Can Styrofoam be safely buried for drainage?

I am looking into an alternative for wood chips for a swale design that could last hundreds of years with no upkeep. The problem (correct me if I'm missing something) with a traditional swale on an intense hill is that it will eventually fill in if left alone.
The purpose of this is to turn eroded wild landscapes into permanent water catching devices that could reinforce the area with water & food forever.
I have been looking into the packing peanuts around perforated pipe they use for EZ french drains (https://www.ndspro.com/products/drainage/french-drains/ezdrain.html). I thought that maybe lining the trench with landscaping fabric, and adding a foot or so deep of crushed Styrofoam and packing peanuts, and folding it all in the landscaping drain fabric to keep it in there may get the permanent mulch effect I'm looking for. Added benefit: getting tons of this crap out of landfills.
I've scoured the internet for reasons why I shouldn't do this, but haven't produced a reason to believe styrofoam has any negative impacts in the soil with no light or heat.
Does anyone have any opinions or resources on this?

Thank you for reading! Have a blessed day

The soil that normally fill up the swale where do you want it to go? It's being created and it needs to go somewhere?
On an intense hill one might use a terrace or other types of earthwork that isn't a swale.

In my head a functioning food forest will generate enough of it own in less than 10yrs.

I believe the styrofoam will eventually become exposed, becoming a blot upon the landscape and eventually it will degrade into tiny particles of plastic, which are a hazard to many creatures.

Thanks. These are good reasons.

I don't know that a food forest compete with the rampant deer overpopulation on the American east coast and I would think that the styrofoam would be less awful in a regenerated landscape than in a landfill, where it would go anyway, but since it is unnatural and in question, these seem like perhaps good enough reasons to avoid it.

Some of us are experimenting with bioremediation of styrofoam:  https://permies.com/t/103412/critters/Superworms-bioremediation-polystyrene-ideas-extending

It's personal choice. I want to leave my properties in a better condition for future generations, so I don't use 'nasty' chemicals unless there's absolutely no alternative e.g. Killing invasive weeds (careful selective painting, never spraying), even minimising the use of PVC piping, etc.

So using synthetic materials in land stabilising is a no-no because of the mutagens often used in their manufacture - downstream water quality et al.

As noted by S. Benji, Swales shouldn't be used on steep slopes (>15%) because of land slip issues, so some other alternatives may be more long lived e.g. Small terraces, a row of rocks or old concrete, gabion baskets, logs pegged into place, etc.

Once plants get a foothold, nature takes over: nature hates a vacuum. (Aristotle must've been into Permaculture too!)

So, I suggest allowing styrofoam to go to landfill in a few already polluted locations is better than spreading its toxins all over the place - including unsuspecting future generations.