In soil and water bioengineering, the technical solution used is very important, and in recent decades quite a lot of research has been done in this field. A German engineer, Lothar Bestmann, more than forty years ago, began to look for technical solutions for plant establishment. After some research, his first finding was that helophytic herbaceous species do not need soil but they can thrive with water, nutrients and a substrate in which to develop.
At substrate level, all kinds of materials were tested: straw, branches, fibres, etc., until an excellent material was found, which was also a by-product at the same time: coir fiber. The first idea, therefore, was to grow plants in pots with coir fiber. The result was a plant unit structured in fiber, which also possessed a vital amount of rhizomes, so it had stock reserves for growth, for withstanding low flows and floods, etc.
Given the demands of modern soil bioengineering, which aims to perform the most effective interventions with nearly immediate results (offering guarantees when there is uncertainty and risks involved in river dynamics) and to operate like conventional engineering solutions, research continued and more complex forms of presentation were developed.
The goal is, thus, to create more developed units in order to accelerate establishment and improve resistance. New materials consisting of grassland structured in fibre and reinforced with a mesh were produced. This provides tangential resistance thanks to a double-mesh made using coir fiber.
This product consists of well-structured herbaceous blankets with a highly-developed root system, which will be prepared in shallow pools. Several technical names have been coined: grassland structured in fiber, plant pallet, plant carpet, coir pallet, etc. These vegetated carpets allow structural stability in water with ordinary speeds of less than 1.5 m/s and their establishment in permanently flooded areas.
However, in some cases plant structure was still not developed enough and therefore research carried on until the true brick of biological engineering was created: cylindrical structures of coconut fibre, pressed and packed in a permanent polypropylene mesh. The key to this finding is that fiber degradation is slower than root growth, so that roots take over the tubular structure entirely and stick to the ground. Currently, in cold and non-eutrophic waters, polypropylene mesh is replaced with coconut mesh.
This product is currently being used all over the world and has different names: fiber roll (the original name), bio roll, coir logs, etc. The key element, we must not forget, is the vegetation, since the structure serves only as a system for the effective establishment of plants in especially dynamic areas. Since the central element is still the plant, the fitted structure is pre-vegetated, and the plant is well-developed. Also, whenever possible, it is necessary to work with varieties typical of the area.