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Natural hazards 3-2013


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  • 1. Natural Hazards 3„Nature to be commanded, must be obeyed“ (Francis Bacon, 1561-1626) W. Eberhard Falck 1
  • 2. Naturally OccurringRadioactive Materials (NORM) 2
  • 3. Problem•  A wide variety of geological materials contain radioactive elements and may expose people to radiation•  Elevated NORM concentrations occur in various geological materials of economic importance, e.g. (metal) ores, phosphate rock, coal, ...•  Human activities may lead to enhanced concentrations and/or environmental contamination•  Large amounts of NORM-containing wastes are produced•  Potential long-term hazards from long-lived radionuclides with relatively high radiotoxicities•  Radon in homes is one occurrence of NORM that needs to be controlled 3
  • 4. NORM hazards•  Direct exposure - generally less relevant for general public•  Direct workplace exposure - can be controlled•  Contamination of foodstuff, if grown on contaminated soils or by contaminated fertilisers•  Contamination of drinking waters by contaminated infiltration•  Unuseable aquifers due to elevated radionuclide concentrations•  Dust inhalation/ingestion•  Indoor (or down-mine) radon inhalation•  Delayed exposure due to failing waste containment 4
  • 5. Example: Uranium in natural rocks•  5
  • 6. Natural background radiation•  Cosmic radiation –  Sea level (0 m) – 0.31 mSv/h –  High mountains (3000 m) – 1.35 mSv/h –  Commercial flight (10.000 m) - 19.00 mSv/h•  Terrestrial radiation - depends on the location –  above granitic rocks (e.g. Massif Central) high –  above limestone (e.g. Paris) lower•  Internal radiation due to 40K (potassium, e.g. in bones)•  Sievert (Sv) is the unit for the equivalent dose and is dimensionally a quantity of energy per unit of mass 6
  • 7. Processes that enhance exposure•  Mining, milling and raw materials processing •  Metals • Oil and gas •  Coal • Phosphate •  Heavy minerals • Rare-earth elements •  Clay, ceramics and building materials•  Groundwater pumping and use 7
  • 8. Oil & Gas industry•  Oil & gas wells produce not only these, but also (saline) water•  Production waters contain dissolved Ra that precipitates on pipes, in valves etc.•  These scales are usually removed by high-pressure water-jets or are chemically dissolved•  Scale were discharged into the sea, leading to a noticeable ‘radiation halo’•  International conventions (OSPARCOM, MarPol, etc.) stipulate that scales have to collected and deposited in low-level radioactive waste repositories 8
  • 9. Drinking water treatment•  Some waters contain dissolved U, Ra and/or Rn•  Uranium and Ra accumulate in water treatment sludges and need to be disposed off•  Rn may outgas in water storage reservoirs that may need to be ventilated - risk to water works personnel•  Little risk to water consumers 9
  • 10. Metal mining and milling•  Radionuclides are often associated with metal ores, particularly copper, gold, silver, iron, lead•  The mining and refinement process (milling) can lead to the generation of residues enriched in radionuclides•  Subsequent leaching of these residues by atmospheric agents can lead to the contamination of soils and aquifers•  Human exposure due to contaminated water, soils or ingestion/ inhalation of contaminated dust•  Adequate disposal facilities with long-term care and maintenance (stewardship) are the solution 10
  • 11. Mineral sands and clays•  Heavy mineral sands (monazite sands) can contain considerable amounts of radionuclides such as uranium and thorium•  Mineral sands are a raw material for various industries, e.g. production of refractive (heat-resistant) materials•  Clays can contain considerable amounts of radium or polonium•  When clays are fired, e.g. the polonium accumulates in soot of exhaust chimneys•  In most cases this only causes controllable workplace exposures or waste management issue•  Little risk of exposure to the public 11
  • 12. Indoor radon exposure•  226Rais one of the decay products of 238U that occurs widespread in most rocks and soils•  When 226Ra decays it produces 222Rn, an inert gas with a half life of about 4 days that further decays to solid radionuclides•  When radon is inhaled the decay occurs in the lung and exposes the individual to radiation from the solid daughter products•  Radon levels are high in areas with relatively high uranium concentrations in rocks, e.g. in areas with granites as bedrock•  Radon can accumulate in houses, particulary in basements and when poorly ventilated 12
