F.Y.2005/2006

JICA Vice - President Mr Ueda Yoshihisa and delegates with JICA (N) Resident Representative and Experts, and DWIDP Director General, Deputy Director Generals and Officers during the visit at DWIDP on May 12, 2006

Department of Water Induced Disaster Prevention (DWIDP) Pulchowk, Lalitpur Post Box No. 13105, Kathmandu, Nepal Phone: 977-1-5535407, 5535502, 5535503, Fax: 977-1-5523528 e-mail: [email protected] website: www.dwidp.org Government of Nepal Ministry of Water Resources Department of Water Induced Disaster Prevention (DWIDP) Certificate Distribution by the Director General Mr. N.P. Bhattarai for the Jica Vice President Mr. UEDA Yoshihisa keenly observing the debris praticipants of 16th General Course Training. flow model at DWIDP (May 12th 06).

JICA Vice President Mr. UEDA Yoshihisa with D.G., D.D.G.s and JICA Checkdams at Mugling-Narayanghat road sector 18+460-3. Expert during his visit at DWIDP (May 12th 06).

Series of Checkdams at Mugling-Narayanghat road sector. Embankment Construction at Left Bank of Daraundi River , Gorkha. Participants of the 16th General Course Training at DWIDP. Participants of 13th Advanced Course Training at DWIDP.

Water Induced Disaster Prevention Roving Seminar in Dolakha. Rehabilitation work for School Building Protection at Matatirtha, Kathmandu.

Landslide Protection Work at Bungamati Model Site. Surface Drain Construction for Landslide Protection at Bungamati, Lalitpur. DWIDP BULLETIN 2005 - 2006 DWIDP BULLETIN July 2006 F. Y. 2005/06

Advisory Board D Editorial Board

Mr. Narayan Prasad Bhattarai W Editor-in-Chief Mr. Lal Chand Pradhan Director General, DWIDP Deputy-Director General I Research, Training and Monitoring Division, DWIDP

D Managing Editor Mr. Shiv Kumar Sharma Mr. Samanta Man Sthapit Deputy-Director General P Chief- Information, Study and Training Section Study and Implementation Division, DWIDP Executive Editor B Mr. Prakash Man Shrestha Engineer- Information, Study and Training Section Mr. Lal Chand Pradhan U Deputy-Director General Members Research, Training and Monitoring Division, DWIDP L Mr. Nokh Bahadur Bashyal L Section Officer- Administration Section

Mr. Toshiya Takeshi E Mr. Rajan Shakya Senior Expert on Sediment Related Disaster, DMSP-FU/ JICA Sociologist- Information, Study and Training Section T Mr. Yam Bahadur Shah I Engineer- Information, Study and Training Section Mr. Heihachiro Nakagawa Mr. Khila Nath Dahal Long Term Expert on Disaster Rehabilitation, DMSP-FU/ JICA N Engg. Geologist- Landslide Section

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Government of Nepal Ministry of Water Resources Department of Water Induced Disaster Prevention (DWIDP) DWIDP BULLETIN 2005 - 2006 DWIDP BULLETIN Preface Fiscal Year 2005/2006 Nepal lies in the central portion of the Hindu Kush Himalayan arc. It has its unique topography, geology and monsoon rains July 2006 which have played a vital role for the occurrence of water induced disasters like floods, debris flows, landslides, bank cuttings, glacial lake outburst floods every year causing loss of human lives, property and severe impact on socio-economic as CONTENTS well as environmental condition of the country. Nepal is a • Significance of the Sabo Technology in Nepal mountainous country. These mountains are quite young and emerged as a result of Himalayan Orogeny. The last phase of the • A Glimpse of the 13th Advanced Course Training of DWIDP Himalayan Orogeny has not yet ben ceased completely; but it is • Application of "Sabo Soil Cement Method" for Water gradually slowing down. This on going orogenic activity, steep Induced Disaster Mitigation relief, weak and fragile geology frequently occurring seismic • Water-induced Disaster Mortality of Nepal activity, excessive monsoon rains combined together to make the • Enginerring Geological Study and Stability Analysis of young mountains as one of the most hazard prone areas in the Shrawan Danda Jyotinagar Landslide Ward No. 5, Butwal world. Municipality, RupandehiI District, Western Nepal • Trends in Human Life and Economic Losses from High population growth, deforestation, steep land farming: Landslides and Floods in Nepal haphazard migration and encroachment of river plain and forest area in the past successive years have added water induced • Rapid Environment Impact Assessment in Disaster In the disasters to many folds. The need for a holistic disaster Context of Nepal management approach to cope with such problems is therefore • A Sustainable Way of Controlling Debris Flows and paramount. This encompasses a whole gamut of issues like Landslides Along Mugling-Narayangarh Road preparedness, response in the form of quick relief and rescue as well as comprehensive mitigative and rehabilitation measures hand in hand with disaster awareness and training at both agency and community levels.

