cats pooping on my carport roof, any advice?

I have a carport attached to my house (which in turn is attached to houses attached to houses, I live in an urban setting. A normal person could walk the whole block on roofs, with a bit of vertical jumping). All the cats in the area are now pooping on top of the carport. Every day I wake up to 5 or 6 turd piles now. The carport is made of transparent polysomethingorother and ah, they also scratch their little feeties on it after pooping. So I get to see the piles and their little footprints and scratches.

The carport, of course, is about 2.5m off the ground and I can only access it from the edge, standing on a ladder. It's not like I can walk out there and clean it every day, it's a major production even to get a hose up there, and it doesn't support human weight.

It is spring and it's raining like nuts, with the El Niño it's forecast to continue like this for months. There is literally a sandpile across the street but the cats want to crap on my carport, I suspect it has something to do with the sand being wet.
I have a dog, but he's a dope and thinks he can attack the cats from beneath (and he might actually break through like the Kool Aid man, since he is jumping on my car to get to the cats). The cats don't care, they seem to think it's funny and it stops them not at all.
I have seen repellants, alarms, motion strobe lights, etc. Our security guy says the only thing would be to put electric fence literally everywhere, which I don't have money for (or desire either. Our shop has electric fencing everywhere and the cats still are all over the place). Ultrasonic repellers, even if they work, would probably make my dog even more insane.
The cats are semi-feral. Nobody is responsible, but I suspect many people feed them.
My kid is a biologist and says nothing is going to keep them away other than mortal solutions, which is not compatible with my organic garden and the animals who live in it (also my dog).
I thought of putting up some sort of smelly stuff but it's raining every day for the foreseeable future. I can wash off the crap every few days (if the rain doesn't get it off) and try to spray something.
The entire thing is 7m by about 5m-- too big to put the suggestions I've seen like sticky tape, spiky things, etc. I can't build a wall between all the roofs and I'm starting to feel like this is absolutely impossible, every solution has a problem.


Might anyone have any advice? Words of comfort? Want to buy an otherwise nice house in a great neighborhood?

Ugh, that's nasty. Feral cats can deposit all sorts of disease/parasites in their faeces.

Aside from lethal measures, a deterrent is needed that will survive the rain.

Do you have access to good sticky clay? Do you have access to powdered cayenne? Not the wimpy stuff that North Americans use, but the absolutely nuclear-hot ethnic stuff that will melt your face?

Perhaps you could create sticky pancakes, mixing these two elements. These would erode less quickly in the rain, especially if dried first, and might coat the roof with hot cayenne as they slowly break down.

A cat with ethnic hot cayenne stuck to its paws will be encouraged to move on.

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Edit: A discarded carpet saturated with the above elements might do the job with less work.

Our daughter recued a dog from Mexico.  It ate all the cayene pper we had put out to keep our dog from eating stuff.

How to the cats get up on your carport?

I have read that cats do not like citrus or eucalyptus.  Try citrus peeel on the carport.

Is there any way to string a lattice work of fishing line across the top of the carport to dissuade the cats from walking across the roof?

The only thing coming to my mind is how much cats hate to walk on stuff that crinkles, like aluminum foil or crinkly plastic - but I can't figure out how to make that work on top of a carport...