'Green roof won't flood 60% of city': CEPT University and IIT Bombay research in Ahmedabad, problem of waterlogging due to concrete

The problem of waterlogging in major cities during the monsoon is also on the rise amid increasing urbanisation. Due to which there are often floods. The flood in Vadodara some time ago is the latest example of this. The threat of flooding can be averted if the problem of waterlogging in cities is reduced. A research conducted by Ahmedabad-based CEPT University and IIT Bombay has concluded that green roof can reduce the risk of flooding the city. Why was this research needed? What is a Green Roof Top? How does it work? How much does it cost? Is this possible in cities of Gujarat? In order to get answers to such questions, Divya Bhaskar spoke to Tushar Bose, professor of faculty of technology and researcher at CEPT University. Professor Tushar Bose's research is the output of his PhD. Which has been done under the guidance of Professor Pradeep Kalbar and Arpita Mandal of IIT Bombay. Water gets filled due to the concrete structure Tushar Bose told Divya Bhaskar, "In recent times, we see that the environment of the whole world is changing. Which we have been seeing from the 1900s to this day. Due to the change in the environment, the cities are getting very heavy rainfall. There are some major reasons why cities in India or cities in Europe or other places get submerged in less rain due to excess rainfall. One of the major reasons for this is that concrete structures have been built everywhere and are also being built. Because of which the water that should have landed in the ground is not coming down. Another major reason is the change in climate. Due to changes in the climate, the amount of intensity of floods and rainfall is falling, it is raining more in less time. Rainfall will increase in South Asia He said that the new reports about climate change have shown that this pattern will increase everywhere. This means that the intensity of rainfall is going to increase in South Asia. So we are seeing that the land of the cities is being blocked. The second is that the amount of rain is increasing. Due to which more water has to be handled in the storm water network. Floods became a big problem Explaining how the idea of doing this research came about, he said that today the flood has become a very big problem for everyone, be it India or any other country. From this we got an idea as to how to prevent floods or reduce their extent. What should be the strategy to adopt it, so we are looking at how to build our strategy using nature-based solutions i.e. natural resources through new research. Which is affordable in terms of cost and can also be spread in the catchment area so that there is awareness among the people. 3 layers in green roof Explaining how the green roof is done, Tushar Bose said that it has three layers. The first is the bum layer in which the vegetation comes. In which a wall is built and water is stored in it. Then comes the substrate layer which is 150 to 200 mm. There is material in which you can grow a tree. If you put more than 250 mm in it, then it is called incentive green roof, if it is less than that, then it is called intensive green roof. While the third layer is of drainage which helps in draining out excess water from the trees. The waterproof layer is finally done. Flood-like problems can be solved in 60 percent of the area Explaining the benefits of green roof, he says that there are two major benefits of green roof. There is an advantage for the city. When there is more rain and due to urbanization, the water is not drained soon, then the water through this green roof will stop and stop so that the water will not be filled at the same time. So that the storm water handle will have to be reduced and the amount of flood situation will also be reduced. Another advantage is that the hit load of their house decreases if those who have a home make a green roof. So that the demand for AC will be reduced. Due to which the roof of the house will also be less hot. In our research, we have seen that the problem of flood situation in 60 percent of the area can be solved with green roof. While the amount of water can be reduced by 25 percent. All data is recorded at the pumping station Talking about Ahmedabad, he adds, "I know Ahmedabad very closely, so I know which area is flooded with water. At the same time, we also got a lot of support from the Ahmedabad Municipal Corporation. In this regard, we started research across the city at the primary level, but at this time it was noticed that if a model is to be done in Ahmedabad, then there is a great need for data for it. How much rainfall has occurred for calibration and validation and how much water has flowed out of the storm water network. At this time we saw that there are many pumping stations in Ahmedabad whose all the data is recorded. Ahmedabad has been divided into a subcatchment. "We divided Ahmedabad city into subcatchments. At this time we saw which area has the highest flooding situation. Out of which the Odhav area came to the fore. There is a problem of waterlogging every two years in Odhav. Odhav has also been chosen because the development work has also been done in good quantity there. Odhav is also an area representing other cities in the country. This is the reason why this area has been selected. The research took 2 to 2.5 years He further adds, "We first took a digital elevation model in which we got to know how much ground elevation is. Based on this, it was found out where the water was flowing. Based on this, we divided the area into a subcatchment. During this time, we saw that the area of our study was a little more than 100 hectares. So