Drought = total rainfall for the season is lower than normal.
Flood = one particular rain event puts enough water in the system in a short enough period of time for it to overflow the usual banks before getting absorbed or escaping downstream.
In fact, if the ground is dry enough, it takes a little time for water to be absorbed. Picture a dried-out sponge - you have to hold it in the water a little while before it soaks enough up to become soft again. You can clean up a puddle a lot faster with a slightly-damp sponge than a hard dry one. When the ground is dry and hard, it takes time for water to work its way in, and meanwhile the excess just flows away and is lost. Thus, if you have a long period of drought and then a short fast rainfall, the ground absorbs less than if that amount of rain was spread out in several smaller slower rainfalls. |
