Flooding event at 23.45 hours on 5^th August 2010 in Leh, Ladakh, India is an extreme geological event of this century in history of Himalayas for simple reason that sediment deposition of 3m to 8m took place in < 1 to 3 minutes in low lying areas and equal amount eroded from upstream parts widening and deepening the valleys. The event was sufficient to destroy and submerge habitations which fell in its natural course; Indus valley civilization in the past was no exception to this event. In Leh & Choglamsar, it was a single depositional event but in Tyagshi, Nubra Valley it was episodic and deposited in 2 short phases of < 1 minute each in 2 days. In all 52 villages were effected, more than 191 lives lost (mainly in recent habitations constructed in traditionally unsafe areas), millions of trees and agricultural land destroyed in villages as the streams widened manifold, people (mainly non locals) still missing probably buried in thick pile of sediments or washed along the streams into Indus. People in the effected villages rose the next morning to see all together a different geomorphological set up. Old men and women were crying as all their plantations and agricultural land was lost and instead the valley was just flowing very near to the houses.

Main aim of this report is to understand geo-mechanism of extreme geological event (land slide, mud slides and flooding) triggered by heavy rains falling for short time span of 5-10 minutes. No evidence of cloud burst are found in studied catchments as the plantation above flooding areas (4-8m high and 8-15m wide) is still intact. Had cloud burst theory been the phenomenon then the plants and small structures on the upstream side of the effected valleys been destroyed.

Paper proposes Reservoir Wall Rupture Theory to explain the geo-mechanism of flooding in Himalayas and selective destruction caused in adjacent catchments in spite of receiving similar rains. Dry glacio fluvial valleys brought in sediments along with water and the thickness of the slush was more than 12meters.Anticipated speed of these flood/mud slush is estimated to be around >120 miles per hour. Concrete buildings of upto 3 levels were just leveled to ground near Leh Bus stop within seconds on that night.

However traditional mud houses stood test of time, since time immemorial in this highest seismic areas of Ladakh with complex geology, extreme climate and fragile environment, because they were located in traditionally geological safe places. It is interesting to note negligible damage was done to old mud habitation in Ladakh below Mani Walls and on hills whereas recent (25-30 years) concrete structures constructed on paleo channels were completely destroyed. Clearly suggesting that flooding event was natural and followed its natural course but destruction was manmade as infrastructure/houses were built on paleo channels in traditionally unsafe areas.

Lastly paper suggest sustainable habitat solutions to be built on hills (Gompas and palaces), using traditional (geological) wisdom practiced by ancestors. Flooding areas in the past were also demarcated by building huge boundary walls (Mani Walls, 600m long and 11m wide and up to 3m, high and Stupas) 400-500 years ago to protect habitations in low lying regions. Proper waste disposal could be an added advantage in reducing the risk of epidemic due to garbage(dumped over the years in the upper parts of the effected stream) which was spread all over the place by the flooding event.

What actually happened??

Study is based on detailed investigations done by the authors in Leh and Sabu catchments to do geological postmortem of the events which led to floods on mid night of 5 August 2012 . Actually this event lasted three days in Ladakh between 3^rd and 6^th Aug 2010 (3^rd Nhey and Nimmu, 4^th/5th Pathar Sahib, 5^th/6^th Tyagshi, Leh, Choglamsar and Rumsay, August 2010). According to affected people, it rained with high intensity and lasted for a short time this led to huge floods in several villages. Since majority of the events happened in midnight of 5^th Aug and one hours of 6^th Aug 2010 in a short time span nobody actually knew what happened.

Recording One of us (Dr Arya) was on his way back after attending the dinner party at Airport Leh and around 11.15pm reached Choglamsar residence. There was Extreme and terrifying lightening in black clouds. The entire scene was very unusual but I was tired and slept to be woken up by neighbors shouting and screaming. I got out with camera in hand and was recording the entire event.

Lightening 5Aug 2010 Leh

Lightening and thundering before the event was followed by heavy rains. Water from the roof was falling as if someone has opened a tap in an otherwise dry area. People were collecting water in their buckets and throwing it out of their house Dangerous sound similar to the sound of landing of an aero plane or a fast moving train. Some saw water tanks and boulders moving up on the slush up to 4.6-7.5m high. Some could remember dry mud, followed by mud slush and then water moving into their houses. Flood mud water remained for couple of minutes when the habitants could actually see their belongings bed, sofa etc. floating. The water after circulating in the entire area left leaving mud slush about 1-2m in the rooms. The flood was episodic and we could here the movement of boulders rolling with great noise on the streets. Lightening at times made the entire scene very dreadful.

Three story building brought to ground at Bus stand : Leh floods

Geomorphology and landscape of the region had changed the next morning. In villages which fell in the upstream high energy regime, streams had widened and deepened up to 12m dramatically, agricultural fields and farms which housed 1000s of trees (upto 1 meters in diameter most of them planted by their grandparents) were no more there in the villages. It was difficult for them to actually believe what had happened as their traditional mud houses remain exposed to the eroded valley portions e.g. in Taru village. In Leh, Sabu and Choglamsar towns majority of the habitation of RCC which was recently constructed (20-25 years ago) on paleo flooding channels traditionally considered to be unsafe were totally damaged. In low energy regimes for example in Choglamsar deposition of mud slush up to 2.5-3m was recorded in a fraction of a minute. Ground floor of all the affected areas was filled with mud and boulders.

My car which was parked in front of the building was transported by flood had the tree not blocked the way It might have been in the Indus but I was lucky and it was relocated with little damage about 15 meter away. But other vehicles were just smashed and transported for kms into the Indus.

Boulders transported and deposited in front of bank Choglamsar

The entire area had become a mud slush trap where 64 lost their lives sinking in this thick deposit. People were trapped in vertical standing positions. It seems they wanted to run from the house but were trapped in the Mud slush from where it was difficult to escape.

