Landslide Risk Management- Landslide hazard zonation mapping
- Landslide hazard identification and assessment of landslide risk
- Application for landslide investigations
- Guidelines for construction and land Use planning in hilly areas
- Landslide mitigation
- Awareness and training programmes
- Landslide early warning
- Landslide database
Landslide hazard zonation mapping
Landslide Research and Risk Management Division of NBRO has implemented a landslide hazard zonation mapping programme within the 10 landslide prone districts of Kalutara, Galle, Hambantota, Nuwara Eliya, Matale, Kandy, Kegalle, Ratnapura, Matara and Badulla. The maps which display the distribution of the severity of landslide hazard potential in a given area, were intended to be used with associated guidelines as a decision making tool for development of central highlands of the country. It is also used for identification of elements at landslide risk and can be utilized in relocation, rehabilitation, allocation of relief funds and insurance purposes also. Mapping is carried out at 1:50000 scale and at 1:10000 scale.
1:50000 scale maps covering the entire districts of Matale, Kandy, Nuwara Eliya, Bdulla, Kegalle, Ratnapura and Kalutara are available for the use of planners, developers, decision makers, and general public.
The methodology adopted for 1:10000 scale landslide hazard zonation mapping is based on an extensive field study and evaluation of six causative factor attributes and their sub factor elements and hence limited to the areas with potential to development and is extremely high vulnerability to landslides (View 1:10000 scale map). Availability of 1:10000 scale landslide hazard zonation maps (Click the district name in the following table to view the areas covered):
| District | Land Area (Sq km) |
| 709 | |
| 920 | |
| 760 | |
| 272 | |
| 360 | |
| Matara | 263.5 |
Generation of maps for 640 sq.km. of land area in Kalutara District and 400 sq.km of land area in Hambantota Districtis are in progress and the maps are expected to be made available in 2013. Field data collection for mapping of another 440 sq.km of land area in Kegalle District will be commenced in 2013.
The execution of LHMP as at present is graphically represented in the map shown in the following key map.
General guidelines for developments within each landslide hazard zone in the landslide hazard zonation map
| Legend colour | Landslide hazard zone | Guideline for development |
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Landslides most likely to occur |
Danger and potential threat to life and property exists. No new construction should therefore be permitted. Essential additions in the existing structures may be allowed only after thorough site investigation and adequate precautions to be certified by specialist(s). Early warning systems should be established if symptoms of landslides are clear and risk levels are high. |
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Landslides are to be expected |
Moderate levels of landslide danger exists. New construction should be discouraged, and improved land use planning practices should be introduced to halt and reverse the process of slope degradation. All essential construction and remediation, and new projects be subjected to landslide hazard assessment. |
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Modest level of landslide hazard exists |
Slight danger of landslides exists. Engineered and regulated new construction and well planned cultivation are permitted. Plans for construction should be technically vetted and ceritified. |
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Landslides not likely to occur |
No visible signs of slope instability or danger exist based on present state of knowledge. No blanket limitations need to be imposed particularly on well managed lands and engineered construction. Location specific limitations may become necessary, particularly for areas prone to flooding and erosion. |
Landslide hazard identification and assessment of landslide risk
At the requests of various organisations, District and Divisional Secretaries, developers and individual owners, Landslide Studies and Services Division of NBRO carries out landslide potential identification and landslide risk evaluation investigations within various areas of the country and provides recommendations for minimizing any landslide risk.
Such landslide potential identifications and landslide risk evaluations are often requested by the government institutions who approve major development projects, rock quarries, and earth removals.
During the catastrophic events such as in May 2003 and January 2007 also, LSSD immediately responded to the requests of the government for evaluating the landslide risk to the life and property of the affected areas and ensure the safety of the people.
Application for landslide investigations
Application for requesting a service from the Landslide Studies and Services Division
Guidelines for construction and land Use planning in hilly areas
Landslide Studies and Services Division of NBRO has prepared a set of general guidelines for construction in landslide prone areas. Following these guidelines minimizes the landslide threat induced by impact due to construction or other development activities. In addition, after performing a landslide potential and risk evaluation investigations, site specific guidelines are provided for land use planning, construction and other development activities to be implemented.
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Guidelines for construction in landslide prone areas (English)
Guidelines for construction in landslide prone areas (Sinhala 1)
Guidelines for construction in landslide prone areas (Sinhala 2)
Download application for landslide investigation
Mitigation of Landslides
Landslide mitigation
NBRO has implemented four major structural mitigation projects for mitigating Peredeniya, Padiyapelella, Mahawewa and Garandiella landslides. Two non structural mitigation projects have also been implemented in Badulla and Matale districts to reduce the landslide risk within those districts by introducing appropriate land use practices.
