Introduction to Natural Disasters

MODIFIED:

POSTED: 16 September 2024

• What is a Natural Disaster?

• event of a natural cause with high death rate or extensive destruction
• event of a natural cause that has a negative impact on the environment
• event of a natural cause with low death rate but occurring often
• a natural trend that has negative long-term consequences

An example of a costly and devastating natural disaster was Hurricane Ike, an Atlantic hurricane in 2008 that reached well into the continent. In more recent times, in 2011, relatively weak Hurricane Irene traveled along the U.S. east coast and affected millions of people. And after 2005 Hurricane Katrina, Superstorm Sandy in 2012 has been the second-most costly natural disaster.

Not all large hurricanes make the news. An example of a truly remarkable hurricane that did not make the news (because it did not kill nor destruct human construction) was Ioke in 2006. Ioke crossed the northern Pacific Ocean in August 2006, passing Johnston Atoll and Wake Island but did not affect permanently inhabited areas. Some residents of Wake Island evacuated. It was the first category 5 and thereby the largest hurricane that ever formed in the Central Pacific Ocean. See the back end of a news clip to get info and link to satellite image.

• Some Obvious Natural Disasters

These include mostly sudden events
• earthquakes
• volcanic eruptions
• landslides and other mass movements (e.g., mudflows, cave collapses)
• floods (flash floods but also longer-lasting floods such as from prolonged rain)
• wildfires
• severe storms (e.g., involving strong winds, heavy precipitation, lightning)
• hurricanes
• tornadoes
• impacts of space objects

• Why Study Natural Disasters?

Effects of Natural Disasters
• natural disasters kill, destroy, cost (prevention, relief efforts and rebuilding)
• costs have increased exponentially over last 50 years
• the gap between losses and insured losses increases

Natural Disasters and Human Interaction
• humans can mitigate disaster risks (e.g. build EQ proof houses; build strong retaining walls)
• humans can increase disaster risks (e.g. build along EQ faults; build on foot of unstable slope)
• humans can enhance effects of natural disasters (e.g. building wrong flood control channels enhances a flood; emission of CO₂ and pollutants enhances climate change)
• humans can trigger natural disasters (e.g. inappropriate drainage can trigger landslides; mining can trigger earthquakes)

The Need to Understand Natural Disasters
• need to understand process involved
• improve identification of risks
• improve prevention of losses (lives and structures)
• improve forecast and evacuations
• increase effectiveness of disaster relief (fight rising costs)

• Some Not so Obvious Natural Disasters

These events may happen slowly
• droughts and extreme weather (e.g., heat waves and cold snaps)
• global warming and cooling
• changing sea level
• coastal erosion
• spread of (new) diseases (e.g. SARS, Ebola)
• shift in resident species (e.g., cutting off food chain)
• solar storms (affecting power grid; rare events but of increasing concern to the developed world, especially the U.S.)

• Worldwide Cumulative Fatalities due to Natural Disasters between 1947-1980⁽¹⁾

	Earthquake	Tsunami	Volcanic Eruption	Flood	Hurricane	Tornado	Other Severe Weather	Mass Movement	Total
# Killing Events	180	7	18	333	210	119	147	45	1059
Fatalities by area
North America	77	60	96	1633	1997	4568	5003	323	13,757
Caribbean and Central America	30,613	-	151	2575	16,541	26	510	260	50,676
South America	38,837	-	440	4396	-	-	340	5262	49,275
Europe	7750	-	2000	11,199	250	39	6816	640	28,694
Asia	354,521	4459	2805	170,664	478,574	4308	34,403	4356	1,054,090
Africa	18,232	-	-	3891	864	548	5	-	23,540
Oceania	18	-	4000	77	290	-	117	-	4502
Totals	450,048	4519	9492	194,435	498,516	9489	47,194	10,841	1,224,534

• most frequent event: floods (333 events)
• highest number of fatalities: hurricanes (498,516 deaths) and earthquakes (450,048 deaths)
• lowest number of fatalities: tsunami (4,519)
  but then the Dec 26, 2004 Sumatra earthquake tsunami killed 245,000 people, making tsunami more fatal than floods in general (194,435 deaths from 1947-1980)
• area with highest death rate: Asia (1,054,090) (high population density)
• area with lowest death rate: Oceania (4,502); North America (13,757)
  somewhat surprisingly, Africa has the third lowest number of fatalities from natural disasters though starvation due to droughts is not included in this comparison

