River management - What's best on the banks?

In the United States, part of the policy for conservation of aquatic ecosystems is to encourage the restoration and protection of stream and riverside forests. A new study of various forested and grassed reaches along a creek in Wisconsin, however, implies that grassy banks are subject to less erosion, at least in some circumstances, and may therefore be more desirable. So many interacting variables are involved in such systems that it is difficult to formulate general management policies. Perhaps it is best simply to let Nature take its course and let bankside vegetation develop naturally