Mitigation of Peradeniya Landslide
Peradeniya landslide is located at Peradeniya town, by the Colombo Kandy main road. This landslide occurred in November 2006 destroying a few boutiques in the town and interrupting road traffic for weeks. Peradeniya is the gateway to the historical city of Kandy. Since the year 2009, the Government of Sri Lanka has already allocated Rs. 102 Million to mitigate this landslide for the benefit of the users of Colombo Kandy main road and the dwellers and commuters to the Peradeniya town.
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| Mitigation Activities in Progress | |
The mitigation work started in December 2008 by the Landslide Studies and Services Division (LSSD). The applied structural mitigation measures for mitigating this landslide include trimming and benching, rock blasting, soil nailing, rock bolting, and construction of surface drainage, and turfing. Out of the total allocation for this project Rs. 87 Million has been spent so far. 75% of the mitigation activities are completed and the total project completion is expected to be achieved in April 2012.
As a result of mitigation sites being monitored by the LSSD teams involved in mitigation activities NBRO was able to immediately alert the responsible authorities and avoid a disaster during the last reactivation of Peradeniya landslide on 15th October 2009 around 2.30 am when the prevailing rainfall was 80.3mm (As at Gannoruwa Agriculture Research Center). LSSD constructed a 40m long 3.5m high protection berm after removing unstable boulders within 3 months time and enabled reopening of the Colombo Kandy main road in January 2010.
Mitigation of Padiyapalella Landslide
Padiyapalella landslide is located at Padiyapalella town, by the main road of Walapane Hanguranketha. The landslide occurred on 12th January 2007 destroying more than three houses and interrupting road traffic. Padiyapalella is the main town in between Hanguranketha and Walapane and the main access to Maturata and Mandaramnuwara also goes through Padiyapalella. The Government of Sri Lanka has allocated Rs. 51.38 Million for mitigation of this landslide for the benefit of the business community, road users, dwellers and commuters to the Padiyapalella town.
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| Mitigation activities in progress | |
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The mitigation work started in January 2009 by the Landslide Studies and Services Division (LSSD) by applying structural methods such as construction of retaining structures, construction of surface drainage. In addition, monitoring of the site for any possible slope movements were continuously carried out by LSSD. The mitigation processeshave been completed in March 2013.
Mitigation of Mahawewa Landslide
Mahawewa landslide is located at Kumbalgama in Nuwara Eliya district. Due to the heavy rain on 12th Jan 2007 more than 65 houses were damaged due to the occurrence of this landslide. Therefore all the villagers had been evacuated from the existing locations. With the recent heavy rains after the initial incident, this area was gradually moving down towards Walapane Hanguranketha main road. In addition, the Keerthi Bandara Vidyalaya situated on the extreme down slope was at the highest risk due to a possible reactivation of this slide With the support from the Sri Lankan government and Japanese International Cooperation Agency (JICA), LSSD commenced mitigation of this landslide in the year 2009.
Installation of automatic rain gauges, extensometers and strain gauges and monitoring the surface movement to study the controlling characteristics of the landslide are completed under the JICA assistance. The estimated cost of proposed mitigation activities is Rs. 441 Million for which the Government’s support is expected.
Mitigation of landslide threat in Badulla District
NBRO has realized that the landslide frequency has been increased in the Badulla district with the increases of human activities and unplanned developments in hilly areas. Therefore, NBRO has implemented a non-structural mitigation project for the Badulla district to reduce the landslide risk by introducing appropriate land use practices. The project will be implemented in association with the Land Use Policy Planning Department (LUPPD) of Sri Lanka. LUPPD is to provide updated maps of land use within the district and NBRO will evaluate the landslide risk.
As part of this project landslide hazard potential evaluation in Uva Paranagama Divisional Secretariate and in Haputale and Bandarawela Divisional Secretariates are carried out. A set of appropriate land use techniques and guidelines for building and other construction will be prepared as the primary out come and the techniques and guidelines will be implemented through LUPPD. The Government of Sri Lanka has allocated Rs. 3.0 M for this mitigation projects.
Mitigation of subsidence observed within Matale District
Unusual behaviors such as cracking of a large number of houses, appearance of sudden ground subsidence and appearance of a large number of springs off the ground had abruptly been occurred in a wide area close to the Matale town in the year 2006. Cracking of houses had been distributed along a specific zone starting from Ukuwela area to Palapathwala through Matale town and the situation was considered as disastrous. About 3000 affected houses were identified within 24 Grama Niladhari divisions of Matale and Rattota divisional secretariats during the project.
After a detailed study and preparation of subsidence hazard zonation maps NBRO has now implemented a non structural mitigation project in the affected area for preparation of guidelines for building and surface water drainage and conducting awareness programmes for educating the communities to be safe concern and on importance on following the proposed guidelines. The total estimated cost of the project is Rs. 2.0 M.
