Don't use organic matter for fill. Unless you live in a completely barren location, it will constantly break down, getting smaller and defeating your purpose.
If you have an erosion problem that should be addressed first. (!!!!!!)
The free fill could have unwanted material; big rocks, trash, building scrap. "Clean" fill USUALLY means none of that, but sometimes indicates that it contains inert material that won't break down like concrete or road scrapings. Verify before they dump it in your yard.

I second alphonse. Organic matter/compost does not act the same as "dirt". It breaks down and you will be right back to where you started.

Fill dirt in my area is nasty stuff, full of bits of everything, usually asphalt. Top soil is really what you want so your instinct was right on.

You might have to expand your looking area. Usually, nurseries will carry top soil in bulk.

Carry on - Val

Alphonse hit the nail on the head with both of the issues that immediately came to mind: do not use compost, leaf litter or any other similar substance. You need something with the mineral portion of soil. I'd advise that you keep looking for a source of top soil. Fill dirt can be (and often is) a very undesirable substance. Why else would they be willing to pay YOU to get rid of the stuff that can't be used in construction?

He also suggested that you figure out and fix the situation that is causing the erosion, in the first place.

Fill dirt isn't necessarily always full of trash, but I still would not use it, mainly because even if it's nice soil with no rocks or debris, it's going to be SUBSOIL with virtually no organic matter (which is what makes topsoil topsoil). If they could have sold it as topsoil they would, since they aren't it's subsoil. If you were filling a deep hole you could use that, and top with topsoil, but you aren't, so if you ever want grass etc. to grow on your new surface, you need topsoil.

Thanks for the advice. I'll definitely skip the fill dirt. I think the erosion happened because I'm at the corner, and a bit higher than the street level. I'll keep an eye out for top soil... and will probably mix in some compost for planting.

Sounds like a good plan.

Yes, organic matter in soil does constantly break down, and that is why it is necessary to replace the organic matter in soil constantly. "Topsoil" is not "topsoil" because it has organic matter in it it is only because it is the top 4 to 6 inches of soil. So, fill dirt and "topsoil" can be, and often are, the same thing. Soil is composed of the minerals, the sand, silt, and clay particles, and organic matter. The mineral particles are what make your soil what you have and the organic matter is what really makes it soil and not just dirt.
Erosion is caused by water flowing over soil faster then the soil can absorb it, and that carries soil particles with it. So why is so much water flowing that fast over those areas? Why won't the soil absorb that water fast enough to prevent the erosion? Erosion occurs more often in soils with low levels of organic matter.

In my area, no one thinks of fill dirt and topsoil as the same. Below is a link to how people here interpret fill dirt or subsoil. You don't want organic matter in your subsoil.

Val

Here is a link that might be useful: Fill Dirt

I think if you ask just about any construction or landscaping person what topsoil and subsoil are, you'll get pretty much the same answer. Maybe it's like obscenity: hard to define but you know it when you see it. :-]

Defining "topsoil" is not at all difficult. Every dictionary and encyclopedia I have read defines topsoil" as the top 4 to 6 inches of soil. That can be something that contains some organic matter or might be nothing more than sand or clay, depending on where it came from. Most people I do get to tell me what they think "topsoil" is tell me they expect that to be loam and it will not be. I have seen stuff sold as "topsoil ranging from spent foundry sand to a mixture of the dredgings from a lake mixed with sand. Even if one were to get some soil with 5 to 8 percent organic matter in it when you put it on your soil that becomes even less so why not just add organic matter to what you have from the start and make your own "topsoil"?

I only see one way to correct the problem. Correct the problem. To much water or to much water velocity. A drainage system should be installed. Treating the symptoms is not the cure.
Fill dirt can be any one of may things and is not designed to grow anything in, it is designed to give the foundation stability. It should be a hard none porous drainage surface, non organic material. Garden soils are designed to grow plants in and should be highly organic.
The fill dirt was installed for a purpose and should not be replaced. The top soil should be on top. The water should leach down through the growing media and drain off once it hits the fill. The original fill should have had an original slope of 6" in 10' feet away from the house as per International Building Code. Disruption or lack of maintenance (erosion) of this fill can and often does create foundation problems.

