Stabilising Eroded Land
This page deals with recommendations made to an Indian group called C.O.R.D by Active Remedy Ltd., for stabilising eroded mountain land in the Sidbari Area, near Dharamshalla, H.P, N. India. If this land is not stabilized many problems are likely to occur, to the local mountain villages and the communities directly below.
This situation is endemic throughout all Himalayan regions and seriously needs addressing for the environmental stability of all Himalayan countries. As these regions are necessary for the fresh water and climatic stability of the entire northern Hemisphere, this will prove to have devastating global repercussions unless it is dealt with in a connected responsible manner.
Due to the high level of erosion in mountain regions worldwide, these suggestions are intended as a general panacea for all mountainous regions. The goal is to restore and preserve indigenous mixed forest and biodiversity in these regions. This document is looking at some of the methods recommended for implementation in order to reach the stage where these mixed forest plants can be re-introduced. This is also intended to bring new employment, resources and cottage industries to mountain areas.
Members of Active Remedy Ltd. hope to be able to work with different groups and mountain communities throughout the Himalayas and the World helping to implement these concepts.
This is a way of directly tackling ‘Climate Change’ and disaster mitigation by averting serious problems and catastrophes while we still have the time and resources to do so. Repairing this serious problem before it gets worst and while it is still potentially possible to do so could save countless lives and resources.
This work of stabilizing eroded land fits with the overall vision of Active Remedy Ltd. of regenerating the indigenous forests of Mountain Regions as fast as possible, to re-balance the regenerative capacity of the Global Fresh Water and Cooling Systems. For any sustainability in human development to be possible we have to consider and protect that which sustains the global eco-systems. Fresh water is vital for this and because all rivers have their sources in mountains it is imperative for humanity to address the problems in mountain regions as one of the top priorities, when considering all reforestation and the protection of forests worldwide.
Stabilisation of eroded mountain slopes and Biodiversity suggested restoration methodology
Here is an image that gives an overview of the terrain that needs to be stabilised.
It can be divided into three Zones:
A. The high slopes, where some grasses and trees grow but that is rapidly eroding.
B. The severely eroded slopes that have very little soil or live plant matter.
C. The lower land that is uneven, with deep gulley’s, sparse plant cover and deteriorating soil conditions.
All three Zones are very dry with sparse plant cover. Zone (B) is the most severely eroded and the area that is most difficult to stabilise. It will take a lot of resources to stabilise it. Zone (A) is likely to become more like Zone (B) if it is not stabilised quickly. If it is stabilised it will have a positive effect on revitalising and stabilising Zone (B). Because it is the highest point, it has a large effect on the other two Zones. Zone (C) is the easiest land to stabilise. It is the Zone that is easiest to access and the area that is most used by local villagers. Presently it provides poor grazing for some local animals. It supports a mixture of hardy shrubs, bushes and grasses. It is rapidly becoming bare rock and should be stabilised quickly. These Zones would give the local community a lot more natural resources and security once stabilised.
This shows a view of part of the same mountain from a distance.
Zones (A) and (B) are labelled in the far right. It also includes a view of the local famous Temple and the lush indigenous biodiversity that grows in its vicinity. It is a stark contrast to the bare eroded land on the near by slopes. This is the kind of forest that is most beneficial to the local communities wildlife and environment.
It also shows what kind of healthy mixed forest could be possible in this region with local villagers support.
Stabilising Zone (A) (photo below gives a clear view of this zone)
There are a few good stabilising methods that can be used for this Zone. One method is called Hedge Draining’ (Brush Laying). It is used to divert water and to mitigate the problems caused when excess water runs down it and which could potentially wash away important soil and foliage. This is particularly important at the boundary between Zone (A) and Zone (B) because at these loose edges most erosion takes place.
Hedge Draining -Drain and slope fascines
Drain and slope fascines are useful for draining and stabilizing wet slopes and slopes that are in
danger of erosion from sudden floods of water. They are installed at a gentle diagonal slope down the hill towards the watercourse. They consist of live branches of willows, which are tied together with at least 2 mm thick wire. The lowest third of the drain should also contain dead branch material which channels the water unhindered. The tip end of the branches always points to the flow direction. The dead Willow soaks up the water and creates a moisture store for the live stems. Usually the fascines are 30 to 60 cm thick and have no length limit. They are put into ditches and then must be covered with soil so that all the branches are embedded and can take root and grow. To prevent the fascines from sliding or washing away, they are fixed every 2 m with wooden/ metal poles. The effect of the fascines is that they channel water immediately after placement and, after the plants have formed roots, they will bind the soil and hold moisture. Baby trees (individual rooted plants) can be planted at intervals in the Hedge Drain.
