Grassed waterways are low maintenance, but definitely not maintenance free. Spring is a great time to check the status of your grassed waterways. They need annual maintenance and need to be check periodically. Annual maintenance includes mowing the waterways about two times per year to keep vegetation short and promote sod-forming vegetation to tiller for soil protection. To keep the grass short in the waterway is important to avoid soil carried in runoff to settle out all at the edge of the waterway. This will quickly lead to formation of a 'bund' at the waterway edge which will block water entry into the waterway - instead water will start running parallel to the waterway creating a rill/gully on the edge of the waterway. Bund-formation at the edge of the waterway is inevitable but it can be slowed by mowing the vegetation in the waterway as described above. After several years, however, some maintenance is needed to remove the bunds - this is an opportunity to enjoy some recreational tillage with a disk to level the edge of the waterway. Don't forget to reseed the disturbed zone so your grassed waterway does not lose its effectiveness.