1.
The Edakkal cave is not a cave;
instead it is a cove (or a sheltered nook in a cliff face) on the near vertical
face of a rocky hill. A typical cave has an entrance created by tens of
thousands of dissolution by natural waters and the entrance will lead to a
hollow chamber. It is typically formed in limestone terrains only. In the
crystalline basement rocks of peninsular India natural caves does not exist as
the rock is insoluble practically, in spite of the monsoon rains and water
supply.
2.
Edakkal cave is then only
a nook or cove in near vertical face of a rock cliff. In fact the “aboriginals”
took shelter in such spots and during leisure time got involved in carving and
painting the free and clean, algal growth free face with their mental
impressions of what they went through daily or whatever.
3.
Obviously the tropical
monsoon season with more than 100 t0 140 moist days not only endowed our rocky
hills with a universal black coat of dead algae, but made it indelible through
decades and centuries and millennia of rain fall.
4.
However by the sheltered
nature the nooks on the near vertical face escaped the intense black coat
instead the coat ended where the water drops disappeared or escaped by
evaporation.
5.
Evaporation is a process
that takes place even at the ambient temperature. But the path of the water
drops on the roof of the nooks will receive some degree of lichen growth and to that extent some degree of
camouflaging of the details of the lithogyphics
like it happened in the Edakkal cave.
6.
The proposition before us
then is the either removal of the pathways of water drops to the roof and/or
wall of the cave, or limiting it entirely or completely. Perhaps this is the only recourse before us
now. This process needs to be implemented by doing no harm to the natural
setting and perhaps very unobtrusively. This therefore needs very careful analysis
of the topographic, climatic and environmental setting of the Edakkal cave.
7.
The orientation of the
rock ridge, dominant rocks forming the ridge, their internal structure like
joint systems, their depth of penetration, foliation sets, quartz veins and
their attitude, and such others need a detailed mapping in a 1:200 or 400 scale
and not more, like we do the lithological and structural mapping of a dam site.
8.
A slope map of the ridge,
like when we make a plan for landscaping, in a 1:200 or 400 scale needs to be
created as an aid in designing a system of sheet flow diversion away from the
cliff façade.
9.
Once this is achieved one
need to assess the volume of surface water flow over the ridge in all
directions to assess, whether or not most of the rain water follows downward
through cove or nook face. Luckily if
the major surface run off is away from the nook’s façade then solutions will be
far more easier and repair or maintenance more cheap and Affordable in the
longer run in the deeper future.
10.
If the structural
discontinuities in the ridge are proved to be leading water away from the nook,
it is a great relief in the refurbishing of the cave and its treasures.
11.
This can be proved only by
an experiment in the field by a dye test in several selected points on the
ridge and during the early or late stages of monsoon. As we do not hold power
knowledge about the end of monsoon it is better to do the same during the early
days of onset of SW monsoon.
12.
This will unequivocally
tell us a) there is influx of water into the roof of the nook or not. If the
latter is proved true, then we have to implement a host of designed
interventions to divert the “gushing” of drops and droplets or micro-sheet flow
of water over and through the roof and then over the cave face.
13.
Now the next set of
experiments is meant to quantify the water volume wetting the roof and face as
well as the humidity and temperature in the cave. Once such data are with us
and then we could go for a design of diversion measure of the streams of rain
drops freely entering the cave roof and then to the face.
14.
Remedial measures for
avoiding the lichen growth, primarily address the removal of the growth
conditions (Lichens are composite
organisms consisting of a fungus and
a photosynthetic partner growing together in a symbiotic relationship. usually either
a photosynthetic green alga or cyanobacterium.)
15.
The
design shall be construction of micri-gutters across the slope3 of the hill
face or side to take the flow off the façade of the cave. The spacing
frequency, dimensions etc need to be designed on the basis of knowledge on the
quanta of sheet flow down the face. Such solutions are to be based on the
actual data and not general presumptions of conjuctures.
16.
The
Lichen growth and the ambient environment for their healthy growth need to be
understood unequivocally to design certain measure that will deflect such
conditions for growth and then at the end infestation by lichens.
17.
Therefore, the GoK may order a study to assess
the physical and biological environment before a conservation plan is designed
for the Edakkal cave – a heritage site that may one day come under the umbrella
of UNESCO.
----------------------------
thrivikramji@gmail.com