The Government of Japan through JICA has been assisting to promote the capacity of HMG/N employees and the communities to cope/face with water induced disaster. The Disaster Mitigation Support Programme Project (DMSP) with JICA cooperation is an attempt to manage water induced disasters in a comprehensive manner with community involvement through model mitigation works.

An integrated approach that can address the issue of water induced disaster throughout the country is indispensable. Realizing this fact the Water Resources Strategy-2001 has given a prime importance to water induced disaster management and identified primary outputs and activities for short medium and long term spanning a period of 25 years.

DWIDP with its seven Divisions and five Sub-divisions in various parts of the country is undertaking river training works as well as flood, debris flows, and landslide mitigation works throughout the country.

One of the prime objectives of disaster prevention and preparedness is to disseminate information and conduct various activities against water induced disaster. The DWIDP is bringing Photographs of Cover Picture out this Bulletin for the dissemination of information about its activities and other related papers. • Background : Landslide mitigation works at 17 Km, Kathamndu- Naubise Road Sector. The DWIDP extends its thanks to all the authors of the papers for • Bottom left : Inaugural Ceremony of 13th Advanced Course Training of DWIDP their valuable contribution. • Bottom right : JICA Vice-president Mr UEDA Yoshihisa and the delegates observing the model of Bagmati River Training, Khokana, Lalitpur at DWIDP. The Editorial Board Layout Design: Ashutosh Multiple Traders 2 DWIDP BULLETIN 2005 - 2006 Significance of the Sabo Technology in Nepal

– Dr. Ramesh M. Tuladhar Senior Division Hydrogeologist Chief, Sabo Section, DWIDP

ABSTRACT Sediments related disasters are common in Nepal. To cope with these disasters there is a need to identify a cost effective and sustainable technology to be applied in Nepal. The Sabo Technology, which was applied successfully in Japan under similar natural condition as in Nepal seems to be suitable to adopt in Nepal. This technology was indeed applied in Nepal several decades ago but became familiar only after the implementation of Disaster Mitigation Support Program Project (DMSP) from 1999 -2004 in Dahachowk Sabo Model Site and Girubari Sabo Model Site. The sediment related disasters risk has been minimized to a great extent by the application of the Sabo Technology in these model sites. Thereby the application of this technology has been extended to other areas including the most important Mugling-Narayanghat highway of the country. Thus the significance of the Sabo Technology is gaining in Nepal. However, the application of this technology in Nepal is challenging due to its geo-tectonic, geomorphologic, climatologic and socio-economic diversity across the country.

1. Introduction 1. Landslide The Nepal Himalayas frequently suffers from various types of In general, the landslide occurs in those areas where thick clay soil sediment related disasters such as, landslide, slope failure, rock is widely distributed. Therefore, the distribution of this phenomenon fall and debris flow. Every year the loss of lives and properties due tends to concentrate in specific areas with significant clay to sediment related disasters is significant in Nepal that eventually development such as Kathmandu Valley. However, there are affects the GDP. These phenomena induce severe hazards to several other landslide prone areas in Nepal. It is relatively easy to development projects and cause damage directly to the people recognize and moreover one can escape from the landslide prone such as deteriorating environment for living and agricultural area due to its slow nature of movement. But it usually continues production thereby causing serious impact on social and economic for longer period and might form a natural dam blocking the river development of the nation. World Bank (2005) ranked Nepal as and/or streams. Sometimes transmission poles and/or towers are the 30th most vulnerable country in terms of water induced destroyed too. Several such cases are observed in Nepal. disasters, the major component being the sediment related disasters.

