Floods can be caused by various factors- heavy rains, breakage of dams, overflowing of water bodies etc. In India, thousands of people lose their homes to floods each year. One of the major reasons is building structures in areas that formerly used to be a water body like a pond or a stream.
Simple strategies can be followed to prevent seepage and flowing of water into buildings.
Building structures to prevent water from flowing into buildings
Elevating the lowest floor of the building
Making foundations flood resistant
Using flood-resistant materials
1. Structures to Prevent Flooding
Some basic guidelines can be followed for preventing flood water from seeping into your buildings.
Place of Construction
Avoid buying plots which are less than 250 metres away from water bodies.
Avoid staying in areas which formerly used to be water bodies.
Choose an area which is uphill, on the higher parts of the contour.
Proper Drainage Systems
Regardless of whether your area is flood-prone or not, your design should have a proper drainage system.
Rainwater should be given proper pathways to move and drain.
Floodwalls
Floodwalls are built of concrete or RCC.
They are usually quite tall (1- 4 metres of height).
Floodwalls are usually built in front of vulnerable openings like garages and underground passages.
Safety Staircases
There will be cases where despite all measures, water still floods into buildings.
Safety Staircases which can be accessed even during flooding to reach higher levels should be built for the safety of the users.
2. Increasing Height of the Lower Level Structures
Water flows from high to low lying areas. Hence, increasing the elevation of buildings prevents water from flowing into them.
Increasing Plinth Height
It's common sense to increase the height of the lowest floor to stop water from flowing inside.
Plinth level of buildings should be 0.6m above the mean annual flood level.
Stairways must be provided in case of flooding for the safety of the building's inhabitants to reach upper levels.
The terrace or roof height should be higher than the 100-year flood level.
Using Stilts
Traditional architecture in areas of frequent flooding usually had stilts to prevent buildings being swept away.
Structures with stilts are built high enough to allow water to flow beneath it.
The space underneath is usually used as storage or for cattle rearing areas.
This also protects houses from insects and other vermin.
3. Flood-resistant Foundations
Foundations should be built strong enough to resist harsh movement of water which might lead to the collapse of the entire building.
Anchoring
During floods, it's common to see the entire building being swept away by the force of the water.
This is why it is important to make sure that we firmly build foundations, so that the structure is anchored properly even in the case of flooding.
Anchor the foundations properly to the ground as well.
Openings in the Foundation
When the force of the water is too much, it is impossible for even the strongest of foundations to hold on.
Instead of fighting against the force of the water, we can simply let it pass.
Provide openings on foundations and walls in the direction of flowing water to reduce the force water puts on the structure during flooding.
4. Material Choice
Foundations should not corrode or wear away by water.
Use water-proof materials in foundations as well to avoid collapse.
Use Flood-resistant Materials for building
There are a lot of materials available in today's market which are considered flood-resistant. Some of the commonly used ones are listed below.
Concrete
Concrete is highly water resilient and also stiff and strong in the face of a flood.
It is also water-proof and impermeable.
Bricks with Water-resistant layer
Brick masonry can be used to prevent flooding, when a layer of asphalt or similar water-proof materials are applied to it.
Careful designing should be done as the building might collapse if seepage happens.
Galvanized Metal
Since metal usually corrodes or rust when exposed to water, it is crucial to galvanise them regularly.
Galvanization is the process of applying a protective layer of zinc coating.
Galvanizing also reduces maintenance and repair costs.
Decay Resistant Wood
Some types of wood are better resistant to decay and rot in comparison to others.
Cedar and redwood are good examples since they have a high quantity of natural oils and extractives in them which repels water.
It is highly dense and hard.
Additionally, they are also highly resistant to fungus, microbe and insect infestation.
Reinforced Concrete
RCC is a highly strong and stiff material which can resist the force of water.
It is also impermeable to water upto a certain extent, which reduces as the structure gets older.
Layering it with water-resistant materials can help with its durability.
Polyester Epoxy Paint
Polyester epoxy paint is highly water-proof and also durable.
It is a synthetic resin used as a coating.
It is also heat resistant.
Flood-proofing a building is very useful, not only in the case of a flood but it also prevents seepage and weakening of the structure over time.
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