Chapter 5. Introduction to Natural Hazards

Environmental  Geology   Chapter  5    INTRODUCTION  to  NATURAL  HAZARDS     Types  of  Natural  Hazards  (e.g.  Volcanic  eruptions,  Earthquakes,   Floods,Hurricanes,Landslides     Natural  Disaster  -­‐    A  particular  event  in  which  ANY  of  the  following  apply:   q  10  or  more  people  are  killed;   q  One  hundred  or  more  people  are  affected;   q A  declaration  of  emergency  is  issued,  or     q There  is  a  request  for  international  assistance.         The  occurrences  of  natural  disasters  on  a  world  scale  are  increasing;  causing  great  loss  of   life  and/or  property  damage.     Earthquakes,  floods,  cyclones  (hurricanes)  have  killed  several  million  people,  with  an   average  worldwide  annual  loss  of  life  of  about  150,000  people.    The  Annual  average   property  damage  exceeds  $50  billion.     Impact  risks  –  depend  on  the  nature  of  hazards,  spatial  and  temporal  relations  to  human   environment.    Natural  processes  become  hazardous  when:  people  live  or  work  in  areas   where  they  occur,    land-­‐use  changes,  such  as  urbanization  or  deforestation,  there  is  poor   environmental  planning:  Simply  not  to  build  on  floodplains,  earthquake  prone  areas,  and   more  energy  resources  are  consumed  and  climate  changes.     Hazard  Magnitude  and  Frequency     Magnitude:  Intensity  of  a  natural  hazard  in  terms  of  the  amount  of  energy  released   Frequency:  Recurrence  interval  of  a  disastrous  event   Magnitude  and  Frequency:  Generally  an  inverse  relation  between  them  (greater   magnitude=less  frequent)   More  damages  associated  with  hazards  of  moderate  frequency  and  magnitudes     Magnitude,  Frequency,  and  Impact  Risk   • Magnitude  and  Frequency:  Largely  controlled  by  natural  factors   • Impact  risk:  Controlled  by  both  natural  and  human  factors   • Low  magnitude  and  high  frequency  hazards  not  always  destructive,  a  high   magnitude  one  almost  certainly  catastrophic   • Commonly,  most  impact  risks  from  natural  processes  of  moderate  magnitude  and   moderate  frequency     Mixed  Blessings  of  Natural  Hazards   • Not  all  hazardous  processes  exert  harmful  or  deadly  consequences   • Benefits:  Creating  new  land,  supplying  nutrients  to  soil,  flushing  away  pollutants,   changing  local  landscape  (examples:  deposition  of  new  soil/sediment  by  a  flood,  rivers   dammed  by  landslides  create  new  lakes,  volcanic  eruptions  produce  new  land  &  and   soil  nutrients)   • • Death  and  damages:  Great  loss  of  human  life  and  grave  damages  to  property   More  life  loss  from  a  major  natural  disaster  in  a  developing  country;  more  property   damage  occurs  in  a  more  developed  country     Catastrophic  Potential  of  Hazards:      Catastrophes  are  disastrous  situations  requiring  a  long   process  to  recovery  from  grave  damages.     Annual  loss  of  life  from  natural  hazards  in  the  U.S.  (Table  5.1  in  your  textbook)   • Most  lives  lost  each  year  in  the  U.S.  from  tornados  &  windstorms     Hazard  Evaluation  Principles     • Most  natural  hazards:  Identified  and  studied  using  the  scientific  method  and   predictable  from  scientific  evaluation   • Risk  analysis:  A  critical  component  in  understanding  impacts   • Different  hazards  are  linked   • Hazardous  events  are  repetitive   • Importance  of  hazard  planning  and  hazard  mitigation   Hazard  Evaluation:    Done  by  studying  historic  information  and  the  linkages  between   events/hazards.     • Study  historic  data:  Hazards  are  repetitive  events   Ø Occurrence  and  recurrence  intervals   Ø Location  and  effects  of  past  hazards   Ø Observations  of  present  conditions   Ø Measuring  the  changes  or  rates  of  change   Ø Historic  trends  of  hazards     • Studying  linkages:  Spatial  and  temporal  links   Ø Linkages  between  adjacent  locations   Ø Linkages  between  past,  present,  and  future  conditions   Ø Linkages  between  hazards  (e.g.,  volcano  and  mudflow,  hurricanes  produce   coastal  flooding  and  erosion,  earthquakes  produce  landslides  and  tsunamis)   Ø Geologic  setting  and  hazards,  e.g.,  rock  fractures  and  landslides       Disaster  Forecast,  Prediction,  and  Warning   Forecast:  The  certainty  of  the  event  is  given  as  the  percent  chance  of  happening   Prediction:  Sometimes  possible  to  accurately  predict  when,  where,  type  and  size  of  the   certain  natural  hazardous  events   Warning:  A  hazardous  event  has  been  predicted  or  a  forecast  has  been  made,  the   public  must  be  warned     Disaster  Prediction  and  Warning   • Identifying  the  locations  of  a  potential  hazard  (e.g.  global  scale  –  earthquakes  and   volcanic  activity  –  high  potential  at  plate  boundaries)   • • • • Determining  the  probabilities  of  a  hazardous  event  at  a  given  magnitude   Observing  precursor  events  or  signs   Forecasting  the  hazard   Warning  the  public     Case  History:  Hurricane  Katrina  -­‐  Made  Landfall  in  August  29,  2005  to  the  east  of  New   Orleans     • Storm  Surge:  3  to  6  m  (9  to  20  ft)   • Diameter  of  serious  damage  path:  About  160  km  (100  mi)   • 80  percent  of  New  Orleans  under  water   • Official  number  of  deaths:  1,836   • Property  damages:  Tens  of  billions   • Estimated  costs  for  recovering  and  rebuilding:  hundreds  of  billions   • Two  levees  capped  with  walls  collapsed  separating  Lake  Ponchartrain   (connected  to  the  Gulf  of  Mexico)  from  New  Orleans   • Another  levee  failed  separating  the  city  from  the  Gulf    of  Mexico   • Regional  subsidence:  1  to  4  m  (3  to  12  ft)  per  100  yrs   • Sea  level  rise:  20  cm  (8  in.)  last  100  yrs  due  to  global  warming  and  extraction  of   GW,  oil  and  gas   • Geographic  location:  Vulnerable  to  hurricanes,  storms,  and  inland  floods   • Aware  of  risks  and  warnings  in  place   • Insufficient  funds  for  monitoring  and  maintaining  the  levee  and  floodwalls   • Poor  coordination  in  initial  emergency  response  efforts   • Rebuild:  Better  design  and  planning,  better  technology  and  knowledge,  broader   awareness   •   Risk  Assessment   • Risk  determination   Ø Type,  location,  probability,  consequences   Ø Risk  estimate:  Product  of  probability  and  consequences   • Risk  Threshold:  Acceptable  risks   Ø Put  probability  and  consequences  into  perspective   Ø Society’s  perception  and  willingness   • Limitation  and  potential  of  risk  assessment     Risk  Impact:  Hazardous  Earth  processes  and  risk  impact  statistics   for  the  past  two  decades   • Annual  loss  of  life:  About  150,000     • Financial  loss:  >  $50  billion   • More  life  loss  from  a  major  natural  disaster  in  a  developing  country  (e.g.,  2010  Haiti   earthquake,      ~200,000  people  lost)   • More  property  damage  occurs  in  a  more  developed  country         Risk  impact  estimate     • To  human  life:  Potential  loss  and  injury  of  life     • To  property:  Damage  and  destruction   • To  society:  Services  and  functions  of  society   • To  economy:  Manufacture,  mining,  commercial,  real  estate,  etc.   • To  natural  environment:  Direct  or  indirect  adverse  impact     Human  Response  to  Hazards:    Reactive  and  Anticipatory     • Reactive  response   Ø Primarily  after  the  hazardous  event   Ø Recovery  phases:  Response,  rescue,  restoration,  and  reconstruction   Ø Recovery  period:  Recovery  length  depending  on  the  magnitude  of  hazard  and   impact  intensity                  >  Hurricane  Katrina  and  Indonesian  tsunami  recoveries  ongoing  for  years     • Reactive  response  and  recovery  priority   Ø Critical  needs:  Emergency  operations,  critical  infrastructure,  hospitals,   shelter,  food,  and  water  supply     Ø Essential  functions:  Transportation,  communication,  education,  and  other   services   Ø Improvement  and  development:  Rebuild  damaged  