Natural Disasters Explained: Floods

Colombia. May 2011. Heavy rains forced riverbanks to burst resulting in vast flooding across Colombia in 2011 (ShelterBox).

Colombia. May 2011. Heavy rains forced riverbanks to burst resulting in vast flooding across Colombia in 2011 (ShelterBox).


ShelterBox provides emergency shelter and vital supplies to support communities around the world overwhelmed by disaster and humanitarian crises. In the second of a series of features looking at the different types of natural disasters to which we respond, we consider the causes and impact of flooding. 

ShelterBox has dispatched teams and emergency equipment to disaster zones on 36 occasions since the beginning of 2013. Almost half of those deployments, to 14 different countries across Europe, Africa, South America, Asia and Australasia, were in response to floods. If that’s surprising, it shouldn’t be; according to the US National Oceanic and Atmospheric Administration, flooding is the most common global environmental hazard.

The dictionary definition of flooding is “An overflowing of water on an area that is normally dry.” So far, so obvious, but there’s more to it than that. The main distinction to be made is between flooding caused by excessive rainfall and storm surges originating from the oceans, triggered by hurricanes or typhoons. We’ll leave storm surges for another day and concentrate here on the impact of abnormally heavy rain.

Excessive rainfall, beyond the capacity of rivers to carry the water away safely, is the most common source of flooding. This can lead to river banks giving way, or the collapse of man-made structures such as embankments and dams. Often the result is a flash flood, which is particularly dangerous because of the speed with which an area can become inundated.

Some floods are caused by random periods of abnormally heavy rain. Recent examples which have called for ShelterBox deployments include the mid-2014 Balkan floods, caused by the heaviest rainfall for 120 years in Serbia and Bosnia. The pattern was repeated soon afterwards in South America, across Brazil, Argentina and Paraguay. In all cases, the result was death and injury, destruction of property and the displacement of tens of thousands of people.

Flooding can also be triggered by meteorological phenomena that recur regularly. The best known example is the monsoon – a seasonal weather pattern that brings heavy rain. The Indian Sub-continent’s southwest monsoon, which occurs annually between June and September, is perhaps the most important in terms of its potentially damaging side-effects. ShelterBox is currently distributing tents and other equipment in Nepal following floods and landslides caused by unusually heavy monsoon rains. Pakistan and India have also been affected.


Colombia. May 2011. Heavy rains forced riverbanks to burst resulting in vast flooding across Colombia in 2011 (ShelterBox).

Colombia. May 2011. Heavy rains forced riverbanks to burst resulting in vast flooding across Colombia in 2011 (ShelterBox).


The impact of flooding on communities is widespread. In human terms, death and injury is caused both by the water itself and also by objects swept up in it. In terms of residential property, flooding can cause structural damage, undermining foundations and rendering homes unstable and unusable. Even where the house remains intact, the lengthy clean-up and repair process means the family has to find alternative accommodation until their home is habitable again. And floods also damage public buildings such as schools and hospitals, infrastructure like roads and bridges as well as crops. This all has a large impact on the economic life of the affected population.

Health and sanitation problems are another key issue. Water supplies are often contaminated as flood water and sewage overflow into drinking water supplies. And large areas of standing water are a haven for mosquitoes, creating a risk of malaria and dengue fever.

ShelterBox’s response to flood related disasters takes account of all these issues. Families who are temporarily displaced will return to their homes once the flood water has receded, but they need somewhere to live while they rebuild their houses. That’s where a ShelterBox tent comes in, allowing them to stay close by during the reconstruction process. We also supply water purification kits to address the problem of contaminated drinking water, while our mosquito nets can help to reduce the malaria risk.

The one thing ShelterBox can’t do is prevent future floods. The rising global population means that humans will increasingly find themselves living in areas with a high risk of inundation, and freak weather events will continue to happen.

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