• The Deadliest Events between 1970-2011

Area	Time	Event	Fatalities
Bangladesh	11/14, 1970	Tropical Cyclone1	300,000
China	07/28, 1976	Tangshan Earthquake	255,000
Haiti	01/12, 2010	Earthquake	222,570
Indian Ocean	12/26, 2004	Sumatra-Andaman Earthquake	220,000 (most from tsunami)
Myanmar (Burma)	05/02, 2008	Tropical Cyclone Nargis	138,300
Bangladesh	04/30, 1991	Tropical Cyclone Gorky	138,000
China	05/12, 2008	Sichuan Earthquake	87,449
Pakistan	10/08, 2005	Earthquake	73,300
Peru	05/31, 1970	Nevados Huascaran Earthquake and Landslide	66,000
Russia	06/15, 2010	Heat wave and peat fires	55,630
Iran	06/21, 1990	Gilan Earthquake	40,000
Europe	06/01, 2003	Heat wave	35,000
Iran	12/26, 2003	Bam Earthquake	26,271
Armenia	12/07, 1988	Earthquake	25,000
Iran	09/16, 1978	Tabas Earthquake	25,000
Colombia	11/13, 1985	Nevado del Ruiz Volcanic mudslide	23,000
Guatemala	02/04, 1976	Earthquake	22,084
India	01/26, 2001	Gujarat Earthquake	19,737
Japan	03/11, 2011	Tohoku Earthquake	19,184
Turkey	08/17, 1999	Izmit Earthquake	19,118

¹A cyclone in the Indian Ocean is the same phenomenon as a hurricane in the Atlantic or East Pacific.
This table is compiled from data provided by Swiss Reinsurance Company.
Things that we learn from this table:
• single-event hurricanes/cyclones and earthquakes are major killers
• high fatality rates in areas with high population density
• this is not necessarily a developing country (e.g. Africa is missing from this table)
• To put this into perspective of what humans can do:
  WW II claimed 73 Mio lives (61 M to allies; 12 M to axis), according to Wikipedia on WW II .
  By January 2008, the Iraq War had cost more than 1,000,000 lives, according to the Opinion Research Business survey.

• The Most Costly Events between 1970-2012 (insured losses)

Area	Time	Event	Cost in Billion $	Fatalities
USA	08/25 2005	Hurricane Katrina	74.7	1,836
USA4	10/29/ 2012	Superstorm Sandy	> 68	288
Japan1	03/11 2011	Tohoku Earthquake	35	19,184
Pakistan2a	08/29 2010	Floods	43 (econ. impact)	??
USA	08/23 1992	Hurricane Andrew	43	25.6
USA	09/11 2001	terrorist attack3	21.2	2,982
USA	01/17 1994	Northridge Earthquake	21.2	61
USA	09/13 2008	Hurricane Ike	21.1	136
USA	09/02 2004	Hurricane Ivan	15.4	124
USA	10/19 2005	Hurricane Wilma	14.5	35
USA2b	08 1993	Mississippi Flood	12	48
Thailand	07/27 2011	Monsoon Floods	12	813
New Zealand	02/22 2011	Earthquake	12	181
USA	09/20 2005	Hurricane Rita	11.6	34
USA	08/11 2004	Hurricane Charley	9.6	24
Japan	09/27 1991	Typhoon Mireille	9.3	51
USA	09/15 1989	Hurricane Hugo	8.3	71
Chile	02/27 2010	Earthquake	8.2	562
Europe	01/25 1990	Winter Storm Daria	8.0	95
Europe	12/25 1999	Winter Storm Lothar	7.8	110
USA	04/22 2011	severe storms/tornadoes	7.3	354
USA	05/20 2011	severe storms/tornadoes	7.1	155
Europe	01/18 2007	Winter Storm Kyrill	6.6	54

¹Total losses exceed $200 billion, making this the costliest natural disaster.
^2anot listed at Swiss Re. Total economic impact.
^2bnot listed at Swiss Re. Majority not insured.
³this is not a natural disaster but puts things into perspective, regarding costs and well as fatalities..
⁴from wikipedia 26 Sep 2013.
This table is compiled from data provided by Swiss Reinsurance Company, and more recent data.
Things that we learn from this table:
• until 2010, the 10 costliest events occurred in the U.S., one of them man-made
• 5 of these 10 events occurred within only 15 months (Aug 04 - Oct 05); the year 2006 was relatively "quiet"
• most of the costliest disasters were hurricanes though major flood events were also very costly
• Again, to put this into perspective, as of 2010, the war in Iraq has cost over $ 3 Trillion (3000 Billion or 3 Million Million).


