The diagram illustrate the change of an area around the Blackstone river after suffering a flood.
The upper part of the diagram showed the situation before flood. The Blackstone river had a huge curve, and there was a bridge accross the river at the end of the curve, surrounding with a few houses. The majority of houses were lived in the woods, which a little far from the river.
As can be seen from the bottom part of the diagram, after flood, river was broke off at the curving part and was seperated to two different parts. The curve part remained as a new lake which called Oxbow lake, while the river itself became straight forwards. Meanwhile, the bridge was vanished and so were those houses and trees next to it. Furthermore, the majorty of houses survived from the flood and were maintained.
In conclusion, the flood caused significsnt changes to the river and the houses nearby but not included the majority of houses.