Friday, September 19, 2014

Slide show of Deluge in Jammu and Kashmir, India.


Heavy rainfalls battered the western Himalayas last week due to a clash between monsoon currents and winds from the Caspian Sea. 

by
Dr. Nitish Priyadarshi
Geologist
Ranchi.

video


Tuesday, September 16, 2014

Deluge in Jammu and Kashmir.



Inadequate surface drainage and encroachment in the floodplains has caused the floods of Kashmir.

By
Dr. Nitish Priyadarshi
Geologist
Ranchi.







Heavy rainfalls battered the western Himalayas last week due to a clash between monsoon currents and winds from the Caspian Sea. The Srinagar weather station – in the summer capital of the Indian state of Jammu and Kashmir – recorded 250 mm of rain between September 3-6.

For hundreds of million years Kashmir Valley is supposed to have remained under Tethys Sea and the high sedimentary-rock hills seen in the valley now were once under water. Geologists have come to believe that Kashmir Valley was earlier affected by earthquakes. Once there was such a devastating earthquake that it broke open the mountain wall at Baramulla and the water of the Satisar lake flowed out leaving behind latchstring mud on the margins of the mountains known as karewas. Thus came into existence the oval but irregular Valley of Kashmir.

In September 2014, the Kashmir region was hit by heavy floods from torrential monsoon rains. The regions of Jammu and Kashmir in India, as well as Azad Kashmir, Gilgit-Baltistan and Punjab in Pakistan, were affected by these floods.

The cause of the flood is continuous heavy rainfall due to which local rivers broke out into the streets. The areas affected by the flood are mostly districts in south kashmir which include Anantnag, Avantipore and Pulwama.

The main rivers in this region are Ravi, Chenab and Jhelum. These rivers are the tributaries of the Indus. They carry quite substantial discharges during monsoon and also large volume of sediment. They change their course frequently and leave behind vast tract of sandy waste. The major problem is that of inadequate surface drainage which causes inundation and water-logging over vast areas.

The river Jhelum rises from Verinag Spring situated at the foot of the Pir Panjal in the south-eastern part of the valley of Kashmir in India. It flows through Srinagar and the Wular lake before entering Pakistan through a deep narrow gorge.

Floods in Jammu and Kashmir aren’t exactly an uncommon phenomenon, if history and indeed its geography is to be believed. Starting last week, the state has seen an unprecedented amount of rainfall, resulting in its worst floods since 1959. Floods in the state are invariably linked to the Jhelum River and its history of crossing the danger mark, its streams and rivulets overflowing and thereby inundating the “Valley” (south Kashmir) in the process.

In the last 60 years, more than 40 percent of lakes, ponds and wetlands of Srinagar have been encroached upon for constructing buildings and roads. The banks of the Jhelum river have been taken over in a similar manner, vastly reducing the river's drainage capacity.

Jhelum which is a main source of irrigation in the Valley has been marred by extensive siltation in last few decades. In absence of any conservation measures, the river had lost its carrying capacity and led to blockage of its lone outflow channel in Baramulla, posing a risk of floods in the Valley.

The resultant floods – which have killed almost 400 people in India and Pakistan and displaced tens of thousands more – were perhaps inevitable. But they would not have become so devastating if the riverbeds and lakebeds had not been raised by silt, while their banks were encroached upon by ill-planned buildings.

There are three reasons why the floods have caused so much damage:
  • deforestation in the catchment areas of rivers – especially Jhelum, Chenab and Indus – and of streams;
  • unplanned construction of buildings and roads, especially in the floodplains of the rivers and the banks of the lakes;
  • rampant and unchecked dumping of garbage in the rivers and lakes;
Taking the factors that exacerbated the floods one by one, deforestation has long been a major problem in the northern half of the Kashmir valley, in adjacent parts of Pakistan-administered Kashmir and in Gilgit-Baltistan.

Without the roots to hold the soil on the steep mountain slopes, it has all been washing down to the streams in the form of silt, and raising the riverbeds. The obvious consequence – the water carrying capacity of the streams and rivers is much reduced.

Coming to the second reason, for decades the elite in the Kashmir valley has been building fancy villas right on the floodplains of rivers and streams, sometimes even on tiny islands in the middle of the river. The process has been repeated and accelerated on the banks of famous lakes like Dal and Nageen in Srinagar, with some hotels and restaurants even being built with their foundations in the lake – a result of the tourism boom.

As the Jhelum River meanders through Srinagar, every neighbourhood adds its untreated household garbage to the river – once again a recipe for choked riverbeds and lakebeds and for the water to overflow whenever it rains heavily.

Overuse of chemical fertilisers, especially in the fruit orchards throughout Kashmir, also exacerbates flooding. The excess fertiliser gets washed into streams and rivers, where it causes eutrophication, and again leads to algae blooms which choke waterways.

Jhelum meanders in a serpentine way from South to North Kashmir and settles in Wullar, Asia’s largest freshwater lake, before pouring into Pakistan administered Kashmir through Baramulla. Experts said the devastating flood in 1959 caused backwater effects to Jhelum due to low outflows from Wullar Lake in north Kashmir which has been nearly chocked by heavy accumulation of silt and narrow outflow channel.