Dr ARYA trapped in Slush

I myself was trapped in the flood slush on that night, it was difficult to come out without external help. I lost my pant when others tried to pull me out of the slush on that night. Majority of the people who died either had no chance to run and those who managed to run ended their lives sinking in the slush or the newly created earth.

Dr Arya trapped in floods he predicted Choglamsar

Story of dead body of mother and child holding each other tight recovered by army 2.5m below the ground is very touching. Perhaps all of the affected people now want to live in safer place in more sustainable geological environment, away from the valley and stream. But to my surprise people whose houses are saved or less affected have decided to stay in the same fragile environment. Simple reason the affected people are relocated and helped by the government but those who were miraculously saved have no help.

MIRACULOUS ESCAPE

For e.g. Mohalla 4 with 120 houses in Choglamsar by the huge boulder 3m came from nowhere and just stopped in front of the Mohalla saving the entire habitants.

Since there was no loss of life and property on that day, these families are not victims and therefore no help and are forced to live in the same fragile environment.

Had that huge boulder not been there then this Mohalla would also have been the worst affected. Today they were miraculously saved by the boulder but their lives or their future generations still face the threat of being victims to the flood any time once that huge boulders move.

Mud slush Garbage and destruction at Bus Stand Leh

UNUSAL FLOODING - INDUS RIVER BLOCKED

Agling Stiptuk Tang village are located on the banks of river Indus. Every year they received the floods from Leh catchment in summers due to melting of glaciers but on 6^th they felt huge waves of water from Indus actually engulfing their entire houses. Everyone was taken by surprise. There was no flooding from Leh but Indus was playing tricks with them. After carefully analyzing the situation one of us (R.Arya) found an interesting phenomenon happening on 6^th August 2010. In Sabu and Choglamsar catchment the first floods followed its original course along the squeezed stream and reached Indus in fraction of time. The slush was so fast and in huge quantity that it crossed the entire course of river Indus and blocked the flow of Indus for couple of minutes resulting in decreased water levels further downstream of Choglamsar. This was observed by the laborers working on the banks of river Indus for construction of the bricks. Some of them actually walked in the river beds to collect useful belongings brought by the flood. Decrease in the level of water in Indus is clear cut example of blockage for few minutes. Since there was no further movement the whole river was blocked and a reservoir was created. Extra slush was forced to move in different direction thereby causing great damage in surrounding areas habited in the last 20-25 years. This reservoir actually busted to effect the people living downstream. The labourers were however saved by the wisdom of their local owner who shifted them to Himank otherwise they would have also lost their lives.

FLOODING- SINGLE or EPISODIC

The episodic movement of the water which was felt by some on that day was because of the blockade of the channel from time to time due to manmade culverts or naturally. These culverts were blocked mainly by the huge uprooted trees or boulders leading to formation of a reservoir. Many such reservoirs were formed across the culvert or bridges. The water kept on moving with great velocity in circular manner and when these walls were not able to withstand the water pressure the walls ruptured leading to movement of great slush downstream. Breaking the bridge and taking it to considerable distance. Perfect alignment of the uprooted trees and boulders on the banks of the flooded stream clearly show evidences of ruptured reservoir whereas grey white sand shows the extent of reservoir formed before they finally ruptured. So the episodes of the water were many depending on the blockades but the main event happened for fraction of minutes when the vibration or tremors were heard/felt.

TIMINGS

So if timing of these vibrations/tremors are exactly the same as that told by the villager in Sabu then the timing of flooding is around 11.50 or 11.55 on night of 5^th Aug and reached Chloglamsar SBI at 12.08. This was the speed of the flow based on testimonies of people living on the sides of the existing stream. But on the upper side there was a huge Mani wall made of boulders, the slush kept on accumulating for some time around Mani wall but at 12.18 the slush crossed Mani wall and later broke it from that point leading to flash flooding activity and unprecedented damage in that area.

Almost 1.5m of mud was circulating in the shop at Choglamsar as told by one of the shopkeeper who used to stay in his shop. He opened the shutter as he thought that someone was knocking at his shutters in midnight but as he opened the shutter he was pushed back by huge force of water slush and by the time he could realize what has happened the water had circulated his things were floating and many of his belongings were taken by the receding water.

BOULDER inside the shop Choglamsar

His shutter was washed but huge stones blocked his entrance and he was saved. Interesting thing to note here is that marking of mud slush with water are found at 1.5m high but the mud deposited was about 0.5-1m. At around 12.35am on 6^th Aug 2010 R.Arya had recorded the last flooding event but by then the entire flooding event had been completed. In the morning entire scenario had changed, new elevated land up to 3m was created in the affected area at Choglamsar. Ground floors of all the affected houses was either washed or completely damaged.

Mud slush up to 3m has been observed in the affected areas. A complete cross section of the affected area can reveal interesting results about the complete history of deposition.

Role of wastage and garbage

Skampari and Bumb Nala (got its name because the army used to keep ammunition, but once the army vacated the civil authorities replaced ammunition with garbage) became garbage dumping site. garbage and waste was dumped by civil authorities for the last 12 years and hype of up to 4m was recorded here. This hype defiantly had impact on controlling the movement of mud slush flood in saving the residents of Housing colony and diverting the entire flow to Choglamsar.

Garbage dump upto 3m

These waste and garbage dumps did play important role in spreading the entire waste to the affected areas. So in normal course where these flooding events created new elevated land in low energy regime after depositing the eroded material from high energy regime, the garbage dumped by the man over the years led to its spread in the entire affected area. Hospital in Leh was the most effect due to the garbage which flooded the rooms and the campus on that day.

Garbage transported by floods- Leh Hospital

Long time effect of these deposits can’t be so environmentally friendly and the foul smell in the entire area was the result of this garbage, which spread due to flooding on that day. However there was no epidemic but due to increased population things will no more be similar and similar event in future could lead to health problems.

Movement of mud slush from observations made slush moved in a very peculiar zig zag manner in high energy regime part. Slush started from reservoir rupture moved along the valley at a very high speed eroding the surface and the subsurface of the already saturated valley because of rains for last 5-6 days.

