Monday, September 29, 2014

Sun Koshi Landslide: Indian Remote Sensing Satellite Data - Visual Analysis

Sun Koshi Landslide: Indian Remote Sensing Satellite Data - Visual Analysis 

Indra Sharan KC
Sept 29, 2014.

This blog is based on data and information made available at
National Remote Sensing Center Website: Accessed on Sept 17, and 29, 2014). Therefore NRSC is gratefully acknowledged. All the images are provided with their original source linksThese images are copy righted to NRSC/ISRO.

National Remote Sensing Center (NRSC) of Indian Space Research Organization (ISRO), Government of India published Satellite Images of recent Landslide on Sun Koshi River in Nepal.

The landslide had taken place on August 2, 2014. The landslide killed 156 people and destroyed 33 houses; a 2.5 KW hydropower plant in Sunkoshi Bazar; intake structure of 10 KW Sunkoshi hydro in Lamosangu; transmission lines and towers and about 1.5 KM of road in Ramche and Jure. There was 67 MW of power less in the grid, due to this landslide which added extra 4 hours of load shedding in the regular load shedding of daily 10 hours. Significant amount of agricultural land and forest was impacted by the mega landslide.

Nepal Army had been using light explosives, heavy equipment and muscle power to clear open channel to release water from the 2.36 km long, 200 m wide lake with a surface area of 44 Ha formed from the 5.5 million cubic meter debris deposit on Sun Koshi's bend that is exactly at the intersection of 4 Village Development Committees (VDCs), namely, Ramche, Mangkha, Tekanpur and Duskhun, of Sindhupalchok district.  So, the landslide affected people and area of those 4 VDCs.

The Indian Remote Sensing (IRS) Satellite images provide a great deal of valuable visual information. First, there was no areal or space view to inform scientists and concerned people on the scale and magnitude of the landslide and its impact area. Second, quantitative data on landslide and lake parameters were all speculative.  The images available at answer these two questions very precisely.

There are two types of  IRS Images provided by the NRSC on Sun Koshi Landslide.

LISS IV - multi-spectral images ( Spatial resolution: 5.8 meter at nadir)

A LISS-IV sensor operates in multi-spectral and Mono mode. This  sensor provides data with a spatial resolution of  5.8m (at nadir) in both the modes.
In the Mono mode, the sensor provides data of a single band in the visible region, with a swath of 70 Km (at nadir) and across track steerability of + 26
degrees. In the multi-spectral mode, the sensor provides data of three bands with a swath of 23Km.

When the lake was fully formed:

 The image was taken by RESOURCESAT on 5th August. Here is the link to the images. The measurements data on the landslide and lake are given on the image itself. The Indian National remote Sensing Center LISS IV images are here.

The landslide width at the top and bottom portions measured 506 and 853 meters.  The width of the dam (across the river) measures to be 200 meter.
Similarly, the  length of the lake (straight from the dam to to Sunkoshi bazar at the confluence of Sun Koshi and Bhote Koshi rivers) is shown to be 2.36 KM. From the measurement on image, the area of the lake is 44 Ha.

The measurement is done on-screen using geo-referenced satellite image, and the value can change slightly from person to person. Perhaps these measured values are close to themselves 95% of the time.

Post- dam opening (post Sept 7) image:

The landslide lake suddenly eroded the channel created by the Army and 60 percent of water released in early hours of September 7, 2014. Not serious damage was noticed, although the villages just downstream were evacuated by the people themselves for fear of being washed away by the landslide lake outburst flood. The image clearly shows the decrease in water level. The upper portion of lake (the area near Sun Koshi bazaar, the confluence of Sun Koshi and Bhote Koshi)) is now out of water. Similarly  the area near the dam where a small stream by name Dabi Khola meets Sun Koshi, is also out of water impoundment. Village called Tekan, at this confluence, which is about a kilometer away from the landslide, was destroyed by the landslide and formation of the lake.  This image of September 17, clearly shows this change.