The Sabo Technology, which has been successfully applied in Japan to cope with these disasters seem to be applicable in Nepal as has been demonstrated by the results of the Disaster Mitigation Support Programme Project (DMSP, 1999) as well as Soil Erosion and Watershed Management Pilot Project (1979). In general, the Sabo Technology is devised to control sediment related disasters such as landslide, slope failure, rock fall and debris flow. ‘Sa’ means ‘sediment’ and ‘Bo’ means control. Photo 1: Typical Landslide in Kathmandu Valley (Chalnakhel Landslide) Collectively Sabo means ‘sediment control’. This technique was used in Japan since ancient times (>200 years ago) and 2. Slope Failure comprises an integrated approach of both structural and non- This phenomenon usually occurs in slopes steeper than 30 degrees structural countermeasures. and the scale is relatively small. But it is extremely dangerous for human lives as compared to landslide due to its rapid movement In Nepal, Sabo approaches were made in the Dahachowk VDC of and suddenness without any visible symptoms. Nepal’s 77 % area Kathamndu district and the Girubari VDC of Nawalparasi as an is covered by mountains and hills, which are all prone to slope innovative model works during the implementation of DMSP and failure. In general, slope failure is intrinsically related to later extended in several other sites including the Mugling- topographic knick–point and triggered by rainfall at large. Most Narayanghat Water Induced Disaster Project. This article intends to slope failure originally tends to take place around the knick-point. elaborate the application of Sabo Technology in Nepal and its significance. It is probably most disastrous amongst all sediment related disasters. Sometimes it could be the starting point for a debris flow 2. Sediment Related Disasters in Nepal particularly in a mountainous country like Nepal. Furthermore, it The sediment related disasters are the most common natural makes the road maintenance a difficult job. For a small-scale hazard in Nepal. This hazardous natural phenomena causing slope failure it may not be a problem but at times, it is of large- mass movement of soils and/or rocks in various forms particularly scale and linked to geo-tectonic setup of the area such as Krishna due to action of water is simply considered as “Pahiro” in Nepal. Bhir (Complex Slope Failure). However, “Pahiro” accommodates several types of mass movements in terms of technical classification as mentioned below. 3. Rock Fall Rock falls are not so common. However, often time highways are

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blocked due to rock fall in Nepal. The term “rock fall” is commonly a. b. used, if the numbers of rock blocks are countable. This phenomenon is dangerous and may cause human lives and damage the infrastructures. Rock fall occurs due to inherent structures in rocks such as joints, cleavage, bedding plane and fractures.

Table 1: Simplified Geo-tectonic and Physiographic Units of Nepal also depicting potential Sediment Related Disaster (SRD) phenomena of each unit. It is to be understood that each of the above geo-tectonic unit are vulnerable to various sediment related disaster phenomena (Table 1) Geo-tectonic Unit Physiographic Units SRD – Phenomena Tibetan-Tethys Himalayan Zone Parts of Higher Himalayas and GLOF, Slope Failure, Avalanche Photo 2: Typical Rock Fall disaster along Photo 3: Typical Slope Failure at 17 Km South Tibetan Detachment (STD) Trans-Himalayan Valleys Butwal-Tansen Road of Kathmandu-Naubishe Road Higher Himalayan Zone Higher Himalayas and Parts of GLOF, Slope Failure, Rock Fall, Main Central Thrust (MCT) Inner Himalayan Valleys Avalanche Lesser Himalayan Zone Midlands, Mahabharat Range, Landslide, Slope Failure, Rock 3. Debris Flow Main Boundary Thrust (MBT) Parts of Fore Himalaya Fall, Debris Flow, Soil Ero sion Debris flow is a collective movement of sediments (sand, gravel, Siwalik Zone Siwalik Range, Churia Range, Dun Soil Erosion, Debris Flow, Main Frontal Thrust (MFT) Vallyes Landslide, Slope Failure, boulders etc.) saturated with water due to torrential rainfall. Collective Terai Alluvium Zone Terai Plain Bank Erosion, Flood movement of sediments takes place in the whole depth of accumulated debris. Debris flow can potentially occur in any torrents The Tibetan-Tethys Himalayan and Higher Himalayan areas are whose unstable sediments deposits in river- bed and/or gullies are vulnerable to Glacial Lake Outburst Flood (GLOF). The disaster steeper than a given critical value (40 degree). could be very much severe due to higher degree slope in these zones. Slope Failures along the local roads (trails) are also In general, the speed of debris flow is high (3-5 m/s) and gains its common. momentum as it flows down almost sweeping everything lying on its way including big boulders, plants and trees. In this process, the In Lesser Himalayan Zone which includes midland valleys where amassed volume of the debris flow increases as it flows further population density is high and the housing lots are build along away from the source. Due to its momentum and energy it can limited gentle slope or in narrow valley plain, there may occur a carry up to elephant sized boulders (5000 kg) and most civil complex movement scenario, debris flow, in particular, resulting in structures may be easily damaged or destroyed. For instance, the shortage of safety place to evacuate in case of emergency. Debris Flow of 31st July 2003 along Ruwa Khola hit the Marsyangdi Power House causing a significant physical and In Midland areas such as Kathmandu Valley housing lots are economic loss (over half a largely developed around valley plain and in recent days extending million rupees) and power cut towards the foothill slopes. These areas without proper planning for over a month. may suffer from all sorts of SRD and flood.

