In article , Timothy Murphy
writes

I live in a small part of a very large building (an old orphanage).
Strangely, there are no downpipes from the gutters
in the front of the 4-storey building.
All the water is transferred to downpipes at the back of the building.
Unfortunately the water goes over a valley in our part of the building.
The quantity of water after a heavy rainfall is immense;
it sounds as though a large river is running over one's head.
There is occasionally a slight leak through the ceiling at one point.

I meant to ask you if you had any access to the valley from your
property and whether it was reasonably deep?

Using tangential thinking[1] I wondered if lining the valley with
something like astroturf might reduce the noise from the water flow or
any resonances in the lead (is it lead?) and improve the situation.

[1] I used to enjoy it more when I misspelled it tangenital thinking.
--
fred
it's a ba-na-na . . . .