NB: The most costly natural disaster in S.D. county was probably the 26 October 2003 Cedar Fire Paradise. It was started by a lost hunter who ignited a signal fire. The Cedar Fire, together with the Paradise and Otay fires that burned on the same weekend was the second largest wildfire in the history of CA (after the Great Fire of 1889). These three fires burned 350,000 acres, claimed 15 lives and destroyed 3500 buildings worth $1.2 billion; these fires were closely followed in significance by the Witch Creek, Rice and Poomacha fires in 2007.

• Average Annual Death Rates Due to Severe Weather in the U.S.¹

Type	(1940-2021)	(1992-2021)	(2002-2021)	(2012-2021)
	82 yr ave	30 yr ave	20 yr ave	10 yr ave
Lightning	115	37	30	23
Flood	103	86	86	94
Tornadoes	96	71	78	49
Hurricanes	34	26	32	12x
Heat waves	-	148	112	105
Cold snaps	-	30	32	38
Winter Storms	-	34	26	29
Wind	-	48	51	57
Rip currents	-	-	57	69
Wildfires	-	7	12	22

^*Data not available over complete time span.
¹This table shows long- and short-term averages.
^xDoes not include death toll in Puerto Rico from 2017 Hurricane Maria.
The numbers are compiled using Hazstats data from the National Weather Service (NWS). Note that the #1 killer depends on the time span over which data are available, i.e. lightning has been the long-term top killer (80 yr average), but the recent short-term killer is heat. This is because of a dramatic (exponential) long-term decline in lighting deaths, see below.

	Floods: The impact of single events in the mid-1950s and around 1970 has been declining and so the average fatality rate from floods has been declining. The background yearly fatality rate is not declining, however, and may in fact be increasing.
	Hurricanes: Recent averages of deaths from hurricanes are much higher than the 72-year long-term average, because they are dominated by the fatalities of Hurricane Katrina in 2005. On the other hand, the 6000 fatalities of the 1900 Galveston, TX Hurricane increase a 1900-2011 long-term annual death rate by 54! It is therefore important to consider over what time period the data have been collected and if there have been single major events. A long-term average is usually a best estimate for a "typical" average because a single catastrophic event does not dominate the statistics.
	Lightning: The death rate due to lightning strikes is intriguing. The typical annual death rate has actually gone down by a factor of 10 (from 400 to 40) since the 1940s. The long-term average is therefore controlled by high death rates in the earlier 1900s. This is presumably because there were many more people outdoors during thunderstorms than nowadays. Taking single events not into account, it is still true that more people die from lightning strikes than from hurricanes but, perhaps surprisingly, heat waves are now the #1 killer in the U.S..
	Tornadoes: A rather disturbing fact is that the number of tornado deaths have not declined over the past 30 years, after a marked decline in the late 1970s. In fact, the average fatality rate has increased over the last 3 decades (see table) though this is due to the fact that the impact of the particularly deadly year 2011 increases the average! A subtle increase in annual fatalities (see figure) could be caused by an increase in more powerful tornadoes though there is currently no convincing evidence to support this idea. But another reason could be that people have become complacent and do, in fact, no longer build tornado shelters. One reason being that such shelters add to the construction price of construction price of a new home.
	The Tri-State Tornado in 1925 has been the deadliest single tornado in U.S. history, with 695 people losing their lives. An additional 52 people lost their lives in other tornadoes during the 18 March 1925 tornado outbreak.
	Heat waves: Records on fatalities from heat waves go back only to 1986. A single event in 1995, the Chicago Heat Wave, dominates recent statistics. However, more people die from heat in recent years than 20 years ago. The big worry is that the trend may be increasing. Over the last 30 years, heat waves have been the #1 killer in the U.S., with floods being a distant second. In the last 20 years, more people died from heat waves than from tornadoes and floods combined.

• Billion-Dollar Losses in the U.S. (1980-2003)

• Heat waves/droughts: 144
• Hurricanes: 102 (before Katrina)
• Floods: 55
• Cold-weather storms: 28
• Wildfires: 13
• Tornadoes: 7
This table is compiled from data provided by Munich Reinsurance Company.