structures  and  develop   better  structures     • Anticipatory  Response  (Adjustments):  Response  to  a  hazardous  event  with  an   intention  to  avoid  or  minimize  its  damages   Ø Land-­‐use  planning  (where  you  can  build)   Ø Building  codes  (How  to  build-­‐  e.g.  materials)     Ø Insurance            >  Required  in  dangerous  locations            >  High  rates  in  particularly  bad  locations            >  May  be  unavailable/can’t  build  in  particularly  bad  areas     Ø Evacuation  plans   Ø Disaster  awareness  and  preparedness  (training/drills)   Ø Artificial  controls  (e.g.  sea  walls,  levees  etc.)     All  adjustments  involve  significant  costs  in  time,  manpower,  and  money     Balance  between  preparation  costs  and  the  costs  of  clean-­‐up/recovery  afterward       • General  response  in  a  given  location   Ø Combination  of  reactive  and  anticipatory  response   Ø Artificial  control  of  natural  processes   Ø Taking  no  or  little  action,  being  optimistic  about  chances  of  making  it   through  disasters     Land  use  planning  in  Rapid  City,  South  Dakota  after  flooding  in  1972  resulted  in  creation  of   green  belt  and  relocation  of  residential  areas  outside  the  flood  plain     Direct  Impacts  of  Disasters  on  the  Population   • People  killed,  injured,  or  displaced   • Property  damage  or  destruction   • Infrastructure  damage/loss  of  communication,  utility  services,  and   transportation  systems   Indirect  Effects  of  Disasters  on  the  Population   • Emotional  distress   • Donation  of  money,  goods,  and  labor   • Paying  taxes  to  finance  recovery   Perception  of  Hazards   Societal  perception  of  hazards  is  critically  important   • More  aware  of  hazards  that  occur  often  (once  per  decade  or  more)   • Often  choose  to  just  bear  consequences  of  infrequent  hazards  (once   every  few  decades  to  a  century  or  more),  without  significant   preparations   • Total  risk  associated  with  an  event  is  product  of  event’s  probability  and   the  likely  consequences  should  it  actually  occur   • Population  increase  and  increased  use  of  marginal  or  hazardous  lands   necessitates  increased  land-­‐use  planning  and  disaster  preparedness  or   natural  catastrophes  become  increasingly  common   • Living  in  hazardous  areas,  such  as  floodplains,  is  not  a  sustainable   practice  because  loss  of  life  and  property  will  continue  to  occur     Nevado  del  Ruiz  Volcano  –  Columbia  -­‐  A  story  of  people,  land  use  and  volcanic  eruption   • Eruption  in  1845  –  mudflow  kills  1,000   • Produces  rich  soils  for  farming   • By  1985  –  23000  people  live  nearby  in  Armero   • November  1985  –  Eruption  produces  mudflows  that  kill     • The  real  tragedy  –  one  month  before  –  hazard  map  circulated  and  town   warned  of  potential  disaster     Global  Climate  and  Hazards:    Worldwide-­‐Severe  weather  hazards  are  increasing  (global   warming?)     Population  Growth  and  Natural  Hazards   • In  question:  Population  growth  as  a  cause  for  natural  disasters   • Under  debate:  Population  as  a  direct  trigger  for  some  natural  disasters,  e.g.,  floods,   landslides   • In  certainty:  Population  growing  into  danger  zones,  e.g.,  floodplains     • Trying:  Artificially  controlling  some  natural  hazards   Increase  in  population  puts  a  greater  number  of  people  at  risk   Asia  suffered  the  greatest  losses  from  1985  to  1997,  with  77  percent  of  the  total   deaths  and  45  percent  of  the  economic  losses   • Deadly  catastrophes  resulting  from  natural  hazards  linked  to  changes  in  land  use,   Hurricane  Mitch  in  1998,  flooding  of  the  Yangtze  River  in  1998,  and  Hurricane   Katrina  in  2005     Number  of  natural  disasters  increasing  worldwide.    Hazardous  events  that  were  previously   disasters  are  now  catastrophes  due  to  increased  human  population  and  poor  land  use   practices               • •