Boulders in houses Choglamsar

This movement was not observed by anyone as this was happening at the peak. As it moved downwards the slush released tremendous energy by creating pressure on the saturated layers. This moved with the speed of 120 miles per hour or more. These subsurface movements in layers created vibrations. Now this is interesting vibrations of the movement of the slush could be felt and heard by many who were living on the banks of the stream. According to eyewitness tremors were felt before the main slush moved in and most of them were suspecting earthquake and nobody imagined a flooding event to cause this impact. The tremors were not due to earthquake but because of the folding and sliding of the glacio fluvial deposits to release the energy created by flooding movement of the mud slush.

In Sabu, tremors of this type were noticed about 11.55pm. Whereas the same were recorded at 12.00am and around 12.08 am along the nala near SBI in Choglamsar which is about a km downstream. The mud slush crossed the Mani wall at 12.18am. The time was exactly known because people thought it was an earthquake or bomb blast and went out to see. Initially they were shocked and frightened as they saw no water but only mud and trees were moving whenever the lightening from the sky lit the area. The Mani (PRAYER WHEEL) was uprooted and brought to the place where one of us (R.Arya) was staying approx 700m downwards. The slush created powerful impact on the saturated land, the stress was build up and released by folding and sliding the ground far ahead. This movement actually uprooted some of the building and trees from its very foundation. The mud was observed in the atmosphere by many before the slush came in. Some events saw complete trees upright moving for considerable distance because of this movement. This was followed by boulders and then mud slush. The slush was followed by water.

In Bomb Nala Choglamsar flood was unimaginable. 14 Nepali labors were staying on the tent just near the army TCP just below the garbage dumb of Bumb Nala and were caught unaware.They just did not had the time to move and were flown by the flood. Three men were saved by MES people at that night however one dead body of laborer was recovered in the house of Principle of KV school. The principle house was one to have the first impact of the floods. The entire strong concrete structure of PHE and MES above the school helped in reducing the impact of flood. Though these structures were destroyed but they considerably helped in reducing the momentum of the flood moreover because of more space and its energy was dissipated in the grounds. Because of the U turn and the concrete un-inhabited structures of PHE and MES devastation and destruction could have been manifold and the Kendriya Vidyala School complex and ITBP would have been severely affected.

Sedimentation All this led to accumulation of more than 1-3m of debris accumulated in a span of <1min. This resulted in the formation of slush. People who were not able to come out from the ground floor room died instantaneously whereas those who were able to make and go to the top were saved but many who ran for safer places were trapped in the slush and were just sinking and died. Some tried to run away by driving the car but were instantaneously overpowered. Similarly all the houses which fell in the changed course were just reduced to ground.

Precipitation in the form of rainfall since last 35 years in Leh is monitored by Indian Air Force. According to this data, average rainfall in the month of August between 1973 and 2008 is around 10mm. The highest rainfall in August ever recorded was around 51.5mm in 1933. However between 5^th August 2010 at 05.30 am and 6^th August 2010 at 05.30 am, rainfall measured was 12.8mm (1). Since the event happened at mid night no body actually knew what exactly happened. According to the villagers, the heavy rainfall lasted for short time between 5 to 10min but the intensity of the rainfall was very high. Rainfall on midnight of 5^th Aug 2010 was higher than the average rainfall quantity recorded during the month of August. Therefore from the records it is clear that the quantity of water which fell at 11.45 pm hours on 5^th August was not the maximum ever recorded. Nevertheless, the rain induced huge flood did not occur even in 1933 when showers were maximum. Clearly showing there is no relationship between heavy rain showers causing floods. So there has to be other mechanism responsible for floods, rain alone has no power to cause destruction. Rains like fire are an element of earth and need ammunition to cause destruction. If rains are fire ammunition, nature is the debris accumulated over the years.

Historical perspective

Floods and avalanches are not new phenomenon to Ladakh region and traditional structures as Mani walls, Stupas, Gompas and palaces built 400-500 years ago speak volumes about geo-scientific wisdom and knowhow of ancestors to effectively deal with these natural disasters of avalanche and floods besides providing sustainable habitats to the inhabitants.

Mani walls were made to protect the population from floods and avalanche in the past.

Mani Walls at Nimmu

According to observations made by author 90% of the glaciers have already receded from the Ladakh Himalayan ranges due to global warming since the last ice age. As a result of which impact of avalanche and massive flooding was never felt by the residents for more than 3-4 centuries. Therefore these traditional geo structures “Mani walls” lost their geological significance and became more to be associated with Buddhists religious rituals and inscription of stones with ‘Om Mani Padma Houm’ inscribed on it were placed on these walls. Today these walls are decorated on religious functions by performing the religious rituals. Geological significance of these walls in disaster management was however lost in time, mainly because no major flooding event of this magnitude happened after the construction of these walls.

Mani Wall at Choglamsar was breached by the floods from BOMB Nala. After this impact the momentum of slush was reduced but it continued to flow downstream and again gained momentum due to slope and broke the retaining wall of ITBP complex at two places before joining the nala which was crafted by the floods which came from the Sabu side near the petrol pump. Majority of the habitation were destroyed because the stream from Sabu had changed its course as the original stream was blocked due to construction and huge boulders.

Traditional wisdom Earlier Gompas and forts were located in the safest places because they housed the most important people in the society and their location and their architecture was role model for the entire town. But today they are built in the most susceptible geologically fragile areas and small changes in the environment are sufficient to create many fold damages.

Anthropogenic growth and need to be to Leh town which is the business center of Ladakh forced the habitants in the last 25-30 years, to flourish in the most vulnerable places, ignoring the traditional wisdom. Habitations in Choglamsar, Leh Bus Stand, Core Headquarters, all army and Border Road establishments on the banks of river Indus or its channels, Diskit and other small township and modern religious places specially Phutong in Diskit and Dalai Lamas Palace in Choglamsar which sprung up in glacio fluvial deposits near the roads are most vulnerable to flooding events now or in future.

