Financial Times

Gem mining, floods and landslides
By Professor P.G.R. Dharmaratne
Recently the country witnessed the worst ever floods and landslides that occurred in the Ratnapura district and down south. Many articles have appeared in newspapers attributing gem mining to floods and landslides. There has been talk of disaster management, rehabilitation, etc, but it appears that everybody has forgotten about it already, perhaps until the next time! I thought it is worthwhile to look at the gem mining in these areas and whether it is the cause or to what extent it assisted the disasters that occurred.

Gem mining
There are several hundred thousand people engaged in the gem industry and also it is one of the major sources of foreign exchange. Of the total gem mining, perhaps about 70% are licensed mining while the rest is illicit mining. Over the years, the National Gem and Jewellery Authority (NGJA) and its predecessor, the State Gem Corporation and the police have done much to eradicate illicit mining, but it has not been successful.

It is not a dilemma confined to Sri Lanka alone. In fact any country which has gem deposits has to face the problem of illicit mining; be it Myanmar, Thailand, Madagascar, Kenya, Nigeria, Tanzania, Brazil or Colombia to name a few countries which have experienced the same problem. While licensed mining is being supervised by the NGJA and have strict conditions laid down by it to safeguard the environment and to fill the pits at the end of mining, illicit miners have no such rules to worry about.

They leave behind unfilled pits and heaps of soil which destroy the environment. It causes soil erosion and the breeding of mosquitoes, just to name a few of the problems. Illicit mining is mainly done in crown lands viz: forest reservations, wild life reservations, road and river reservations, etc. where gem-mining licences cannot be issued. Most often, they indulge in illicit mining at night, unless of course they have political patronage. While gem mining in major rivers such as the Mahaweli, Kelani, Kalu and Walawe, etc. is not permitted by the NGJA, the rights to dredge for gems in minor rivers are alienated through public auctions.

However, some sections of these minor rivers are not auctioned due to the restrictions imposed on them by the Environmental Authority. Illicit mining prevails in major rivers and in sections of minor rivers which are not auctioned. So it is not possible for the NGJA and the police to completely eradicate illicit mining in all the crown lands, rivers and reservations. Gems are as good as currency and when they exist a few feet below the ground, naturally, people will attempt to dig for it. In fact there have been many occasions when gem deposits occurred on or near the surface in private lands, land owners even with the support of the armed forces could not prevent the invasion by hungry gem miners. So how could government officials who are sometimes threatened and also mostly confined to day time work prevent illicit mining in crown lands?

Floods
So is gemming the cause of floods? When you look at the phenomenal amount of rainfall within a short period that we experienced last time, I would have been surprised if there was no flood. Could we have prevented the rain and therefore the floods? Well, Bangladeshis would have been the happiest lot to hear it, if there was a way of preventing rain, for they have floods almost every month causing much more damage than what we experienced last time. They say a depression in the atmosphere around the Bay of Bengal which shifted towards Sri Lanka caused the rain and therefore the flood. India, Bangladesh and China had more disastrous floods and also landslides causing very much higher casualties and damage. Of course, compared to the size of these countries, the damage was comparatively more severe for us.

So has gem mining contributed to the flooding? Well; they have said gemming in rivers causes damage to river banks which causes spillage of water, causing floods. Let's look at whether there is any truth in this statement. When gemming is done in rivers, the river bed gets deeper and rivers widen due to collapse of river banks. Now won't that in fact help to increase the flow of water and facilitate it to reduce the threat of floods? In fact during the recent floods at Nivitigala, the 'We Ganga' took a new turn bursting its banks and with it washing away four houses. Depending on the intensity of the rain, river banks will go whether gem miners assisted it or not. So it is debatable, whether the negative aspects of gemming supersede the positive aspects.

One must not think that I advocate the destruction of river banks and widening of rivers to facilitate the flow of water. I am also opposed to rivers getting muddy due to dewatering of gem pits, and tea and coconut lands being washed into the rivers due to illicit gem mining.

The issue of licenses to dredge rivers, is not done purely for economic benefits, but because illicit mining cannot be stopped. Once again I do not mean that all improper things should be legalized because they cannot be prevented fully. The Kalu Ganga being a major river has been issued with a dredging licence but if you go from Idangoda to Ratnapura along the river you will see several hundred illicit miners resorting to manual dredging and a few mechanical dredging using gravel suction pumps.

Manual operations need only a few mammoties and when the NGJA and/or police raid such places, miners run away leaving behind those implements. They are not very expensive and hence dredging resumes with new equipment as soon as the raiding team departs.

Gemming in rivers or over land has very little effect on flooding. It does not appear to be the cause for the floods; it possibly may have helped in a small way. There are suggestions for mechanized dredging of the Kalu Ganga and other major rivers. That of course must be done after very careful studies since the salinity of water has increased upto Horana due to sand mining below the sea level in the Kalu Ganga. The damage to the river banks could be very severe if suction pumps are not monitored properly.

Landslides
Let's look at the causes of landslides. They occur when (a) either a slide occurs along a discontinuity plane and it is called 'plane failure' or (b) the rock and soil mass slides along an intersection of two planes and the sliding mass taking the shape of a wedge and hence is called a 'wedge failure' or (c) the sliding of a mass usually soil or highly weathered and fractured rock taking a circular form called 'circular failure'. The first two sliding occurs on weathered rock and it may be covered on top with soil sometimes. We all know that almost all the landslides occurred during the rainy seasons. Rocks and soil which get saturated during the rain result in increasing weight of the block that is liable for sliding. Water also causes the reduction of friction for sliding.

