4. Where do floods occur?

Usually floods occur along river courses, coastlines and around lakes and dams. Flash flloods can happen almost anywhere. Around the world Floods can occur anywhere around the world.  Records are usually kept of floods that affect the lives of large numbers of people. Large floods along rivers flowing north in Asia or North America/Alaska and affecting huge areas but not many human lives are only reported for information. At the end of the 20th century, the largest floods impacting many human lives usually occurred in the countries of the tropical and equatorial belt, along the main river valleys, or countries with sea or ocean coasts, and very rarely in countries of the temperate belt. As a result of climate change, especially during the last decade, large-scale floods increased in the temperate belt in Europe in Germany, France, Poland, Serbia, the Czech Republic and Hungary, etc. (see Table 4). At the same time, the intensity, frequency and consequences of floods in countries in the tropical and equatorial belt increased, with a significant and ongoing impact on regions in the interior of these countries e.g., Pakistan, Thailand, the Philippines and Indonesia, etc. Climate change produced a combination of a number of flood causes: strong hurricane winds, heavy and continuous rainfall, high tides, unpredicted flash flloods, etc., in a number of countries (e.g. the Philippines, Indonesia, Pakistan, Thailand, Bangladesh, India, Japan, Bolivia, Argentina and Ecuador). In the countries of the temperate belt, the main causes of flooding are usually cyclones and strong winds bordering on hurricane level, etc., which in the past occurred only exceptionally.

At regional level The monsoon rains are an annual cause of seasonal catastrophic floodings, which, in combination with other hazards like landslides, cause numerous victims on a yearly basis (e.g. in the last five years: 60 victims in India in 2015, about 500 victims in India, 57 in Bangladesh and 30 in Nepal in 2017, more than 350 victims in nothern India in 2018, about 200 victims in India, 27 in Pakistan, about 100 in Bangladesh and Nepal in 2019 and , till to middle july 2020, monsoon floods and landslides killed at least 221 people in India, Nepal and Bangladesh (see Fig. 4),

At local level

At local level, floods affecting people’s lives occur most frequently where human activity has taken place without proper assessment, and with no planning or control. The media constantly show reports of high water sweeping through town centres because of illegal, uncontrolled construction, as well as images of huge areas of land flooded as a result of failure to build or maintain hydrotechnical installations. Floods in populated areas are usually the result of a lack of necessary maintenance of existing drainage systems, growth in settlements and low capacity of drainage systems. Floods occur where local authorities fail properly to meet their obligations in terms of construction, maintenance of hydraulic structures, the cleaning of river beds, logging and maintenance of drainage in settlements, etc.

Tab. 4. List of some of the bigger floods occurred in Europe in the decade  2010 – 2020

Year River basins Countries affected Type Causes Fatalities
2010 Vistula Poland Riverine Intense rainfall 9
2010 Danube Slovakia, Serbia, Hungary, Romania, Moldova Riverine Intense rainfall
2010 Several rivers Germany, Poland, Czech Republic Riverine Intense rainfall 6
2010 Sava Slovenia Riverine Intense rainfall 3
2010 Var France Flash flood Intense rainfall 25
2010 Drin Albania Riverine Intense rainfall
2011 Rhine, Oder Germany Riverine Intense rainfall, snow melting 2
2011 Several rivers Ireland, Italy, France Flash floods Intense rainfalls 2 Ireland. 6 Italy, 6 France
2011 Cyclone Berit England Storm surge 0
2011 Ebro Spain Riverine Intense rainfall 2
2012 Several rivers Russian Federation Flash floods Intense rainfall 172
2012 Several rivers United Kingdom Riverine Intense rainfall 9
2013 Elbe, Danube, Vltava Germany, Czech Republic, Austria Riverine Intense rainfall 25
2013 Several rivers Sardinia Riverine Intense rainfall 18
2014 Several rivers Bosnia & Herzegovina, Serbia Riverine Intense rainfall 86
2014 Several rivers Bulgaria Riverine Intense rainfall 16
2016 Several rivers Austria, Belgium, France, Germany, Moldova, Romania Riverine Intense rainfall 20
2016 Vardar Macedonia Republic Flash fllod Rainstorm 21
2018 Several rivers Spain, France, Italy Riverine Flash floods Intense rainfall 13 Spain 16France 36 Italy
2020 Storm Gloria Spain, France Storm surge Riverine floodings  associate to storm 13
2020 Island of Evia, Greece Flash flood High winds Intense rainfall 7
Fig.4. Abc news on people killed by monsoon floods and landslides up to 17 july 2020 in India, Nepal and Bangladesh (source: https://www.abc.net.au/news/2020-07-17/monsoon-floods-landslides-kills-221-india-nepal-bangladesh/12467954 )

