If you are interested in a grassed waterway,
After the waterway is cut according to design, it needs to be seeded and mulched down as soon as possible. The sooner it is seeded down, the better the fescue grows. Waterways are seeded with turf type fescue. The approved NRCS seeding dates are between March 15th to May 30th in the spring and Aug 1st to Sept 15th in the summer.
The grass-lined waterway is one of the most commonly used conservation practices. When rainfall exceeds the infiltration rate or available water holding capacity of the soil, surplus water will run off over the land. Since the success of any soil conservation program depends on the removal of this surplus water without undue erosion, the area needed for waterways should be dedicated to this purpose and forage production should be secondary consideration. Grassed waterways are applicable only to those areas where rainfall or irrigation provides the moisture needed to grow and sustain a good grass cover.
The finished product of a successful waterway should look similar to these photos. The seed coming up uniform throughout the waterway and the dirt that is taken out of the waterway laid along the side, spread out across the field.