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  • Writer's pictureBenny Kuriakose

Site Planning in Flood Prone Areas

Kerala floods 2018, and the recent Chennai flood is proof of the extreme effects of global warming. They are expected to get worse as the years go by. Out of the lot, flooding is the most frequent and urgent problem that needs to be addressed. The damages caused by floods can be ever-lasting to infrastructure and the natural environment. In the previous blogs, we saw the effect of floods on buildings, and how to repair them. However, flood damage can be minimised through proper site planning and land use planning. In this blog, we will explore a few flood management techniques that can help in building houses in flood prone areas.

List Of Contents

1. Planning of the Site Access

The distance from the river or water body is not as important as the elevation of the place. A flood mapping exercise can be carried out to ascertain the areas that would be submerged at the various levels of water above the maximum flood level. The elevation of a place is more critical than the distance from the river.

Elevation Is More Important Than the Distance From Water Bodies
Elevation Is More Important Than the Distance From Water Bodies

When preparing new site layouts, the layout of the roads shall be in such a way that evacuation is easy from a rescue point of view. The new building should be located such that there is a safe path of access to and from the site. This will ensure the safety of the people from fast-flowing floodwater, and allow them to enter or leave the property during the time of floods as well.

Site planning in flood prone areas
Cul-De-Sac Showing Street Planning for Efficient Evacuation

2. Proper Orientation of the Building

Floodwater travels faster through smaller passages between tall buildings. This rapid rush of water has the potential to destroy homes in its path.

Vulnerability of Plots
Vulnerability of Plots

So, it would be appropriate for the shorter side of the buildings to be oriented towards the flow of water to minimize the damage caused by a flood. This damage can be intensified further by floating objects such as logs or vegetation striking against the walls of the building.

Square Shaped Houses Are Preferred as They Are Generally Stronger in Flood Conditions
Square Shaped Houses Are Preferred as They Are Generally Stronger in Flood Prone Areas
If the House Is Rectangular, the Shorter Side Should Be Aligned Towards the Flow of Water
If the House Is Rectangular, the Shorter Side Should Be Aligned Towards the Flow of Water

Additionally, circular-shaped buildings or those placed at an angle (placed diagonally) can withstand the velocity of water to a much better extent.

Diagonally Oriented Buildings Will Withstand the Velocity of Water Much Better
Diagonally Oriented Buildings Will Withstand the Velocity of Water Much Better

3. Elevating the Plinth Level

Even the best engineering and architectural solutions will not be able to save a building if it is not built in accordance with the standards. Make sure that the ground floor level is at least 60 cm (2 feet) above the maximum flood level. Such minor differences in elevation can drastically improve the safety of a building during the time of flooding.

Elevated plinth for protection from floodwater
Elevated Plinth for Protection From Floodwater

4. Correct Landfill Practices

Landfill wrong locations can cause damage to properties that were never flooded before. Inappropriate filling of land will reduce the rate of receding of floodwater and increase stagnation. For example, filling along the riverside to gain elevation or to create an elevated floor level causes increased flood levels because of a reduction in the cross-section of the river.

Improper landfill aggravate the effect of floods
Inappropriate Landfill Aggravate the Effect of Floods

Thorough site planning and protection of critical facilities like generator rooms, electrical rooms, etc., can decrease the damages caused by the risk of flooding. Making use of the natural contours of the site and using the low lying areas for less occupied spaces like car parking and landscaping, the chances of the critical facilities such as living room, kitchen and bedroom getting impacted can be avoided.

Decreasing the Effective Flow Width of Floodwater
Decreasing the Effective Flow Width of Floodwater
Construction in accordance with the natural landform
Construction in Accordance With the Natural Landform

5. Buildings in Flood Prone Areas

When a building is constructed in a flood prone area, it is susceptible to flooding, even if the floor level is raised above the maximum flood level by earth filling. Scouring and erosion of the filled earth may occur during flooding, which may cause foundation failure. In such locations where floodwater is likely to flood the region no matter what, it is better to avoid any landfilling.

Restricted flow of floodwater due to poor extension proposalsRestricted Flow of Floodwater Due to Poor Extension Proposals
Restricted Flow of Floodwater Due to Poor Extension Proposals

The new building shall not restrict the free flow of floodwater; otherwise, it will lead to higher flood levels or destructive flow as it happened during the 2018 Kerala floods.

6. Public Buildings and Higher Standards of Safety

Critical facilities such as hospitals, flood shelters, schools, electrical substations, fire stations, police stations, water supply stations, godowns, etc., shall be built by strictly following the National Building Code and standards of safety. Failure to do so will create severe safety issues.

7. Conclusion

Building in flood prone areas can be a tricky task. But, in inevitable circumstances, proper planning of low lying areas can help in evading serious flooding and can create flood-resistant houses. Site planning is done to make sure that the floodwater reaches the ocean directly without entering places of habitation. Small changes such as elevation of floor level or changing the orientation of the buildings can be used right from the site planning stage to avoid major damages caused by floodwater. A specific design for that region needs to be developed, and the standards of safety have to be followed more rigorously.

The public also has to be more conscious of the impact of construction on the environment and make decisions accordingly. It is not right to blame the government and rely on them for everything. We, as an individual can also start by making small changes in everyday life. All in all, the damage caused by flooding is a grave problem that can be controlled by taking it into account right from the first stage of designing houses.


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