  • 13. Phosphate fertilisers•  Phosphate ore from various sources (i.e. countries) contains significant amounts of radionuclides that either end up in the product or waste stream Sulphuric acid Rock Gypsum Neutralisatio n Acid treatment Filter Matrix (optio nal) Ra w Aci d 238 U 100 % 232 Th 100 % Gypsum pile 226 Ra 100 % Concentration and 228 Ra 100 % Purification Steps 238 U 70 % 23 8 U 30 % 232 Th 86 % 23 2 Th 14 % Phosphoric acid 226 Ra 20 % 22 6 Ra 80 % 228 Ra 20 % 22 8 Ra 80 % Fertiliser Other production applications 13
  • 14. NORM mitigation measures•  Avoidance at source - choose a different raw material, if possible•  Avoidance at source - buy food from other sources•  Adequate (long-term) waste management strategies and techniques•  Workplace exposure control•  Ventilation of houses in areas with high Rn background Material Source Processing Application Application Effect Original Enchanced Increased Environm. Concentration Concentration Exposure Impact Mitigation Avoid Cahnage Precautions Condition or at Source Process or avoid use Remediate 14
  • 15. Socio-economic impacts•  Generally limited impacts•  Change in working or living practices•  Cost of mitigation measures, e.g. in indutrial processes•  Avoidance of NORM-containing raw materials will have impact on producers•  Indoor Rn mitigation created a market for consultants and retrofitters (ventilation)•  Cost of long-term stewardship for waste management sites 15
  • 16. Exogenic Hazards 16
  • 17. The hydrological cycle 17
  • 18. Water-related processes•  Precipitation - condensed water vapour that falls to the Earths surface as rain, snow, hail, fog drip, graupel, or sleet.•  Canopy interception - precipitation that is intercepted by plant foliage•  Snowmelt - runoff produced by melting snow•  Runoff - the various ways by which water moves across the land; includes both surface runoff and channel runoff•  Infiltration - flow of water from the surface into the ground to become soil moisture or groundwater•  Subsurface Flow - flow of water underground in the aquifers•  Evaporation - state change of water from liquid to gas phases•  Sublimation - state change directly from solid water (snow or ice) to vapour•  Advection - movement of water in the aquifer or in open water bodies•  Condensation - state change of water from vapour to liquid water•  Transpiration - release of water vapour from plants into the air 18
  • 19. Hydrologic balance 19
  • 20. Climate•  The Intergovernmental Panel on Climate Change (IPCC) defines: „Climate in a narrow sense is usually defined as the ‚average weather‘, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. ... These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system.“ 20
  • 21. Global distribution of temperature 21
  • 22. Global distribution of precipitation 22
  • 23. Climate variability vs. climate change•  Variability is random variation around a mean•  Change is a long-term trend•  The climate has been changing at all times, resulting e.g. in ice ages•  The triggers and mechanisms for these changes are not yet very well understood•  Both phenomena are difficult to deconvolute 23
  • 24. Example: extreme year vs. long-term pattern•  Comparison of one extreme year with average climatic pattern•  Such extremes can be very disruptive to economic activities 24
  • 25. El Niño and La Niña•  A change in the Pacific circulation patterns that occurs about every 2 to 7 years•  As the Pacific Ocean is an important heat reservoir, the phenomenon has global climate effects•  The first signs of an El Niño event are: –  Rise in surface pressure over the Indian Ocean, Indonesia, and Australia –  Fall in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean –  Trade winds in the south Pacific weaken or head east –  Warm air rises near Peru, causing rain in the northern Peruvian deserts –  Warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.•  El Niños warm current of nutrient-poor tropical water replaces the cold, nutrient- rich surface water of the Humboldt Current•  When El Niño conditions last for many months, extensive ocean warming occurs and its economic impact to local fishing can be serious 25
  • 26. Anthropogenic climate change ?•  In recent years certain changes in climatic features have been observed on a global scale –  increased average temperatures –  increased local rainfall –  higher frequency of storm events•  The change in these features has been correlated with changes in atmospheric properties, e.g. the CO2-content•  The change in these features has been attributed to anthropogenic influences•  It is, however, not (yet) possible to establish a mechanistic cause-effect relationship between the observed changes•  Rapid climate changes can have natural causes, such as volcanic eruptions, changes in the Earth’s orbit, solar output variations•  There are many back-feed mechanism that are not well understood•  It is prudent to apply the pre-cautionary principle and try to limit GHG emissions 26
