Deck 1 - Lectures 1-6 - Jamie Flashcards
Hazard definition
A dangerous phenomenon, substance, human activity or condition that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption or environmental damage.
Disaster definition
A dangerous phenomenon, substance, human activity or condition that HAS caused loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage.
Hazard management definition
what humans do, or should do, to minimise the effects of hazards.
Aggravating factors definition
There are a range of challenges (e.g. climate change, unplanned urbanisation, underdevelopment, poverty) that can exacerbate the effect of hazards, resulting in increased frequency, complexity and severity of disasters.
Hazard severity
definition and controls.
Severity - how much it can impact, severity can change through time. It is controlled by many factors:
* Duration - difference depending on the duration.
* Magnitude - drizzle versus downpour
* Predictability
* Speed of onset - tornado - sudden onset.
* Frequency - how often it comes back.
* Spatial concentration - EQ happens at the plate boundary
* Extent - global regional or local
* Number - one or a number of hazards.
Hazard prevention
definition
risk management (before the event) and emergency management (during the event).
“prevention” is inaccurate and may lead to complacency - we cannot prevent a flood but we can manage it better.
Natural disaster
definition
A consequence of the combination of natural hazards and human vulnerability.
Only becomes a disaster when it impacts human life, property and the environment. A social construct and without human involvement there is no disaster.
Vulnerability increases due to poor risk management or poor emergency management.
How do we reduce vulnerability?
- economic development
- better risk management
- better emergency management
Risk
Disaster risk definition
The potential loss of life, injury or destroyed or damaged assets which could occur to a system, society or a community, in a specific period of time, determined probabilistically as a function of hazard, exposure, vulnerability and capacity.
Risk is defined by:
* the hazard - the intensity, low or high activities? what is the likely outcome? how likely is something going to happen?
* vulnerability - exposure of the popualtion (how exposed to the event are you?) and susceptibility - are you going to be harmed by the event?
risk = (the likelihood of a hazard occuring) x (consequencfes of that hazard occurence)
Vulnerability
Definition and key variables
The characteristics of a person or group and their situation that influence their capacitu to anticipate, cope with, resist and recover from the impact of a natural hazard (an extreme natural event or process).
vulnerability is highly differentiated.
key variables explaining variations of impact include:
* class
* occupation
* caste
* ethnicity - differentiation - maori and pasifika - less affluent and live in less safe areas.
* Gender
* Disability
* Health status
* Age
* Immigration status - illegal immigrant -identified by authorities - could be deported
* Nature and extent of social networks
Vulnerability is determined by social systems and power not natural forces.
Less relative vulnerability in NZ? Why?
Recognition of rights in NZ. and we are relatively affluent so can deploy resources to save situations. Compared to afghanistan - no resources, divergence between rights of men and women - women disproportionately affected because they don’t have same rights as men according to the taliban.
Benefits of an improved understanding of disaster risk
- focuses public attention on controllable societal consequences of events instead of on uncontrollable natural processes
- identifies regions or areas that may warrant new risk-adaptation strategies, prepardness plans, public education, or land-use changes
- serves as baseline for information for response efforts
- highlights were additional hazard, risk or mitigation assessments may be needed or improved.
Resilience
Definition
A process linking a set of adaptive capacities to a positive trajectory of functioning and adaptation after a disturbance.
Can you recover after a disaster has happened?
Post disaster trajectories
in relation to resilience - draw graph
Whether communities are resilient or not resilient. How can you recover after a disaster?
The disaster occurs, the conditions deteriorate as a consequence of the disaster. Then you can have a relatively rapid readjustment and recovery, a slow gradual recovery, or things can spin out of control. For example, the haiti earthquake of 2009, the aftermath → the civil society of haiti was so weak that communities started breaking down and a decade or more later, haiti has not recovered from that earthquake, showing a trajectory saying that society doesn’t recover.
