Lazise, Italy. Photo: David Pietralunga.

In a 250-year perspective — 10 generations — flooding is the most common type of natural disaster. More than 50% of all natural disasters are caused by floods. Nearly half of the Earth's population lives close to a coastline. A planner of a new industrial estate, port, village, town or city needs to have knowledge of the historic floods in the area of planning. The more people and the higher investment planned for, the longer record is needed. It is less surprising that floods are so common and costly in the number of drowned people and material losses when we look a little deeper into some different kinds of floods. Floods are often only one part in a long chain of Nature's normal high speed processes.

Sea water inundates land because of

Water in lakes and rivers floods surrounding land areas because of

Land area is sinking, water covers due to

Some of the causes of floods do not recur even once per generation and oftentimes planners are no longer alive when the disaster hits. Politicians and high-level decision-makers involved in city planning must know the historical flooding record to plan correctly and to keep future generations safe. Countries with coasts exposed to stormy seas are in a particular risk zone. The Netherlands, "the Low-lying lands", must be praised for their skills in avoiding flood disasters. When 1/7 of the country was invaded by the North Sea on 2 February 1953, killed >1800 people, destroyed 47,300 residentials, the Sea paid no respect to the Dutch building code for the seawalls constructed to withstand the North Sea floods. In some places the seawater rose 5 m in 15 minutes. In 1953 the water rose 3.8 m higher than ever observed before. A statistical probability analysis shows that the maximum water level of the North Sea could rise another 1.2 m higher than in 1953 once every 10,000 years in a landward gale when it was spring tide. The new barrier was built to withstand such a situation. My database has information about all severe North Sea floods in history. The Dutch have published 3 thick volumes about the floods that have hit the Netherlands in our time. Very few countries have a similar flood resistance safety for their citizens because of lack of knowledge about floods and science in general among their top level decision makers.

Egypt has probably the most complete flood data record in existence for a single river system. The water levels of the Nile have been recorded in writing at Nilometers during 1300 years, but the water levels have been gauged for more than 5000 years. The river is 6670 km long and runs through 11 countries. Its river basin is 1/3 of the size of Europe. What happens in the Nile is important climatically not only for Africa and Europe but globally. In Europe, very few rivers have long written records of water balance — nothing comparablle to the Nile.

China has very long written records of everything. When it comes to floods and drought there are detailed records written through the latest 2000 years even for the individual provinces. But we know that out of the 3106 major floods in our time recorded in China, 51.6% took place in 5 provinces, most of them in Hebei (surrounding Bejing) and Zhejiang (south of Shanghai). It is interesting to note that these two provinces also had the most severe droughts. Zhejiang province also holds the record of floods and droughts per 1000 km2.

The amount of data in my database on the Floods topic is shown in the table below.

FLOODS subregister (pages) 1558
Africa 52
of the 19 entries 5 dominate
Egypt 17
Kenya 7
Tunisia 5
Lakes - Africa 6
Rivers - Africa 3
America Central 12
C America + W Indies 7
Costa Rica 1
Guatemala 1
Puerto Rico 1
America North 67
Canada 2
Mexico 8
USA 56
Rivers - USA 1
America South 11
S America 1
Argentina 2
Chile 1
Paraguay 1
Peru 3
Venezuela 3
Rivers - S America 11
Arctic, Greenland 1
Asia 356
Floods 322 p of which
China 154
Thailand 46
Japan 14
Korea 13
India 13
Vietnam 8
Laos 8
Cambodia 8
Lakes - Asia 14
Lake Aral Sea 6
Lake Black Sea 1
Lake Caspian Sea 5
Lake Dead seas 2
Rivers - Asia 20
Australia - New Zealand 4
Europe 1050
Indian Ocean 1
Mediterranean area 4