Factors Affecting Earthquake Damage
Population Density Quality of warning preventative measures response Strength and depth of earthquake Time of day
when do tropical storms occur in the northern hemisphere?
july to october
causes of hazardous mass movements
shear stress overcoming shear strength, pore pressure or increased rainfall or sudden thaw creating snow melt result of hazardous activity eg earthquakes they destabilise slopes volcanoes produce snow melt and engender lahard intense storms can also bring about slope instability human activities can also contribute although their influence is more limited deforestation undercutting and overloading can all affect slope stability as off piste skiing
when do slab avalanches occur and why?
spring partial melt occurs at depth leading to instability at a well defined failure surface
explain the threat of storm surges from tropical storms?
it can lead to extensive and very sudden costal inundation which will swamp many costal defences EG New Orleans where the levees and costal protection was completely overwhelmed by the storm surge resulting from Hurricane Katrina
What conditions are needed for tropical storms to form?
Sea temperatures must be 27 degrees, at a depth of 60m Far enough from the equator that the Corilosis force creates sufficent rotation in the rising air mass
EFFECTIVE response to a tropical storm case study example
hurricane mitch 1998 affecting honduras and nicaragua: less developed country (GMP is $700) short term: armed guards sent to guard businesses that could be looted, 200 arrested long term: homes were rebuilt crops replanted reconstruction (lowered unemployment and refit homes) AID US offered $70M medico offered rescue personnel medics etc
explain the hazardous effects of a tornado?
The winds destroy buildings, uproot trees, and hurl lethal missiles into the air Walls of buildings buckle and as the winds blast over the roof, they cause lower pressure above the roof allowing the winds to carry it away The lower pressure outside the structure can cause it to explode
how can mass movements be forecasted using hazard maps?
susceptible factors: bedrock: rocks that are jointed or with bedding planes parallel to the slope past history slope steepness hydrology: vegetation and precipitation therefore, development is controlled to mitigate the hazard
preparedness of tornados
Apps exist eg American Red Cross allow mobile warnings advice about tornadoes allows people to indicate their safe post event Advice from FEMA is presented on their website: Organisations eg schools hospitals malls must identify a place of refuge eg small interior windowless room below ground Individuals in mobile homes are advised to leave and go to a secure pre identified location Those outside should take cover in stationary building and drive to a secure building Many areas in the US have warning sirens and many institutions practice tornado drills
what latitudes do tropical storms occur at
explain the hazardous impacts of tornados?
destruction of property as movable bodies are uplifted and dumped, extreme low pressure can cause some buildings to explode due to pressure difference flooding due to heavy downpours of rain and hailstorms extreme high winds drawn into an ascending vortex causing crop destruction killer tornados (less than 2%) may creates swathed hundreds of metres wide and up to 150km long loss of life is generally low
describe and explain the development of tropical storms
intense evaporation from warm seas warm air rises and condenses to form towering clouds (cumulonimbus) and heavy rainfall this occurs without any wind shearing the uplift of air is accentuated by the release of latent heat as a result of condensation the rising heat creates intense low pressure in the centre with warm air sucked in and rising as storm develops upflow of warm and humid air continues air that surrounds the low pressure zone at the centre flows in a spiral (very high speeds, anti-clockwise in NH) coriolis force of the earth creates spinning motion around the eye of the storm air is ejected at the top of the eye
why are there continental deserts?
more heat as land heats quicker than sea, is transparent and large of deep less rain as rain comes from the sea eg afghanistan is thousands of miles from sea
explain how a tornado develops
they develop along a boundary where cold air meets moist air and there is violent uplift producing thunderstorms eg Gulf of Mexico and Rockies from west a violently rotating vortex develops from the shearing effect of air streams meeting in an inversion the reason for the spinning effect is not fully understood if this shearing is strong enough, the horizontal cylindrical spiral of air will tilt into a vertical funnel as uplift intensifies, an area of intense low pressure is created the process continues, aided by latent heat transfer, to grow in a vortex of rapidly spinning air descending from a thunder cloud, until it hits the floor
when do powder avalanches occur?
