Natural Hazards

Risk equation

hazard x exposure x vulnerability

4 aspects of risk society

fate

accident

risk

sacrifice

why is there a need to communicate hazards

save lives

increase resilience

minimise vulnerability

educate

imporve trust and relationships

collect data and improve hazard modelling

what do we need to consider when communicating hazards to people

age

ethnicity

gender

economic status

education

understanding

culuture and religion

agenda

how should we be commuincating before a hazard

education

community programmes

historical and cultural understanding

how should we be communicating during the hazard

whats happening

where

need to evacuate

where should you go

what should you take

how should we communicate after a hazard

what happened

is it safe to return

what help is availabke

what do we need to commuincate

danger

what are the hazards

what are their impacts

where are no go areas

what are evacuation procedures

has this happened before

human origin of earthquake

fracking, mining, reservoir building

volcanogenic earthquake orgin

movement of magma causes surrounding rocks to crack

fault movement orginiating earthquakes

90% of all

generation of earthquake along faults

sliding prevented by friction

rocks are elastic so deform

strength exceeds and so rebound

shock waves spread

seismic waves

earthquake distrubution - convergent margin

collision

generate earthquakes range of depth

earthquake distrubution - divergent

spreading of plates by ridge push and slab pull

as move apart, crack and fault

earthquake distrubution - conservative

lateral movement creates shallow earthquakes

focus

point of origin of earthquake

epicentre

surface point direclty above focus

P waves

compressional

fast

travel through solid and liquids

S waves

shear perpendicular to travel direction

slower

travel through solids

surface waves

rayleigh and love waves

detecting earthquake - seismogram

graph of displacement vs time

arriaves - p, s, surface

P-S time lag gives distance to epicentre

locating epicentre

atleast 3 seismoters converge at a point

measuring earthquake magnitude

richter scale - logarithmic

moment magnitude

earthquake size - intensity

effects of earthquakes

depends on magnitude and distance from epicentre, depth of focus and local geology

intensity scale for measuring damage of earthquakes

modified mercalli scale

primary hazards of earthquakes

ground shaking

• building collpase

• surface subsidence

earthquake secondary hazards

liquefaction

• disturbance of unconsolidated sediment due to shock

• temporary fluid behaviour

landslides

• number induced decreases with distance from epicentre

• number increases with magnitude

tsunami

• water pushes up and moves rapidly at sea then when near lands slows and squeeze in height before heading inland

fires

infrastructure and communication loss

clean water and waste system

disease

hazard assessment - event analysis

geological mapping

monitoring

recurrence intervals

• instrumental records

• historical records

• palaeosismicity

hazard assessment - paleoseismicity

dating movement on faults

dated landslides and tsunamis

evidence for liquefaction

hazard assessment - monitoring - EQ

evidence of strain build up

• local seismicity - foreshocks

• ground deformation

• water levels

• gas discharge

• electromagnetism

• satellite geodesy

problems with forecasting EQ

fault system complex

recurrence records too short leads to false alarms or unexpected events

mitigation EQ - deisgn

solid and stiff or flexible

rubber shock absorber

fire resistant

open areas for evacuation

automatic window shutters to prevent falling glass

EQ mitigation - land use planning

hazard maps

EQ vulnerability modification

education and planning

warning systems

• US shakealert system

• Japan system stops bullet train

Volcanic hazard - tephra

fragmentation of magma

ash - <2mm

lapilli - 2-64mm '

blocks - >64mm

pyroclastic density current

fluidizied mixture of solid to semi solid fragments and hot expansing asses

dense basal flow made of large blocks confied to valley

upper more turbulent flow fed by mixing at head of flow

reducing volcanic risk

assess hazard and hazard map

monitor volcano

modify volcano

modify events

prepar

volcano hazard assessment long term eruption forecase

style of previous eruptions - frequency, magnitude

seismic monitoring

magma rises into reservoir beneath volcano

rising magma and volcanic gases exert pressure

high pressure causes rocks to break = earthquakes

ground deformation for predicting EQ

electronic distance measurement

global positioning system

tilt measurement

satellite radar interferometry

gas monitoring for earthquake prediction

ground based remote sensing

direct gas sampling and analysis

continuous on site gas monitoring

soil CO2 flux

hydrological monitoring for volcanoes

detecting lahars

survey river channels

measuring sediment on the move

sampling / analysis of water samples

modification of volcanic events - cooling lava

sea water slows down lava

modification of volcanic event - degassing

degass of lake by pumping gas rich bottom waters to the surface of the lake through pipes

