flood events.

In New Zealand, central government since 1984 has resolved to reduce public subsidies on public works, likeflood control, and to devolve responsibility for local problems away from central government to localcommunities for most matters. This approach may bring sufficient pressure on local authorities to moreseriously implement the land use management and community preparedness measures that legislation has fordecades enabled them to do.

Resource Management Act 1991

In this respect, the Resource Management Act 1991 is clear. Section 2 of the Act defines the meaning of"natural hazard" as

any atmospheric or earth or water related occurrence (including earthquake, tsunami, erosion,volcanic and geothermal activity, landslip, subsidence, sedimentation, wind, drought, fire, orflooding) the action of which adversely affects or may adversely affect human life, property, or otheraspects of the environment...


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The meaning of "effect" is described in Section 3, and includes: positive or adverse effects; temporary or

permanent effects; past, present, or future effects; cumulative effects: potential high probability effects;and potential low probability, but high potential impact effects.

Section 31 describes the functions of territorial authorities (regional and local councils) as including:(a) The establishment, implementation, and review of objectives, policies, and methods to achieve

integrated management of the effects of the use, development, and protection of land and associated

natural and physical resources of the district;(b) The control of any actual or potential effects of the use, development, or protection of land, including

the implementation ol rules for the avoidance or mitigation of natural hazards...(c) The control of subdivision of land...(e) The control of any actual or potential effects of activities in relation to the surface water in rivers and

lakes.

Section 35 requires local councils to gather information, monitor, and keep records needed for effectivelycarrying out these and other functions under the Act. This includes keeping records on natural hazards(S35.5J).


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APPENDIX 1

GLOSSARY

Human use:

Natural events:

Extreme natural events:

Natural hazards:

Natural disaster:

Magnitude:

Frequency:

Mitigation:

Adjustments

The use made by people of an area. Use can be defined in many ways.For example, land uses such as residential, industrial, recreational,commercial, farming and so on.

The complex natural forces that occur in a given area. For example, theclimatic and geomorphic processes that give rise to winds, rains, slopes, andrivers.

Those natural events that vary significantly from normal conditions. Forexample, very high or very low rainfalls cause floods and droughts.

The potential consequence of an extreme natural event on human use of agiven area. For example, the possibility that a flood could inundate part of acity, or, thai city development could encroach or is encroaching into areasprone to flooding. A natural hazard is the perceived interaction between apotential extreme natural event and human use (actual or potential) of agiven area, including what people do to reduce the consequences ofextreme natural events.

The actual consequence (or impact) of an extreme natural event onhuman use ofa given area. For example, when a flood inundates part ofa city or farmland.

The size of an extreme event, such as a deep flood, very strong earthquakeor very large landslide. The more rare the event the larger its magnitude.

The expected occurrence of future extreme events. Future events are

estimated from the record of past experiences of events. Very large eventsare very rare, that is, they have low frequency or likelihood ofoccurrence.

To appease, to alleviate, to reduce in severity, in the context of naturalhazards, to reduce the hazard and thereby the losses should an extremeevent occur.

The measures oractions or coping strategies taken to reduce the hazardand/or losses. These may be taken by individuals (insurance, flood-proofing a house) or collectively (emergency preparedness, flood controlworks).


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REFERENCES CITED

Burton, I., and Kates, R.W., 1964: The perception of natural hazards in resource management. NaturalResources Journal, 3 (3), 412-441.

Burton, I., Kates, R.W., and White, G.F., 1978: Environment as Hazard. New York: Oxford University Press.

Ericksen, N.J., 1971: Human adjustment to floods, N.Z. Geographer, 27,105-129.

Ericksen, N.J., 1976b: The role of the planner in flood plain management: an overview, Town PlanningQuarterly, 43, 13-25.

Ericksen, N.J., 1986: Creating Flood Disasters? Wellington: NWASCA Miscellaneous Publication No. 77.

Ericksen, N. J., 1986: Forecasting for whom and what? In D. I. Smith and J.W. Handmer (eds), Flood Warningin Australia. Canberra: Centre for Resources and Environmental Studies, 123-132.

Ericksen, N.J., 1988: Integrating insurance and relief into unified floodplain management, Proceedings ofInsurance and Relief in Floodplain Management Conference, 24-26 February 1998. Canberra: AustralianNational University, Centre for Resources and Environmental Studies.

Ericksen, N.J., 1988: Natural Hazards: Basic Concepts: Hamilton: Department of Geography, University ofWaikato. (Booklet prepared for Secondary School Geography Series -- Form 5.

Ericksen, N.J., 1991: Flood Hazard Mitigation: Concepts and Problems. Hamilton: Centre for Environmentaland Resource Studies (Booklet for a Training Course 132: Civil Defence Planning for the National CivilDefence School, 4-8 November 1991.)

Ericksen, N., Berke, P., and Dixon, J., 2000: Managing Natural Hazards under the Resource ManagementAct, in A. Memon and H. Perkins (eds), Environmental Planning and Management in New Zealand.Palmerston North: Dunmore Press, 123-132.

Kates, R.W., 1970: Natural Hazards in Human Ecoloqical Perspective: Hypotheses and Models.Toronto: University of Toronto, Natural Hazards Research, Working Paper No. 14. Reprinted inEconomic Geography, 1971.

Haylock, H.J. and Ericksen, N.J., 2000: From state dependency to self-reliance: agricultural drought policiesand practices in New Zealand. In D.A. Wlhite (ed.), Drought: A Global Assessment: Vol 2, Natural Hazardsand Disasters Series, London: Routledge, 105-114.

May, P., Burby, R., and Ericksen N., (et al.), 1996: Environmental Management and Governance:Intergovernmental Approaches to Hazards and Sustainability. London and New York, Routledge.

White, G.F., 1945: Human Adjustment to Floods: A Geographical Perspective. Chicago: University of

Chicago, Department of Geography, Research Paper No. 29.

White, G.F. (ed.), 1974: Natural Hazards: Local, National, and Global. New York: Oxford University Press


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Acknowledgement

This paper is an update of previous versions used in several different contexts, such as: NZ National CivilDefence School, Course 132: Civil Defence Planning; Course 222: Natural Hazards, University of Waikato,Department of Geography; and Natural Hazards and Planning, Guide for Teachers of Secondary SchoolGeography - Form 5.

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