Any time of the year following a heavy snowfall over a partially frozen snow surface
when are tropical storms most hazardous?
when they cross densely settled coasts or islands their effects can be maximised by funnelling into low shelving coasts
perception of risk tropical storms
American Meterological Society of 2014 Residents had a poor understanding of hazards underestimated the potential damage that winds could cause misconstrued the greatest threat as coming from wind rather than water wrong preparation: residents prepared for a modest wind event of short duration BUT NOT significant wind and water catastrophe
what factors cause a landslide
climate eg permeable rock overlying impermeable faults or joints allowing water buildings increase weight deforestation increases infiliytation removal of the foot slope heavy rainfall overwhelming through flow
describe the hazards associated with tropical storms
intense high rainfall up to 125mm recorded usually lasts for 6 hours from the storm centre - results in: extreme flood events, landslides, breaching of levees and slope settlements destroyed - eg hong kong winds of over 250km/hr denote a category five storm on the Safir-Simpson index - results in: structural damage, contribution to the development of storm surges by whipping up waves and driving them on shore storm surges develop from the low pressure, causing a rise in sea levels; wave generation from high winds being driven on shore very hazardous when combined with high tide - results in: costal inundation, especially when low lying (Bangladesh) or on a river estuary (New Orleans) combined with high rain this has a multiplied effect
areas most at risk of tropical storms
caribbean bangladesh SE america
fact about tornadoes in the USA
80% occur here tornado alley especially Kansas Oklahoma Missouri
what is the Coriolis force
force causing the rotation of the Earth
describe the nature of avalanches
generally have a speed of 60km per hour, can be up to 200 classified by: breakaway (single point vs slab movement) the movement of snow pack open slope vs valley powder avalanche (airborne) or flow (ground) tend to occur on slopes over 22 degrees especially north facing slopes as the lack of sun inhibits the stabilisation of snow
IN EFFECTIVE response to a tropical storm case study example
buses government 2008: only permitted some flights and denied visa requests in the background of an isolationist government under military control since 1962 aid only distributed 2 weeks after in May food rations became unsuitable forced UK government it consider forced air drops this is responsible for the $10 billion damage as the hurricane itself was only category 3-4
appearance of tornadoes
small funnel shaped violently rotating vortex e tending down from cumulonimbus clouds vortex in contact with the ground
definition of a tropical storm
a generic term that includes hurricanes cyclones and typhoons low pressure weather system up to 600km/hr in diameter with wind speeds of up to 300km/hr and bringing up to 30-50cm of rainfall
describe the nature of tornados
intense rotating (anti-clockwise) masses of air funnel shaped swirling cloud full of debris and dust extreme wind speeds in excess of 70knots generally 20-40 knots intense precipitation with large hail stones local meteorological hazards (usually less than a km wide) 100-600m the track can extend for km last a few minutes
explain the threat of intense torrential rainfall from tropical storms?
They destabilise slopes bringing about slopes landslides and mudflows particularly hazardous in LIC where shanty towns are located on unstable slopes
conditions for tornado formation
warm air high humidity near ground level fast moving winds about 70 knots about 3k. above ground level travelling in different directions
describe the method of prediction to reduce mass movement hazards
land use planning assessed by evaluating the magnitude and frequency of past mud flows mapping and testing soil and rock this determines their susceptibility to destabilisation Ineffective where they are largely ignored in impoverished areas with informal squatter settlements
describe tornado alley
Mid west USA Oklahoma Kansas Missouri warm moist air from the north from Canada or the rocky mountains
why are he hazardous impacts of tropical storms worse than tornadoes?
power of tropical stones is immense, impact leads to thousands dead and widespread destruction of property death toll of tornadoes rarely reaches hundreds tropical storms affect costal areas that are often densely populated (receiving high winds storm surfers and floods) - lower course of river but tornadoes produce heavy hail storms cyclones have a diameter of 500-800kn whilst tornadoes rarely exceed 10km in path and may only periodically touch the surface BUT wind speed is higher for tornadoes as can reach 500km/hr, double that of tornadoes pressure at the heart of tornadoes is 20% below normal ambient pressure
tornado preparedness case study
apps eg american red cross: allow mobile warnings, including preparedness advice, indictate people are safe advice from FEMA, organisations eg schools of malls identify small windowless room below ground warning sirens tornado drills people in homes or offices should go to pre identified location take cover under a sturdy table
disadvantaged with aid as a response
culture of dependency corrupt distribution system
how fast do slab avalanches travel?