Christchurch is sitting somewhere between a and b. We’ve recovered moderately well but now we are 10 years down the track from the major earthquake and we are still in a post disaster recovery mode in part.
Whta resources influence post disaster recovery?
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- Resources How affluent are you? If a disaster happens in the global north (relatively affluent societies), typically the response is that it is possible to mobilise resources from elsewhere in society, get relief efforts, and build structures after the event. If a country doesn’t have those resources, the recovery is much less effective.
- Community size and diversity The more homogenous a community is, in some ways the better it can respond to a disaster. I.e. covid → NZ team of 5 million, the community worked on a unified response. US → no unity in response to the event, enough people going in the opposite direction → there were two ways to go, you could ignore it or attempt to deal with it. The US did neither very well and a lot of people died and there was high economic cost for the US, high in NZ but higher in the US.
- Connectedness vs. isolation When something bad happens its much harder to get the resources there.
- Duration and intensity Short events tend to be easier to respond to compared to events that continue. Flooding event within a couple of days - after a few days the event is over and you can start your response effort. A volcanic eruption might last a decade - the eruptive sequence - make responses much more difficult.
- The actions and timings of external agencies NZ - had these earthquakes and formally war damages condition - in place to gather resources so that if a major city got struck by a large earthquake the country would be able to respond. Never intended that the money would be largely expended on chch. If it happens again it may be an issue because reserves have not been built up to what it was before the chch earthquake. The fact that we have that puts us in a resilient position.
- Attitude If you believe that you can achieve anything then you will have difficulty doing it. You do see in some parts of the world - the community does not respond by pulling together - this is where homogeneity helps → meaning the people feel to be a community, they don’t have to be the same naitoanlity, same sex etc. - they just have to behave like a community. Looking after neighbours etc.
- Political initiatives that inspire confidence Fairly rare - most aren’t inspired by our politicians. The NZ government did make a public commitment to invest in the recovery of chch. Governments can and do play important roles.
Broad patterns of response to disaster
relationships to local environment, what the response emerges from
new relationships to the local environment:
1. moving away
2. staying and coping
3. staying and struggling/not coping
4. adaptation and flourishing
each of these responses emerges out of:
* the impact of hazard
* people’s understanding of its likely reoccurence
* the resources availible to them
* the oppourtunity they have to respond.
Flooding
Definition
Temporary innundation of normally dry land by water from:
* rivers which have “burst their banks”
* surface runoff, particularly from heavy rainfall (pluvial flooding)
* tidal or coastal waters e.g. storm surge
In normal circumstances rivers have a channel whereby the river flows within the channel. For a single thread river the channel is easily defined. Braided rivers in Canterbury have a braid plain - the channel of the river is across the entire braid plain.
Fluvial or riverine flooding
Definition
main causes: widespread/long-duration precipitation and melting snow. can take hours, to days or weeks, depending on river basin size.
Riverine floods are not always associated with local rainfall. In NZ this doesn’t have a massive impact (rain in the headwater countries in the southern alps or the north island - a few hours to a few days before the peak of the flood is visible down on the low country adjacent).
Extreme case - Australia - the interior of Australia is extremely shallow in terms of slopes. Any rainfall in the headwater regions of the larger rivers, can take a month of six weeks for a flood to come through.
Spring melting snow generates them. In NZ we don’t really have that because there is lots of snow but the climate is so variable that our snow melts at various times during the winter.
Flash flooding
Definition
- rapid-onset, short-duration flooding
- main causes: intensive rainfall (e.g. from convective thunderstroms)
- catchment conditions (e.g. topographic steepness, geology)
- associated with drainage pathways (including rivers)
Associated with very steep countryside (NZ). A lot of rain over a short distance, very steep catchment, geology in the catchment - very thin soil, bedrock just below the surface so cannot sop up the moisture going in, after a very small amount of time water starts flowing downhill.