far, about two to two and a half years have been spent in this research. Use of different data On where he got the data for the research, he said, "For this research, we also got rainfall data from the Meteorological Department for the last 30 years. From this data, it was easy for us to understand what the rainfall pattern is like and how it is changing. We use the technical term in this through which we created the IDF curves. From which we came to know that if we look at the duration of two hours, three hours, four hours, then according to one probability, how much rainfall comes once in 25 years or how much rainfall comes once in 10 years. This has helped us a lot in determining from the data of the Meteorological Department. Secondly, as I said, the digital elevation model whose data was obtained from nrsc (National Remote Sensing Center) data that we used. Apart from this, data has also been obtained from the municipal corporation. After this, we surveyed every type of building to see if there could be a greenroof where the building of every house on the field is used. During this time, data of automatic weather station in Odhav was also obtained. Based on which we developed storm water management model which is a computer rated model. Through this model, it is known how much rain has been received in which area, through which how much water will be drained out. After getting its computer data we compared it with actual data. During this time our model was working very well due to which the model was established. We made the scenario after the model was finalised. In which 25 percent of the houses where green roof is possible, what will happen if green roof is made, 50 percent of the houses where green roof is made, what will be the result and 75 percent of the houses where green roof is possible, what will be the result. In which we have seen what will happen if there is a period of two hours, three hours and four hours, as well as for rainfall intensity, we have tried to see what will happen if there is one intensity rain in five years, what will happen if it rains in 10 years and 25 years. How feasible is green roof top in India? Giving information about green roof tops, he says, "Our research is on greenroof. We have seen that green roof is very prevalent in Europe. China's Sponcity Initiative has also been its major contribution. People in foreign countries are trying to reduce the amount of flooding using green roof strategies. We wanted to know from this research how much the green roof that has been successful in foreign countries is applicable in our country. Claiming that it is very important to implement this strategy in India, he said, "The roofs that we have there are not designed with that capacity. Secondly, there are many slum areas in our city, which mostly have tent roofs or sheets of cement, but the green roof cannot come over it. Our major objective was to see if green roof is an established strategy, we can practically implement it in our country. And what kind of benefit can it have if we do it where it is possible in the roof? Can it really reduce the amount of flooding? So with this agenda, we started researching. Work was done on green roof in most countries He said that when we are doing any research or reviewing the literature, we are mainly looking at what work they have done in this direction. In the meantime, we found that research is going on in most countries to see how effective greenroof or other nature-based solutions are. We found that work has been done in most countries, but there is not so much work done in this direction in India, so if we are adopting a strategy, if we do not do any study or experiment, then how do we know how effective this thing will be there. This was also one of the reasons behind doing this research. Secondly, when you go abroad, you get to see many strategies, the same green roof strategy you see in the Netherlands. At the library there you will see a green roof. The Netherlands is at the forefront of the green roof strategy. The reason behind this is also that the Netherlands is located at The Billo C level. Due to which there is a big problem of flooding. His research began much earlier than us. That's why we should also bring a strategy there in which we have a contribution. He said, "In this research, I was accompanied by Professor Arpita Mandal of IIT Bombay and Professor of Department of Environmental Science and Engineering. Pradeep was Kalbar. Professor Arpita Mondal is a climate scientist, so she saw how the Future Rainfall Patent and Extreme Rainfall event take place. How does its trend change? So his contribution to this research was how rainfall is changing and how to make a scenario by knowing it so that the changing of rainfall can be checked with the effectiveness of green roof. While Professor Dr. Pradeep Kalbar helped in the scenario establishment in this research. On the basis of which scenario should the green roof be checked? He helped on whether it should be done on a two-hour rainfall duration or on a three or five-hour duration. It is necessary to pay attention to rain water harvesting Stating that it is difficult not to pay attention to rain water harvesting, he said that in the Development Control Regulation, some policy is fixed for rain water. Similarly, there is a rain water harvesting mandate in Ahmedabad. But when the building is given to the Residential Welfare Association, it should be kept in mind where the rain water harvesting facility is, how it is installed and maintained. Because it is very necessary for the permission of the building. We do not take care of this, due to which sometimes there is a problem, so everyone needs to check about it too.