Lining the high-flow channel with boulders appears to be an effective means of controlling the invasion of reeds from the low-flow to the high-flow channel. From an amenity perspective, this is an important point, since local communities were opposed to the creation of a dense reedbed channel. Alternative low-growing wetland species (e.g., Carex spp.) would have provided water quality, and even habitat functions, without threatening human security.