In recent years, debris flows, In Terai area, extensive soil erosion from Siwalik Hills, formation of in particular, are gaining alluvial fan and rising of river bed are the major hazards that significance in Nepal. For trigger flood and erode river banks intensely. instance, out of 13 major disasters of July 2003 along 4. Application of Sabo Technology in Nepal Mugling-Narayanghat To cope with the problems of sediment related disasters the Sabo Road, 9 disasters were due Technology was introduced in Nepal by undertaking Sabo works at to debris flow. A significant Dahachowk Model Site of Kathmandu Valley and Girubari Khola portion of Nepal lies under Model Site of Nawalparasi. Various Sabo works were carried out that debris flow prone area include the Structural as well as and the Non-sstructural measures. After including most parts of the successful application in these two model sites, this technology has Photo 4: Debris flow disaster at Matatirtha. highways. been extensively applied in several

parts of Nepal including the most Field 3. Geo-ttectonic Set-uup of Nepal important highway of Nepal- the Monitoring Investigation The Himalayas including the Nepal Himalayas is still rising at the Mugling-Naryanghat Road to rate of few mm/year is formed by the collision between Indian Plate control sediment related disasters. Problem Implementation and Tibetan Plate some 40 million years ago. This Himalayan However, in the latter one Non- Identification orogenic movement has resulted in several tectonic zones aligned structural measures are not Sabo in ESE-WNW direction (Figure 2, Table 1) considered. The application Planning scenario of Sabo Technology in Figure 2: The Nepal Himalayas lying between Indian and Chinese Nepal may be illustrated Civil Measures Social Measures Plate – a) Plan and b) Cross-section. diagrammatically as below. Bio Measures 4 DWIDP BULLETIN 2005 - 2006

For the sake of clarity, common structural countermeasures practiced in Nepal are briefly described and illustrated wherever possible.

4.1 Structural Measures Several cost effective structural countermeasures for debris flow and/or other sediment related disasters are applied. Selection of appropriate structure and its design depends upon the site conditions. Structures constructed in above mentioned model sites are briefly illustrated below wherever possible.

4.1.1 Check Dam – it is constructed across the river/stream perpendicular to the flow direction to control the debris. The construction materials comprise the gabion boxes, locally available boulders. Sometimes, small portions of stone masonry were used so as to make a firm joint with the irremovable big boulders at the site. However, these are all permeable dams. Series of such Check Dams were constructed in Dahachowk as well as in Girubari Sabo Model Sites. This has been the most common Photo 7b: Hillside works combined with Bio-engineering works at Dahachowk Sabo Model Site. method to control soil erosion along the ‘khola’ (gully) in Nepal. 4.1.4 Groundsill – it is constructed by digging foundation at the bottom of the river/stream so as to control the scouring, which is so much prevalent during debris flow. All other features remain same as that of the Check Dam. Sometimes soil-cement mixture is used as the construction material on an experimental basis e.g Bhagra Khola of Girubari Sabo Model Site.

