River capture is the process whereby a strong river diverts a parallel weak river and forms a strong stream through a pirate stream. It is a pirate stream that advances towards the weaker stream and captures it.
In order for river capture to develop the following conditions should be in operation:
- There must be a strong river flowing adjacent to the weak river so that the powerful stream may capture its weak neighbor
- The powerful river must have greater energy to undertake both vertical and headward erosion
- The powerful river must be flowing at a lower and steeper gradient than the weak river
- The capturing river must be flowing over rocks that are more easily eroded than the weak river