Although the main reason is not known for the declined, there are many factors and theories that led up to the fall of the civilization. One factor was the forces of nature, the Indus relied on rivers that were prone to change their course and were unpredictable causing excessive flooding. Environmentalists studying the deposits in and around the city Mohenjo Daro have theorized that the city had experienced a massive amount of flooding more than the usual because the movement of the tectonic plates in the north and west caused mud to erupt, which in turn, dammed the Indus, causing massive ponding and flooding for many decades. Another theory is the decay of their sewage system since it was made out of baked bricks, the wastewater from the drains could have contaminated their drinking water, giving them diseases like cholera. Another possible reason is famine, skeletons found from Mohenjo-Daro showed individuals had suffered from malaria and death by other diseases, and since the Indus people didn't have immunity to these diseases, it could have caused an outbreak, decreasing the population of the Indus. There are much more out there, but these are the most plausible that were linked to
Although the main reason is not known for the declined, there are many factors and theories that led up to the fall of the civilization. One factor was the forces of nature, the Indus relied on rivers that were prone to change their course and were unpredictable causing excessive flooding. Environmentalists studying the deposits in and around the city Mohenjo Daro have theorized that the city had experienced a massive amount of flooding more than the usual because the movement of the tectonic plates in the north and west caused mud to erupt, which in turn, dammed the Indus, causing massive ponding and flooding for many decades. Another theory is the decay of their sewage system since it was made out of baked bricks, the wastewater from the drains could have contaminated their drinking water, giving them diseases like cholera. Another possible reason is famine, skeletons found from Mohenjo-Daro showed individuals had suffered from malaria and death by other diseases, and since the Indus people didn't have immunity to these diseases, it could have caused an outbreak, decreasing the population of the Indus. There are much more out there, but these are the most plausible that were linked to