Starting a lawn is a daunting task for the typical homeowner. Much preparation and time goes into the process from preparing the seedbed all the way to planting the seed. One of the biggest challenges after going through all that work is keeping the grass seed in place until it germinates. Erosion of grass seed is a common problem--especially on hillsides. There are many steps you can take to stop erosion of new grass seed.
Rake the seeds into the top 1/4 inch of soil after seeding the planting area. To do this use a garden rake and gently drag it across the planting area to pull the seeds underneath a light layer of soil.
Spread a thin layer of compost, soil or mulch over the planting area. A depth of 1/4 inch is sufficient. You just want to cover the seeds lightly with soil to keep them from blowing away.
Use a grass erosion mat on hills and slopes. Place the mat over the seedbed on top of the soil. The grass will germinate and grow though the mat. It will then decompose into the soil.
Water the seedbed frequently to keep the soil wet. Moist seeds and soil can't blow away as easily. Ideally water the seedbed two to three times per day for five to 10 minutes per watering until the grass seed germinates.