Use of Vetiver in Controlling Water Borne Erosion with Particular Reference to Bangladesh Coastal Region

摘要

Vetiver grass (Vetiveria zizanioides ) is commonly found in different districts of Bangladesh but not common coastal region including offshore islands. Traditional use of Vetiver is very limited like-fixing paddy field-boundaries, thatching, making baskets etc. Using Vetiver to control erosion remains untouched excepting a few small-scale trials in foreign aided projects. Private level polderization had been started since time immemorial mainly to produce rice. To support the agrarian economy, institutional efforts of polderization started in late sixties. The purpose of coastal polderization is to save the crops from saline water affect as well as to support lives and properties during cyclones and tidal surges. The main problem in maintaining those earthen embankments is water borne erosion either through surface run-off or from wave action or both. Traditional engineering measures involve high costs, which the country cannot simply afford. Coastal Embankment Rehabilitation Project (CERP) aimed at developing cost-effective systems of maintaining embankment system. Through continuous efforts of information dissemination, training, small scale field implementation and motivation, the important role of vetiver grass technology (VGT) has been well recognized by the implementing agency (Bangladesh Water Development Board), NGOs and about one thousand families involved in field implementation and the larger community nearby. Vetiver has been introduced in eighteen coastal polders over eighty-seven kilometers of earthen embankment combined with other economic plants. Vetiver has also been included in different types of low-cost toe-protection trials with soil-cement mixture bags, pre caste concrete frames, zigzag, beams, octagonal hollow blocks etc. There are successful cases where initial protection and watering could be ensured but vertical growth of roots found shorter than expected in some places. Human and animal interferences, sea sonal variations in soil moisture content and coastal peculiarities like changing seawater level, salinity, threat of washing away by cyclones or tidal surges etc. found as limiting factors. Currently bare root slips/ tillers of naturally grown Vetiver are being used as propagation materials. However, tissue culture might be the cost-effective solution for future extension. Further extension in the coastal polders and other erosion prone areas, study on different ecotypes, utilizing Vetiver parts for value-added products etc. still remain to be done taking lessons from effective users like Thailand, China, India, USA, Australia and so on.