Coastal flooding
Definition
- Low-lying coastal areas
- main causes - tides, storm surges, tropical cyclones, high wind, tsunami
Tidal cycle - if the storm coincides with the lower part of the tidal cycle, it offsets the elevation of the storm. If you get high tide and the storm coinciding, they stack → leads to waves going a long way inland.
Floods in NZ
Common events
Bias towards south island - temperate lands, tend to get extreme amounts of rain in the alps and then rapid delivery from the alps to places adjacent - more civil emergency type flooding in south compared to north island.
We currently are getting a lot more weather out of the north, traditionally - big ex tropical systems hit NZ in the end of summer (march/april). East coast of the north island and northland is the primary to be hit. In the winter we are only supposed to be getting southern ocean weather. Shouldn’t be weather coming out of the tropics at this point in time.
Global Floods
Lots of floods globally. How they impact varies from place to place.
When talking about how many people were killed we don’t see the same places coming up compared to financial damage → most affected: China (pretty good well organised emergency responses to floods - they do have fatalities - but resilient systems). Highest deaths - india, pakistan, thailand, bangladesh, the phillipines - not necessarily poor but share dense populations on floodplains with less well organised flood responses than you get in China.
Risk avoidance
definition
- don’t invest in property etc. to avoid the liability that goes with it
- but by avoiding risk you are avoiding the potential rewards
- some lovel of risk is necessary (acceptable risk)
issues
* assumes that risks are known
* to avoid buying a house at risk of flooding you need to know whether it is likely to flood
Risk reduction
definition
- methods to reduce the likelihood and/or severity of loss. e.g. flood protection measures
issues - to be effective the risks must be properly understood.
Flood protection measures - in chch we have flood banks along the sides of the waimakariri. Designed to prevent a flood from the waimak. Not the same height on both sides of the river. 30cm difference - if we get to a critical position where the stop banks were going to fail it’s designed to fail north towards Rangiora and not south in chch city. 400,000 people at risk on one side and 50,000 people at risk on the other side.
But waimak can breach well before the stop banks. Then everyone is at risk.
Risk retention
Definition
- accepting loss when it occurs
- includes “self-insurance”. common practice in business - setting capital aside
- all risks that are not avoided or transferred are retained by default: uninsurable risk, unknown risk
issues - to be effective, the risks must be properly understood. how much should be set aside to cover potential losses.
What happens when you choose to take the risk without external support?
Need to know what you are up against - self insurance - build up a reserve by setting money aside so that when the event occurs you can do the maintenance to respond to it.
If you are in a risk situation and have not mitigated the risks (put in stop banks) you are effectively retaining the risk.
Uninsurable risks → westport has flooded several times and now insurance companies will not offer flood insurance.
Unknown risk → climate change. If you get a change in the general environment, you didn’t know about the risk before it happened.
How much should we set aside to cover our potential losses? The expected recurrence interval of the risk divided into the sum of money that you need to restore the damage that you want to repair.
Risk transfer
definition
- casuing another party to accept the risk
- insurance
- individual or company at risk pays a premium to am insurer, on the agreement that they will cover losses if/when an event occurs
- for the insurance company, over time income from insurance premiums must be enough to cover losses from pay-outs (but note reinsurance)
issues: assumes losses are all economic or can be compensated for financially. to be effective risks must be properly understood.
Buying an insurance party.
The premiums must be high enough. Small chance of a really big event. Reinsurance industry - insurance companies then buy further insurance from a big international “re”.
Loss of life is something that you cannot be reassured in anyway.
Low-land river flooding
definition
- innundation of areas of low lying land from a river that has “burst” it’s banks
- large and less dynamic event than flash flooding and usually further downstream. Flash flooding and low land flooding are often connected. Flash flooding in the headwater regions and then in the lowland regions there is low land river flooding.
Normal flow occupying the river channel. When the river channel is full (regardless of the river type) it will overflow the channel and occupy an extensive area. Called the floodplain. A flat area beside an area in a lowland or upland area - a floodplain so a flood risk in those locations.