4.1.5 Spur/Levee – it is constructed to control the turbulent flow Photo 5: Series of Sabo Check Dam along Photo 6: Gabion Step Dam along Girubari Mugling-Narayanghat Road. Khola. and undercutting of the river- bank. It is constructed across the river/stream covering only partial width of the river. Number of 4.1.2 Step Dam – it is constructed either across or along the layers and its layout depends upon the site condition. This structure river/stream to control further yielding of the sediments also helps deposit sediments. For instance, series of such Spur depending on the site condition. As the name itself signifies it is were constructed across the Girubari Khola. This structure is constructed in steps with desired overlap. Other things remain probably the most popular in Nepal to control the rivers. the same as in Check Dam. Such type of Step Dam was constructed to control the Landslide No.3 of the Girubari Sabo 4.1.6 Bio-eengineering Measures– after the construction of all Model Site. This type of structure is not so common in Nepal. above mentioned gabion structures, it is essential to reinforce them with Bioengineering Works to ensure their sustainability and make 4.1.3 Hillside Works – it is carried out for the stabilization of unstable them environment friendly. This task is easily achieved by slope and is done by cutting the hillside to bring it to a stable slope enhancing various Bioengineering Works ranging from simple (Photo 7a). Both, the cutting as well as filling works may be required grass to bush to tree to fruit tree plantation. This measure is most depending upon the site condition. The fresh cut-slope is later treated important for Nepal. by various Bioengineering works as desired. A combination of such Hillside Works and Bio-engineering Works were applied in the Dahachowk Sabo Model Site (Photo). This type of work is very important for Nepal, particularly along the hillside roads where we come across unstable hill slope. But due to several reasons such works are ignored.

Photo 8: Participatory Plantation Works and Bamboo Fencing Works at Dahachowk Sabo Model Site.

4.1.7 Sand Pocket – in some rivers/streams carrying huge Photo 7a: Hillside cutting works for stabilization of unstable slope at Dahachowk Sabo Model Site. volume of debris may not be controlled by Check Dams alone, in such case it may be necessary to built a sediment storage basin called ‘sand pocket’ in the downstream side. In general, it is a fan-shaped concrete structure constructed across the river/stream by digging foundation in the river- bed. It is so designed that sediments deposited each year would be excavated periodically to accommodate the sediments for the next season.