  • 27. Extreme weather events•  Average, long-term conditions for most places on the Earth are quite well known•  Longer-term trends are more difficult to predict due to global interconnectedness•  Human perception and actual data-supported facts may deviate considerably•  Events perceived as extreme, may well be within the natural variability range 27
  • 28. Weather-related Hazards•  Storms•  Tornados / typhoons / hurricanes•  Ligthning•  Heavy rainfall•  Droughts•  Sand storms•  Hail•  Snow 28
  • 29. Weather forecasting•  Originally based mainly upon observing in barometric pressure, current weather conditions, condition and manually drawing maps•  A dense network of ground-based, air-borne and satellite-borne observation stations exists that can relay real-time data•  These data are used to calibrate and feed numerical atmospheric and ocean circulation models•  Ocean surface temperatures can be predicted over several months•  Human input is still required to pick the best possible forecast model, which involves pattern recognition skills, knowledge of model performance and model biases•  The chaotic nature of the atmosphere and an incomplete understanding of atmospheric processes mean that forecasts become less accurate for longer periods into the future 29
  • 30. Forecasting limitations•  Temperature distributions, wind directions and strengths can be reasonably well predicted over a few days in not too unstable weather conditions•  The actual local occurence and streghts of rainfalls is still difficult to predict•  Local weather conditions may vary considerably as a function of the topography and, hence, maybe difficult to predict in more mountainous terrain•  Predictions of general conditions during a season (e.g. „will it be a nice summer ?“) are still very uncertain•  For this reason predictions of droughts or flooding events are difficult 30
  • 31. Wind and storms•  raise, when a center of low pressure develops, with a system of high pressure surrounding it•  this combination of opposing forces can create winds and result in the formation of storm clouds•  storm is a wind measuring 10 or higher on the 0-12 Beaufort scale, i.e. a wind speed of 24.5 m/s (89 km/h) or more•  metereologist can predict storms in principle over a period of 2 to 4 days, but their actual strength and movement is difficult to predict 31
  • 32. Tropical cyclones: typhoons and hurricanes•  are names for similar phenomena in the NW Pacific and the tropical Atlantic•  the primary energy source is the release of the heat of condensation from water vapor condensing at high altitudes•  warm tropical waters and solar heating are the main drivers 32
  • 33. Distribution of tropical cyclones 1985-2006•  33
  • 34. Has the number of cyclones increased ?•  there appear to be cycles of cyclonic activity•  the risk of tropical cyclones increases with increasing sea surface temperatures•  if there is an (anthropogenic) global warming this may also increase the risk of tropical cyclones 34
  • 35. Tornados•  A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud•  Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust•  Most tornadoes have wind speeds less than 180 km/h, are approximately 80 m across, and travel a few kilometers before dissipating.•  The most extreme can attain wind speeds of more than 500 km/h, stretch more than 3 km across, and stay on the ground for more than 100 km. 35
  • 36. Tornado formation•  They often develop from thunderstorms - ‚supercells‘.•  Supercells contain mesocyclones, an area of organised rotation a few km up in the atmosphere, usually 2–10 km across.•  Most tornados follow a life cycle that begins when increasing rainfall drags with it an area of quickly descending air.•  This downdraft accelerates as it approaches the ground and drags the supercells rotating mesocyclone towards the ground.•  As the mesocyclone approaches the ground, a condensation funnel appears to descend from the base of the storm.•  Initially, the tornado has a good source of warm, moist inflow to power it, so it grows until it reaches the ‚mature stage‘ that can last from a few minutes to more than an hour, and during that time a tornado often causes the most damage. 36
  • 37. Tornado occurence•  37
  • 38. Common forms of tornadosWaterspout Dust devil 38
  • 39. Effects and impacts•  storm damage to crops, houses, infrastructure•  damage and injuries due to flying debris•  storm surge and large-scale inundation (re. ‚Katrina‘) lead to severe damage•  inundation and resulting standing waters promote tropical diseases such as malaria or dengue fever•  crowded shelters promote disease propogation 39