CartoSat Panchromatic Images: (Spatial resolution: 2.5 meter at nadir)

National Remote Sensing Center, Hyderabad also acquired CartoSat-2 data over the landslide on August 23, 2014, when the lake was still intact. Cartosat data are high resolution (2.5 meter), and the measurements on this data yields better results.  This image provides a great view of the landslide and the extent of the lake.  Satellite CartoSat carries two PAN sensors with 2.5m resolution and fore-aft stereo capability. The payload is designed to cater to applications in cartography, and terrain modeling.  However, the NRSC has only provided measurement data using LISS IV MX data, which is 5.8 meter in resolution.  

This image although has some clouds at the upper part of the landslide, has best captured the landslide and the lake in great details.

Quantitative measurements of Sun Koshi Landslide, Dam and Lake  as provided by NRSC

The data from the satellite imagery provides the following information.

Length of Landslide:  

The length of the longest portion of landslide on plan view is 1.5 km. NRSC using LISS IV image  labels it 1.3 KM. 

Width of the landslide:

The width at top is about 500 meter. The width at the bottom part is 900 meter. The landslide tapers from 900 meter at the bottom to 428 meter at the bottle neck portion above at 1.14 KM from the river bed. The average width of the landslide is 600 meter. The NRSC's LISS IV data is labelled as: 506 and 853 meters.

Landslide Dam:
Height (most of the reports) : 55 meter
Dam length: 300 meter
Length of toe of the dam: 700 meter
Gradient of the toe: 1:6 (calculated from photographs taken in the field).
Width of dam: 150 meter.

Landslide Lake:

Straight line distance as given by LISS IV data: 2.36 KM.
Area as LISS IV,  reported by NRSC: 44 Ha.

Further analysis will follow in next blog.

CARTOSAT 1, Data User's Handbook, National Remote Sensing Center, Indian Space Research Organization,  available here.
RESOURCESAT-2, Data User's Handbook, National Remote Sensing Center, Indian Space Research Organization, available here
National Remote Sensing Center Website: Accessed on Sept 17, and 29, 2014).

Friday, November 22, 2013

Constituent Assembly Election Results Map as of November 22, 2013, 4PM

As of November 22, 2013, by 4:pm

The counting of the votes, from the Constituent Assembly Election held on November 19, 2013, have shows that out of 240 seats, the winning parties and candidates for 93 seats have been declared. There are only 3 women candidates elected so far.

The below map shows the spatial patterns of political parties winning the CA seats.

The NC and UML have 40 seats each. UCPN (Maoist) has won 8 seats.
Download the map for viewing the results on your own.

Friday, July 5, 2013

NASA's products point towards heavy rains on 7th July, in the Far-west Nepal and North India

I have been following the products published by NASA - TRMM (Tropical Rainfall Measuring Mission). It appears like these products are really experimental. They are on higher sides of estimations. The rains are less frequent and less intense than what is mapped and communicated. Let us see for the data 7th July in the image below:

Clearly, the Ghaghra and Tista and Mahananda rivers will swell affecting in many parts in India.

The pink color is clearly 250 mm rain which is concentrated in the Mahakali/Sharada and Karnali/Ghaghra in the western part of Nepal and on Mahananda/Mahakali, Tista and some Brahmaputra basin in Assam.

NASA has clearly said these are experimental products. We should see how close they are with the real rainfall. We do not measure, we just compare from the news.

Thursday, June 20, 2013

Rainfall Update: More flooding expected coming days

Rainfall Update: More flooding expected coming days

Please see the visualization of rainfall intensities in the form of maps in the following pages.  The colored patches are the areas where heavy rainfall occurred in the past and is expected in the coming week. The red colored areas are where minimum rains and the purple ones are the areas where maximum rains occurred. You will see two kinds of maps (a) forecast for June 19, and June 22 and (b) trend of rainfall that caused heavy floods in western Nepal and North India.

Scientists have found that if the rainfall exceeds 144mm in a day, the likelihood of landslides increase unexpectedly in Nepal. The  forecast shows rains will exceed the range of 200mm. So, more landslides to be expected. More loss of lives and property, sad news.

1. Forectasts
Forecast for June 19, 2013
This is rainfall prediction for June 19, UTC 1200. Heavy rains expected in the region of the range min 100 mm to max of 250mm for June 19 at about 1200 UTC.