60-80 miles an hour
perception of tornado risk
depends on experience if experienced it is threatening simple and inexpensive enhancements to building codes: 30% less damage Oklahoma frequently experiences damaging tornadoes support for mandatory building codes in this conservative state would be opposed cautious of regulatory action and sceptic about climate change
how can high rainfall be protected against?
leads to flooding and landslides flood control measures can be put in place along rivers deforestation if slopes floodplain management can be developed to protect critical assets; building on slopes can be controlled or prevented Protective river embankments, levees and dukes should be regularly inspected for breaches and opportunities taken to plant mangroves to reduce braking wave energy Vegetation cover can be improved This helps to reduce the impact of erosion and landslides and facilities the absorption of rainfall to reduce flooding
example of LEDC lack of preparedness
$2 million in funding from the UN and a volcano and environmental risk management unit was set up helping experts to train local scientists allowing the volcano to be monitored and eruptions predicted
list of human activities on slopes
deforestation building on or on top of cutting base of slopes mining or quarrying filling large resovirs weapons testing shear stress strength balance affected
what factors cause avalanches?
weather temperature wind direction terrain slope steepness orientation snowpack conditions vegetation mass snow and a slope for it to slide down when the snow pack becomes unstable and layers of snow begin to fall natural avalanches are released
What is a tornado?
A violent destructive weather system with powerful rotating winds up to 300km/h Intense low pressure systems Their development depends on instability in the atmosphere convergence and strong updrafts in the air
natural causes of desertification
long term climate change prolonged drought
tornado perception of risk
depends on experience simple and responsive enhancements to building codes 40% less damage Oklahoma frequently experiences this
describe the distribution of tornados?
80% major tornadoes occur in the USA generally at their most hazardous tornadoes occur widely throughout the world from australia to birmingham
what latitudes do tropical storms occur at
how do slab avalanches occur
slab of compact snow slipping forward requires wind speeds of 16-50km h to maintain movement very cold periods
how do powder avalanches occur
start from a single point accumulate snow as they descend most commonly following heavy snow
definition of a tornado
S violent destructive weather system Powerful rotating winds up to 300km/he Tornadoes are intense low pressure systems and their development depends on instability in the atmosphere convergence and strong updrafts in the air
general explanation for the causes of avalanches?
build up of material until reached critical point where mass overcomes friction often triggered by an earth tremor or sudden rise in temperature loud noises occur best on slopes of 25-40 degrees
when do tropical storms occur in the southern hemisphere?
January to April
tornado prediction case study
no monitoring as events are short and unpredictable 5 satellites orbiting 22,000m above earth taking snapshots of cloud formation doppler radar 10-20 minute notice of the event NOAA issue daily forecasts based on weather observations and forecast models
how does a tropical storm develop
over warm ocean area higher than 26 degrees more than 50m deep 500km both and south of equator 5 degrees in late summer when sea temperatures are at their maximum so moisture and energy enters the system via evaporation where the trade winds converge (NE and SW -NH) developing low pressure the undistrubed upper atmosphere allows the development of massive uplift of cold air is forced to rise rapidly forming cumulonimbus clouds no wind shearing the coriolis forces helps generate strong spinning winds, around the low pressure at the centre of the storm (eye)
prediction of tornaods?
not able to predict the actual path of a tornado; can alert potential of doppler radar uses light sound waves to determine wind direction, looking for intensifying rotation five satellites oribiting 22,000 miles over he earth taking snapshots of cloud formations every few minutes radar watches for rotation inside the storm storm spotters are alerted reporting to the National Weather Service if either indicates a strong tornado threat a warning is issued usually only 10-20 mins in advance
describe the method of draining slopes to reduce mass movement hazards
Drainage pipes - hard engineering Reduce build up of water decreasing water pressure in the soil preventing oversaturation Effective, low cost covering a large volume of ground HOWEVER requires regular maintenance or it’ll become ineffective
explain how cold ocean currents cause deserts
less evaporation any air blown on shore is drier and cooler off coast of peru or chile cold peruvian current
what are the most damaging type of tropical storms?
