River sand with decomposing matter

We went on a drive to the river today.  I planned to get some river sand but opted to fill my bags with this instead.  It looks to be 1/3 -1/2 sand and the rest decomposing leaves and sticks.   This was on the high point of the sandbar and I'm assuming this was deposited there by flooding.  I'm planning on incorporating this into a mix for my raised beds, so I'll be adding decayed and crumbled wood and what compost I have.  I'm planning to sift out the larger leaves and sticks but wondering if I'll be tying up the nitrogen in the soil?  I have blood meal and have been adding deleted urine to some of my other beds with the decayed wood.

Looks like useable stuff Michelle. Decomposing at first takes nitrogen, before it gives nitrogen. This looks half decomposed, but it's a mix of many stages. I wouldn't take the chance personally to mix it in all the beds compost. I would try it out in one bed or a part of a bed. Observe the difference.
I use a straw layer when i start a new bed on grass to kill it off and add a mount of compost on top. This river debris looks like it could perform a similar role and because there are many stick in it they could take longer to decompose and start to act like spunges later on. Which is better than the straw/hay i use. So there is that.
If i have garden waste i just pile it somewhere out of the way, it's a great refuge for some animals that eat snails and the likes, also for snakes, so maybe not good where you are.
If you've got an animal waste stream, like chickens or cows, i would dump it in their bedding. It contains that much nitrogen, pile it up and compost that, it will make a beautiful compost.
Or use it on pathways between beds, it will compact because you walk on it, keeping it moist-ish and mycelia will enter it, take the nutrients and exchange it with sugar at the root tips of plants.
Anyhow, very usable! If clean.

Thank you Hugo!

I have sifted the larger leaves and sticks out of half of it and will be using the finer stuff in the next bed I build.  The larger debris and the other half will compost a bit. After sifting, I would actually say this is about 25% sand as there's lots of organic matter present.  

Oh and it seems very clean. I only found two small pieces of plastic in it and thankfully the spot where I collected this is only five miles from the river's origin.  

Update to this thread:

To date I've used the sifted sand and decomposing matter in two beds with great results so far.  The beds were made using this, a small bit of sand, composted cow manure, top soil and a bit of compost.

In the beds, I have a combination of tomatoes, beans and peppers and all are looking fantastic. The slugs made lace of my pepper transplants but they have recovered and actually have flower buds forming.  Tomatoes will need to be staked soon and a trellis is already in place for the beans.  

So, for a free and unexpected resource, I am more than happy with the results. I still have two buckets of the sand/leaf mix left and hoping I can score more of it soon if the state hasn't cleared the sandbar.

The large chunks of debris that were left after sifting have become the bottom layer of my new compost pile.

Another update:

Beds using this mix have performed magnificently!  I did have a large trash can of sand/decomposing leaves left and added a bit of compost to it so it has decomposed even more. I'm about to incorporate it into a new bed where I'll be planting some fall salad greens. It was definitely worth the effort to gather it.