Stories about destructions due to floods was known and flooding events around 105 years ago in Lamdon area engulfed the main bazaar with mud slush. Around 74 years entire swampy grassland of the valley which today houses the Army Core Headquarters was flooded and the entire grassland valley was turned into a flood deposits. These data just came from the villager’s recollection and the facts need to be re established. On 3^rd Aug 2010 a flooding event had happened in Nimmu and everyone thought that all was over for this season. Because this is what has been happening since the last decade noticed by the author (R.Arya). Nubra flooding in 2006 in Tinggang Nala Diskit resulted in deposition of about 1-1.2m of debris mainly mud slush and boulders. Similarly in streams/nalas of Khalsar, Main Diskit, Hunder, Phyang and Leh Gompa flooding also occurred but the debris impact was less because quantum of water was more in these streams.

No major loss of life was reported because the event happened at around 8pm and everyone was awake and moved to safer place. These flooding events have been happening and excess energy released by the system naturally. Process of erosion, transportation and deposition were continuously taking place but with low intensity and since there was no loss of life the events went unnoticed. A small event of 5^th Aug if repeated in these locations now will be the biggest disasters in the history of Ladakh as these areas are now thickly populated and house important defense establishments.

Paleo flooding events discovered for the first time by author in Sabu valley clearly show that what happened on 5^th Aug 2010 was just a trailer; the real picture is still to come. Evidences of two major paleo flooding events were found in Sabu main nala which show massive events of flooding had happened in the past. As per rough estimations the dating of these events were before the Mani walls were actually constructed. Because it was only after the flooding events that the Mani walls were actually constructed. So generally these flooding events happened around 400-500 years ago.

Paleo Flooding events (1500-1000 AD) – Leh Ladakh

Lot of research is required to actually date these events. Cyclicty of these events once established will go a long way in helping to predict the flooding events in future. No information is available with the locals about flooding. These events in the past went unnoticed because habitations were less impacted moreover nobody occupied the valley or channel areas which were traditionally considered unsafe. Therefore loss of life was negligible.

On 5^th of Aug 2010 in spite of the huge loss of life and property due to flooding in selected portions the overall destruction caused was negligible in comparison to the flooding events which had happened in the past or will happen in future, when the main channels/streams are affected.

Present study is restricted to four catchments in Leh district which were worst affected

by the floods.

· Sabu – Choglamsar Mahabodhy catchments (Sabu, Choglamsar Indus)

· Shakshilino - Mani Tsering catchment (Bus Stand, BSNL, hospital, airport,

Indus)

· Skampari catchment (Skampari, DC office, Polo Ground)

· Bumb nala catchment (Housing board, Golf course, main impact on Choglamsar, Indus)

Affected areas due to floods are in black thick lines, representing high energy, black thin lines, low energy and blue color represents change in course.

SKAMPARI

. . Location of the various catchments studied in Leh district

All these are remains of glacio fluvial valleys in which glaciers had receded due to global warming in the past and no record of flooding activity was available from these nalas for the last 400 years where upto 8m of moraines remain. These are non perennial streams as all the glaciers had already receded. Mainly due to melting of winter snow the water comes occasionally from these streams in summers.

Changed Course of the Digar stream or rather the stream had just straightened up causing unthinkable damage to the houses (which were recently constructed 20-25 years ago in traditionally unsafe areas) as well as the Mani wall near the petrol pump and few meters away in Choglamsar

Impact of this whole mechanism can therefore be related to simple mechanism of transportation of sediments in nature. This is really an event which would happen once in centuries actually creating a new surface of about 3m in Choglamsar and 8m in Tyagshi in a span of less than a minute.

Choglamsar

Max effected

Mani Wall

INTACT

Mani Wall

BROKEN AT TWO POINT

Modified ISRO Satellite imagery to show deviation of stream in Choglamsar

due to floods on the 6^th Aug 2010.

Index

Blue stream before the 6^TH Aug 2010

Red stream after the 6^TH Aug 2010

Green Mani Wall

Deviation of the natural bed stream in Choglamsar can be one of the reasons of the huge building destroyed near this area. In fact, during the flood, two new bed streams appeared this could be due to the habitations or naturally. According to the satellite picture there were presently three streams. Initially it was believed that maybe the natural bed has been deviated by the man-made constructions, but after detailed investigations it was found that the original flood flowed through the steam but washed all the houses in its way and reached Indus.

Selective destruction

Selective destruction in these catchments is attributed to the formation of reservoirs or its absence and RWR theory best explains these mechanisms. In catchment 1, 2 and 4 the destruction is maximum because of formation of natural reservoirs due to landslides in the past which blocked the main stream.

Old houses in bustand saved but NEW building destroyed

The mud slush flood on 6^th Aug therefore took an almost U turn when it had to go Choglamsar. Seeing the general geomorphology of the region it is hard to believe that such a phenomenon could actually take place. And for the last 12 years the Kendriya Vidyala School, ITBP and Himank areas are considered to be geologically safest place. U turn taken by the flood forced it to reduce its initial momentum which could be anything above 120 miles per hour on 6^th shook my belief about the safety of the places from a different perspective.

Cloud burst theory propagated by the media and the administration to explain this flooding event is not based on any investigations but is based on presumptions and assumptions as it fails to explain the basic concept of selective destruction as only some parts of the valley is affected for e.g. Skampari, Sabu and Shakshilino Nala though originate from the same point on the hill but the destruction was more in Sabu and Shakshilino Nala in comparison to Skampari where the mud slush moved but the impact was negligible. Moreover evidences of plants remaining intact on upper parts of the hills in the catchments studied are yet to be incorporated in this cloud burst phenomenon.

