Whitewater descent: How is the difficulty of a stretch of river measured?

These are the difficulties of rafting and how is it measured he classification of whitewater, which is governed by an international system of grades or classes.

A stretch of river can be grade II, III, and so on until the VI.

Grade II: suitable to start children in rafting. 

Grade III: without being dangerous in general, grade III rivers are perfect for children, families and groups. Its sections include waves and rapids that make rafting or white water rafting in kayak a very fun and dynamic activity.

Grade IV: emotion in rivers of this level is served. They are not suitable for all audiences, it is convenient for a monitor to determine if a group is suitable for rafting in a scenario of these characteristics, since the obstacles are multiple, the steps involve technical difficulties, etc ...