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So far this structure has not been constructed in Nepal. But it would Place Purpose Measures(Activities) be much useful to construct a ‘sand pocket’ in a medium sized Tributaries to Reduce Sediment - Check Dam Construction river such as Tinau River as a pilot project and to demonstrate the Main Discharge to Main Stream Stream possibility to control the rampant mining of boulders and other The Whole Awareness Raising of - Awareness Seminars (Land Use, aggregates from rivers of Nepal. Catchment Area Community People Construction Skill, Plantatio n, Facility Maintenance - Nursery Management 4.2 Non-sstructural Measures Non-structural Countermeasures (Soft part) without which the effort and investment on structural measures would be in vain. In a 5. Significance of the Sabo Technology country like Nepal where the awareness on Natural Disasters is so Major portions of the relatively young (40 millions) Nepal very low, the Non-structural measures have special significance. Himalayas comprise of soft rocks (Argillites) and covered by semi- But in practice there is a tendency to overlooking this measure in consolidated soils highly susceptible to all kinds of sediment Nepal. There are indeed numerous Non-structural measures that related disasters or “Pahiro”. Almost all events of sediment related were applied in Nepal based on site specific socio-economic disasters including debris flow in Nepal are largely governed by situation. It is beyond the scope of this article to cover geo-tectonic, geomorphologic and climatologic causes. Under methodological details but for the sake of clarity they are such circumstances, sediment related disasters in Nepal are mentioned here as below. inevitable and ubiquitous. Such undesirable natural conditions are 1. Participatory Rural Appraisal (PRA) further reinforced by human induced factors such as practices of 2. Roving Seminar wrong land use increases the disaster risk further from sediment 3. User’s Group Workshop related disasters. 4. Disaster Mitigation Education (DME) 5. DME Teacher’s Training Nearly 77% of Nepal is occupied by hills and mountains 6. Drawing Competition (School Level) covering largest section of the Hidukush Himalayan Region. 7. Community Interaction Meeting There are over 6000 known rivers flowing from north to 8. Nursery Naike Training south for majority of its length either across or along the 9. Evacuation Drill dominant lineaments (alignment of geological structures). 10. Street Drama The volume of debris that would be generated by river is 11. Video Show governed by its location and path wherefrom it flows down. 12. Disaster Preparedness Map Rivers originating from the Mahabharat Range (Lower Himalayas) show a typical fan-shaped watershed area with Above mentioned structural and non-structural countermeasures apex lying south of the most active mega-fault (Main have been successfully applied in the DMSP model sites and they Boundary Thrust). These shape, size and position of any are summarized below (Table 2 and 3). flowing river determine its debris generating capacity. Table 2: Countermeasures applied in Dahachowk Sabo Model Site Unfortunately, the major portion of the East-West National Highway lies south of the Main Boundary Fault as well as the Location Purpose Countermeasures apex of the watershed and henceforth highly prone to debris Upstream Stabilize Landslides - Earth Removal Work - Drainage Channel flow hazard. Similarly, other north-south aligned highways Stabilize Hill Slope - Bamboo Fencing such as Mugling_Narayanghat also passes through such - Plantation/Nursery Establishment lineaments rendering them highly prone to sediment related - Seedling Production in Nursery Prevent Riverbed Erosion - Series of Gabion Groundsel/C heckdam disasters. Indeed, those areas with the intersections of the Downstream Prevent Riverbank Erosion - Gabion/Concrete River Training Work longitudinal faults and the transverse faults are the most Prevent Overflow critical places and need due attention. The Whole Awareness Raising of - Disaster Preparedness Map ( Hazard Map) Catchment Area Community People - Street Drama, Video Show - Warning System/ Evacu ation Plan Quantitative data on rate of erosion in Nepal is meagre. - Awareness Seminars (Land Use, Warning, Available data varies in a wide range. Higaki et.el (2004) Construction Skill, Plantation, Facility reported up to 1.53 cm/yr of soil erosion in Midlands of Maintenance) - DME Activities (in 3 primary schools for Nepal, while Laban (1978) estimated soil loss as high as 10- teachers and pupils) 200 t/h/yr (including other forms of mass waste such as - Nursery Management landslide). Table 3: Countermeasures applied in Girubari Sabo Model Site

Place Purpose Measures(Activities) The existing natural conditions of the Nepal Himalayas such 5 villages in Land Use Diversity to - Sub-Nursery Establishment as geomorphologic and geotectonic setup cannot be Upstream Forest - Nursery Naike Training changed. But at the same time development works has to go - Seed and Material Supply (Reduce Traditional - Plantation ahead but then how? The simple answer to this question is “Khodiya Fadani”) none other than the application of Sabo Technology in Along Girubari Land Use Diversity to - Main Nursery Establishment Nepal. It is a cost effective technology to handle the Khola near Forest - Nursery Naike Training Jhyalbas - Seed and Material Supply problems of sediment related disasters in Nepal on a long - Plantation term basis as has been demonstrated in the Dahachowk and Three Landslide / Reduce Sediment - Retaining Wall Construction (Step Girubari Sabo Model Sites. Its significance is further judged Slope Failure Discharge to Main Type) Site along Main Stream - Bamboo/Grass Plantation by the indiscriminate considerations of socio-economic, Stream natural and philosophy of local community. 6 DWIDP BULLETIN 2005 - 2006 A Glimpse of the 13th Advanced Course Training of DWIDP