Had the impact of cloud burst theory significant then

all the plantation at the top of the hills and debris in the studied catchment should have been affected but that was not the case.
Investigations also failed to find any evidences of cloud burst as the entire plantations were intact and not uprooted or destroyed at the hill visited by the authors.
In some case small wooden bridges on small streams are also intact, showing negligible amount of rain and its impact on the hill adjacent to the hill where maximum devastation took place on that day.
In the valleys also destruction was very selective and confined to channels of small tributaries only.
It is important to note here that no vegetation was destroyed even in affected valley portions where the flooding event had no impact.

This clearly shows that rainfall was not significant on that day and cloud burst phenomenon is nonexistent in all the valleys studied. Had cloud burst like phenomenon been in existent than the entire valley should have been affected.

No evidence of cloud burst found

In all the flooded valleys the maximum effect on valley as well as plantation was restricted to not more than 8m. Clearly showing the impact was from the flooding in valley areas and not from the rainfall or cloudburst because then the entire valley specially vegetation above 8m should have been destroyed. Since no such evidence was found therefore the cloud burst theory to explain the flooding events is totally negated. Nevertheless, in same district some catchments and places were more affected by the flood than others.

No evidences of cloud burst were found as the destruction was very selective. Most of the catchments studied start from the same hill top and then move in different directions. Vegetation at the top of these catchments was scanty but intact. Destruction of vegetation is confined to selected low lying portions of the valleys which flooded on that day even though the entire catchment received same amount of rainfall. Therefore cloud burst theory is ruled out because the vegetation at the top is not destroyed.

Scheme of the main stream’s valley in Sabu village

At the confluence (1) there are two different landscapes which are difficult to explain by cloud burst:

In the Paltsa valley, there are no evidences of the flood. The small wooden bridge on the stream, which is not very higher than the level of water, is not broken. The agricultural fields in both sides of the stream are not damaged. There are no traces of a recent transport of granite boulders and the vegetation is not destroyed.
In the Chumek Chan valley, there are evidences of the recent flood. The level of the flood can be determined by discovering recent deposition of mud, sand and granite boulders in the affected valley (up to 4m high and about 8m wide portion). Selective destruction in valley is important as this can be explained only by RWR theory

In confluence (2) the valley is further divided in two others portions:

In the Chumek Chan valley: the main stream is not affected, plantations are intact and no evidences of a recent flood
In the Patsa Chan valley: there is a no-perennial stream and evidences of a recent flood are found. Vegetation is disturbed. In fact, at the bottom of the Patsa Chan valley, there are a lot of recent granite boulders, evidences of a new deposition. The tributary is perpendicular to the main stream and huge boulders, result of reservoir wall rupture, have been perfectly aligned. These boulders form a line, parallel of the main stream. They were transported by the mud slush which originated after reservoir wall which ruptured on 5^th Aug and created massive runoff of the mud slush strong enough to move massive boulders.

Late night of 5^th Aug and early morning of 6^th August 2010, quantity of rainfall was almost same in the Chumek Chan valley and in the Patsa Chan valley. Nevertheless, only one non perennial stream had an enough discharge and energy to transport the granite boulders. And align them in a particular manner on both sides of the affected valley. Reservoir Wall Rupture Theory best explains the geo-mechanism of the events triggered by heavy rains for short time on 5^th Aug 2010 on top of Patsa Chan valley. The phenomenon is almost the same that in the other case studies in Sabu and other village catchments.

At the bottom of this Patsa Chan valley when it meets the main channel, vegetation above the confluence is intact and no flooding evidences are seen above the affected portion. However evidences of paleo flooding activity were observed and it took wild imaginations to actually reconstruct the paleo environments in the past. In fact, there are three distinct lines of huge granite boulders, all parallel to the flow of the stream of the Chumek Chan valley and perfectly aligned at different elevations. Showing two major flooding events happened in the past at different timings. Since these were affecting the main channel so the impact could have been manifold in comparison to what happened on 5^th August 2010.

Old and young deposition can be distinguished in the field by:

Color of the rocks: older granite becomes brownish red due to oxidation
Presence of cracks
Vegetation/algal growth still intact

Extreme geological event triggered by excessive rainfall in short time span of 5-10min can best describe what actually happened on night of 5^th August 2010 in Leh. Heavy almost incessant rains in 1^st week of August 2010 in Leh region and heavy rains and abnormal lightening for a short span of 5-20 min were a peculiar phenomenon on 6^th Aug 2010. Rainfall for over a week had already saturated the mountain debris as well as glacial moraines in the low lying valley region making the beds fragile and susceptible.

Excess rains for short time on 5^th Aug created kinetic energy imbalances in debris deposited over the years and these energy imbalances resulted in abnormal floods on that day. These floods can be categorized into three types depending upon the majority of the debris transported by it:

First: water floods
Second: boulders (0.1m to 3.0 m) floods
Third: huge mud and sandy floods

Whenever any major event happens all these three floods work in unison and this debris in this paper is referred to as mud slush because of the dominance of mud. First type of flood actually acts as a lubricant in nature so that boulders, sand, mud can be easily transported. Eye witness says that their houses were first intruded by gushing waters followed by mud slush. The water remained in their room for few minutes and left 0.5-1.2 feet of debris. Floods, especially second and third type, deeply affected the human life, destroying houses, roads, bridges and claimed several lives (many persons are still missing, probably washed by flood waters or just sank in the mud and boulders slush) besides destroying millions of trees which fell in their natural course. In terms of energy imbalances, the flooding event can be described as transformation of potential energy of the debris into kinetic energy (triggered by rain) and then again into potential energy (depositional environment).

Possible reasons to explain high discharge on 5^th Aug 2010 and intense power of the flood are the creation of a natural reservoir in the valley. Intense heavy rains in short span led to accumulation of water in the reservoir.

Reservoir Wall Rupture Theory is based on simple geological phenomenon wherein landslide creates a natural wall across the channel to form a natural reservoir. Heavy rainfall for short span of 5-10min on any day was important for accumulation of water in the reservoir. As volume of water increased the pressure on the reservoir wall increased proportionately. The hydrostatic pressure reached its threshold, the reservoir wall was not able to withhold the water and wall ruptured under the pressure of water.

