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  • Writer's pictureBenny Kuriakose

Kerala Floods 2018: Flood Damage and Other Effects on Buildings

Rainfall is extremely important for life on earth, but an excess of it can result in floods and damage to livelihood and life. Floods can be natural occurring due to topography of the region or man-made due to insensitive building practices near river beds. The extent of flood damage is determined by many factors such as the time duration for which the building was flooded, the depth of the water in the flooded building, etc. The damage is not limited to the period of the flooding, rather continues even after the water recedes. The causes and effects of flood damage on buildings is discussed in detail in the article.


Table of Contents



1. What are the damages Caused by Flood on Buildings?

1.1. Damage Due to Forces of Floodwater


Upwards and sideways thrust created by water on structural members of the house damage it. The buildings are also damaged from the floating objects like timber logs, cars, etc. The force of water on the wall if it reaches the eave level is approximately equal to the load of 8 cars stacked on top of each other.


Pressure exerted by flood water on  buildings
Pressure exerted by flood water on buildings
The degree of unbalanced force on the walldue to flood water
The degree of unbalanced force on the wall due to flood water

1.2. Flood Damage on Materials


Building in contact with water over a long period of time can lead to damage and loss of material strength, especially earth walls and construction of burnt brick walls made with mud mortar.

Loss of material strength due to floodwater
Loss of material strength due to floodwater

1.3. Structural Failure from Soil Movement

The foundation damage and structural failure in buildings may occur due to change in soil conditions and movement beneath.

 Foundation failure due to changes in soil condition
Foundation failure due to changes in soil condition

1.4. Flood Damages to Homes due to Differential Pressure

If the doors and windows of a building are closed, there will be a difference in water level between the inside and outside of the flooded buildings. This difference in level will exert a pressure on the walls and may lead to damage. The internal rate of flow depends on the amount of water getting inside the building through openings. The difference in water level creates pressure on the wall.

Pressure on walls due to difference in water levels
Pressure on walls due to difference in water levels
Pressure on walls due to difference in water levels
Pressure on walls due to difference in water levels

2. Factors Influencing Flood Damages


The flood water damages will depend on certain factors.


2.1. Depth of Water


More the depth means more water pressure on the structure thus increasing the chances of the walls getting collapsed/ cracked.

Damage based on the depth of water
Damage based on the depth of water

2.2. Velocity of Floodwater


When a certain volume of water moves through narrower areas, the velocity of water flow increases intensifying the damage further.

Flood damage by increase in velocity of water
Flood damage by increase in velocity of water

2.3. Period of Submersion


Longer the duration of submersion, greater the effects of flood on the buildings since prolonged exposure will lead to both absorption and pressure exertion. It will lead to both structural and aesthetic deterioration.

Damage based on period of submersion
Damage based on period of submersion

2.4. Type of Material


Certain materials such as conventional earth buildings (which are not stabilized) will get more damaged when compared with burnt brick or concrete buildings.

More damage in earth walls
More damage in earth walls
Damage based on materials of construction
Less damage in burnt brick walls (Damage based on materials of construction)

2.5. Water Contamination


In most cases, the flood water will be contaminated with drainage, dead bodies, chemicals, etc. and will contain many floating objects. Even though the contamination is diluted by the huge volume of water, the salt in the water impacts the buildings.


Damage caused by water contamination
Damage caused by water contamination

3. Negative Effects of Flood on Buildings and How to Identify Flood Damage


3.1 Dampness


It is difficult to find out the source of water in the case of dampness in buildings. There are various ways through which water may enter the buildings and damage it. In case of buildings completely immersed in flood water, multiple damages can be caused.


But the effects of dampness can have serious consequences in concrete and timber members of the building, especially roof. If concrete is left damp, the reinforcement will start corroding and the slab will degrade beyond repair, losing its structural strength. The English proverb "a stitch in time saves nine" is apt in the case of repairing concrete components of a building.


In the presence of water, the salts in the wall or in the ground will crystallize and damage the walls and the surface decoration. On further seepage the plaster may start to flake off as well. Paint finishes may start flaking off as dampness enters the building. Many defects hidden all these years may surface with the floods.

Each person exhales 1 litre of water as vapour each day
Each person exhales 1 litre of water as vapour each day

If a porous walling material such as brick or stone is in contact with damp soil, moisture will be drawn into the pores by a physical process called capillary action. Until a balance is created between the rate of evaporation and the rate of action of capillary forces, the height of moisture absorbed will rise in the wall. The rising damp height will vary in accordance with the level of the water table of the soil. The more the thickness of the wall, the more water will rise.


Rising dampness usually contains salts carried up from the soil or dissolved from the walling material. Some of these salts are hygroscopic; i.e. they absorb moisture from the air. Their presence will maintain dampness even after the rising damp has been eliminated.


The signs of rising damp usually extend from 3 cm to 100 cm above floor level and exhibit a sharp change from wet to dry on the wall. Moisture will be present throughout the wall thickness. Contaminating salts may be seen as white deposits or crystals. Presence of a damp proof layer will prevent the ground water from rising in the walls through capillary action.