Rain Water Management

In Continuation of my previous post regarding Water Management, written a long back, there is still a need for Rain Water Management.

Yesterday, one of my team members asked me the question Why nature is so harsh to us!, is all the current scenario of fash flooding in India is due to Global Warming and Climate Change?

I thought for a moment and replied: Yes, the uneven rain is due to the Climate Change, Global Warming is one of the reasons of the same, however, the flash flooding is due to poor practices and governance in India.

He stared at me and asked me What is Government to do with all, heavy rain and flooding are a natural phenomenon, why you always so skeptical with Government Policies, this time I won't accept your justification?

I asked him, What is the surface area of Surat City?

He replied, Let me search, it's around 327 km2.

Immediately I took the calculator, did the calculations and replied, Ok, the city will generate about 910 m3/Sec of water, considering 10 mm Rain per Hour. The same can be easily managed by 35 Nos. of Storm Water Drainage Pipe of 1.2 m Diameter.

He was amazed and said, This is paperwork, what is real on a ground solution?

Exactly, this is just an approximation, now here comes the important part, we have to consider the land elevation as well, I conveyed.

I opened floodmap.net and pointing towards Surat map, and said to consider one comparatively small area of 10 km2 having an elevation of 13 m and calculate the downflow of the same towards area having an elevation of 9 m. The downflow comes around 28 m3/Sec, which will be added to the same area of 10 km2 having an elevation of 9 m, gives a total flow of 56 m3/Sec.

He was shocked.

I further told him the same will need about 9 Nos. of Storm Water Drainage Pipe of 1.2 m Diameter.

He further asked, Ok, all these are for 10 mm rainfall in a day, what if the rainfall is 25 mm in a day?

I recalculated the said For 25 mm rainfall the cumulative flow will be about 140 m3/Sec and there will be a requirement of 14 Nos. Strom Water Drainage Pipe of 1.2 m Diameter.

He questioned, Why only 1.5 times increase in the number of pipes when I increased 2.5 times the rainfall?

As the rainfall is the length, giving us the volumetric flowrate. This volumetric flow rate gives us the pipe crossectional area, which ultimately gives us the pipe diameter, it's due to cube root and square root, I clarified.

So we have to install 14 Nos. of Strom Water Drainage Pipe of 1.2 m Diameter to avoid flash flood?, He questioned.

I replied, Yes, for that area.

He again asked, What if rever if flooding, just like today's Tapi River conditions?

I humbly replied, Just do the same calculation for the River as well.

I further said, For rivers, you can go for open seasonal canal systems supplying water to other areas. Even, the same can be incorporated with Sadguru's rally for rever initiative.

For your ready reference, I had made the projections of average annual rainfall on the elevation map of India.

P.S. Flash Flood can be managed and the same water can be utilized for the betterment of India.

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