Some of the biggest world floods of the last decade of the past century and the first decade of the present century are shown at the table below.
Continent Country River Lake Sea Year Type of flood Causes Injured territory Injured population Victims Economic losses
Thailand South China Sea 2011 Combination – Riverine and Costal Floods Intensive and long Monsoon rainfalls after 3 Hurricanes 300 000 km2 11 Millions p. 600 p. 16 Milliards $
Pakistan Indi 2010 Combination – Riverine, Local drainage and high groundwater levels Monsoon rainfall with Change model 350 000 km2 13,8 Millions p. 1500 p.
Philippines Island 2011 Combination of floods Hard and long Tropic cyclone. Sea tide 300 000 p. 1000 p.
Bangladesh Gang Brahmaputra 1998 Combination – Riverine and Costal Floods Combination – Monsoons and Tropic Cyclone 100 000 km2 70 Millions p. 1300 p.
Bangladesh India Nepal Gang 1993 Combination – Riverine Flooding Costal floods Intensive Monsoons Rainfall 6 Millions p. 3084 p. 8,5 Milliards $
China Yangtze 1998 Riverine flood Intensive rainfall 180 Millions p. 3656 p. 31 Milliards $
1993 11 Milliards $
1995 8 Milliards $
1996 24 Milliards $
South East China 2011 Combination Riverine floods Several Mud flows Intensive and very long rainfall 12 Provinces 5 Millions p. 355 p.
Japan Pacific Ocean 2011 Coastal Flooding Tsunami (Earthquake – 8,9 Richter) 400 km Sea Cost 5 Millions p. 15781 p.
India Several rivers 2005 Rivering flooding Intensive and long Monsoon Rainfall 700 p.
2008 Rivering flooding Intensive early Monsoon Rainfall 1,2 Millions p. 150 p.
2011 Rivering flooding Intensive Monsoon Rainfall 335 p.
North Korea Taedong River 1995 Rivering flooding Intensive rainfall Secondary effect-hunger 300 000 homelles 2 Millions p. 800 p. 15 Milliards $
Indonesia India Ocean 2004 Tsunami wave Earthquake(9,0-9,3) near to island Sumatra 15 countries 1.7 Millions p. 283 000p. (9000 tourists) 14100 p. – disappear 16 Milliards $
USA Mississippi 1993 Riverine flooding Intensive rainfall 9 states 50 p. 21 Milliards $
Texas 2001 Flash flooding, Tropic Storm ”Allison” Intensive rainfall 23 p. 6 Milliards $
New Orleans 2005 Combination Revering floods Hurricane “Katrina” 233 000 km2 1836 p.
West Virginia 1972 Dam break of coal mine 125 p.
Argentina Ecuador Bolivia Several rivers 2008 Riverine floods Intensive and long rainfall – El Nino 150 000 p. 50 p. 16 Milliards $
Brasil Several rivers 2011 Riverine flooding Intensive rainfall 1 35 p.
Venezuela Rio San Julian 1999 Alluvial fan flood Rainfall storm 19 000 p.
Mozambique Limpopo river 2000 Riverine Flooding Torrential rain 1400 km2 800 000 p. 800 p.
The Republic of South Africa Orange river 2011 Riverine flooding El Niño 100 p.
Algeria 2001 Flash Flood, Alluvial fan flood Torrential rain 827 p.
AUSTRALIA Quenensland Floods Fitzroy Burnett Coudamine Ballone Mary 2010 Riverine and Costal flooding Intensive rainfall and strong wind 800 000 km2 200 000 p.

Some of the biggest European  floods of the last decade of the past century and the first decade of the present century are shown at the table below.
Continent Country River Lake Sea Year Type of flood Causes Injured territory Injured population Victims Economic losses
Oder 1997 Riverine Intense rainfall 115 p. 6 Milliards $
2010 Riverine Intense rainfall 80 000 km2 3 Millions p. 9 p.
Germany Rein
2011 Riverine Intense rainfall
Melt of snow
2 p.
Several Rivers 2010 Riverine Intense rainfall 6 p.
England Several Rivers 1998 Riverine Intense rainfall 5 p. 3 Milliards $
2009 Riverine Intense rainfall
Strong Wind
9 p.
2011 Riverine Intense rainfall
France Several Rivers
South France
2010 Riverine Intense rainfall 25 p.
Mallpas-et Dam 2011 Riverine Intense rainfall 3 p.
Several rivers 1959 Dam-break flood Dam break 421 p.
Italy 2000 Riverine Intense rainfall 5 p. 8,5 Milliards $
Vaiont Dam 2004 Riverine Intense rainfall 9 p. 9,3 Milliards $
Ebro 2011 Riverine Intense rainfall 6 p.
1963 Devastating flood Landslide 3000 p.
Spain 2010 Riverine Intense rainfall 3 p.
2011 Riverine Intense rainfall 2 p.