Reservoir rupture mechanism

Consequently, the accumulation of a huge amount of water in a reservoir along with mud, sand and boulders referred to as mud slush busted with huge speed. Evidences of ruptured wall are found in the form of perfectly aligned boulders at considerable heights along both sides of the valley. This is the best explanation to show high discharge and power of the flood in the affected catchments.

Geo-mechanism of extreme geological event is therefore necessary to understand the selective destruction due to flooding event on 5^th Aug 2010 in totality.

Four affected catchments Sabu, Shakshilino, Bumb Nala and Skampari in and around Leh emerging from same hill top were investigated. Investigations revealed that all these catchments received same amount of rains on that night but Skampari catchment was comparatively less affected as compared to Sabu and Shakshilino.

Clearly showing that phenomenon other than rain was actually responsible for flooding on 5^th Aug midnight. Actually it was simple geological phenomenon. All the affected catchments can be broadly divided into two parts:

High energy erosional part
Low energy depositional part

Main impact on this catchment can be divided in two regimes:

1. High Energy erosion and transportation regimes (e.g. Sabu and Leh Shakshilino)

This can be further dived into 4 parts:

CHOGLAMSAR SABU

Low Energy High Energy

Depositional environment Erosional environment

+ + + + + + + + + + + + + + + + + + + + + + + +

ITBP + + + + + + + + + + +

affected area

+ + + + + + + + + + + +

Solar

Proposed site + + + + + + + + + + + + + +

Landslides

Natural wall Reservoir formation Water: 244 m³

Reservoir rupture

Mahabodi

affected area

Figure 2: Scheme showing geo-mechanism of flooding in Ladakh catchments on 6^th Aug 2010

Index:

+ + Fractured granite

+ + Weathered granite affected valleys and streams

Direction of flow

Slide and reservoir formation

First part (non affected top part) is generally the space between upper side of the natural reservoir and the hill top, there is no evidence of flood. There is no recent erosion; the grass and the moss on the rocks are not removed, showing no evidence of cloud burst. The reservoir formation generally occurs in this part of catchment. Narrow portion of the valley with steep slopes >85 degrees of gradient are blocked by landslides, leading to reservoir wall formation. Landslides block the main stream with huge boulders 2-3m large mainly near the top of the catchment (with steep gradients). There can be one slide or two slides from both sides of the valley and over the year boulders, sand and mud keep on accumulating to form a wall/dam and creating a reservoir. Landslides triggered due to rains result in movement of huge boulders of granite (1m-3m) due to steep slopes. Because of their size, they block the flow of the stream. One or more slides often happen and form a wall/dam. This event normally happens couple of years ago or may be triggered on that day. These boulders once block the main stream are not easily transported because of low intensity of the stream. As a result debris keep on accumulating and form a reservoir but because of porosity the small quantity of water which falls as rains is not stored and moves as runoff as a result the reservoir is never filled with water. Therefore if rains are normal there is hardly any impact due to these rains in creation of water reservoir. These reservoirs are generally 3-4m high, 10-12m wide and approximately 20-40m long.

Second part is the reservoir wall rupture. Heavy rains in short span leads to water accumulation in reservoir; this creates hydrostatic disequilibrium and pressure on the natural reservoir walls increases. Once it reaches threshold reservoir wall ruptures as they are not able to withstand the excessive pressure created due to accumulation of rain water. Mud, sand and boulders along with water hereafter referred to as mud slush move with high speed > 100 km/h downstream. Perfect alignment of the boulders on both sides of the affected valley shows the evidences of rupturing phenomenon at the sites.

Third part is the high energy erosional and transportation part in the narrow valley generally without habitation. The bed streams are generally narrow but slopes are very steep. As water, mud and boulders (mud slush) move along the narrow valley with steep slopes after the reservoir wall ruptures, it gains momentum and gathers all the eroded materials from the beds of saturated glacio fluvial deposits in the valley.

In the both sides of the channel beds evidences of recent erosion of in situ granite rocks and paleo glacial fluvial deposit are seen which proofs of recent erosion and high energy environment are. All along the stream route, evidences of flooding can be finding. Roughly 0.3-4.6m of bed debris is eroded and completely washed from fragile valley saturated by the rains falling for more than a week. The height of the affected area due to erosion is around 3-4m high and 8-12m wide.

The impact is maximum on the curves up to 10-12m and is evident from the fact that the in situ bed rocks are exposed. Due to high elevation and steep slopes this portion actually provides the maximum amount of momentum to the outburst deposits. Speed of the debris moving in these channels could be anything between 160km/h or more. These slush debris keep on accumulating more and more deposits as it moves along the saturated fragile valley. By the time it reaches the distal part of the catchment where the power and momentum is maximum and its impact to cause destruction increases manifold e.g. Leh Bus Stand, PHE and MES power house on way to Choglamsar. Evidences of 2 tons of generator lifted to 7.5mabove on second floor in New Bus Stand and parts of cars and boulders lifted to 3m high in Sabu are perfect examples to show the intensity and power of mud slush on the flooding day. Concrete buildings were completely destroyed within seconds in affected areas and buses parked in the bus stop were piled one upon the other as if they were toys. All showing the unimaginable dimensions which the dry stream obtained on that day and is the best explained by the Reservoir Wall Rupture Theory.

Fourth part is the low energy habited with a deposition and creation of new elevated land. The catchment area considerably increases in this part. Here the energy of the flood is considerably reduced because the valley widens up forcing the slush to lose its momentum. Traditionally these were not habited as everyone was aware of the disasters which might be waiting to happen in these traditionally unsafe areas. But due to anthropogenic increasing, shortage of land near main townships, greed, limited land choices, political compulsions and uncertainty in actually calculating time of disaster makes the geoscientists suggestions easy to be over ruled and generally ignored by the administration and people at large. Thinking that these are dry beds in low lying area the construction cost and low cost of land results in maximum habitation. Even small channels of the streams are occupied and normally encroached by the human settlements. The 5^th Aug disasters wake them up for some times but everybody waits for the time to be the best healers till these disasters are forgotten.

