Roof valley downflow overshoots gutter

[2CV67]

We have a 1970's-built tiled-roof house in Alsace.
In heavy rain (several times per year) the flow from 2 roof slopes pours down a zinc valley so fast it overshoots (not overloads) the gutter & cascades onto the garden below.
In prolonged heavy rain, I suspect this could induce damp in the adjacent basement.

I rigged up a deflector plate which worked perfectly...

...until we just had a moderate snow-fall.

Then, a roofload of snow avalanched down & (fortunately) tore the plate off.
If I had made a better job of fixing it, I suppose it would have torn the gutter off.

So now I am looking for a smarter idea, to prevent water cascading over the gutter, but survive avalanching snow.
Maybe a flexible version of my plate?

I suppose I am not the first person to meet this problem, but I haven't found any solutions in my searching so far.

Thanks for any suggestions!

 

[Tuck1]

The angle of the zinc valley doesnt look as if it would overshoot the gutter, but could the valley be trimmed back so it just overhangs the gutter?
Or you could fit a good size snow box/ hopper here and downpipe?

 

[SurreyRoofingEstimator]

Agree with above, a hopper / downpipe would be a good idea methinks, there's a lot of water that will come down that valley for quite a small gutter section, the hopper would catch that and the downpipe will take it away speedily

 

[datarebal]

i think i have seen the item your lookin for in a builder supplies near Grenoble last year.. i'll try nd remmber where and post. i am spending xmas in la rochelle i'll look there too. although snow is not a problem there. i like to see whats on offer

 

[anchorbay]

one trick for long steep valleys is to silicone baffles onto the face of the valley
use something like a piece of plastic trim cut into short sections and stick them on alternating sides of the valley for as far as you can safley reach
it slows the flow down
or just screww something substancial to the gutter