Forecast for June 22, 2013 at UTC 300
This is rainfall prediction for June 22, UTC 300. Heavy rains expected in the region of the range min 100 mm to max of 250mm more frequently that  for June 19.
2. Recent rainfall trend
24 hours accumulated rainfall on June 19 by UTC 300
Minimum 35 mm, central region of Nepal, India, Myanmar and China.

3 days  accumulated rainfall on June 19 by UTC 300
Minimum 100 mm, max 200mm central and western regions of Nepal, India, Myanmar and China.

7 days  accumulated rainfall on June 19 by UTC 300
Minimum 200 mm, max 500 mm central and western regions of Nepal, India, Myanmar and China.

For more on TRMM, please visit: To understand the process, please refer to this literature: Algorithm 3B42 - TRMM Merged HQ/Infrared Precipitation;

Monday, June 17, 2013

Constituency Map of Kathmandu District and valley

The 2008 Constituent Assembly Electoral District Maps of Kathmandu district and Kathmandu valley:

Kathmandu had 10 constituencies. It is likely that the 2013 CA election will have 16 Constituencies in Kthmandu.

Kathmandu valley Constituencies. Kathmandu valley has 4 districts: Kabhre, Kathmandu, Lalitpur and Bhaktapur.

Preliminary Analysis of Constituencies: Which districts gain and which districts loose?

As per constitution of Nepal, after a census is taken the constituency areas will be re-delimitted.

Census of Nepal 2011 taken by Government of Nepal's Central Bureau of Statistics (CBS) has been published.

On comparison of data between Census 2001 and Censu 2011, the following information is gleaned:

1. Total 48 districts had increase in population. The blue color on the map shows these districts.
2. Total 27 districts saw decrease in population. The red colored districts on the map.

2001 Population: 23,151,423
2011 population: 26,494,504.

See the pattern of decreasing population trend:

See the pattern of increasing population trend below:

The pattern of gain and loss in the number of constituencies appears to be as given below:

I will update on the changes and new findings in future blogs.

Thank you

Nepal Constituent Assembly (CA) election date announced for 19 Nov 2013

Government of Nepal announced Constituent Assembly Election date as November 19, 2013 (BS Mungsheer 4, 2070).
See the link here.

KATHMANDU: Putting an end to the long-drawn-out period of uncertainty, the government today decided to hold Constituent Assembly election on November 19.

A Cabinet meeting took a call on the poll date after sorting out all contentious issues related to election laws. The government endorsed the Election to the Constituent Assembly Ordinance and forwarded it to the Office of the President for the seal of approval, said Minister for Information and Communications Madhav Prasad Poudel.

The Election Commission-proposed threshold provision, much-debated by four major forces at their innumerable High Level Political Committee meetings, has been removed, in an apparent bid to appease the fringe parties. The government, however, has upheld EC’s proposal on eligibility criteria for CA candidature. “A person convicted of heinous crime by a court will be disqualified from contesting the election,” Poudel told THT.

He said the government has kept existing provision on inclusiveness intact, exempting any party fielding less than 30 per cent candidates under proportional representation from being inclusive for other than woman category. The Nepali Congress and CPN-UML had been demanding that all the parties, irrespective of their strength, should follow the principle of inclusiveness equally in other categories as well. The government has also cracked the ‘other groups’ conundrum and has put Brahmin, Chhetri, Thakuri, Sanyasi and others who have not been defined in this category.

President Ram Baran Yadav’s press adviser Rajendra Dahal said the Head of State would take a call on the government-forwarded ordinance tomorrow.

Panel to delimit constituencies

KATHMANDU: The government on Thursday formed Constituency Delimitation Commission which will be led by former Supreme Court justice Tahir Ali Ansari. Geographist Netra Dhital, administration expert Madhunidhi Tiwari, Sociologist Dambar Chemjong and Secretary at the Prime Minister’s Office Raju Man Singh Malla are the members. The commission will complete delineation of electoral districts for the 240 first-past-the-post seats within next 30 days.