Flood is the catastrophic event would have the BIGGEST impact on a watershed
Explanation:
Sometimes, the water may enter the watersheds very quickly for the land to absorb it. These results in flooding.
The consequences may be quick melting of winter snows, tropical storms and events of precipitation. When the river flow is forecasted in an accurate way, it can save many human's life and dollars in millions. The conditions of the watersheds and its association with the rest of the water cycle are the factors that are considered by the Hydrologists for this forecasting.