Why does flooding occur? By Phillip

I have learned that flooding can occur with or with out warning and there are many flood levels like the major and minor flood warnings.  All these flood warnings have threat levels like the minor which is the lowest threat level.  Plus the major flood warning is the highest flood warning. The flooding can occur when is rains or snows.  Then the snow melts and it rolls down a hill that the core is bed rock.  The the water can't go to the nearest river and a flood occurs by the water building up and that's how a flood occurs.