Mitigation of Garandiella Landslide
Garandiella landslide is located by the 41st kilometer post on Nuwara Eliya-Gampala main road in Kothmale Division. Mitigation of this landslide was commenced on Auguat 02, 2011 for reducing the landslide risk on the users of the Nuwara Eliya-Gampala main road, Kothmale reservoir, 230 families living in the Ramboda Grama Seva Wasam in Kothmale Division and the built environment in the Kothmale town.
Geological and geotechnical investigations which consists the first stage of mitigation activities are completed by the end of the year 2011 and based on the results of those investigations, appropriate mitigation measures will be designed and implemented within the year 2012. The total estimated cost of mitigating Garandiella landslide is 90 Million which is invested by the Government of Sri Lanka through the District Secretariat of Nuwara Eliya.
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| Resistivity testing at the site | Director General is on an inspection tour |
Mitigation of Galabada Landslide
Galabada landslide is located within the Gallella Grama Seva Division of the Ratnapura Divisional Secretariat. 10 families living in the down slope area, shops, Rathganga (Punch Dambadiva) temple, Galaboda estate, Ratnapura Wewelwatta main road and the users of this road are at the risk of being affected by this landslide. In March 2010, with the financial assistance of JICA, LSSD implemented monitoring and mitigation of Galaboda landslide. As at December, 2011, installation of automatic rain gauges, extensometers, strain gauges and monitoring the surface movement to study the controlling characteristics of the landslide are 100% completed.
In addition to that, two boreholes were drilled up to 40 m depth in month of July 2012 and effectible properties of underneath soil layers upon landslide have being analyzed. The mitigation measures of proposed retaining walls and horizontal drain system will be implemented on month of October 2012, with the technical and financial assistance of JICA.
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| Newly formed cracks | Borehole drilling at Galaboda |
Mitigation of NewBurgh Landslide
Based on the recommendations provided by LSSD, mitigation of NewBurgh Landslide in Badulla was implemented as a community based mitigation (CBDM) project which is laboured by the state community living in the toe area of the landslide. With the maximum coorporation by the estate management, the project is financially supported by USCOD, an NGO working in the Badulla district. The mitigation activities were commenced with cleaning existing drains and drainage paths on the body of the destabilized slope, in December 2010. During the period of down pours between December 2010 to February 2011, Badulla area was affected by a large number of landslides within the proximity, but with only a few cracks on the referred site. Motivated by this favourable situation, the remaining mitigation activities were commenced on 16th July, 2011. Landslide risk on estate communities, a school and infrastructure will be reducded by this mitigation.
Mitigation of Malhewa Rockfall
The scientists of NBRO has successfully mitigated the rock fall threat in Ambahela, Hunuketapitiya kanda located in Malhewa Grama Seva Wasam in Kothmale Administrative Division. Due to this rockfall, the residents in the down slope area of Hunuketapitiya kanda and the users of Kothmale, Thawalamthenna - Pundaluoya road were frequently at risk for a long time.
In addition to the removal of unstable rock boulders in up slope area, NBRO scientists has applied mitigation structures consisting trenches, bunds and fences. The mitigation activities which were commenced in December 2011 and completed in March 2011 has significantly reduced the rockfall threat in this area.
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| Mitigated Malhewa Rock Fall |
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Integrated Landslide Mitigation Project
In addition to above LSSD has already identified 47 critical landslides which need to be mitigated to reduce the risk of landslides on the residents, public and private entities, infrastructure and plantations within the districts of Badulla, Nuwara Eliya, Kandy and Matale. Out of those 47 sites NBRO has prioratized 16 sites which needs urgent action for mitigation. Discussions are being made with the Ministry of Disaster Management and the Department of National Planning for necessary investments.
Awareness and training programmes
LSSD conducts awareness programmes for the people who are living in the hill slopes to increase their knowledge about landslides and living with landslides. Programmes are targeted for school children, decision makers, planners, administrators, grama niladaries, samurdi niladaries and villagers as well. Many number of awareness material have also been prepared by NBRO in the forms of book, posters, video clips, and manuals.
- Request for landslide related awareness/training programmes
- Upcoming events
- Staff training programmes
- Landslides in Sri Lankar
- Pre warning signs of landslides
- Steps to reduce landslide threat
- What to do during heavy rain?
- What to do when I receive landslide early warning?
- What to do during a landslide
Landslide early warning
Even though the landslide hazard zonation map itself acts as an early warning tool which can be used for avoiding highly landslide potential areas from developments, most of those high landslide potential areas are also settled by people. Therefore, based on the rain fall data and severity of landslide potential, LSSD issues landslide early warning to safeguard the lives of those communities.
- View sample early warning message
- What to do during heavy rain?
- What to do when I receive landslide early warning?
- What to do during a landslide
Click here to get more details
Landslide database
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