Why do homeless people want to live on the riverbanks in cold weather climates?

Inspired by this question. I know that in my own area there are tent cities that the homeless are living in that are on the riverbanks. I live in an area where there are miles and miles of hills and mountains that are uninhabited. I would think it would be warmer to live in the woods than on a riverbank when the temperatures dip to below 20 degrees. On the coldest night of the winter in my town, the mayor closed the tents down to force the homeless to go to shelters. They were infuriated and refused to go to the shelters. Their homes were dismantled. So why would the homeless want to live where it is even colder?