|
|
||
 Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
enough to justify rock. Then, vegetation is planted or grown in the roll to form part of the
splash zone. Figure 23 is a schematic of a coir roll abutted to an unshaped bank with some
backfill. Figures 24 a-d show such a treatment in a stream in Germany and planted with
emergent aquatic vegetation, such as bulrushes, iris, and sedges. Vegetation can be grown
in the roll at a nursery and then transferred to the planting site with vegetation almost
established.
Coir rolls and emergent aquatic vegetation have also been used in this country recently.
One such use was on the North River near Colrain, Massachusetts. It was monitored as a
part of this work unit for two growing seasons. That case study is presented in Volume II.
Both single and double coir rolls were used in different sections of the streambank. In the
latter case, another roll was placed upslope from the first one. Both were planted by inserting
clumps of emergent aquatic plants in them. Where overhanging banks occurred and were
void of woody vegetation, an evenly sloped bank was achieved by shaping and backfilling
using a small front-end loader. Shaping, however, was minimized where possible in an effort
to prevent disturbance of the bank and existant vegetation. It should reiterated that the coir
rolls should be keyed well into the upper and lower ends of the reach being treated. The
authors discovered after the two-year formal monitoring period, that the coir rolls had
apparently been flanked at the upper end as a result of flooding in the fall of 1995 and that
sections of the project unraveled.
Figure 23. Coir geotextile rolls are used to stabilize streambanks and
permit planting of wetland vegetation within them. The coconut fiber
accumulates sediment and biodegrades as plant roots develop and
become a stabilizing system. (From Bestmann Ingenieurbiologie,
Wedel, Germany)
B-38
|
||
|
||