Category 5 on the Saffir Simpson Scale Wind speeds in excess of 250km per hour Storm surge of more than 5.5m This can lead to extensive damage to property and cause deaths and injuries from flying objects
causes of instability in slope?
inherent: weaknesses in the rock structure, composition of soil caused by heavy rain or snow melt caused by tectonic or seismic activity human triggers: changes to slope angle and form decrease in toe support increased load on the head interference with drainage
how much rain happens every day from a tropical storm
more than 500mm
tornado response case study
2013 mississippi tornado internal response schools were repopened 4 days later buses borrowed from neighbouring school districts 13,000 power outages quickly fixed red cross and salvation army provided shelter local regional ngo and government are swift and effective
effective response to a tornado
2013 Mississippi Tornado coordinated swift effective tornado response local regional and national level with NGOs schools were reopened 4 days after Buses borrowed from neighbouring school districts 13,000 power outages quickly fixed Red Cross and Salvation army provided shelter
explain rain shadow effect?
leeward sides of mountain are driver this is because the prevailing winds from the sea move towards the mountain, clouds pass over mountain and the flat land adjacent had descending dry air eg south america
tropical storm prediction case study example
long term: atlantic caribbean satellite imagery and computer modelling predictions made in April, % probabilities short term: 3-5 days in advance Indian Meterological Agency predicted but nothing done national hurricane centre Miami relies on 2 models, UK and US global models, predict hurricane tract within 80 miles only useful if monitoring is regular eg Hurricane Mitch 1998 100,000 evacuated from Honduras
methods of limiting the hazardous effects of avalanches
reinforcing buildings snow fences tree planting artificially triggering avalanches preventing access to dangerous slopes
ineffective response of a tornado
1996 Bangladesh tornado government underestimated disaster Red Cross not permitted with valuable medical supplies Despite widespread injury 1,000 injured in a 200 bed hospital in Tangail
how can high winds be protected against?
High winds Cyclone or hurricane shelters can be constructed Marked evacuation routes established Along with earnings The removal securing of vulnerable structures
definition of a tsunami
a series of water waves caused by the displacement of a large volume of a body of water, generally an ocean (can be a large lake)
how can storm surges be protected against?
Sea walls can also be constructed but these are not much defence against category 5 hurricanes, warnings given to costa moorings the evacuation of coastal areas
what is an avalanche
a type of mass movement involving the movement of snow and ice downslope under the influence of gravity
reducing the hazard of mass movements
Afforestation Prediction Draining slopes Regarding slopes
describe the method of regrading slopes to reduce mass movement hazards
The slope is shaped into a more stable configuration by flattening it or leaving benches in the slope face The slope could be excavated or filled to produce a gentler slope Ineffective in the case of slopes that are not easy to access as the mechanical means of slope excavation requires machinery
describe the method of afforestation to reduce mass movement hazards
Planting vegetation to remove water through transpiration Reducing overland flow and increasing interception Effective and attractive but can have adverse effects such as reducing biodiversity and taking up space and possibly increase mass movement by adding weight to slope
how large can the central eye be in a tropical storm
tropical storm preparation case study
fox point hurricane barrier 3,000 foot tidal barrier in rhode island national flood insurance program classifies flood zones, into A V B building designs: elevated structure, open foundation and reduced flood risk perception: american meteorological society 2014 noted people conceive greatest hazard to be wind when it is actually WATER
low pressure systems up to 600kn in diameter with wind speeds of up to 300km/hr typically 160km/h rostov around a calmer core eye bringing up to 30-50cm of rainfall