I'm mainly thinking of large floods, like the [St. Marcellus flood](https://en.wikipedia.org/wiki/Saint_Marcellus%27_flood_(1362)) or the Buchardi flood, but also city fires or other catastrophes of a larger size.
What would happen in the aftermath to address the destruction and the victims who have lost everything they owned? Would the local lord send food and clothes, or workers to bury the dead and rebuild the houses? What about the king? Would the church collect donations throughout the land? Would there be any private endeavours, maybe neighbouring towns or single rich burghers acting on their own vocation?
Since noone answered, perhaps a piece of info from the roman times could prove interesting, even if largely unrelated to your question. A flood destroyed a dam in central Greece. It was the dam that kept lake Copais dry (the previously submerged land was now farms but the flood destroyed the crops and some infrastructure). Locals, who at the time were conquered by Romans (I think the incident took place in 1st century AD) sent an "embassy" to Rome, then Rome decided to give them some funds for rebuilding the dam plus 5 years tax-free status. Sorry for not having the Greek source available now. My point is that if this happened so early, then it is very likely that similar relief actions would have taken place in the period you are interested in.
This lake was dried many times since at least 1200 BC but natural disasters or acts of war (usually by the neighbours) often flooded it again.