Coconut fiber log used to control erosion.

Coconut fiber logs are frequently used in shoreland restoration projects – usually to protect an eroding shoreline (see From Shore to Shore Nov-Dec 2003) or to protect newly installed aquatic plants from wave action. They are made of compressed coconut fiber surrounded by a mesh tube. They are usually 10 feet in length and range in diameter from 6-20 inches. Their life expectancy is 3-5 years – herein lies a potential problem…

In 1999, a shoreland restoration project was installed on a Minnesota lake, using coconut fiber logs anchored at the water’s edge to protect the planting. Native plant seed and plants were installed in the upland and wet transition portions of the project, and aquatic plants were established offshore in shallow water. One…two…three years passed. Aquatic, wet transition and upland plants all flourished under the owner’s care and spread to form a beautiful shoreland buffer. The fiber log held fast in spite of waves, floods and ice action. Some “volunteer” plants started to grow in the fiber log itself. The owners were pleased…until year four. In 2003, the fiber log began to decompose (as expected), the log and plants growing in the log were gradually swept away by wave action, and the soil and well-established plants behind the log were soon to follow. By mid-summer of 2003, only the upland portion of the shoreland planting remained.

While a very unfortunate situation for the shoreland property owner, future users of coconut fiber logs can benefit from the lessons learned at this site:

1. There is a limited window of time (3-5 years) to establish dense vegetation in and around the coconut fiber log. (There was limited vegetation growing in the fiber log and none growing between it and the aquatic vegetation at this site.) The logs should be placed so that they are partially submerged along their entire length during the average summer water level. At this location they can protect the plants behind it from uprooting, protect exposed soil from eroding, and provide favorable moisture conditions within the log to promote plant growth. Dense plantings of wet transition and emergent aquatic plant species directly behind the logs will naturally spread water-ward and grow through the fiber logs in the process. Aquatic plantings directly in front of the logs will further protect the area from wave and ice action.
2. The vegetation established in and around the coconut fiber log must have a very dense and/or stout perennial root system that can withstand ice and wave action, as well as seasonal water fluctuation. (The vegetation that established by itself on the fiber log at this site was primarily fine, shallow rooted flower species – some annual.) Plant selection is crucial in this area of high erosion. Species with underground stem and root systems that are very resistant to erosive forces and adapted to fluctuating water levels include: hard- and soft-stemmed bulrush, three-square, spike rushes, sedges, sweetflag, arrowhead, and burreed. Plantings at the water’s edge should be predominantly these species. Further up in the wet transition zone, willow, redosier dogwood, other flood-tolerant shrubs and flowers can be added. Many of the showy, wet transition flower species do not have root structures that will resist erosion and should be used sparingly at high-energy sites.

To view a very successful shoreland project at a very difficult site (extreme water fluctuation, wave action, and high human use area) visit Lake Phalen. The Ramsey- Washington Metro Watershed District and the City of St. Paul Division of Parks and Recreation have worked together to established a shoreland buffer along the southern portion of the lake that is a wonderful example of effective use of vegetation for both shoreline erosion control and upland beauty. For background information on this project visit www.rwmwd.org.

Posted in Care of Shoreland Property |