There are number of rivers, tributaries and nullahs which are joining Jehlum River. For proper water resources management, sufficient amounts of hydrological data are required. But sufficient hydrological data on these rivers, tributaries and nullahs are not available. Some of the reasons behind the lack of the data are:

1) The area is mountainous with some of the world’s highest mountains situated in it.
2) The accessibility of many places is very difficult, especially in the winter season.

Observers are bemoaning that Srinagar is looking like a vast lake. Urban planners, environmentalists or anybody with common sense is not surprised. Without immediate corrective action, the calamity is likely to strike again.

Reference:

http://www.thethirdpole.net/choked-riverbeds-worsen-floods-in-kashmir/




Friday, September 5, 2014

Geology of Pithoria hills near Ranchi city, India.


The hills of Ranchi are generally small isolated residual hills. 
By
Dr. Nitish Priyadarshi.

 Fig.1. A small hill in Pithoria.



The hills of Ranchi are generally small isolated residual hills. In Ranchi hills are generally steepsided made of massive granite-gneiss. We have also found the hills which are not steepsided but a mere irregular pile of huge boulders were found on the hills especially in Pithoria area of Ranchi district. This is the result of highly jointed elements of granite gneiss.

According to climatic geomorphologist like Tricart qualify such hills as inselbergs. They are steepsided residual hills made of massive granite-gneiss. But close by within a few kilometers or a few hundred meters we have residuals which are not steepsided inselbergs but a mere irregular pile of huge boulders.




The rocks disintegrate along these joints under the hydrothermal and atmospheric effects thus leading to the formation of tors or rounded shapes of these ancient granite rocks are the result of cracking and erosion from exposure to sun, wind and rain. The hill slopes are subjected to complex attack by a variety of erosive weapons, water being the most active agent for the removal of waste material from most of the slopes. 


A tor commonly appears as a pile of rock slabs or a series of slabs standing on end, according to whether the dominant joint system is horizontal or vertical. Weathering proceeds most actively along joint planes, thus reducing an originally solid mass first to piles of slabs and ultimately to a heap of loose boulders. Tors usually overlie unaltered bedrock and are thought to be formed either by freeze–thaw weathering or by groundwater weathering before exposure. There is often evidence of spheroidal weathering of the squared joint blocks. Tors are seldom more than 15 metres (50 feet) high and often occur as residues at the summits of inselbergs and at the highest points of pediments.

Fig.2.  This is a picture of small granite tor near Ranchi city.

Fig.3. Tor like structure on top of Pithoria hill.


  Fig.4. Irregular pile of huge boulders on the top of Pithoria hill.



Fig.5.Irregular pile of huge boulders. They are the result of highly jointed elements of granite gneiss. 



Fig.6. A balancing rock was also seen on the top of the hill. 
  
A balancing rock, also called balanced rock or precarious boulder, is a naturally occurring geological formation featuring a large rock or boulder, sometimes of substantial size, resting on other rocks, bedrock or on glacial till. Some formations known by this name only appear to be balancing but are in fact firmly connected to a base rock by a pedestal or stem.

Its an erosional remnant rock formation that remains after extensive wind, water and/or chemical erosion. To the untrained eye it may appear to be visually like a glacial erratic, but instead of being transported and deposited it was carved from the local bedrock.  

 

 

Tuesday, August 12, 2014

Beware of the hills.


Frequency of landslides in India is indeed increasing. 



By
Dr. Nitish Priyadarshi
Geologist.

Malin, the village in Pune district that was flattened by a landslide few days back claiming more than 130 lives, has brought the focus back on the management –or mismanagement – of the vulnerable hills of India especially Western Ghats, Himalayas and North Eastern states.

The torrential rain on July 30 near Pune perhaps would not have brought down a side of the hill had it not been weakened by quarrying, leveling and deforestation activities banned in the old weathered hills and ecologically sensitive areas.

Last year it was Uttrakhand this year it is Malin and Nepal. A massive landslide in Nepal  triggered by continuous monsoon rains, caused 10 deaths, displaced 5,000 families and destroyed dozens of houses. The landslide has also blocked the Sunkoshi River and forming a lake which is threatening to cause downstream flash floods.

Heavy rainfall in June last year wreaked havoc across Uttarakhand, causing rivers and glacial lakes to overflow and triggering massive landslides – killing almost 6,000 people. Construction of hydroelectric dams, deforestation and the spread of unregulated buildings along riverbanks magnify the impact of the monsoons.

Development works carried out in pursuit of greater economic growth – such as the construction of dams and deforestation – are putting people and the environment at greater risk when disasters strike.
India is one of the most disaster-prone countries in the world, and many of its 1.2 billion people live in areas vulnerable to natural hazards such as floods, landslides, cyclones, droughts and earthquakes.