  • 40. Sandstorms•  Can be extremely disruptive to social and commercial life•  Damage infrastructure - engines, airconditioners, industrial plant, ...•  Cause or aggravate health problems (eyes, respiratory system) 40
  • 41. Desertification•  is the degradation of land in arid and semi-arid areas•  usually has complex climatologic as well as anthropogenic causes•  plant loss due to droughts, overgrazing, salinification etc. result in topsoil loss, which results in further plant loss•  overpopulation of wild or domestic animal species results in overgrazing and topsoil compaction•  anthropogenic causes also include unsuitable agricultural practices, e.g. to leave barren fields or wrong plowing techniques promote topsoil erosion•  since the Holocene deserts have been growing and diminishing - e.g. the Sahara once was a fertile savanna and Tunisia the ‚corn chamber‘ of Rome•  over the last century there has been a significant increase of desert 41 areas e.g. in the USA, Africa and China
  • 42. Desertification - impacts•  loss of pasture and arable land•  loss of biodiversity•  dust storms cause impacts in other regions•  displacement of populations•  conflicts over remaining land-use 42
  • 43. Droughts•  a serious deviation from the average precipitation pattern is usually damaging to the local vegetation including farm crops•  a vicious circle: droughts can lead to increased erosion due to loss in vegetation, which in turn makes it difficult for vegetation to re-establish•  result in a lack of groundwater recharge•  promote wild-fires 43
  • 44. Lightning•  an atmospheric discharge of electricity•  the exact mechanisms are still being debated•  lightening is a major cause of forest fires in some parts of the world•  In e.g. the UK 30-60 people are struck per year and about 3 killed•  Disruptive to electricity supply and electronic comunication and control systems 44
  • 45. Lightning - frequency of strikes•  45
  • 46. Precaution•  Avoid wide, open spaces or exposed hilltops and dont shelter beneath tall or isolated trees. Seek shelter inside a large building or a motor vehicle.•  If you are swimming, windsurfing or sailing, get to the shore as quickly as possible.•  If caught out in the open during a thunderstorm, stop carrying umbrellas, fishing rods, golf clubs and other large metal objects. Keep away from metal objects such as motorcycles, golf carts, bicycles, wire fences and rails•  If your hair stands on end or nearby objects begin to buzz, move quickly away as lightning may be about to strike. These effects happen because the positive electrical charges forming at the ground are streaming upwards to try to make contact with the advancing downward negatively- charged leader‘.•  If caught out in the open with no shelter nearby, move to a place of lower elevation, such as a hollow or dry ditch. Crouch down with both feet close together. Do not place your feet wide apart or lie flat on the ground as this will increase the difference in voltage across your body, increasing the electrical charge you may receive from radial ground currents.•  When indoors, keep away from windows, avoid touching metal pipes or radiators. If lightning strikes a television aerial, the cable may conduct the current into the building, where it can jump to other wiring or metal piping circuits. Do not use a fixed phone except in an emergency.•  Give first-aid (and contact paramedics promptly) to anyone struck by lightning to help them recover. 46
  • 47. Lightning protection•  The lightening conductor was invented by Benjamin Franklin in 1749.•  It‘s exact functioning and best layout is still being debated scientifically•  The conductor usually takes the form of pointed rods mounted on the highest point(s) of the object to be protected (house, ship, etc.) and connected to a grounding rod in the soil or water 47
  • 48. Atmospheric precipitation hazards•  Typical forms are rain, sleet, hail or snow•  Long duration or high intensity of precipitation events may cause problems, when they exceed the design-base of infrastructure –  gutter/storm-water drainage capacity –  snow-load on roofs –  strength of roofing material in case of hail•  Physical exposure to such conditions 48
  • 49. Hail•  Hail is a form of solid precipitation that consists of balls or irregular lumps of ice - hail stones•  Hail stones consist mostly of water ice and measure between 5 and 150 millimeters in diameter•  Hail formation requires strong, upward motion of air with the parent thunderstorm and lowered heights of the freezing level•  Hail stones grow while circulated in the updraft until their weight exceeds the carrying capacity of the air flow 49
