NCESS rules out soil piping at Puthumala, affirms massive debris flow

A team from National Centre for Earth Science Studies (NCESS) said that the destructive landslides at Puthumala in Wayanad happened due to massive debris flow, contradicting the report given by the department of soil survey and conservation which had attributed the same to soil piping.

The team from NCESS – which completed preliminary site inspection at Kavalappara, Puthumala, Vilangadu and Pathar – inferred that translational landslides occurred at Kavalappara while all other areas experienced fatal debris flow.

“These areas experienced excessive rainfall before landslides. It led to oversaturation of soil, causing it to move downward with a strong momentum. When soil gets oversaturated, the binding between bedrock and soil is released, causing forceful downward movement,” said researcher Vincent A Ferrer, who was part of the site investigation team. The preliminary site inspection report is expected to be finalized this month.

NCESS did preliminary investigation using the newly-developed near-real-time geo-hazard mobile app for the first time. Data regarding landslides, damages, type of land use, slope deformation and other factors are recorded using the app and uploaded, which is then received at the geomatics lab of NCESS.

The NCESS team said that at Puthumala, the debris flow gained mass and width along its descent. “If we look at the landslides, we noticed an increase in width from top to bottom, which is unlikely in the case of soil piping. Besides, the slide started from the crest of the hill whereas in soil piping water bursts out of holes and it gets exposed along the sloping surface,” said K K Ramachandran, who heads the central geomatics lab at NCESS.

He added that not many piping incidents were reported in this area before. The team estimated that debris flowed for nearly 2km at Puthumala and 600m at Kavalappara from the point of trigger to impact.

IMD data showed that the districts where devastating landslides occurred had received excess rain. The rain in Malappuram was 500% more than the normal rainfall between August 8 and 14. In Wayanad, the percentage variation between actual rainfall and normal rainfall was 400%. Kozhikode, which usually gets 130.4mm rain, received 680.8mm, a variation of 422%.

NCESS had done a study focusing on soil piping in Western Ghats and its foothills in 2016. Soil piping or tunnel erosion is the subsurface erosion of soil by percolating water to produce pipe-like conduits below ground, the study had said.

The first major soil piping incidence reported by NCESS was at Chattivayal, Thirumeni village in Kannur in 2005. The study had recommended that areas where earthen dams are present shall be monitored to rule out the presence of dispersive soil, present near Banasurasagar dam in Wayanad.

NCESS identified soil piping as the main reason for land subsidence in Western Ghats and the study found that the phenomenon occurred where deforestation had taken place. Except Alappuzha, Kollam and Thiruvananthapuram, all districts are prone to soil piping. A recommendation was made to the government to declare soil piping as a state-specific hazard.

Source : The Times Of India, Thiruvananthapuram Edition, Aug 21, 2019, 04.04 AM IST

Experts suggest new land-use policy, Act for hilly terrains

Even as weather conditions improve after the extremely heavy rainfall events for the second consecutive year, the state government will now have to start looking to update its ‘Rebuild Kerala’ plan as more areas of vulnerability have come to the fore. Experts suggest that Kerala will have to enforce a new land-use policy that will reduce the tragic proportions of environmental disasters.

The disasters highlight the need for better land-use planning and location-specific building codes. “In the long run, it is not enough to do the response and relief operations better. We need to ensure that people are not living in vulnerable areas,” said Muralee Thummarukudy, operations manager, UN Environment Programme (UNEP).

He said the recent disasters, from Cyclone Ockhi to the intense rains, which triggered landslides causing high causalities, all indicate the need for more reliable weather forecasting systems, which can assist the authorities to take timely action to prevent weather events turning into disasters.

“Just like our Wetland Act and Coastal Regulation Act, we will need to have a separate Act for activity in hilly terrains. Our neighbouring state Tamil Nadu has it. It will enable us to clear all activities based on the disaster possibility under the Kerala state disaster management Act,” said K K Ramachandran, group head, Atmospheric Processes (AtP), National Centre for Earth Science Studies (NCESS).

He suggested that the way river bank mapping is done by revenue department, which is then cross-checked by scientific experts, hazard zone-mapping should be done for flood plains also. “Any structure in the flood plains should be vetted in the lines of a disaster plan too.”

Ramachandran said every hill at an angle of more than 20 degrees should be considered as a possible vulnerable zone and hence, any construction activity should be looked with serious concern for a possible natural disaster.

Kerala State Disaster Management Authority (KSDMA) member secretary Shekar Kuriakose said that most of the rehabilitation activities for the people hit by the floods last year, have been completed. The cases of a few people were held up because of legal procedures. “There have been families who have left Idukki and moved to Ernakulam. We have had cases where people are reluctant to move because of emotional reasons but the government is addressing them also.”

He said that a team from the Geographical Survey of India will visit Kerala’s affected parts next week and submit a report on various vulnerability zones. “The events at Kavalappara and Puthumala were not similar. We will understand the scientific aspects after the visit of the GSI team.”