Landslides are a natural hazard that affect at least 15 percent of the land area of our country, covering an area of more than 0.49 million sq. km. landslides of different types occur frequently in the geo-dynamically active domains in the Himalayan and North-Eastern parts of the country as well as relatively stable domain in the Western Ghats and Nilgiri hills in the southern part of the country. Besides, sporadic occurrences of landslides have been reported in the Eastern Ghats, Ranchi plateau, and Vindhyan plateau, as well. In all 22 states and parts of the Union Territory of Pudducherry and Andaman and Nicobar Islands of our country are affected by this hazard, mostly during monsoons.

Landslides Zonation Mopping is a modern method to identify landslides prone areas and has been in use in India since 1980s.The major parameters that call for evaluation are as follows:
  1. Slope-Magnitude, length and Direction
  2. Soil thickness
  3. Relative relief
  4. Land use
  5. Drainage- pattern and density
  6. Landslide affected population
Causes of Landslides

Landslides can be caused by
1. Poor ground conditions
2. Geomorphic phenomena.
3. Natural physical forces
4. Quite often due to heavy spells of rainfall coupled with impeded drainage.
A Checklist of Causes of Landslides Ground Causes
  1. Weak, sensitivity, or weathered materials
  2. Adverse ground structure (joints, fissures etc.)
  3. Physical property variation (permeability, plasticity etc)

The Himalayan mountain ranges and hilly tracts of the North-Eastern region are highly susceptible to slope instability due to the immature and rugged topography, fragile rock conditions, high seismicity resulting from proximity to the plate margins and high rainfall. Extensive anthropogenic interference, as part of developmental activities, is another significant factor that increases this hazard manifold. As a result, the landscape in the Himalayan and North-Eastern regions is highly susceptible to reoccurrence of landslides.

Similarly, the Western Ghats overlooking the Konkan coast, though located in a relatively stable domain, experience the fury of this natural hazard due to steep hill slopes, overburden and high intensity rainfall. The Nilgiri hills located at the convergence zone of the Eastern Ghats and the Western Ghats bear the innumerable scars of landslides due to their location in a zone of high intensity and protracted rainfall where overburden is sensitive to over-saturation.

Vast areas of western Sikkim, Kumaon, Garhwal, Himachal Pradesh, Kashmir, and several other hilly regions have been denuded of protective vegetal cover, which has been reduced to less than 30 percent, which is less than half of what would be considered desirable. As the pressure of population grew rapidly, more and more human settlements, roads, dams, tunnels, water reservoirs, towers and other public utilities came up in vulnerable areas. The road network in the Himalayan region is more than 50,000 km in length. A large number of dams have been built in the Himalayan region. Quarrying and mining, for example, in the Doon valley, Jhiroli (Almora) and Chandhak (Pitthoragarh) have inflicted heavy damages to the slopes and the associated environment.

According to the information obtained under RTI, In Mumbai city over 22,483 hutment in 327 hilly areas across 25 Assembly constituencies in the city, including Western and Eastern suburbs, are dangerous and the people living there need to be shifted as soon as possible. In the main city, 49 spots are dangerous in which total hutments are 3986, while in Mumbai Suburb 278 spots are most dangerous.

An overall evaluation of the pattern and nature of landslide occurrences in the Kerala part of Western Ghats and its corresponding eastern flank falling within Tamil Nadu reveals the following main features:

1.      Almost all mass movements occur during monsoons (SW and NE monsoon) in the western flank of Western Ghats and during occasional cyclonic events in the eastern flank indicating that main triggering mechanism is the over- saturation of overburden caused by heavy rains.
2.      There seems to be a relation between intensity of rainfall and slope failures.
3.      Majority of the catastrophic mass movements is confined to the overburden without affecting the underlying bedrock.
4.      Improper land use practices such as heavy tilling, agricultural practices and settlement patterns have contributed to creep and withdrawal of toe support in many cases.
5.      A common factor noticed in most of these vulnerable slopes deforestation in the recent past, cultivation of seasonal crops and increase in settlements.
6.      In some areas developmental activities like construction of buildings, road cutting, embankments, cut and fill structures causes modification of natural slopes, blocking of surface drainage, loading of critical slopes and withdrawal to toe support promoting vulnerability of critical slopes.

Frequency of landslides is indeed increasing. The main reasons for this are primarily unplanned development in landslide prone areas which can change the geomorphology of that area. Because of accelerated deforestation, rampant urbanization, high frequency of earthquakes, fragile geological structures, steep topography and intense rainfall in the mountainous regions of the South Asia, the number of fatal landslides, casualties and economic loss is increasing year by year. Increasing extreme events due to climate change are also responsible for this phenomenon. Rainfall is becoming extreme in India, either heavy or scanty. If there is a lot of rainfall in a short span of time, then the soil is not able to absorb the moisture, which makes it vulnerable to erosion and slope instability, eventually leading to landslides.



The Himalayan and North-Eastern regions are potential sites where landslides dams have formed at many places in the past and the potential of such occurrences in the future is high.

Reference:

National disaster management guidelines, June 2009. National disaster management authority, Government of India.