  • 50. Hail - hazards and impacts•  Hail can cause serious damage to automobiles, aircraft, skylights, glass- roofed structures, livestock, and most commonly, farmers crops•  Hail can accumulate to snow-drift like features•  Hail knocks off leaves from trees that block gutter leading to flooding 50
  • 51. Hailstorms•  51
  • 52. Hail - forecasting and detection•  Hail is associated with severe thunderstorms•  Doppler weather radar is a very useful tool to detect the presence of hail producing thunderstorms 52
  • 53. Rain•  The intensity (mm/time) is measured by rain gauges of various designs•  It can range from light (<2.5 mm/h) to violent rain (50 mm/h)•  1 mm is equivalent to 1 dm3/m2•  The wettest regions receive on average up 11 m annually, with a maximum of up 26 m in wet years•  100 year rains are events the have a statistic recurrence of 100 years 53
  • 54. Rain - impacts•  The fallen rain drains as surface run-off, interflow and infiltration•  Dry soil absorbs rain until it reaches ist saturation point•  More rain can only be absorbed as infiltration proceeds, excess water is shed as interflow and surface run-off•  Water-loged soils are more prone to erosion and mud-flows than dry soils•  Surface run-off quickly reaches surface water courses and can lead to high-waters and flooding•  Too high rainfall intensity can exceed the design capacity of storm drainages and lead to flooding of urban areas•  Prolonged rainfall, resulting in water-logging can damage crops 54
  • 55. Snow•  Precipitation in form of crystalline water ice•  Snow crystals form when tiny supercooled cloud droplets (~10 µm in diameter) freeze•  On the ground snow properties can range from powdery to slushy, depending on the temperature and temperature history•  The Inuit have several dozen terms for different types of snow 55
  • 56. Snow - impact•  Powder snow can be piled up to drifts several metres high by wind - road/rail blockages•  Beyond-design snow-loads can make collapse buildings and other infrastructure - monitoring and removal is required•  Heavy snow-loads can bring down trees - commercial loss, road/rail blockages•  Snow can block ventilation and other ducts - see Eurostar•  Snow can form avalanches 56
  • 57. Blizzards and ice storms•  wind driven snow and freezing rain can cause widespread and long-lasting disruption to the functioning of infrastructure and traffic•  exposure of unprepared human, e.g. in immobilised vehicles•  disruption of power supplies can cause significant economic damage•  untimely events can damage crops 57
  • 58. Avalanches•  58
  • 59. Common features of avalanches•  The basic feature of all avalanches is that shear forces exceed the cohesive forces by which a snow mass is attached to the surrounding snow or the ground•  Certain conditions promote the formation of avalanches: –  a wet, then frozen ground without initial snow cover provides a shear-plane –  partially melted and then re-frozen snow surfaces provide a shear-plane for freshly fallen snow –  a certain minimum steepness of the slope of about 30° –  certain types of snow composition 59
  • 60. Types of avalanches•  Powder-cloud avalanche –  dry snow suspension created by turbulence –  can move at speeds of up to 300 km/h –  can create strong, devastating pressure waves•  Dense flow avalanche –  primary motion is by flowing, gliding, slipping•  Slab avalanche –  sheets of snow get into motion and break up during the course•  Ground avalanche/full-depth slab avalanche –  involves the whole snow pack –  erodes the underlying soil•  Full-depth snow-slide –  creeping movement of the whole snow pack•  Ice avalanches –  ice breaking off steep glaciers, can evolve into powder-cloud a. 60
  • 61. Mitigation and prevention•  Certain slopes are known to produce avalanches every year and can be avoided•  Tradtionally, forests provided protection of settlements in the valley and were protected accordingly•  Artificial barriers (e.g. snow fences) can be used to retain and break up avalanches•  Controlled triggering of avalanches by blasting/bombarding•  Protection of railways and roads by galleries and tunnels•  Avoiding of skiing/snowboarding/hiking in avalanche-prone terrain 61
  • 62. Avalanche survival•  Survival depends on the type of avalanche, burial depth and time of burial•  90 % survival, if freed within 15 min•  30 % survival, if freed within 30 min•  0% survival, if freed after 45 min•  Death occurs due to asphyxiation because either wet snow compacts the lungs, or oxygen runs out•  With sufficient oxygen supply death occurs due to hypothermia•  In powder avalanches death can also occur by aspiration of snow and freezing of the lungs•  Conclusion: avoid off-piste skiing/hiking in avalanche-prone terrain = hazard avoidance is better than mitigation ! 62
  • 63. Next sequence•  Glacier-related hazards•  Flooding•  Landslides / Rockfalls 63