The concrete channel is a common existing condition of the LA River and features a trapezoidal or box shape channel with a low-flow channel in its center. While this condition does not support native plant communities, the concrete absorbs heat from the sun and warms the water in the channel enough to support abundant algal growth. Often water overflows the low flow channel or is intentionally spread across the channel and a mat of algae forms across the channel bottom.

This algae is a food source for many shoreline and other nesting birds, such as the great blue heron and black-necked stilt. This is especially important in the estuary area of the river near Long Beach, designated a Significant Ecological Area for bird habitat and migratory birds.