United Kingdom 
I have a bank of length nine metres down the slope that has been covered largely in bramble. I am removing the bramble over this spring and summer and intend to grass the slope this autumn. The surface of the slope is clay. I estimate the slope to be approximately 45 degrees. The slope faces South
My questions are;
Do I need to spread topsoil on the slope and if so how deep a layer and how do I prevent the topsoil washing down the slope in heavy rain and when applying essential watering What will be the best specification for the grass seed and again how do I retain the seed in position in heavy rain.
Should I spread the seed first and cover with topsoil to also eliminate the risk of birds feeding on the seed.
Roger
18 Jun, 2011
Answers
Don't forget that this bank will be quite difficult to mow. In the same situation I went for ground cover plants - not grass - so it didn't need to be mown. If you really want grass, I think Inverglen's suggestion of turf is a good one. I don't know of anything temporary that would hold the soil while the plant roots get growing to hold the soil in place.
18 Jun, 2011
Try pushing short lengths of garden cane through the turf once it is place, this will keep everything in place until the turf has rooted, then simply pull the canes out after 6 or 8 weeks. I used this technique to great effect when turfing some 'telly tubby' mounds.
18 Jun, 2011
Might it be simpler to lay rolls of turf instead ?
18 Jun, 2011