Soil erosion is one of the biggest problems in the world today. Top soil erosion by rain water runoff, river bank erosion, landslides cause havoc in many parts of the world. River bank erosion and landslides are blatant but loss of the fertile top soil has colossal effect on food production. The top soil loss can be as high as 90 MT per hectare per annum.

Soil is the greatest asset of the earth. It provides us food. But loss of food security is real now. Food and water shortage is already palpable. Assam has lost about 7.5% of its plain area to river bank erosion during the last 50 years. The problems we face are growing at a pace that challenges our ability to solve them. Solutions are often too complex or costly given existing resources and capacity.

The effectiveness of available solutions are stymied by the complexity and high cost of engineering and structural designs, ambitious and impracticable environmental protection and remedial practices, bureaucratic accounting and bidding procedures, low potential for sustainability due to lack of funds for maintenance and unsuitability to local conditions/capacity.

Nature provides solution to natural problems. Applying engineering to gifts of nature to solve problems is today’s engineering philosophy. Bioengineering, using plantation of a wonder grass called vetiver (botanical name Chrysopogon zizanioides), has caught the attention of the world since 1986. Initially the World Bank and now the Vetiver Network International propagates the vetiver system to prevent erosion, for water and soil remediation, increasing agricultural productivity, alleviating poverty through handicrafts. Eastern Vetiver Network, India has been established in Guwahati to work exclusively in the eastern states of India. Dr NK Choudhury, former vice chancellor of Gauhati University is the president of the society.

Vetiver is a Tamil name for a wonder grass which can survive and thrive almost anywhere. It grows on any kind of soil — sandy, loamy, clayey, alkaline, acidic, saline, polluted with heavy metals — and tolerates very heavy rainfall as well as prolonged drought. The most important property of this plant is its ability to survive in total submergence in flood water for as long as five months.

Why is vetiver the focal point of geo-technical experts to mitigate the erosion problem? It is its root system that has attracted all concerned to use the plant and has, in fact, been used successfully in over 100 countries of the world, from poor developing countries to the richest — the USA. Its root system attains a length of about 3 metres (10 feet) and has tensile strength of 75 MPa which is equivalent to the strength of nylon (1/6th of steel). Readers can understand the unique root system from the diagram itself.

Traditional engineering methods failed miserably in Assam. The state exchequer has been drained dry to control the erosion problem. They are so costly that state budget is never sufficient. They are also neither environment nor community friendly. Engineers here are now advocating alternatives like geosynthetics. But will such measures create sustainable development or create an economy with a hole at the bottom?

Erosion control regime needs a paradigm shift; time has come to look at development sprout from the community. Technology especially for poor countries must be community friendly which can supplement multiple community benefits.

Vetiver system is exactly the technology a welfare country looks for. It can totally arrest the hitherto unmanageable river bank erosion, prevent landslides, reduce runoff and consequently the associated top soil erosion. This system can work alone but in certain cases needs to be used in combination with traditional engineering measures. Erosion by Mekong river has been brought under control by the vetiver system (VS) only. The major advantage of VS over conventional engineering measures is its low cost and longevity. In addition, the annual maintenance costs are significantly reduced once vetiver hedgerows are established.

As with other bioengineering technologies, VS is a natural, environmentally-friendly way to control erosion control and stabilize land that ‘softens’ the harsh look of conventional rigid engineering measures such as concrete and rock structures. Long-term maintenance costs are low. In contrast to conventional engineering structures, green technology improves as the vegetative cover matures.

VS requires a planned maintenance programme in the first two years. However, once established, it is virtually maintenance-free. Therefore, the use of vetiver is particularly well suited to remote areas where maintenance is costly and difficult.

Vetiver is very effective in poor and highly erodible and dispersible soils, particularly well suited to areas with low-cost labour forces.

The main disadvantage of VS applications is the vetiver’s intolerance to shading, particularly within the establishment phase. Partial shading stunts its growth. The vetiver system is effective only when the plants are well established. Effective planning requires an initial establishment.

There are some technical precaution that has to be kept in mind. There are several sub-species of vetiver. The proper sub-species must be used to get good results. Improper planting materials may cause disaster. The planting materials have to be certified by the vetiver network. Any biological control has to be handled with care, otherwise, it may cause ecological disaster. Hence, the variety of vetiver used for bioengineering must be absolutely non-invasive. Also the planning, design and execution of vetiver system must be carried out by experienced geo-technical and agricultural experts. The Vetiver Network provides support with expertise and, if required, brings in experts from abroad.

There are five aspects which need careful consideration during decision-making, planning and organization. They are:

· Timing: Planning should consider the seasons and the time it takes to grow planting materials as only mature vetiver can give the results.

· Maintenance and repair: Planning and budgeting should anticipate replacement, replanting, watering, manuring at the early stage.

· Procurement: All inputs can and should be procured locally (labour, manure, planting materials, maintenance contracts, etc). Employment opportunity provides an incentive for the local community to protect the plants during their infancy and adolescence, and to maintain the quality and sustainability of the works.

· Community involvement: As much as possible, local communities should be included in the design, materials procurement, and maintenance stages.

· Integration: Policy-makers should recommend vetiver system as part of a comprehensive approach to infrastructure protection, applied on a scale large enough to ensure a tangible increase in expertise and a gradual, spreading effect.

In conclusion it can be said with conviction that there are now enough evidence that vetiver, with its many advantages and very few disadvantages, is a very effective, economical, community-based and environmentally friendly sustainable bioengineering tool that protects infrastructure and mitigates natural disasters, and, once established, the vetiver plantings will last for decades with little or no maintenance. VS has been used successfully in many countries in the world, including Australia, Brazil, Central America, China, Ethiopia, India, Italy, Malaysia, Nepal, Philippines, South Africa, Sri Lanka, Thailand, Venezuela and Vietnam to name a few.

However, it must be stressed that the most important key to success are good quality planting material, proper design and correct planting techniques. Apart from erosion control, vetiver can help in poverty alleviation, reducing global warming (each plant can sequester 2.5 kg of carbon) and develop the economy in a green way. The Government of Assam, PWD and Water Resource Department have been very proactive in the application of vetiver system and we definitely see a silver lining in the cloud.

Shantanoo Bhattacharyya.