Further, there is profuse archaeological evidence including the presence of sacrificial altars that go to show that the Harappans were part of the Vedic aryan fold. As a result, it can safely by said that the Vedic age also ended with the Harappan civilisation. From all this it is clear that the loss of these sites must have been associated with some natural catastrophe. A few scholars have pointed to evidence of frequent floods to account for the abandonement. But, floods are invariably local in nature and do not cause the collapse of a civilisation over a vast belt.
Floods bring death but they also sustain life.
It is the loss of water or dessication that causes massive disruptions on the scale witnessed at the end of the Harappan civilization. Thanks to the latest data from two major archaeological and satellite based studies, we now know that this is exactly what happened. It was ecological change that ended the great civilization not only in India but over a vast belt that included Mesopotamia, Egypt, and the Aegean. On the basis of extensive explorations carried out in Northern Mesopotamia, a joint French-American team led by H. Weiss of Yale University has determined that most of the old world civilization were severely affected by a prolonged drought that began about 2200 B.C. and persisted for about 300 years. The most drastically hit region seems to have been the Akkadian civilization neighbouring India.