You mentioned getting bagged top soil. Bagged top soil is not dirt — if you read the bag — it will say under top soil “soil conditioner” or something like that. If you read the ingredients you will see bark, peat, compost. Some brands add in a few other things in very small quantities to make you think you are getting something special— you aren’t because it’s in such small amounts compared to the bark, peat, and compost. And that’s providing what they say is in the bag is in the bag. The compost can be anything from municipal waste (including human waste) or it can be trees that have been chopped down or storm downed that could be diseased or full of pests, or it can be yard waste which is what landscapers and homeowners get rid of and includes leaves, branches, grass clippings, etc. The wood components in all mulch with the except of true bark (pine or hardwood) can be anything from trees as mentioned above, to recyled pallets, recyled furniture, discarded house trim, siding, etc when remodeling is done or a house or building (residential or commercial) is torn down — whatever and wherever they find wood. My issues is that the recyled wood can contain lead paint, heavy metals and pesticides, herbicides, paints, all types of chemicals etc stored on pallets for long periods and have leaked. You don’t know until you look at them. Also house and building debris may have all kinds of chemicals, and discarded furniture has varnish, solvents, paints, etc in those. The premise is folks are mulching their lawns and ornamentals with these mulches so should be okay, however, once broken down they end up in “compost” and are mixed in with expensive turf and garden bed mixes in bulk and bagged. No matter what they tell you — there is no one checking the wood or trees etc to see if there are termites, lead paint or paint period or some disease. They do check the line to make sure rocks, concrete, metal, etc doesn’t slip through but that’s because they don’t want to tear up their grinders. But truly once this stuff is broke down, know one knows. But what makes me so darn made is they call it topsoil when they know there is no soil in the bag. Potting soil is pine bark, peat moss, perlite, and sometimes vermiculite along with other good sounding things. Top quality like ProMix — you can go to their website, find the type and search their site for the ingredients. It is usually pine bark (the actual bark of the tree - not the interior wood), peat moss, perlite, and lime to adjust pH plus you can buy some with mycorrhizae and biofungicides already added which is what I get. Good luck. As others mentioned — buy bulk and try to find someone who will mix to your liking and who will give you a soil test or least the pH for the pile in front of you. But sly ones will even take sub/fill dirt, run it thru grinder and screen to make it look fluffy and add in compost (aged or dyed ground wood) so it looks dark and rich when it is mostly crap dirt. In addition, on the cases where they are paying you to take — you better run for the hills and in free too. A friend had about 50-75 yds delivered to his farm to spread in low area so he could get to it a little better each spring. After he planted corn, it was dying and in awful shape, got the extension folks out and it was tested. It was so bad and he was above a creek — full of heavy metals and toxic chemical substances from a remediation project - he got fined and was ordered by the state to have it removed and pay to clean up the creek. He gave them the guy’s name and guess what — no one answered, no one knew him, nothing - it was a big mess and a whole lot of money but as he said - he should have done his due diligence and he was in such a hurry for free and fell for the story. Lucky for my friend, the state or federal whichever worked with him because they had similar situations with others over the same guys. Apparently these guys were paid to take the bad soil to a specified dump site that’s lined and set up to handle such stuff — instead they dumped it on vacant land, put ad in paper for free pickup and then charged to deliver it to you — and disappeared having given false information. And of course, no one thought to ask for identification, or to write down license plates, nothing. The owners of the land didn’t know anything, didn’t even live in the same state, just empty inherited land they hadn’t sold due to prices, weren’t even renting the land, hadn’t seen the property for decades. They were in hot water too — same issue of contaminated soil able to wash to a small river off the edge and already causing issues downstream on someone’s native plantings. Obviously, these scoped the property out and was accessing the back where no one ever saw them. When the authorities went there after someone reported issues but were a pickup not a delivery — they saw where the dirt had been and some still was but no hide nor hair of the guys. It took months to unearth the folks who had gotten caught up in this mess. So be careful - free can be quite costly to the tune of tens and tens of thousands of dollars, fines, time in jail, etc.

As someone mentioned — you want native top soil - actual dirt with minerals and organic matter. If buying bagged products, only get from “reputable” companies you can get back to in order to get your money back. Compost and top soil/soil,conditioners and many mulches are not standardized so each load is different. Higher brands of bark only mulch will be as close to what it says as anything but still it will vary because the types of hardwoods vary and there is a big difference between bark mulch, and just mulch. “Mulch” is any and everything wood; pine bark mulch should only be the bark of the pine tree. And hardwood bulk mulch should only be the bark. If it doesn’t say bark...it’s anything, might be hardwood tree but could be any part of the tree and it does make a difference. Also, ask if they have dyed any of their compost or mulch products. They will call it aged and then dye it to make it look like it has aged for a longtime. The longer mulch has aged, and is getting close to dirt consistency, the less it will tie up the nitrogen and some of the other nutrients in your soil while it tries to break down the mulch. This means it draws those nutrients from your plants. I grow orchids, when you grow them in bark, you always have to supplement with more frequent applications of nitrogen — I use a basic 20-20-20 and then supplement around with my other items like calcium, magnesium, trace minerals, etc.