Description: In an unlined waterway, the earth surface is liable to erosion by high velocity flow. Where flow is intermittent, a grass cover will provide protection against. By reinforcing the grass cover the resulting composite armour layer will enhance erosion resistance and reduce the risk of failure of grass protection due to localised poor cover. A variety of reinforcement systems have been developed for this purpose using either geotextiles or cellular concrete. The principal applications of reinforced grass are in steep waterways such as auxiliary spillways on dams, and protection to embankments against erosion by overtopping during extreme flood events. This report sets out the procedure and principles for the planning and design of reinforced grass waterways. Hydraulic, geotechnical and botanical aspects are covered, worked examples are given. Considerations relating to specification, construction and on-going management are discussed. Various proprietary reinforcement systems available in the UK are described. Data from full-scale trials on prototype reinforced grass channels are provided.