The use of rooted and un-rooted layers is one of the best methods to stabilize loose rock slopes. Fresh, green willow cuttings and rooted plants are layered on 1-1.5 m wide ditches on the face of the slope. The ditches should have an angle of inclination (sloping up) of 10-20% to the outside and are dug out by hand or machine. Wherever there is a risk of slope failure, ditches should only be dug in short segments. The plants are placed close together and the tips or the leafy ends should be allowed to protrude slightly beyond the face of the slope. Rooted and un-rooted plants should be used as vegetation and these should be resistant to rock fall and rubble and have the ability to produce adventitious root systems. The plants are buried with the material from the next, above ditch, so that 15-20 cm of the tips protrude. Vertical spacing between layers is dictated by the erosion potential of the slope and may be between 1 and 2 m.
This method is also very useful in protecting dumped slopes and dams where the plants are layered in a successive terrace system during the dumping. On very steep dams a coconut mesh should be used to stabilize the earth between the brush layers. For brush layering we have three different techniques with different names:
Brush layer consists of only willow cuttings, which have the ability to regrow;
Hedge brush layer or rooted and un-rooted layer is a combination of willow cuttings and rooted plants;
Hedge layer or rooted brush layer is a method where only rooted plants are used.
Planted pole wall
We use the so-called planted pole walls instead of wattle fences on slopes, since wattle fences are covered with little soil with consequent short lifetime and no protection against soil movement. Iron or wood poles are hammered into the ground and a larch log is attached to them. The deciduous trees are placed on the logs and covered with soil. On sites where there is light rock fall and shallow soil movement and erosion has not been stopped completely, this method can correct these problems gradually. In addition, due to the stabilizing function of the plant, the logs prop up the soil material. It is necessary to use stump sprout deciduous trees since they are so durable that mechanical damage through rock or rubble does not matter much.
Natural Fibre Netting
On very steep slopes Jute, Hemp or coconut mesh should be used to stabilize the earth between the
brush layers. This should be pinned down using small wood or metal stakes.
Biomass, compost and straw will be able to hold into the mesh. It is useful to include sticks and small branches that will tangle in the mesh and form niches for soil and biodiversity to hold. Initially fast growing pioneer plants should be introduced, as they will form the strong root system, fresh soil and ground cover that will protect plants with a slower growth rate. These pioneer plants could consist of fast growing weeds, indigenous grasses and bushes.
Some examples of these are: Nettle, Vetiver and Barley.
Resilient pioneer plants will also form a barrier that holds soil and rocks that otherwise would erode down the slope.
This effect can be seen in these photos of strong grass and Nettles.
Vegetated stone wall
Vegetated stonewalls are useful for the stabilization of slope toes or steep slope cuts. They are flexible, permeable, durable and can be adapted to every slope angle.
During the building of the stone wall, live plants are placed into the joints between the stones so that they reach into the soil behind the stones.
The joints must be filled with soil material to ensure plant growth. Green willow branches and rooted plants, which have the ability to produce adventitious root systems, should be used as vegetation. The branches should not protrude from the wall more than 10 cm to prevent desiccation. Additionally, a greening with hydro-seeding is possible. The function of the plants is the stabilization of the construction with their root system and the absorption and transpiration of water by the vegetation, which drains the slope.
Stabilisation of Zone (B)
This Zone is extremely eroded and unstable. It will take a lot of work to stabilise it. It would probably be better to put most focus and resources into the Zone above it.
The spread of biodiversity from the above zone should eventually stabilise this zone. However there are a few methods that could be applied to this land if necessary.
Live slope grid
Very steep eroded slopes with compact soil can be secured with a live slope grid. It is essential in repairing a steep slope where the soil must not be dug up and the slope angle cannot be reduced. Vertical logs are driven into the soil and propped up on the base of the slope. Logs are then nailed horizontally on to these. The space between the logs is filled up completely with live branches and soil, so that very dense vegetation is quickly obtained. The whole slope grid is secured with iron poles and covered with soil.
Live wooden Cribwall
Live wooden cribwalls are one of the best methods of securing immediately endangered parts of slopes and toes of slopes. They can be erected as single or double cribwalls and are built from logs and anchor logs held together with nails or bolts. The anchor logs should not be above each other but should be placed alternately. For higher stability against sliding, cribwalls should not be placed horizontally on the slope but at an angle of 10-15 % towards the slope.
