The Sacramento River is filled with salmon, steelhead trout and Delta Smelt.  If workers were to just add rocks and soil to weakened levees, the fish would lose their habitats.
So E.J. Koford, with the state Department of Water Resources, says they’re sticking branches underwater for the fish to hide in, and they’re planting trees on top:
 
Shade is critically important in the summer, when fish are coming upstream, the water gets hot and shallow, and also it’s easy for aerial predators to dive down and pick off fish if they don’t have a place to hide out of the sun – overhanging trees are very, very important.
 
With miles of levee repairs planned, Koford says if branches and trees weren’t part of the process, the banks of the Sacramento River would be rocks and cement only, something environmentalists at the department don’t want to see.