Annexure V: Report by B.K. Dikshit, IFS, Conservator of Forests (Research)

REPORT OF FOREST DEPARTMENT IN THE MATTER OF MUD SLIDE INCIDENCE IN MADIBAGH 
JARIVADI VILLAGE ON 01 OCTOBER 2009

INTRODUCTION :
“Mudslides”, defined as rapid movement (upto 80 kmph) of soil mixed with stones, small vegetation and debris due to the shearing force of high intensity rainfall is a phenomena that is not uncommon in coastal regions.  They attract our attention when they cause some damage to property or obstruct traffic, but when they result in human casualties they are viewed very seriously.  In coastal areas, the presence of lateritic soils which are notorious to lead to mudslides along with long hot summers and high intensity prolonged period of rainfall, is a perpetual and potential hazard.

HISTORY : The mudslide that caused severe damage in the village of Kadwad was on 01st October 2009.  It was a day on which 443 mm of rain was received in 24 hours.  But is that the highest intensity and hence the mudslide?

Data shows that on 12 June 1999 there was 469.3 mm.  of rain and on 29 May 2006 there was 439.8mm of rain received in 24 hours in Karwar.  These are greater than the figures of 01st October 2009. There are no mudslides reported on these days.  This does not mean that mudslides did not take place on those days.  Probably they happened in areas away from human inhabitation and were thus not spotted and reported.

Another possibility to be borne in mind is that ainfall figures for 24 hours is not a veryreliable measure of peak intensity. Had all the rain fallen in a period of just 2 hours within the 24 hour period we are looking through, the peak intensity which is actually responsible for mudslides, was more than that reported will be 12 times more than what will be computed. My inquiries with the local people reveals that almost 75% of the rain reported on the day of mudslide had fallen in just 4 hours. Thus the actual intensity of rain on the day of mudslide was much more than that reported on 12 June 1999 and 29 May 2006 .Had the national highway not been breached by the district administration  the town would have remained under water for days together.

There is also a definite pattern in mudslides.  They will frequently occur in high gradient bare slopes but will not occur in low gradient forested slopes.  This can be seen if one walks along Haider ghat (nearly 14 kms of jungle path made by Hyder Ali from Todur to Shirwar).  I have done so along with Mr. Pankaj Kumar Pandey, IAS., (he was an IAS Probationer attached to Karwar and is now Deputy Commissioner, Shimoga), Dr Bhandari of Government Arts and Science College, Karwar, and my staff.  From Todur side upto about 8 kms the country is fairly well covered with multi storeyed forest.  No mudslides and its indications are seen there.  But as one crosses a ridge near Nagahalla, the land gets denuded od big trees.  In this stretch many incidences of mudslides are seen.  The soil and slope in the entire stretch is almost the same, the absence of good tree cover can be thus be taken as a cause of mudslides.

GEOLOGY : My experience of working in Karwar from 2000 to 2003 has provided me some insight into the geology of the area.  The underlying rock is almost everywhere granite which is nonporous to water.  Though granite hills look monolithic, one of the inspections of the railway tunnel that I was required to do along with Konkan railway authorities (the first tunnel towards Ankola after Shirwad railway station) in 2000-01, revealed that there were many deep cracks in the granite rocks that were draining rainwater that fell on the hill surfaces.

Over this granite is the  soil, rich in oxides and hydroxides of iron and aluminum, of varying thickness bound and staying in place primarily due to cohesive and adhesive binding forces.  It is plastic but rock like hard in dry summers, but becomes a viscid mass capable of moving under sufficient shearing force in the form of a semi solid mass having great momentum along slopes, and thus capable of causing great damage.  And rainwater that falls on the lateritic soil hills, when draining through the natural cracks in the granite, accumulate huge quantity of water that provides the shearing force which tends to move the soil. The four facts that cause mudslides are –

1. High intensity rainfall,
2. Non porous nature of underlying rock,
3. High slope gradient of hills, and,
4. Porous nature and shallow depth of  soils.

The first two factors are beyond human control, the third one can be modified to some extent by engineering measures (having contour terracing done or by building retaining walls of small height etc.,) and the fourth one can be improved by introducing vegetation, only shrubs and deep rooted trees.

CAUSE OF THE PRESENT MUDSLIDE : My inspection of the mudslide on 14-10-2009 reveals the following :-

1. The hill abutting the village was quite steep,
2. The soil is deep (more than 5 metres),
3. The tree cover is not  good, the deep rooted huge trees that bind soils at depths and retard the speed of rainwater flowing along the slope giving shearing force for mudslides  absent,
4. The houses that were affected were precariously close to the base of the hill,
5. and the most important fact is that the hill in the forest portion was vertically cut to a height of upto 20 mts and the soil  sold by the malkidar for monetery gain or to enable him to encroach forest land (a very very common thing in the entire district) thare by craeting an unstable land mass standing against gravity.

The cause of the mudslide, in my judgement is purely natural.  But had the hill been covered with good vegetation and the hill not cut as detailed above, the tragedy could have been averted or the damage would have been less. Regarding mudslides along the national highway, the main cause is quarrying including the use of explosives.

RECOMMENDATIONS
Based upon the above, I would make the following recommendations:-

1. No one should be allowed to cut any hill for any purpose nor any activity that vibrates the soil continously be allowed in the area.
2. All the hills that fall close to inhabitations may be planted with trees along contours.
3. Since fire becomes the first cause of denudation of hills, all the hills close of inhabitation should be rigidly protected against fires.
4. No activity that can cause or alter cracks in the underlying rocks (using explosives, working with heavy machinery etc.,) and/or those which increase the slope of hills (examples: quarrying, mining on the curved surfaces of hills between the base and the top) are to be allowed.

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