''My bolding. So for this 'dullard' can you please advise what causes floods apart from heavy rainfall, or other precipitation?''
smarter question is what makes rain and heavy rain
that way, one gets an understanding that warm water makes rain
and, it doesn't have to be in the spot where it rains - because one learns about things like atmospheric rivers and such
one other thing is that 'precipitation' - that causes flooding, doesn't always cause flooding immediately
snowmelt - months after falling can create flooding.
So, massive snowfalls in Europe in the last months - sit there waiting for warm enough weather to come.
And, come it will. ATM - the ground is wet, the water tables are full, there's always a potential for summer rains - and a huge amount of snow sitting above just waiting to join in for the next floods from the mother of flood gods
