Botanical support: How can plants help control landslides?

Landslides account for huge destruction to both life and property. What landslides are and what are the measures one could take to prevent them has been already mentioned here. When it comes to prevention of landslides, a neat relationship between landslide and botany is seen. One of the measures is to grow trees up slope as it will slow down the flow of water and roots binding the soil will thus prevent soil erosion. But just planting any tree or shrub won’t be beneficial…

What kind of trees work best?

Tree species with low soil moisture requirement and capability to withstand unfavorable conditions are favored. These species are quite light in biomass but coppice well (Wendlandia excels or takuli, Erythrina suberosa or Mandara). Shrubs being chosen for landslide area must have high quality to resist drought, high temperature and other adverse conditions (Agave cantula or Rambans, Vetiveria zizanioides or Khas-Khas etc) and grasses available round the year and surviving in wide range of climatic conditions are preferred (Saccharum Spontaneum, Pogonatherum species). It is, however, important to note that the plant species that are selected are native to the region. Such species can produce the best soil-binding results.

But before going for any kind of plantation in a landslide prone area or for landslide treatment few things should be kept in mind. These are:-

1. Area of the landslide
2. Nature of the landslide
3. Type and quantity of soil present and,
4. Topographical details – aspect, slope etc.

All this information help us decide the type of the species to be used.

An example from the Himalayas…

In 1981, HESCO (Himalayan Environmental Studies and Conservation Organization), launched a programme to botanically control an intense landslide zone between Kotdwara-Dugadda road in district of Pauri of Uttarakhand hills. Now, the plantation in a landslide area is difficult during monsoon season so a drill was followed. Plantation was done in three phases.

Phase 1– Plantation of grasses other than monsoon months, this is the preliminary treatment, done after 3 months of the occurrence of the landslide.

Phase 2– Plantation of cuttings of shrubs/trees in winter season (duration: 8-12 months).

Phase 3– Plantation of shrubs/trees at the end of the monsoon season (duration: 12-24 months).

The total labor involved was calculated on the basis of hours, mandays and cost involved.

S.No.	Area of the slide	Hours	Mandays	Cost
Landslide 1	2795 m2	350	43.7	Rs. 1748
Landslide 2	4220 m2	184	23	Rs. 805
Landslide 3	10448 m2	205	25.6	Rs. 824

Of the 21 major landslides that were given botanical treatment, 17 were well in control by 8 years. The rest four, owing to steep slopes, needed mechanical measure (construction of check dams) and were taken over by the Public Works Department (PWD). These areas today, are no more under threat of landslides and present lush green forest.

Do you need more persuasion to plant trees?

In fact, botanical support for landslides can be extended by adopting large scale forestry options. With greater urbanisation happening in hilly areas, there is a potential to develop urban forestry in Indian cities with a target of landslide risk reduction.

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Reference: Dr. Anil P. Joshi, Dr. Rakesh Kumar and Dr. Kiran Rawat, 2001. The Disaster Management. Himalayan Environmental Studies and Conservation Organisation, Uttaranchal.