Neglected terraces & enhanced landslide risk

Might sound bizarre, but you are soon to realize the logic as also the seriousness of the issue and if not addressed effectively it is to pose a major threat for the hilly terrain of Uttarakhand.

Terracing: Agriculture + 

Terracing is one of the techniques often utilized even today for treating the landslide. It  reduces the pace of erosion by transforming a long slope into a series of shorter, more level slopes that allow water to flow at a relatively slower pace, and soak into the soil. It thus checks uncontrolled downslope flow of atmospheric precipitation while also promoting recharge of groundwater.

Soil formation is a biogeochemical process and takes long span of time ranging from decades to hundreds of years. In the mountainous terrain, particularly in the middle slopes of the hill, landslide is the most potent natural process facilitating soil formation, and it is therefore no wonder that except for alluvial terraces most agriculture in the mountains is carried out on the terraces developed over landslide debris.

The agricultural terraces developed painstakingly on the hill slopes have thus helped in not only stabilizing the slided mass, but also in facilitating stability of the entire hill slope. In the absence of scientific investigations and studies on this aspect it is hard to comment if these terraces were developed after the stabilization of the landslide, or the development of the terraces actually facilitated the landslide to stabilize.

Economy of the region

Whatever be the sequence of events, agro-horticultural pursuits on these terraces were until recently the mainstay of the economy of the region. Having a direct bearing on the economic well-being of the family these terraces, as also their retaining walls were regularly maintained and repaired on slightest sign of weakness.

Really speaking, the region never had enough gainful economic or employment opportunities and agro-horticulture and animal rearing were the sole activities in which the people could engage locally, to make the ends meet.

The people of the region, particularly able bodied men, therefore migrated traditionally in search of employment and other economic opportunities. The migrant population however remained connected to their villages where their families resided, and they invariably returned home after retirement.

The remittances sent home regularly by the migrants infused vigor in the economy of the region.

Migration

The scenario however changed fast, particularly in the previous few decades. With weakening social bonds and nuclear families getting common, the migrants started to take along their families. The migrants now had no incentive to return home except for fulfilling social as also religio-cultural obligations. They at the same time started to settle down permanently at their chosen place of migration. This reduced the quantum of remittances, and had adverse impact on the economy of the region.

Moreover, the families still residing in the villages had little incentive to continue with agricultural operations as there was little demand in the market for traditional coarse food grain resulting in insignificant appreciation in their prices. Increasing menace of wild animals and lack of manpower were other disincentives for continuing labour intensive agricultural operations in the hills.

The children of the early migrants got better opportunities of education and exposure, and did well in different walks of life. Socio-economic upliftment of the early migrants thus became an incentive to migrate, for those left back.

The migration was both from villages to the towns in the hills and to the plains, and the region soon witnessed large scale migration – sometimes in the name of education of children, healthcare of the elderly or in search of employment and economic opportunities.

Changing landscape

With rampant migration many villages in the hills have turned to be ghost villages, with large tracts of hitherto cultivated agricultural terraces turning barren. With the passage of time agricultural terraces have been encroached upon at many places by wild plant species, and are on the verge of turning into a jungle.

With agricultural operations restricting fast, nobody in the region cares to maintain the agricultural terraces, and repair their damaged retaining walls. Consequently, with the passage of time retaining walls of many have actually been damaged and worn out.

Soil and other unconsolidated material thus rests behind these damaged retaining walls in a precarious condition. It is therefore no surprise that this material often starts to flow under the impact of heavy rainfall incidences.

Landslides

Both erosion potential and transportation capacity of the flowing water is a function of its density and velocity. Heavy rainfall incidences often initiate flow of high density soil laden slush from behind the damaged retaining walls of the agricultural terraces on middle slopes of the hill. This high density flow moves at a high speed along the hill slope, and carries along everything that comes in its way – vegetation, boulders and rock mass – soon creating deep gully and turning into a massive landslide.

In the absence of research on this aspect of slope instability, it is really hard to comment on the proportion of landslides that get generated in this manner. One can however say that this would certainly be significant, and increase with the passage of time.

Implications

Moreover, it is worth consideration that most agricultural terraces, particularly on the middle slopes of the hill, are located at the site of previously active landslides that have stabilised with the passage of time. Despite the landslide having been stabilized, geomorphic conditions making the site vulnerable have not changed much, and if destabilised by external forces these could get reactivated.

The landslides initiating from the agricultural terraces could therefore result in large scale destabilization of the hill slopes and making the region chronically prone to landslides. This is to aggravate the problem of landslides in the region by manifold.

In order to tackle this problem effectively, it is primarily required to better understand this slope destabilising process through in depth research and studies. This is however a long term proposition, and mitigation works cannot really be delayed for want of that, once the problem has been identified. Or else, continuing neglect of the terraces has the potential of reactivating long dormant slide zones, and undertaking stabilization and treatment works after that would be challenging, both financially and technically.

A geological problem

In order to cost effectively address this issue it is necessary that the geoscientific community be consulted to better understand the seriousness and long term implications of this issue.

Moreover, to initiate any dialogue on this aspect it is necessary to accept and appreciate that slope instability or landslide is a geological problem, and therefore geologists alone can suggest viable solution of this issue.

It is however interesting to note that many a policy makers consider slope instability as being an engineering problem and therefore solution of this long standing problem has been eluding us despite massive engineering interventions and investment on the hill slopes. Inability to find sustainable and cost effective solution of landslides therefore needs to be accordingly analysed.

Way forward

The problem having been identified and seriousness of the issue understood, it is necessary that timely action be initiated to ensure that the hill slopes remain stable.

Since the root cause of the problem lies in weakened retaining walls of the agricultural terraces, logical and simple solution lies in ensuring regular and timely maintenance and repair of these.

To begin with, areas that have habitation, infrastructure and others in the downslope side of the agricultural terraces can be taken up for maintenance in the first phase. Moreover, there is no dearth of finances  for undertaking this task as the state at present has State Disaster Mitigation Fund (SDMF) at its disposal.

Be what, 10 paisa spent on this is to save resources worth many rupees in times to come. Moreover this would save the soil that is a major resource, and takes long time to get replenished.

The investment is worth making as the dividends are real high.