– Mr. Samanta Man Sthapit Chief- Information, Study and Training Section/DWIDP

ABSTRACT The Department of Water Induced Disaster Prevention(DWIDP) has been conducting the Advanced Course Training (ACT) since the then Disaster Prevention Technical Center (DPTC) in 1993.The conclusions and recommendations from the site visits of Okharpauwa, Kathmandu-Naubise Road,Chalnakhel landslide sites and Matatirtha Rehabilitation site reported by the participants of the 13th ACT recently concluded are useful and important for the further action by the concerned "Landslide Section" and Rehabilitation Section "of DWIDP. This paper is mainly focused on the documentation of these conclusions and recommendations. A.BACKGROUND in Nepal A combination of natural factors such as unstable steep 2. To enhance the capability of engineers and technical slopes, weak and fragile geological formation of young officers for mitigating water induced disaster to ensure a mountains, torrential and concentrated rainfall safer livelihood and the reduction of poverty of the accompanied by intense noetechtonic phenomena people. combined with human blunders like deforestation, 3. To disseminate the knowledge on water induced disaster haphazard migration, wrong agricultural practices, and management, prevention and mitigation by encroachment of river bank and forest areas have rendered incorporating the topics like Sabo, landslide prevention hills , mountains and terai areas of Nepal excessively and river training works. vulnerable to water induced hazards. Our country is highly 4. To give practical knowledge for the counter measure of affected by water induced disasters like landslides, debris these disasters through various lectures and field visit etc. flows, slope failure, soil erosion and flood every year. Many human lives and properties including vital infrastructures are C. The13th Advanced Course Training damaged by these disasters. It is estimated that more than The DWIDP has been conducting the Advanced Course 300 people are killed by floods and landslides annually. Training since the then Disaster Prevention Technical Since these natural disasters cannot be stopped, efforts Center(DPTC) in 1993.The first training was started with should be made to reduce the impact of the disaster. Our seven participants, two each from DOR, DOI, country cannot afford to spend for the disaster preparedness DSCO/DSCWM and one from NEA and it was conducted as and when required but only relief, rescue and some for five weeks from April 5 to June 10, 1993.In continuation rehabilitation activities are carried out after the disaster , the same training that is the 13th Advanced Course occurrence with the limited budget. Training ( 13th ACT) has been recently concluded on June 9, 2006.This training was conducted for a period of 30 The Department of Water Induced Disaster Prevention working days from May 4 to June 9, 2006.Although this (DWIDP) was established on February 7, 2000 with the training was designed to train 15 participants ,14 objective of mitigating water induced disasters in the participants from six line agencies and DWIDP took part in country. As the mitigation of these water induced disasters is the training.(Table No 1) very important for the community, the country needs disaster managers/trained personnel who are well acquainted with Table No 1.List of Participants of the 13th Advanced Course Training innovations and recent technologies in the field of water S.No Name of the participant Line Agencies/Organization induced disaster prevention and management. For this 1 Mr Fanindra Bahadur Shrestha Dept. of Irrigation (DOI) purpose the DWIDP is conducting two types of trainings, 2 Mr Mitra Baral Dept. of Irrigation (DOI) 3 Mr Ramesh Bahadur Shrestha Dept. of Irrigation (DOI) namely General Course Training (GCT) for non-gazetted I 4 Mr.Madan Kumar Shrestha Dept. of Roads (DOR) level technicians and Advanced Course Training(ACT) for 5 Mr.Sita Ram Shrestha Dept. of Roads (DOR) 6 Mr. Gaya Prasad Ulak Dept. of Local Infrastructure the gazetted level engineers/ technicians.Recently the Development and Agricultural Road DWIDP concluded the 13th Advanced Course Training. (DOLIDAR) 7 Mrs. Kamini Vaidya DTO, Lalitpur, DOLIDAR 8 Mr Kashi Prasad Gupta DOLIDAR B. OBJECTIVES OF THE TRAINING 9 Mr.Diwakar Maskey Dept. of Soil Conservation & Watershed The course has been designed for the engineers and Management (DSCWM) 10 Mr.Ram Singh Thapa District Soil Conservation Office(DSCO), gazetted technical officers of different line agencies Baglung , DSCWM mentioned in Table 1.The main objectives of the training are 11 Mr. Ram Dhar Singh Nepal Army 12 Mr. Bharat Lal Shrestha Nepal Army as follows: 13 Mr Ganesh K.C. Nepal Electricity Authority (N(NEA)EA) 1. To make aware of the water induced disaster prevailing 14 Mr. Purna Kumar Shrestha DWIDP Total participants: 14 7 DWIDP BULLETIN 2005 - 2006