Additionally, the whole construction is secured with 2-2.5 m long iron poles, which are hammered into the ground. The space between the logs is filled with soil material and plants, which should not stick out of the wall more than a quarter of their length. To reach vegetation quickly it is advantageous to use green willow branches and strong rooted pioneer plants as mentioned for the construction of the hedge brush layer. In order to achieve good plant development the face wall should be 50%. If this is not the case the plants will not receive enough light.
Stabilising Zone (C)
This Zone is the most stable yet it is greatly effected by the other two Zones.
All of the techniques used in the other two Zones can also be used in this Zone.
This zone could be cultivated to provide many resources for the local community.
Stabilising the land using filled bags can also be a useful method in stabilizing this zone. It can be a quick method for making walls, terracing and filling gaps. These bags can be made of natural or synthetic fibres and filled with a variety of different locally available materials and waste materials such as rubble. These bags can be sewn quite simply, by local people. Dipping them into a watery cement mixture will add to their long term durability
The most common method of hill and slope stabilization is the seeding of a grass and herb mixture. Dry seeding is an easy method where seed (10-25 g/m2) and organic fertilizer (100 g/m2) are scattered by hand or machine. It can be applied on flat slopes with rough surfaces. It is also possible to use hay flowers instead of common seed and then it is called hay seeding. On steeper slopes where it is necessary to cover the soil quickly, a cover crop of weed and cereal seeds can be used. Special types of rye (in fall) and barley (in spring) are spread in a mixture of 10 g/m2 and covered with soil.
On less steep slopes with rough surfaces and no erosion problems tree and shrub seeding can be spread. Seeds of trees and shrubs are mixed with sand in a ratio of 1:3 and spread as broadcast, pit or row seeding.
Separate Areas for Animal Grazing
Creating separate grazing areas for animals is important because these animals are vital for the welfare of village communities.
Areas of particular nutritious grasses should be cultivated and allotted for animal grazing. This also helps to protect the newly forested areas because it diverts all grazing to particular areas that can be managed.
Plants that form a natural barrier against animal grazing
The main function of fencing in the context of afforestation and erosion control is to keep grazing animals out of the planted areas where there are fragile saplings.
Spiky bushes and grasses are very useful to grow as a hedge to protect areas from animal grazing. This can be grown alongside fences to give double protection.
The two different kinds of bushes in the photos grow quite well in this terrain and have sharp thorns that protect them from grazing animals.
A combination of such plants would be useful in growing protective hedges.
It is important to know which plants animals like to eat and which plants deter animals. The Nettle plant is a very good plant for stabilizing land as it has very strong roots, grows fast, puts Nitrogen into the soil and animals generally do not like to eat it.
When it comes to making fences, there are many different types of fences but it is important to remember that a fence is only as strong as its supporting posts. Therefore it is important to use strong wood or metal for the posts. Larch posts are strong and durable. Larch can be grown sustainably in India. Posts should be approximately 2meters long. Where the land is not rock hard, it is useful to have a point on the bottom of the post.
The post should be set in the ground approximately 25% of its length. If the ground is not too hard, the post can be knocked into the ground using a Sledge Hammer or a special tool that is indicated in the diagram.
This kind of fencing (as shown in the diagrams below) is a flexible, durable and versatile type of fencing. It allows the wind to blow through it, thus making it quite resistant to harsh weather. It is difficult for both humans and grazing animals to climb, as it is slightly wobbly. It therefore forms a good barrier of protection. The materials used to make Paling Fencing are simple and generally easily available i.e. wood and wire.
The wood used to make the pales should be able to be easily split vertically but otherwise strong and durable. In England Sweet Chestnut is traditionally used but in the Indian Himalayas, Bamboo (whole or split) could be used to the same effect.
When using Bamboo, a saw cut should be made (very shallow) to give a secure grip for the wire. The Ends of the wooden pales should be diagonally cut or pointed.
Once these initial stabilization methods have been put into action, then the local indigenous mixed forest species can be systematically re-introduced. Utilizing the methods of companion planting and Permaculture will be essential for theses plants to be able to take root and thrive. It is the natural indigenous mixed forests, which naturally control erosion. All of the above methods are simply ways of regenerating and protecting fresh water and local biodiversity.
These are the recommendations that Active Remedy Ltd. has given for this specific area of mountainous land in Himachal Pradesh, Northern India. However the methodology could be applied to stabilize erosion in many different mountainous regions worldwide.
Supporting and empowering rural mountain communities is key to the success and long-term sustainability of this work.
(Photo- Members of Active Remedy Ltd. and CORD with local village people)