If this happens, Yamuna will cease to exist in Delhi… 75% of the river’s floodplain is illegally encroached upon

In the country’s capital Delhi, 75 percent of the floodplain of India’s fourth largest river ‘Yamuna’ has been encroached upon. People have built permanent houses in the river’s catchment area. How did such a large scale illegal occupation take place in the national capital under the nose of the central and state governments? According to