Gabion Baskets (right/wrong)

Although they have been among the most commonly used methods to stabilize eroding or degraded stream banks for the past several decades, gabion baskets (the metal baskets you see) may not always be properly used. The following is a typical "mixed review" of this fairly traditional gabion installation:

• Right: The gabions are more erosion-resistant than the bare soil of the untreated stream bank would have been.



• Wrong: The gabions are filled with too much gravel which can easily erode out of the coarse mesh and lead to the gabions collapsing or slumping during floods. Instead, filling them with a larger proportion of cobbles and boulders would ensure that the gabions are more stable.



• Wrong: The gabions, by themselves, have a finite life span and will break down. A better technique would be to grow woody plants in among the baskets, so that the trees' extensive root systems will be well-established before the baskets break down.



• Wrong: The gabions, as placed here, create a nearly vertical bank face. Instead, a stepped slope could have been constructed, leaving the uppermost baskets less vulnerable to tumbling into the stream channel during a severe flood. A stepped slope could also have been designed so that each layer of baskets would allow moderate floods to diminish some of their energy by spilling out across the top surface of the baskets, rather than be confined in a narrow channel at higher velocity that could cause damage downstream.