OB15

Other then reducing the risk of erosion and bank failure, a Riparian Zones also creates lot of habitats and helps with light penetration. The debris from fallen trees creates a small ecosystem for small creatures and slows down the speed of the river. Also, when vegetation decays into the river, it creates Tannin, which helps with light penetration.

There are many different ways a Riparian Zone affects streams. Among them, Riparian zones can reduce the risk of erosion. The root systems of trees and shrubs reinforces cohesion into the soil and by providing a protective surface matting. Also, trees use the water from the stream to increase the drainage in the soil, which reduces the risk of bank failure.

https://www.water.wa.gov.au/__data/assets/pdf_file/0008/3113/11441.pdf