Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
The biological attributes of an area containing a bioengineering site are very important and
plants are no exception. They are there because they have adapted to the ecological
conditions of the area, such as climate, soils, etc. To use bioengineering effectively, one
should learn to identify and evaluate plants that are growing in the area that have become
adapted. These should include plants that are growing along all parts of the streambank,
lower, middle, and upper. In bioengineering, these conditions and species should be emulated
as much as possible. Native plants or plants that have become naturalized in the area should
normally be used. Exotic plants should be avoided since there are species that may get out
of control and become nuisances. One only has to look at examples such as purple loosestrife
(Lythrum salicaria) to gain an appreciation of the problems exotic plants can cause.
Plants chosen should have some tolerance to flooding. Some will need to be highly
tolerant (those planted lower on the bank) while others (those planted higher on the bank) can
be less tolerant. Plants chosen also will have to withstand some dry conditions as well as
flooded conditions because of the fluctuating nature of water levels in streams.
A mixture of grasses, herbs, shrubs, and trees should be used, if possible, to provide a
diversity of wildlife habitats. Some legumes such as yellow sweet clover (Melilotus
officinalis), white sweet clover (M. alba), and crownvetch (Coronilla varia) are possible
choices because of their nitrogen-fixing attributes. These, however, should be used at an
elevation subject to only intermittent and short periods of flooding, such as in the upper bank
and terrace zones discussed below.
Plan of Development
The plan of development is the culmination of answering all the questions in the various
categories mentioned above. Many of the questions regarding the above components can be
answered off site, but a site analysis is mandatory before plants can be procured or before
project implementation can occur. In the site analysis, each component must again be
examined to include the various factors or parameters and what will influence vegetation
development for bioengineering and the stability of a streambank. A general guideline for the
site analysis is to be a keen observer as to the conditions occurring at the project reach as well
as upstream and downstream from it. From observations of a reference site, many answers
can be found about what kinds of plants to use, invader species that are apt to occur, causes
of problems, such as overgrazing, road construction upstream contributing to a high bed load
of sediment, etc. The same or similar plant species that occur at the reference site should be
acquired. In a site analysis, much of the data from a reference streambank area can be taken
to answer the questions posed.
B-12
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