tsunami wave in deep water

900 km/hr

100km wave length between crests

10s cm wave height

tsunami wave in shallow water

10s km/hr

5km length between crusts

height larger than 10m

trough and crest

water drawback

behaviour depends on coast geomtery and bathymetry

volcanic eruption triggered tsunami example

Krakatau

1883 - VEI 6 = 36,000 deaths l

landslide triggered earthquake example

La Palma flank collapse

primary hazard of tsunami

related to inundation of water

loss of life by drowning and debris impact

flooding and erosion

damage to structure

secondary impact of tsunami

polluted water supplies

fire

transport disruption

disease outbreak

recurrence intervals for tsunami minimisation

deposit records

historical documentation

tsunami detecting and warning systems

pacific tsunami warning system

network of seismometers

most expensive EQ triggered tsunami

2011 Tohoku

deadliest EQ triggered tsunami

2004 indian ocean

why was the indian ocean EQ tsunami so deadly

no warning system so knowledge

sumatra struck - high population

indian air force warning failed

230,000 deaths

rip current

strong localised currents that flow perpendicular to the coast

flows within rip currents can reach 2 m/s

identifable as areas of calm water cutting across breaking waves

formation of rip currents

waves break as hit shallow water overlying sandbars

water flows downhill into deeper areas where there are no sandbars

water flows back out to sea in deeper channels between sandbars

3 types of rip currents

boundary rips

bathymetric rips

hydrodynamic rips

why are rip currents so deadly

let guard down

show off

don’t swim on lifeguarded beaches

visit outside of lifeguard hours

over estimate swimming ability

drunk

panic

don’t know how to escape

mitigation of rip currents - understand science

understand different kinds of currents and their formation

understand impact of seasonal tides and changing beach morphologies

develop current forecasting systems

understand people and their behaviours

RNLI image recognition research

rip currents mitigation

beach safety flags

beach safety signs

lifeboats and lifeguards

education

education for rip currents

RNLi - flat to live campaign

NOAA - break the grip of the rip

australia - surf lifesaving australia - swim between the flag

aus - science of the surf

climate

statistics of weather prevailing in a location for more than 30 years

El Nino

ocean

warm surface waters off the coast of Peru lead to reduced fish harvests in some years

Southern oscillation

atmosphere

normal years - high pressure in central pacific and low pressure to the west

in some years - low pressure in the central pacific

ENSO

natural climate variability

2-7 years

change in interaction between ocean and atmosphere in the Pacific

Trade winds collapse leads to cold upweeling at equator weakening - similar temperature on east and west edge of pacific

ENSO impacts on western pacific

drought

wildfires

ENSO impacts on eastern pacific

floods

utility damage

collapse fishing industry

Measuring ENSO

Multivariate ENSO index

More el nino since 1980

ENSO mitigation

prediction, warning and prep

early warning

peru in 2015 declared 60 day state of emergency and built flood and drought prevention

challenges when mitigating ENSO

need for better understanding

uncertaininty of how ENSO may be afected by climate change

some say more intense super EL nino and some predict more extreme ENSO more often

North Atlantic Oscillation

base on surface sea level pressure difference between subtropical high and subpolar low

both phases associated with basin wide changes in the intensity and location of north atlantic jet stream and storm track and in large scale modulations of heat and moisture transport

thermohaline circulation

freezing of surface ocean water leaves denser salty water which sinks to form deep water

this drives the Atlantic Meridional Overturning circulation part

this supplies 1/3rd of Europe heat energy

reduced deep water formation may lead to a slow down in thermohaline circulation = cooling europe

cryosphere and climate change

1901-2013 NASA GISS surface temperatures increased on average over most of globe

cooling of north atlantic sea surface

linked to changes in cryosphere

impact of increase sea ice melt on temperatures

antarctic and greenland ice loss = increases in freshwater input to ocean surface

ocean becomes more stratified with cold fresh water at surface and warmer salty water at bottom

positive feedback as ice shelves in contact with deep warmer water so drop in surface air temperature

climate change impact on atmospheric hazards

heatwaves and droughts become more frequent

intensification of tropical cyclones and increase in aridity and fire weather

increase in frequency and intensity of heavy precipitaion will increase rain generated local flooding

UK occurrence of wildfires

many 1000s every year

almost all by arson

South Wales - greatest frequency of arson and fire in UK

8 x UK average

4 measures to classify wildfire

intensity and severity rating

intensity energy

flame height

severity impact on vegetation

impacts during wildfires

direct fatalities

damage through gas and smoke - suffocation; CO2 posioning; lung tissue damage, traffic

post wildfire impacts

flooding and erosion

negative ecological impacts

emissions of toxins and greenhouse gases

fires emit equivalent to ¼ global C emissions from fossil fuels

positive ecological impacts of wildfires

removal of old vegetation

trigger for seeding or germination

increases in species diversity

pyrophytic plants

plants adapted to tolerate fire and may even favour as it triggers reproduction

risk and trends of wildfires

globally average area burned declines 20% in last 2 decades

but increases in fires in most of worlds forest

mitigation of wildfires

prevention - open fire ban, fuel reduction burning, building guidelines

observation - fire towers, aerial patrols and closure of high risk areas

event modification - hosing, water bombing, back burning, fire breaks

evacuation

flood

temporary indundation of normally dry land by water

causes of river floods

atmospheric hazards

tectonic hazards

technologic hazard

cause of costal floods

atmospheric hazards

tectonic hazard

floodplain

relatively flat landform adjacent to a river channel composed of alluvium and subject to episodes of flooding

floodway

part of floodplain where there is rapidly flowing water in times of flood

flood prone environments

low lying parts of major floodplains

low lying coasts and deltas

basins subject to flash floods

areas below unsafe or inadequate dams

low lying inland shorelines

alluvial fans

measuring floods - flood dimensions

1 - discharge - volume of water transported through a given cross section

2 - stage - level of water over a datum

3 - flood stage - stage at which water body rises to a level that causes inundation of land and danger to human life

calculating recurrence intervals

analyze frequency of floods of various sizes to develop recurrence intervelop

years +1 / rank

based on probability by multiplying by 100

measuring flood frequency before observational records

boulder impact

stemp damage

root exposure

tilting stems

change in channel position

prolonged inundation

palaeoflood data - sedimentary data

climatic change changing flood intensification

increased rainstorm magnitude frequency

increased rainfall

more extreme depressions and tropical cyclones

sea level rise

urbanisation impact on flood intensification

impervious surfaces decrease deep infiltration and increase run off

impermeable prevent deep and increase run off

primary flood hazards

damage and loss of property and infrastructure

sediment deposited

loss of crops and livestock

drowning

secondary hazards of floods

drinking water quality

disease

mental health

services disrupted

highest population exposed to flood risk

bangladesh - 80%

exposure related to high rural population density and location of urban area long river and coast

forecast and warning of floods

modelling of storm rainfall and flows

real time data handling

coupling of weather, precipitation data and hydrological models

flash flood forecast

warning systems

communications