I'd like to cover my run and put down gravel or something maybe to help with mud but there is a tree in the run and its on a slope, Anyone got any ideas??? should I terrace it or leave it sloped with gravel??
If you have access to rocks you can just stack them up and make a lttle wall.
or Broken slabs of concrete from a demolitions site stacked like rocks. Sand works great but it does tend to want to travel. Id make the dirt only come up to within about six inches of the top of the retaining wall then top it off with sand. Get the kind that is kind of rough with small and medium sized grains and little rocks. River sand is what I am thinking of. Here we use Decomposed granite (DG). DG is wonderful stuff water permeable and yet it doesnt get muddy like top soil or clay does. And it packs down hard if you let it almost like concrete. both should be available from a Sand and gravel company bought by the yard is rather inexpensive too.
Oh and from the looks of your slope Id do a couple of terraces at least. Remember the retaining wall blocks are only rated for a certain height so chat up the Home depot people for info.
Some people also use Car tires for a retaining wall. Not glamerous but recycling at its best.
Your run looks looks a lot like the one that I am building. It is being built on land that slopes 1 foot down for every three feet out. I have researched the issue and am placing river sand in the run. If it matters, I am sinking 4 x 4 cedar posts below frost line in my area. I don't know if that applies to your situation but in my area they will be 4 feet underground. The posts are 4 feet apart. On the back of the posts I am attaching 2 x lumber that is treated. The box 'interior' of the run will then be filled with a layer of pea gravel and topped by river sand. If you decide to go this route keep in mind that all treated lumber isn't equal. You need a .40 or above rating on the treated material or it will rot. Good luck.