Willow spiling for bank revetment. The technique uses woven living willow to form flexible, live, growing structures that resist and deflect water flows, enabling the bank and vegetation to naturally re-generate and stabilise to prevent further erosion.
As if I needed a reason to want willow trees. More on permaculture -- each element performs multiple functions. NOTE from Cindy Barg: Willows drink a lot of water so be sure you don't plant it if there's danger of it draining your pond, for instance.
Reducing soil erosion is important to preserve the nutrient rich soils and natural or unnatural topography. Using plants for erosion control is an excellent method. This article will provide more info.