Ecotechnical methods in order to stop erosion of riverbanks

and slopes

Răzvan Voicu

Method 1

Coconut fiber rolls or fascine rolls will be placed in a semicircle, on the slope, at a

distance varying between 0.5 m and 3m. These rolls can be made in one piece (which is

preferable) or more pieces, depending on the width of the slope. Being placed in a semicircle or

half-buried in the soil, the rolls will redirect the water flow on the lateral side. (Fig. 1- fascine

rolls or coconut fiber rolls, slope, drains, Positioning of fascine rolls – indicative scheme)This

solution is viable for both a convex slope and a concave slope.

fascine rolls or coconut fiber rolls

slope

fascine rolls or coconut fiber rolls

slope

drains

Figure 1 Positioning of fascine rolls – indicative scheme

This solution is viable for both a convex slope and a concave slope. Some species of grass with

fascicular root should be planted between the rolls, helping to fix the slope. Bamboo cuttings will

be fixed at the top of the rolls, which in turn will form a drain that is connected to main

drains(fig.2).

bamboo cuttings

system (hemp ring) for fixing bamboo cuttings to fascine rolls

fascine rolls or coconut fiber rolls

slope

drains

Figure 2 Positioning of bamboo cuttings – indicative scheme

After a while, the bamboo cuttings will fix their roots into the slope so that they could not

ever slip down(fig.3).

system (hemp ring) for fixing bamboo cuttings to fascine rolls

bamboo cutting

fascine rolls slope

Figure 3 Fixing bamboo cuttings to fascine rolls – indicative scheme

With such a support system, the rolls can never slip down. The two outside drains should

be ecotechnically arranged, where possible(fig.4).

riparian vegetation

wood

Figure 4 Ecotechnical arrangement of drains - indicative scheme

Method 2

Another method suggests fixing several lines of (willow, alder, bamboo, etc.) cuttings

into the slope, perpendicular to each other(fig.1).

cuttings

hemp fixing system

cuttings

slope

Figure 1 Positioning of cuttings – indicative scheme

This fixing system on the slopes stops tangential efforts and eventual sliding of different

pieces of the slope (action and reaction) (fig. 2).

cuttings

F1

F2

F3

F4

slope

Figure 2 Action force of the slope and reaction force of the cuttings – indicative scheme

The conditions of fixing these cuttings(fixing angle) diversify in function of land texture,

the erosion of land, the angle of slope etc).

Method 3

Another method of stabilizing slopes would be drilling cylindrical holes in line where

coconut fiber rolls to be fixed. These rolls are surrounded by 3 or 5 (alder, willow, bamboo, etc.)

cuttings (fig. 1). Positioning of these cuttings is performed in line or rhomboidally.

cuttings

coconut fiber rolls

slope

Figure 1 Positioning of cuttings – indicative scheme

Method 4

Stopping pronounced erosion of watercourses is an important process for the dynamic of

rivers, biodiversity and to protect the human settlements in their vicinity. Therefore, on the river

bank, near the eroded area, wooden poles will be set parallel to the eroded area. Cuttings (alder,

willow, bamboo, etc.) will be fixed to these wooden poles by using hemp canvas (fig. 1).

cuttings

watercourse

wooden poles to support the cuttings

Figure 1 Fixing the cuttings – indicative scheme

After the roots have been developed, cuttings will stabilize the bank directly, but they

will also redirect the watercourse outside the eroded areas. First, to achieve these solutions, a

channel along the eroded area must be done. After the channel has been performed, a wooden

pole will be set crosswise or transversal to the channel, but on an inclined plane (fig. 2).

supporting pole

Figure 2 Fixing the supporting pole – indicative scheme

After that, the bank is drilled on the outside so that the three rows of cuttings to be fixed

on the supporting pole. (fig. 1). After the cuttings have been fixed on the supporting pole using

some hemp clothes, the channel is sealed. The bed is linearized before stabilizing, where

possible.

Method 5

Another method of strengthening the slopes consists of their fixing by the means of straw

rolls. Using cylinders of hemp, some cuttings will be laterally fixed on the straw rolls (fig.1).

straw rolls

cuttings cylinders of hemp

Figure 1 Fixing the straw rolls – indicative scheme

The straw rolls can be placed all over the slope or only in different areas (fig. 2).

straw rolls

Figure 2 Placing the straw rolls on the slopes – indicative scheme

The advantage of this solution is that it can successfully stop the massive dislocations of

the slopes.

Method 6

This method consists in fixing the soil (slope) using wooden poles arranged

longitudinally on the slope (fig. 1). The poles are arranged uniform all over the slope. Some

cuttings with a branched root system will be fixed perpendicular to these wooden poles (fig. 2),

which in turn will support the slope.

wooden poles

Figure 1 Placing the wooden poles on the slopes – indicative scheme

cuttings

fixing system for the cuttings

slope wooden pole

Figure 2 Positioning of cuttings – indicative scheme

Cuttings are fixed on the wooden pole using hemp canvases allowing their growth. Due

to their elasticity, the wooden poles keep the soil under tension by fixing it (fig.3).

F1

F2

F4

F3

Figure 3 Action force and reaction force – indicative scheme

Method 7

The arrangement of the river banks can be achieved by using some pols and cuttings.

Two horizontal wooden pols are attached to other two vertical wooden poles, which in turn are

attached to the river banks in the eroded area. (fig. 1).

wooden poles

Figure1 Positioning of wooden fence – indicative scheme

The wooden bars are attached together by the means of a metal catching system in order

to form a fence. The fence is in the form of an inclined plane and a set of compact cuttings are

fixed on it by using hemp rings (fig. 2). These cuttings will fix the soil and stop the erosion. They

will operate as a bank which cannot be eroded. As the method 4 presented above, a channel

parallel to the eroded area must be developed in order to achieve these results.

erosion of the river bank

watercourse cutting wooden poles

Figure 2 Positioning of the cuttings on the river bank – indicative scheme

Method 8

Other possible solution against slope erosion consists in making exclusive wooden

rectangular gabions. Cuttings are fixed to the horizontal sides (fig. 1). As presented before in

other ecotechnical methods, the cuttings will be fixed on the gabions using some cylinders of

hemp fixed by these gabions.

wooden gabion

cuttings

Figure 1 Positioning of a wooden gabion– indicative scheme

Fascine rolls for gabions stability will be set at the bottom of these gabions (fig. 2).

cuttings

wooden gabion

fascine rolls

Figure 2 Positioning of fascine rolls – indicative scheme

After a time period, the cuttings will fix their roots into the slopes. For greater

effectiveness, the gabions are arranged rhomboidally all over the slope. (fig.3).

wooden gabion

Figure 3 Positioning of gabions on the slope – indicative scheme

Conclusions

All these ecotechnical solutions can be applied worldwide according to previous surveys

on slopes or watercourses. Costs are lower than for traditional solutions; ecological materials are

used in order to restore the study areas effectively.

Bucharest 2012