Flash flooding
definition
- rapid localised flooding of low lying areas usually along streams/rivers
- caused by the sudden accumulation of water usually from intense rainfall (often from thunderstorm events). can also from sudden release of water e.g. a dam breaking
- More dangerous. Big floods down big rivers tend not to kill many people but tend to cause a lot of economic damage, flash flooding can be deadly.
- intense rainfall from convective thunderstorms may only last a few hours, but can result in serious flooding in catchments that are small, steep or highly urbanised.
Non-climatic causes of flashflooding - geomorphology
- steepness of slope
- Landscape - geomorphology - tend not to get the full event - not a huge amount of damage associated - human life/economic damage in low land areas. You need steepness of slope.
- upstream contributing area
- relief - is area confined or a wide floodplain? narrow valleys are more likely to experince serious flash flooding.
- Relief needs to be confined - to maximise these floods, or what you don’t want to do to minimise them is to constrict them, a larger catchment area flowing into a constrained valley, concentrates the flow in and amplifies the effect of the flow.
Non-climatic causes of flash flooding - permeability of land surface
- if water cannot be absrobed into the ground it will quickly be moved down slope
- Specific geology and soil types. How permeable (ability of land surface to take water in) is the land surface? If permeable you won’t get flash flooding. In chch areas down by the beach will not flood because sand layers are completely permeable and the water will go into the sand - not going to get overland flows.
Climate change and flooding predictions
- Predictions. The right → representative contribution pathways → if we do nothing about emitting CO2 and continue a growth pattern, this is the likely amount if change. These are in watts per square metre of the atmosphere.
- The left → changes predicted for the latter part of the current century based on the rainfall for the 20th century (last century). What we can see is 100 year return events - big events in the system - massive increases in the mid latitude westerly zone, except for chile - west coast of the US, north western Europe gets it - not a one way system. The predictions are that there will be fewer flood events in other parts of the world - so extreme drought and risk of large flooding happening at the same time.
Annual series versus a partial duration stress
annual series - compare the maximum floods (what we use in the assignments and labs).
Partial duration series - annual peak and measure other ‘significant’ flood peaks. Annual and partial duration peak and then a second partial duration peak - second high flood gets measured because it’s a partial duration peak.
Annual series are much easier to measure, less analysis of the data. Better for longer series and larger less frequent events.
Have to handle data more carefully for the PDS. PDS - for looking at a catchment in great detail. Better for shorter series and smaller, more frequent events. Events need to be independent - can be a problem.
wet vs. dry catchment and antecedent condition - extreme event probability
definition and for chch
A rain storm with a particular probability will have a different impact of a wet vs. dry catchment.
Antecedent conditions - what is the condition of the ground before the rain arrives?
A rainstorm with a particular probability will have a different impact on a wet vs. dry catchment. Therefore a 25 year fall event is not the same as a 25 year flood event. Smaller rainfall event may have a bigger flood if the ground conditions are right for flooding. A big rainfall event may be sopped up if the ground is previously dry.
In Christchurch - our antecedent conditions are that our water tables are very high because we’ve had high amounts of rainfall recently. If we were to have an extreme events in the next few weeks the catchment would be saturated before the rain starts and the water cannot infiltrate into the ground and as a consequence you will get surface flow across the ground surface straight into the river, creating a flood hydrograph which in terms of time, the peak rises quickly and falls quickly. If the same catchment were dry most of the rainfall would infiltrate into the ground and seep slowly into the river, so that the rain starts at the same time, but the peak is later and lower because the ground conditions before the rainfall are dry.
Annual exceedence probability
definition and equation
The probability that a flood will exceed a given level in any year.
Annual exceedance probability (P) → what is the chance of any given year exceeding the event that you’re looking at. One over T (basically the same formula), if you flip the formula, you have the rank on top and number of years plus one.