The movement mud slush reaches the distal part of the catchment, the impact area increases many fold, the energy is dissipated and therefore the impact of the slush becomes considerably less.

Energy of the floods is considerably reduced because of wide area available for movement of slush. But at the point of contact between low energy and high energy regimes the impact is maximum which decreases with further movement downstream. It is in this part that the slush starts depositing the eroded material brought by it. Up to 1-3m of slush is reported to be deposited within minute on that day in Choglamsar and up to 8m in Tyagshi.

Thereby changing the entire geomorphology of the area by creating a new elevated land up to 3m in Choglamsar and 8m in Tyagshi within minutes the energy of the slush depending on the area and distance of its dissemination at the point of deposition. Thereby the flood had affecting the entire habitation which falls in its way. These deposits are actually capable of destroying and submerging habitations and also civilizations in the past and Indus valley civilization was no exception.

It is important to note that the deep and broad gully erosional features created in the high energy regime was compensated by creating new elevated land in low energy regime part.

Recommendation

1. 5^th Aug 2010 disaster should be taken as an opportunity to build sustainable habitats in geologically sound locations so that our future generations should be safe from the natural disasters of earthquakes and flooding.

2. Role of Mani walls and Stupas in disaster management needs to be re-emphasized.

3. All channels or paleo channels should be properly identified, demarcated and protected.

4. No habitation should be allowed in and around these channels.

5. Already established structures if any on the channels should be dismantled.

6. 300m wide stream channel from Ganglas to Indus to be constructed in affected catchments.

7. Mani walls to be constructed 1-2m away from the channel boundaries especially on the curves.

8. 2-3m from Mani wall plantation should be made and declared green belt.

9. No plantation to be built between the stream and the Mani walls

10. Natural unobstructed flow of Khardungla melt will go a long way in solving the disaster due to flooding.

11. Hills in and around Leh should be the most promising habitat as they are made of granites and are geologically stable and free from the flooding events.

12. Before living on the hills necessary precautions to be made and proper fracture/joint patterns to be studied.

13. Engineering designs of building should meet highest seismic activity.

14. In case of limited space efforts should be made to give these channels a free way so that they can reach Indus without obstruction and hence cause minimum destruction.

15. Near airport the channel should be wide and straight.

16. In case of paleo channels or dry channels they should never be habited and in case necessary only walking trails or motor roads should be constructed.

17. Drilling experiments by (R.Arya) revealed glacio fluvial debris of more than 100m at south polo. Two lakes are also visible their impact on Leh in case of outburst and flooding is just unimaginable.

18. The impact of rains on these lakes needs to be assessed.

19. All construction in Ladakh region should be made in geologically sound and safe areas so that our future generations can live happily with nature. Many people fainted after seeing the lightening on 25^th September 2010 almost two months after the event. Showing the psychological trauma faced by the people.

20. Proposed solar colony for rehabilitation is not the safe and sustainable solution because the area lays sand witched between the two streams Digar and Lungmuchay which were badly affected on that day. Moreover the area lies in the Sabu, Choglamsar and Mahabodhi catchments and is presently dissected by many nalas or streams.

21. The area in general is as unsafe as the Choglamsar was from where they have to be shifted.

22. Rehabilitation colony should be taken as an opportunity to make model colony for the entire Ladakh region in geologically stable environment capable of withstanding seismic as well as flooding impact, but solar colony is not the solution because it is located in geologically fragile environment.

23. Hills should definitely be the preferred destination.

Conclusion

In spite of the fact that paper is titled an extreme geological event but after forming an unbiased opinion the studies suggest that the magnitude of this event was 3 if there was a scale of 10 to measure the intensity of the floods. Worst is yet to come as in the present study it was seen that only non perennial dry tributaries were affected main channels remained unaffected.

CLIMATE CHANGE AND ITS IMPACT

Climate change and the global warming is predominant phenomenon world over and Ladakh has also not remained untouched. 19.5 km of Khardungla glacier had receded since the last glaciations. Today this glacier is on the verge of extinction. Precipitation in the form of rain has considerably increased leading to saturation of land and change in agricultural pattern. Interesting thing which has happened is the increase in flooding events and on 5^th August 2010 the impact was visible. Mud houses with mud and wooden roofs are now being changed with concrete structures and steel sheet roofs to avoid leakages due to rains. Small window panes are replaced by big ones to have the maximum impact from the sun. Dry toilets are being replaced by wet toilets all showing considerable impact by on the life of people due to climate changes. Need of the hour is to monitor the climate change in proper scientific manner so as to understand the impact of climate change both in positive (increased agricultural production and better tourism opportunities) and negative in terms of coping with the natural disasters mainly flooding and earthquakes.

GEOMORPHOLOGY

All the flooding events on 5^th led to erosion, transportation and formation of deep gullies in high energy regime and deposition and creation of new elevated land in low energy regime. Entire geomorphology of the region is changed within minutes. Flooding events gradually lose their energy in low energy regimes because of vast area and gradual decrease in the gradients. Streams start depositing the eroded material downstream. 2-3m of debris were deposited in fraction of a minute and the whole land was elevated to up to 3m in Choglamsar. Now this is remarkable phenomenon creation of new elevated land.

RESERVOIR WALL RUPTURE THEORY proposed in the present paper successfully explains geo-mechanism of the selective destruction due to flooding on that day in spite of the fact they received uniform rainfall. There are clear evidences for the formation of natural walls due to landslides blocking the main stream and their role in creation of reservoirs which ruptured once they were not able to bear the hydrostatic pressure of the water accumulated due to heavy rains in short span of 5-10min on 5^th Aug 2010 causing massive floods in selected dry streams. In all the studied valleys where floods and mud came, it’s possible to find evidences of ruptured wall in the form of recent erosion and deposition of boulders perfectly aligned on both sides of the affected valley. Landslide evidences and destroyed vegetation is restricted to selected portions of affected valley portions only. In the entire flooded valley the effect of flooding was restricted to up to 8m high and 12m wide. All these clues enable to find a place on the valley bed where a wall was created which ruptured due to the heavy rains causing floods.

