Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
taken to assure that pest species, such as purple loosestrife, are not collected and transferred
to the project site.
The availability of plants of the appropriate species, size, and quality is often a limiting
factor in the final selection and plant acquisition process. Some native plant species are very
difficult to propagate and grow and many desirable species are not commonly available in
commerce, or not available as good quality plants. As demand increases and nurserymen gain
more experience in growing native plant species, this limitation should become less important
(Leiser, 1992). Plant species composition and quantity can often be determined from the
project objectives and functions desired. As a general rule, it is advisable to specify as many
species as possible and require the use of some minimum number of these species. Maximum
and minimum numbers of any one species may be specified. See Part III for additional
information on plant acquisition, times of planting, and plant handling techniques.
Implementation is the natural followup to the plan of development and is integrated with
the planning process. It cannot really be separated from it. It is the final stage of the
conceptual and detailed design but may require feedback into design plan formulation for
possible on-site corrections. It includes site preparation and construction, planting,
monitoring, and aftercare. For the bioengineering design to be successful, it must have close
supervision throughout by someone familiar with implementation of bioengineering projects.
This stage requires close attention to detail. It is important in this stage to maintain
continuity of the same interdisciplinary team who planned and designed the project and keep
them involved in this part of the project. Those capable of actually carrying out the project
should be a team of persons with knowledge and experience of both stream morphology and
mechanics, hydraulic and geotechnical engineering, and bioengineering. Regarding
vegetation, the person should possess both training and experience in wetlands plant science
and development. It is mandatory that person be on site intermittently at least during project
construction and especially planting. All of the efforts to address the various components
of design will be in vain unless plants are handled and cared for properly when planted and
even after planting in many cases.
There are several planting techniques for bioengineering ranging from simple digging with
shovels or spades and inserting sprigs (rooted stems) or cuttings to moving large pieces of
rooted material, such as sod, mulch, and root pads (large rooted shrubs). Other methods
consist of direct seeding, hydroseeding, or drilling individual seeds such as acorns of wetland
oak species. All of the above methods capitalize on combining the attibutes of plants with
some kind of engineered material or structure or relying on the plant itself to form a resistant
structure to erosion, such as a live willow post revetment. Various techniques will be
discussed in detail below.