That is why landslides are common during the rainy seasons. We have very often noticed that in places where sliding occurs, there are vertical cracks behind the crest of the slope which are almost parallel to the crest. These cracks get filled with water during rains and exert pressure on the block of slope that tends to slide. There is also water seeping along the sliding plane or planes causing an upliftment while reducing the friction for sliding, thereby helping it to come down.

After the floods, I visited the Ratnapura, Balangoda, Nivitigala and Elapatha areas and noticed that there were hundreds of rock and soil slides on to the roads.
The Ratnapura - Balangoda road is being widened and in many places weathered rocks are seen. In some places these unprotected slopes have slid carrying with them several houses. In Thirivanaketiya four houses situated on the roadside have been crushed by a sliding soil mass.

There are many methods of preventing this kind of sliding as we learnt in Geotechnical Engineering. The first and the most easiest method would be to prevent slopes being saturated with water by constructing drains on the upper slope surface to divert rain water away to nearby culverts or streams.

Possible discontinuity plane or planes can be drained by installing drain pipes on the slope face so that it will reduce the build up pressure. If the slopes are very high they can be broken into several steps to reduce the load and in extreme case slopes can be anchored into the solid rock mass behind the discontinuity by rock bolts or cables. If there are structures around, slopes can be further protected by having wire mesh, chain - linked mesh and/or a layer of shotcrete (a mixture of cement, sand and water pumped at high pressure onto the surface thus creating a sort of plaster of several inches in thickness). There are so many other ways in addition to this.

In Norway, Switzerland and Malaysia, I have noticed all these kind of devices within a few hours of driving in the countryside. Have we seen any such thing in our road slides? No! Naturally we should have expected what had happened. And I could not see any gem pit around any of these minor slides.

The National Building and Research Organization (NBRO) with UNDP sponsorship has conducted extensive surveys and produced a substantial amount of landslide hazard zone maps and discussed in their reports the precautionary measures to be taken in such areas. Has any responsible government authority taken notice of those?

Look at the two major earth slides at Palawela in Ratnapura and Deniyaya. Where the slide occurred at Palawela, there were no gem pits at the slope or within 500 metres from the toe of the slope. At Deniyaya of course, you don't see a gem pit within miles of the landslide. So there is no basis for trying to connect the recent landslides to gem mining.

It does not mean that if gem mining is carried out on the slope / around or in the vicinity of the toe of the slope, it has no effect on sliding. In fact continuous dewatering day by day may result in the water table being dropped with probable re-storing overnight and this cyclic process could destabilize the slope. But as far as I am aware, there has never been a landslide that was directly or remotely connected to gem mining.

Environmental degradation
I agree totally that gem mining degrades the environment. In fact every time a human being is born, the environment gets affected. Why? He needs food, so new lands have to be cultivated and when he grows up, he needs a dwelling and lands have to be cleared for it.

He needs further lands which is cleared to grow economic crops for his survival. But can we stop the increase in population? The answer is, no. All we should do is plan to minimize the destruction of the environment and be ready to face the disasters that occur.

The Ratnapura Divisional Secretariat had two boats but at the time the floods came both were out of order and boats had to be borrowed from the Navy and from the fishermen in Negombo. Can you imagine that? Every year Ratnapura gets flooded. So much for the preparedness for floods!

After the floods and landslides, the government spoke of many things, about a Disaster Management Authority, etc. We don't have any more news about it. Maybe perhaps they will reactivate these projects when the next flood and landslide occur.
It is very unusual if Ratnapura doesn't get floods at least once a year. Several measures were taken in the past to avoid floods, but nothing seems to be working.

In fact at the end, it was decided to shift the city to a higher elevation. But the commercial activities and even some government offices are still in the old town. There was yet another proposal to divert the Kalu Ganga to Udawalawe thus not only reducing the threat of flood but also to better utilize water for agriculture. Even such a project would not have prevented the last flood but it could certainly prevent minor floods that we encounter every year.

With regards to minor and major landslides, we must only blame ourselves. Lands are cleared with no concern to the environment and who should care whether such lands are within the landslide prone areas or not? In some parts of Ratnapura gem deposits are depleting and miners have turned to the cultivation of tea.

In fact even in their small gardens they grow tea and not vegetables like they used to do. So naturally we expose new lands every day for erosion. Soil erosion also causes sand being accumulated in the riverbeds as clay get washed away to the sea. Sometimes factories are built with no consideration whatsoever for the environment.

Politics most often override scientific findings. But some serious effort must now be taken to implement the work already done with regard to earth slide prone areas. The clearing of lands for tea cultivation, building dwellings and gem mining in and around such lands must be stopped.

Where serious earth slides are likely, preventive measures must be taken.
One must not talk about stopping gem mining to save the environment as it is economically and socially important to the country as the gem and jewellery industry probably sustains millions of people. Maybe both landslides and floods could not be prevented fully but at least we can be happy that we had done all what we could do.

The writer who hails from Ratnapura is a Chartered Mining Engineer and a qualified gemologist. He is attached to the Department of Earth Resources Engineering, University of Moratuwa and was a former Director General and Chairman of the National Gem and Jewellery Authority.

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