Floods refer to huge amount of water reaching land in a short span of time, causing land surface to be submerged under water – at places, where, land surface is usually not covered with water.
Floods could be caused due to natural causes, or, human activities, or, a combination of both. Floods are caused by discharge of huge volume of water in a short span of time, at a rate, such that the water can not be carried away from the scene of discharge.
Some of the possible reasons for such huge discharge of water could be:
1. very heavy rainfall (say: due to cyclones, typhoons etc.) in a short span of time. It should be noted that the amount of rainfall itself is not a sufficient cause, the duration within which the rainfall is receive is equally important contributor
2. breach in levy, dams etc
3. very high tidal waves (sometimes in the aftermath of a seismic activity, e.g. earthquakes) etc. – also called tsunamis
Usually, flooding impacts a large area, wherein entire district or states might be flooded. However, sometimes, flooding is very local, i.e. limited to just one city, or, parts of it. Most often, the localized flooding is caused due to human activities, rather than natural phenomenon. A natural phenomenon might seem like the immediate trigger, but, in reality, this is caused by human activity.
There are some places, which get flooded almost every year. One such example is Bangladesh. Some of the other places which had incidents of bad flooding in the recent past include:
● Florida, in the aftermath of hurricane Katrina (2005)
● Myanmar (2008)
● Portions of Coastal India get flooded almost each year
Among various kinds of disasters, flooding is unique in the sense that it has a very high degree of predictability, both in the short term, as well as long term. In most situations, flood prone areas are quite known – in the sense that they have a history of flooding. Only in very rare situations, a place might be flooded – without having any past history of flooding. Even in such cases, a careful study of the area could give an indication of possible flooding.
Flood Prone Areas
The areas, which are prone to flood-risks are:
1. places, which have a history of flooding (most important)
2. area receiving heavy rainfall, with not much naturally sloping landscape
3. areas at the lower levels of naturally sloping landscape – where, the higher areas are receiving heavy rainfall
4. areas around sea-coasts, or, river banks
5. areas downstream of dams etc. As water level upstream of dams might rise, the dam authorities might be forced to release water (to safeguard the dam) – which might cause flooding of downstream areas
6. areas on the other side of levies (in case, the levy gets breached)
7. low-lying areas (say: foot of an overbridge etc.)
Loss due to Flooding
The most common kinds of loss that are caused during flooding include:
1. Lack of water: Its an irony, that a disaster which mean water everywhere, results in lack of water to drink and sanitation. Lack of proper drinking water and sanitation causes widespread outbreak of diseases.
2. Lack of food: Most of the food items get damaged, causing a severe shortage of food. This shortage could be for the food to be consumed in the near future, or, even standing crops could be damaged, causing long-term food shortage.
3. Lack of utilities: Utility services might have to be turned off, for the fear of electrocution, as, there is water everywhere.
4. Widespread damage to structure
5. Drowning: People, livestock, goods etc. might get drowned.
6. Snakes and other creatures: Some of the dangerous creatures which usually stay underground would be forced to come up, as their natural habitat becomes unlivable. These could prove dangerous to human beings and cattle.
7. Submerging of vehicles and other equipments: Vehicles and other equipments might get permanently damaged – as they remain submerged under water – for prolonged duration.
Because of wide-spread impact of such floods, the suffering could be long-drawn, besides the immediate impact – as mentioned above.
Indicators of Possible Flooding
Usually, any of the following situations should indicate the possibility of flooding:
● heavy rainfall in/around the vicinity, especially, if the specific location falls in the pathway of the water-discharge system from the area receiving heavy rainfall
● if there is heavy rainfall/flow of water/accumulation of water, on the other side of a boundary, e.g. across a dam, across a levy, side of a river-embankment etc., because, these boundaries might get breached
As can be seen, both the above situations can be predicted to a reasonable degree. These days, the meteorological predictions are accurate enough for upto 4-5 days. Hence, its usually possible to know about the possibility of heavy rainfall about 4-5 days in advance.
Also, areas which are prone to heavy rainfall, cyclones, typhoons etc. are also well-known. Hence, the predictability is very high even in long-term, in the sense, that certain areas are known to be flood-prone. The advantage of long-term predictability is that people might be able to take long-term precautionary measures also – requiring heavy investments.
Also, for situations, where, there is a boundary between huge mass of water, and, your living place, again, keeping an eye on the following two situations should be a good indication of the possibility of flooding:
1. increase in the volume/mass of water being built up on the other side of the boundary
2. general maintenance and upkeep of the boundary
General level of civic maintenance is a good indication of the possibility of flooding, during rainfall. If the drains and streets are generally clean, the possibility of flooding gets reduced; on the other hand, if the drains and streets are generally choked or dirty, the chances of flooding (atleast at the local level) gets increased.
Now, that we know, how can we figure out the possibility of flooding, lets look at the possibility of preventing it.