Why Delhi roads get flooded every monsoon?

Professor Emeritus of IIT Delhi talks about how a drainage master plan, if implemented, could have offered a lasting solution

In Delhi’s case, flooding could be due to two reasons: floods in the Yamuna or local rainfall. In 1978, Delhi had witnessed a flood due to a rise in the Yamuna water level. But the annual urban flooding we see is due to local rainfall. The run-off water (water left after being absorbed by the earth) from the local rainfall is supposed to drain into the Yamuna through storm water drains. But due to a combination of reasons, including sewage flowing in storm water drains, it does not properly drain into the Yamuna and leads to urban flooding. The drains were made decades ago to handle a particular amount of run-off water. Over the years, the paved area has increased due to development. So, if earlier, a particular amount of rainfall generated 50% of run-off water and the rest was absorbed by the earth, now the run-off water is about 90%. Also, due to climate change, the intensity of rainfall has increased and this also increases the amount of water. But the drainage system is the same and it is unable to handle the excess water.