By the end of the decade, scientists predict a sharp increase in the number of people at risk of flooding.
In a new study, Cloud to Street employees use satellite observations to find that the population in areas with a high risk of flooding has increased.
Basically, the authors of the work note demographic and financial reasons: housing in areas with a high probability of flooding drops in price, so poor people settle there, and it so happens that due to overpopulation, it is not possible to choose another housing. This trend is observed in several countries at once and, presumably, their number will only increase.
Vulnerable populations often have no choice but to settle in inundated areas.
According to them, from 2000 to 2018, floods affected 2.23 million square kilometers worldwide, affecting 255 to 290 million people. At the same time, almost 90% of floods occur in the countries of South and Southeast Asia.
In addition, a similar trend is seen in southern Latin America, the Middle East and sub-Saharan Africa.
The most common causes of flooding are heavy rainfall, tropical storms and melting snow and glaciers. Dam breaks account for only 2% of all floods, but they tend to cause the most damage.
The authors of the study suggested that by 2030, floods will affect the population of 25 more countries.
Flood types:
Areal
Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope.
Riverine (Channel)
Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the world’s largest rivers. When overland flow occurs on tilled fields, it can result in a muddy flood where sediments are picked up by run off and carried as suspended matter or bed load. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, or beaver dams.
Estuarine and coastal
Flooding in estuaries is commonly caused by a combination of storm surges caused by winds and low barometric pressure and large waves meeting high upstream river flows.
Coastal areas may be flooded by storm surges combining with high tides and large wave events at sea, resulting in waves over-topping flood defenses or in severe cases by tsunami or tropical cyclones. A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. Research from the NHC (National Hurricane Center) explains: Storm surge is an additional rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with spring tide, resulting in storm tides reaching up to 20 feet or more in some cases.
Urban flooding
Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Although sometimes triggered by events such as flash flooding or snowmelt, urban flooding is a condition, characterized by its repetitive and systemic impacts on communities, that can happen regardless of whether or not affected communities are located within designated floodplains or near any body of water. Aside from potential overflow of rivers and lakes, snowmelt, stormwater or water released from damaged water mains may accumulate on property and in public rights-of-way, seep through building walls and floors, or backup into buildings through sewer pipes, toilets and sinks.
Catastrophic
Catastrophic riverine flooding is usually associated with major infrastructure failures such as the collapse of a dam, but they may also be caused by drainage channel modification from a landslide, earthquake or volcanic eruption. Examples include outburst floods and lahars. Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes.