Source : The Times Of India, Kochi Edition, Aug 18, 2019, 12:04 IST

Sea-Saw: Shores shrink despite protective walls

As heavy showers flatten terrains and bury varied habitations in state, an ecological tragedy of equal proportions is unfolding in coastal areas for the past few decades. Successive state governments – saddled with the conservation of fast-eroding beaches and rehabilitation of displaced fishermen – have over the years tried, in vain, to do a balancing act. Most of them chose the quick fix; shifting families during monsoon and launching housing schemes after monsoon losses were gauged and submitted.

Protecting beaches mostly centred on placing structures; seawalls, groynes, geo-bag and so on and this resulted in creation of artificial coasts. Now so many structures have come that they occupy over half the actual length of Kerala’s coastline. “The concept of defensive structures for beaches emerged in 60s and 70s saw the proliferation of these structures along coastal areas. Now, we have got over 388 km of coastline covered with such structures. These structures (mostly) were built without giving much consideration to the needs of the coast,” said KK Ramachandran, who heads the central geomatics lab at NCESS (National Centre for Earth Science Studies)

State government was forced to spend crores for rehab of fishermen families and construction of structures to prevent sea erosion. When cyclone Ockhi hit Kerala in 2017, another Rs 8 crores was spent on repairing these structures that were damaged. Harbour engineering department submitted a proposal worth Rs 145 crore to KIIFB (Kerala Infrastructure Investment Fund Board) to extend the length of breakwater in five fishing harbours and coastal protection measures in six.

KIIFB gave sanction for coastal protection measures worth Rs 82 crore in seven areas. Simultaneously housing schemes and rehab projects – involving purchase of land expending crores – are being implemented.

Preliminary survey by fisheries department in 2016 showed that 24,454 families lived within 50m of the high tide line and 10,000 of them inhabited stretches prone to heavy sea erosion. The latest ongoing study by NCESS researcher Jyoti Joseph on shoreline change (1973-2019) in state puts the erosion rate at 60.49% while accretion (increase of land by the action of natural forces) is 16.22%. “The impact study and functional performance assessment of the interventions we did (in terms of artificial structures and harbours) were never carried out. The solutions we had given seldom addressed actual causes. At present, sea walls as high as 2m can be seen along coastal stretches. Big waves come crashing near the sea wall and rise over the structures. Once it does that, it poses damage to buildings. Earlier the presences of natural beaches would lessen the impact,” said coastal scientist KV Thomas, who was formerly associated NCESS.

Over the years, a government UP school at Valiyathura in Thiruvananthapuram illustrates how coastal erosion has slowly ceased to become a seasonal affair. The school has remained a relief camp since 2015 and even before the advent of monsoon this year, rows of houses were devoured by the sea. Fishermen along the coasts no longer enjoy the emotional act of hauling their boats filled with fresh catch or venturing out with jerry cans and food packets in their native shores. With beaches receding, they transport fishing boats by road to nearby coastal villages.

Researchers said a combination of reasons resulted in high erosion rates. Human-induced alterations were aggravated by serious lapses in design of structures placed at beaches for shore protection which were never rectified. “There is a natural distribution and re-distribution process of sedimentation varying between upstream and downstream owing to seasonal changes. Erratic design of structures disrupted natural processes at many places,” said Thomas.

Source : The Times Of India, Thiruvananthapuram Edition, Aug 16, 2019, 4:49 IST

Highlands in Kerala on shaky grounds

NCESS finds land subsidence, lateral spread, and soil piping immediate threat to life and property

Destabilising geological processes, coupled with extreme rainfall events and unscientific farming and construction activities, pose a serious threat to human habitation in the highlands of Kerala, according to scientists

A team of scientists from the National Centre for Earth Science Studies (NCESS) here who carried out an investigation in the wake of the heavy rain and devastating floods in August 2018 had found that land subsidence, lateral spread, and soil piping were an immediate threat to life and property in the uplands.

During the investigation, which primarily focussed on landslip-prone areas in Thrissur and Kannur districts, the researchers found huge cracks across farmlands and dwellings.Many houses had developed cracks on the walls and basement, rendering them unsuitable for habitation.

Monitoring network

Based on the recommendations of the NCESS, the Union Ministry of Earth Sciences (MoES) has initiated steps to establish a network of landslip monitoring stations in the highlands. The units based on acoustic emission technology will also have an early warning mechanism to alert the local community. Secretary, MoES, M.Rajeevan said moves were afoot to set up 10 monitoring stations.

“Heavy intense rainfall triggers slope failure in locations where lateral spread and soil piping have occurred,” explains V. Nandakumar, Head, Crustal Process Group, NCESS.

“In the areas we surveyed, most of the slopes were used for raising crops and farmers had blocked the natural drainage systems. Any developmental activity like construction of roads and buildings in such vulnerable areas requires remedial measures for slope stabilisation.”

The team also surveyed areas in Malappuram and Wayanad, including Kavalappara and Meppadi, where rescue teams are still sifting through the debris of destructive landslips which occurred last week.