• Lightning, Heat Waves, Tornadoes and Statistics - Things that we learn from all this

• in the long term, lightning has been the #1 killer in the U.S. but the fatality rate has declined exponentially
• single catastrophic events, such as Hurricane Katrina, may dominate short-term averages, causing an apparent increase in average fatality
• more people in the U.S. die from heat than from severe cold (at least 5 times more!)
• over the last 30, 20 and 10 years, heat waves have been the #1 killer
• even not counting the particularly fatal year 2011 deaths from tornadoes have increased over the last 20 years!
• not counting Hurricane Katrina as single event, on average, heat waves and droughts are the costliest natural disasters in the U.S.

• Heat Waves and the Elderly

	In 2004, a year without heat waves the 60-90 age group accounted for 21% of the people dying from severe weather. In 2006, a year with heat waves, they accounted for 34%. Elderly people cope with heat less well than younger people. Older people, especially those living on a limited budget, also may not have air conditioning in their houses.
	A particularly troubling heat wave occurred in 1995, almost exactly 10 years before Hurricane Katrina devastated New Orleans. The Chicago Heat Wave July 12-16, 1995 claimed more than 1000 lives, and there are remarkable parallels to the Katrina disaster: increased fatalities among elderlies increased fatalities among poor people who lived in sub-standard housing increased fatalities among Black people lack of preparedness/overwhelmed emergency facilities Aggravating factors included: temperature inversion trapped heat, humidity (natural causes) and polluted air near ground (human cause) urban heat island effect (human causes): paved ground retains heat during night lacking vegetation prevents release of cooling water at night during respiration/evaporation A/C cools interior of buildings but heats environment poor people had no A/C or no money to use A/C overloaded power grid failed causing power outages overtaxed emergency facilities had to turn people away people afraid of crime did not open doors and windows (during the heat wave of the 1930s, people left windows open at night to cool homes or slept outdoors) Check out entry at Wikipedia.org.
	Heat waves may always have been a major killer but no long-term data are available at the NWS to test this. However, typical annual numbers have increased by a factor of four since the late 1980s (from 40 to 160). One could argue that the increase in heat-related deaths is a consequence of global warming but this hypothesis is difficult to test due to the lack of earlier data. Climate also has not change uniformly over the last 100 years. In fact, the 1970s were unusually cold. We will revisit this topic in lectures 15 and 23 on global climate change.

• Severe Weather - An all too common natural disaster

On average, severe weather causes the most fatalities of all natural disasters. Tragically, some fatalities may be avoidable.

For example, the weekend of September 23, 2006 brought severe weather to the Midwest (Missouri) and South (Kentucky and Arkansas), with 8 fatalities by Sept 24 (12 by Sep 25). Of these 8, 1 was killed by a tornado, 1 was traffic related in heavy rain, 1 person was killed by lightning and 5 people died by flooding. All of these 5 people died in cars while the driver tried to cross a creek or other flooded regions. Trying to cross flowing water is dangerous! This includes creeks and flash flood areas in the desert.
1. The water may be deeper than expected.
2. The current of even shallow water can be strong and can carry cars away.
3. Once the water reaches the exhaust pipe of a car, the engine stops running and people are trapped.

• Recommended Reading

• ⁽¹⁾"Natural Disasters" by Patrick Abbott, 7th edition, 2009.
• "Heat Wave, a social autopsy of disaster in Chicago" by Eric Klinenberg; ISBN: 978-0226443225; list price: $15. This book describes the weather conditions during the July 1995 "Chicago Heat Wave" and what factors contribute to the disasters like this one. It discusses why so many people died and provides demographical insight into this particular event. It also tries to convey what it was like during this crisis.

• Additional Resources

study guide to book chapter 1
not-for-credit online quiz for practice testing (do not request edit access!)

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• Five Random Review Questions

1) Which area experiences the highest number of fatalities caused by natural disasters?
1. Africa
2. Europe
3. Asia
4. Australia
5. North America
2) Which area has experienced most of the most costly natural disasters?
1. Japan
2. Europe
3. China
4. U.S.
5. Africa
3) In the U.S., on average, more people die from extreme cold than from extreme heat?
1. true
2. false
4) Which of these is NOT a natural disaster?
1. earthquake
2. volcanic eruption
3. hurricane
4. 9/11
5. sea level rise as a result of global warming
5) Over the last 20 years, which of these natural disasters killed the most people in the U.S.?
1. hurricanes
2. floods
3. earthquakes
4. wildfires
5. heat waves


Answers: 1c; 2d; 3b; 4d; 5e