NO CLOUD BURST

Nevertheless, in adjacent studied valleys in the same catchment, where reservoir wall was not formed or broken the impact was nominal as in Skampari. There are no clues for the presence of flood. Therefore, the rainfall on its own is not responsible for the huge floods observed. Reservoir Wall Rupture Theory best explains the geo-mechanism of flooding on that day. These floods are triggered due to the high intensity of rainfall, in a short time, leading to accumulation of water in reservoir, thus creating hydrostatic pressure which the natural walls are not able to withstand hence rupture causing flooding. Only those valleys in which the walls due to slides were created before 5^th Aug 2010 are subject to flooding on that day in all other valley regions there are no floods even though the intensity of the rains and its duration was same. It is important to note that this reservoir wall rupture theory is based on geological field observations.

GEO-HAZARD MONITORING /MAPPING

Therefore extensive geological surveys and geo-hazard mapping should be done so as to have overall view of these entire valleys specially those which are thickly populated.

Strong vigilance on these channels and any slide which blocks the main stream should be immediately brought to the notice of the administration so that effective steps to mitigate any natural disaster which might come due to this can be effectively prevented. An institute specially dedicated to study earth sciences, climate change and energy should be set up in Leh with the sole aim of providing world class research on these mountains which are actually the head water regions of the Indus Basin. Studies should be focused on understanding the geology, climate change induced flooding and its impact on habitation and meeting sustainable energy demands from the natural resources like water, sun, wind and geothermal energy. Role of traditional knowledge in identification and delineation of natural disasters and role of massive man made geo-structures like Mani walls and Stupas and their role in actually protecting the population from future disaster.

This extreme geological event was triggered by unprecedented climate change and might occur more often in the mountains and intermountain valley regions of entire world courtesy global warming.

MANI WALL, PALEO FLOODING

The deposition led to destruction of habitation just above the 400-500 year old Mani wall. The wall itself was damaged on that day at two point, interesting thing to note here is the wall in the past had holes through which the flood waters could pass through, these were known as ………but these holes were blocked by Border roads GREF when they were making roads and the price was paid on 5^th August. Had the holes not blocked the water could have passed through the holes and the damage to the wall minimized. However in absence of Mani wall entire Choglamsar would have been destroyed. Majority of people living below Mani wall were safe and therefore the 400 years old wall actually solved the purpose for which it was made on 5^th Aug 2010.

Had any such event happened in the last 400 years then the walls would have been built at a higher elevation. Since this was not the case so no flooding is observed in last 400 years after the Mani walls were constructed.

There is therefore urgent need to actually raise the level of Mani walls at Choglamsar to further 1.5-2m or built a new wall at the elevated land so that these Mani walls remain effective and solve the purpose for which it was made. If this is not done then Mani wall will not be able to act as protection wall and therefore will lose its significance in protecting the habitations lying below it from flooding. We saw what happened to Mani prayer wheels which were recently constructed at Choglamsar opposite SBI, at Sabu and Bus Stand. All of them were washed because they were recently built in geologically unsafe area.

In order to keep the faith in religion and not religious rituals alive it is necessary to rethink about the relocation and reengineering of these walls in nearby newly elevated land.

REHABILITATION

Efforts should be made to build geologically sustainable habitats and not concrete buildings in geologically and traditionally unsafe areas. Location of rehabilitation site at Solar colony Choglamsar will be a great disaster for our future generations. The impact of flooding was negligible in Solar colony this time but even a laymen can see that the entire Sabu- Choglamsar catchment from ITBP to Mahabodhi were affected by the impacts of flooding from eastern and western sides of the catchment. Central portion of this catchment (Solar Colony)was not affected because of obvious reasons this time but evidences of paleo flooding in the form of huge boulders are present in the entire Solar colony area.

WASTE DISPOSAL

Need to dispose the solid waste at proper site in low lying areas so that these dumping sites donot create any problem in near future.

Bibliography

Ritesh Arya Sustainable Habitats in cold climatic conditions of Ladakh 2006

Ritesh Arya Global warming, groundwater, flooding in Himalayas SIWI Sweden 2008

Ritesh Arya Impact of global warming on groundwater resources of Himalayas

Impact of Climate Change on local livelihoods in the cold deserts of the Western Indian Himalayan region of Ladakh and Lahaul & Spiti.

Tundup Angmo & Leo Philipp Heiniger (GERES)

July 2009

L.B.A Ladakh Buddhist Association (testimony of the number of persons impacted)

R.S.S Sewa Dal (testimony of the number of persons impacted)

Web site

(1) http://blogs.wsj.com/indiarealtime/2010/08/06/lehs-flash-floods-how-much-did-it-rain/

Leh’s Cloudburst How much did it rain?

Tripti Lahiri and Krishna Pokharel

www.nrsc.gov.in (Satellites pictures of Leh district)

http://enjoyglobalwarmingisnatural.blogspot.in/

www.ritesharya.com

Video recordings

Ritesh Arya

http://www.youtube.com/watch?v=iImZVXSK3AY

http://www.youtube.com/watch?v=Btqcat0wDsk

http://www.youtube.com/watch?v=RxEa2uxZnK8

Photographs

Erwan Cabon

Press

Geologist caught in mudslide he predicted- Times of India

http://articles.timesofindia.indiatimes.com/2010-08-07/india/28287029_1_mudslide-choglamsar-village-leh

CONTACT

Dr Ritesh Arya

09316722291

aryaritesh111@gmail.com

aryadrillers@gmail.com

www.ritesharya.com

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Leh Floods -2010 A report - ARYA Ritesh Arya, CABON Erwan, VICHIER-GUERRE

Table of Contents

Summary