Alarming situation

“We had found the situation in the highlands alarming,” says Dr. Nandakumar. “Lateral spreading, subsidence, and crack development are quite unusual phenomena and the sites need immediate rehabilitation.”

The team alerted the District Collectors in Thrissur, Kannur, and Kasaragod, outlining the remedial steps to be adopted. The scientists also recommended the formation of a trained task force for the highlands to monitor ground signatures like hollows, cracks, and water spouts that often precede land subsidence, lateral spread, and landslips.

Source : The Hindu, Thiruvananthapuram Edition, AUGUST 14, 2019 10:34 IST

NCESS to update decade-old landslide zonation map

With over 1,000 landslides reported in the state in August 2018 and two fatal ones happening this year, National Centre for Earth Science Studies (NCESS) is working on updating landslide hazard zonation (LHZ) for susceptible areas in the state. Equipped with advanced digital elevation models (procured from Japan), which can identify vulnerable areas more accurately, the first phase the process will be done for Idukki and Wayanad in Kerala.

The present landslide zonation map for the state is a decade-old one and in the wake of unsustainable land use in fragile landscapes which are identified as susceptible to slope failures, NCESS is switching to a new technology which will ensure high resolution maps for such areas in the state.

``As per the old map, 1cm on map is equal to half a kilometre on the field. With the new technology, 1cm would mean 100 metres on ground which ensures higher spatial resolution for better classification of vulnerable areas and chalking out evacuation plans in cases of harsh weather warnings. Idukki, Wayanad and Kodagu are the three places we have chosen in the initial stage,” said K K Ramachandran, Head, Central Geomatics Lab, NCESS.

Wayanad and Kozhikode districts are prone to deep seated landslides while Idukki and Kottayam are prone to shallow landslides as per the state disaster management plan 2016. The photogrammetrically generated data on elevation will enable NCESS to have far accurate data on terrain and its slope, the scientists said. The present model; shuttle radar topography mapping mission (SRTM) is being replaced to accomplish this feat which could go a long way in advance warning process.

NCESS has assessed rainfall threshold capacities after landslides in 2018 in Wayanad and the process will be repeated this year. A study by researchers Shruti Anna Samuel, Vincent A Ferrer and K K Ramachandran focused on rainfall thresholds, which resulted in landslides in Wayanad in 2018. The study showed that spells lasting less than 40 hours with a cumulated rainfall of about 50mm-250mm accounted for majority of the landslides in Wayanad in 2018.

“Bad land use practices coupled with drastic changes in rainfall patterns act as perfect triggers for landslides. Our study found out that extremely heavy rainfall over short durations or continuous rainfall of low intensity in 2-3 days in susceptible areas resulted in landslides,” said Ramachandran.

“There were over 200 landslides which were reported in Wayanad last year. We reconstructed rainfall events and took measurements from rain gauges closest to each landslide spot and rainfall events associated with the landslides were recorded to arrive at threshold capacity which caused landslides,” said Shruti Anna Samuel.

NCESS has already deployed a team in Wayanad for preliminary data collection. A mobile app is being used for the purpose which analyses various parameters and sends data to the server at NCESS where it is collected and stored for further analysis.

Source : The Times Of India, Thiruvananthapuram Edition, Aug 14, 2019, 4:00 IST

A new way to tap oil reserve

Drilling for oil could turn out to be a whole new experience using a novel technique developed by scientists here at the National Centre for Earth Science Studies (NCESS). NCESS scientists V. Nandakumar and J.L. Jayanthi have patented a method which, in layman’s terms, could give oil exploration teams valuable knowledge — practically as real-time data — about the quality of oil contained in a basin during the drilling process itself. What they have devised is a method to precisely determine the API gravity of hydrocarbon-bearing fluid inclusions (HCFI) using fluid inclusion techniques and microscope-based fluorescence emission spectroscopy.

Information droplets

The American Petroleum Institute (API) gravity denotes the commercial value of crude oil. HCFIs are minute ‘droplets’ of petroleum oil trapped inside isolated, microscopic rock chambers. The important point is that their composition may have remained unchanged since the time of the ‘entrapment’. For oil explorers, HCFIs hold priceless information about oil reservoirs deep inside the earth.

The Government of India granted the patent to Dr. Nandakumar, Scientist (G) and head, Crustal Processes Group, NCESS; and Dr. Jayanthi, who is Project Scientist (C), NCESS; on July 3. The Oil and Natural Gas Corporation (ONGC) has evinced interest in adopting their technique, which, the scientists say, holds vast potential for application in the petroleum industry. “In general, 40% of exploratory wells end up as dry wells. Our methodology that employs a non-destructive, micro-spectroscopic technique could give fresh impetus to further exploration in locations adjoining abandoned or dry wells,” Dr. Nandakumar said. The ONGC had supplied rock samples from the Mumbai offshore basin for the research. The research, which took six years to bear fruit, was undertaken with funding from the Ministry of Earth Sciences.

Source : THE HINDU, Thiruvananthapuram Edition, July 14, 2019 22:59 IST