In the past few decades, major rivers in Kathmandu valley like Hanumante, Bagmati and Dhobikhola have been regularly overflowing during the monsoon season. Each year, the floods damage an immense amount of property, and sometimes people die too. In the past few years, the government has built embankments in many places to limit the damage. But they seem to have had limited impact. In this context, Pratik Ghimire of ApEx interviewed Bishal Nath Upreti, geologist and president of Nepal Center for Disaster Management.
Bishal Nath Upreti
Kathmandu apparently witnessed a record rainfall this monsoon. But can the flooding of homes here solely be attributed to that?
Rivers overflowing after rainfall and urban flooding of Kathmandu are two different things. It is monsoon so of course it will rain. And whenever it rains, Kathmandu is flooded because of its poor drainage system. This time, the rivers overflowed and residential and slum areas near them drowned.
So why are our rivers overflowing?
Simply because we have narrowed the rivers’ path. The rivers in Kathmandu flow down from the surrounding hills and it rains quite a lot there compared to the valley. But when the water doesn’t find its natural course, it sweeps away everything in its path. Eventually, the settlements near the river get drowned. Although we can see the government building embankments on many corridors, they are not enough. Riverbeds have been shrunk from 500 meters to 10 meters.
What then is the solution?
The solution is to allow our rivers to follow their natural course, which is now impossible. There are now settlements on the banks, and no one can even think of displacing the residents. So I don’t think there is a quick fix solution to prevent the overflow of rivers in Kathmandu. We have seen parts of Kathmandu submerge. Kathmanduites will have to face this problem for a long time as it is a manmade disaster, not a natural one.
How deep are the rivers of Kathmandu these days? Do they have natural depth?
Since water in the valley comes from the hills, it carries some mud. It is a natural process. Additionally, sewage from all of Kathmandu mixes with the rivers. They might also have a minimal impact on the depth of rivers, but I don’t think depth is the problem. Breadth is what matters.
As you said, we have a poor drainage system. Can we improve it?
A couple of centuries ago, the underground canals were almost eight feet in diameter. In European countries, trucks can still run through underground drainage canals. But over the decades, the diameter of our drainage canals have been brought down to two or four feet. Moreover, all the sewage passes in the same drainage, so there is no place to bypass collected water. This is an engineering problem. We can resolve it by rebuilding our drainage system, but again, I don’t think anyone is interested in this. I have repeatedly talked about this with policymakers and governmental engineers, but to no avail.