“RIDGE TO REEF – A CRITICAL ROLE FOR VETIVER GRASS” – A QUICK FIX?

The tropical island watershed conservation “Ridge to Reef” concept is a popular strategy for reducing soil erosion and sediment/pollutant movement from the upper watersheds to populated coastal areas and in-shore waters. Ridge to Reef programs could be accelerated and be more effective if Vetiver Grass Technology (VGT) was applied more widely and through community initiative.

Vetiver Grass Technology (VGT) can often be used for treating contamination at source. For poor tropical island nations VGT provides a low cost and relatively easy solution that can, and should, be community driven.

VGT, when correctly applied, can provide a “quick fix” that within 6 months can positively impact on erosion control, rainfall runoff reduction and pollutant removal. The “quick fix” can extend into the long term as stand-alone vetiver or take over by native vegetation, all depending on the objective, location, and land-use preference of the owner.

Excessive sediment pollutant flows can often be traced to specific sites within a watershed that discharge high volumes of polluted water from factories, mining, intensive agriculture, and domestic sources; and in the case of soil from highly eroded and exposed topographical and construction/industrial sites. The best way to deal with the problem is to locate the source and apply remedial measures at the site.

Most islands are small, with equally small but often numerous watersheds. It is therefore easier (aided by satellite imagery), to identify point source pollution. Once identified and prioritized mitigation measures can be planned and executed.

Vetiver planted on highly eroded slope – Vanuatu

In Vanuatu inshore fisheries and coral reefs were seriously affected by sediment flows from a highly eroded area in a small watershed behind Port Patrick. Don Miller (New Zealand) and Henry Kathecau, Henry Naumu, David Lauthep, and others from the Port Patrick community rehabilitated an extremely degraded site (C horizon soils) first by planting vetiver to create stability and an enabling micro-climate for associated tree planting and native plant regeneration.  Sediment flows to in-shore water were reduced significantly, see presentation There are other less well documented examples of VGT capability.

Many communities do not have effective solutions for treating domestic wastewater and sewage effluent. Most often this polluted water ends up on the local beach, inshore lagoons and other water bodies. The point sources of this pollution can be easily identified (particularly if community members are involved in the process). VGT, when used as a simple constructed wetland, can help reduce this pollution by treating the outflow of septic systems (that invariably are of poor design) and other household effluent. The wetland is often small (less than 100 plants). Paul Truong created a model to determine the number of plants needed to treat specific effluent volumes. The model provides the first step in designing remedial applications for small domestic and industrial treatment systems.

Islands often have many small/short streams that transport these pollutants. Soil from riverbank collapse and eroded soil from adjacent land is increasingly adding to downstream sediment loads and flooding. VGT can be used for bank stabilization, as well as acting as a riverbank buffer/filter trapping both soil and chemicals. Projects in Fiji and the Cook Islands are being designed to do this.  It is important to remember that many “point sources” in a watershed can contribute to serious effluent/sediment outflows into coastal waters. To have a successful outcome it is essential that all these locations are identified and “fixed”. Often members of the affected community, once trained, can identify them better than the official “planner”.

Road culvert drain stabilized by community

There is overwhelming evidence from research and the field that VGT can mitigate many land and water problems at minimum cost. The work can be done by individuals and communities if they are given access to training and start up plant material. An example of this is the training provided by Robinson Vanoh to a community in Papua New Guinea — quote “A father and son Vetiver farmer combination, from Tagitagi village in East New Britain Province of Papua New Guinea, took the leading role in helping their village community to plant Vetiver grass to mitigate the never-ending erosion problems the province has been facing. It was very encouraging to see their works after a one-day training session. It is a success story which the province can learn and adapt to help battle the erosion problem. This is a project initiated and done without financial support from the Government”.

There is a growing urgency to accelerate remedial programs to correct current land and water problems. Communities must be involved and trained in identifying the problem and in methods of correction. VGT is one such nature based remedy, and because of its ease of use and very wide range of application, it is a very good one. In a “Ridge to Reef” project every village community in the watershed needs to be involved and trained in the technology.

Dick Grimshaw