Fifty percent of total time was allotted for classroom lectures, 4. Proper scientific study should be carried out before 25 percent of time for field visits and the remaining 25 issuing a license for a contract of quarry site by the percent time for report preparation, presentation and concerned authorities. evaluation. For the evaluation, 60 percent of the marks is 5. Environmental analysis should be carried out before the allotted for written examination, 10 percent for attendance implementation of the project. and the rest 30 percent for report preparation and presentation. This batch was evaluated the excellent batch Specific recommendations for Kathmandu - Naubise Road with all participants scoring more than 80 percent.The site: report preparation and the presentation were also 1. Intensive bioengineering works should be promoted execellent.Their recommendations for the respective site along the road corridor with proper study of basin visits will be forwarded to the respective sections for the management. implementation in the forthcoming programs. 2. Certain amount of fund collected from the local taxes ( e.g. contract of natural resources like sand , gravel and Field visits and the Report Presentation stone etc.) should be allocated for river basin The participants were assigned to prepare reports on management. different field visit sites and present them by everyone.They 3. Operation and maintenance works should be carried out regularly. were grouped into two groups , seven each in a group.The 4. Awareness program at local level should be conducted. group A is assigned to study on Kathmandu-Naubise l and 5. Rapid action disaster preparedness and mitigation team Chalnakhel Landslide model sites.Another group B is also should be formed and activated at local level. assigned to prepare reports on Okharpauwa Landslide model site and Matatirtha Rehabilitation site.All the Specific recommendations for Chalnakhel site: participants visited these sites .They presented existing 1. Further geological investigation is recommended. situations of the sites and recommended the important and 2. Water balancing model should be adopted for useful suggestions to be implemented by the concerned investigation and analysis of the project. sections of DWIDP.The important conclusions and 3. Proper land use pattern and agriculture practices might recommendations presented by the participants are as be effective to reduce the annual sinking problem of the follows: project area. 4. Horizontal drainage system using perforated pipes may Conclusions and Recommendations (Group A) be used to reduce sinking problem of existing road CHALNAKHEL AND KATHMANDU-NNAUBISE ROAD SITES: corrider ( Kathmandu -Dakshinkali). Conclusions: 5. Infrastructure construction should be discouraged until The general conclusions made for both of these sites are as the complete investigation of the project.House follows. developers should not be given license to build colony in 1. Mitigation measures for water induced disasters should such a hazardous area. be implemented with proper planning and with 6. Awareness campaign should be provided to stake coordination between different line agencies. holders of the project area. 2. While planning for infrastructure development, engineering and land use practices should be analyzed Conclusions and Recommendations (Group B) and technical norms should be strictly followed during OKHARPAUWA (KATHMANDU -TTRISHULI ROAD) and implementation. MATATIRTHA SITES 3. For the effective implementation of disaster mitigation Conclusions for Okharpauwa site: measures, political stability and peace within the country 1. The settlement of road is continuing. is essential. It will help to carry out the intensive 2. Formation of gully erosion and debris flow were noticed preparedness and mitigation measures works within the landslide area. 3. The problem of debris flow from upper crown part and Suggestions: blockage of drainage were noticed during the visit, The general suggestions for these sites are mentioned however it was a pre- monsoon season, so further below: problems might occur during monsoon season. 1. Advanced technology like GIS, remote sensing and 4. Although catch drains are functioning , the regular satellite imagery could help to analyze and finalize the maintenance is extremely necessary. appropriate decision making process for disaster 5. Grazing and farming were found common practice in management. the landslide area which ultimately promotes the soil 2. Integrated approach has to be adopted. erosion. 3. Good coordination system has to be established 6. The measures for reducing the ground water level are between different line agencies working in the sector of not sufficient, the level is found to be near the surface soil erosion and landslide. part of the down stream area.

8 DWIDP BULLETIN 2005 - 2006

7. No involvement of local people in the project activity is bank should be discouraged. observed. 3. The local people should be encouraged to plant fast growing species and cash crops that will stabilize the Recommendations for Okharpauwa site: cultivated area. Some awareness program for the local 1. It is recommended to construct retaining wall along the people should be organized to minimize the soil loss. road to minimize the further settlement of road within the 4. The remaining two houses should be relocated to a safer landslide area. place. 2. It is necessary to add some gabion wall with geo- 5. Silvi cultural operation should be adopted in the lower synthetic material at the toe portion. par of the landslide area. 3. It is recommended to control leakage from the joints and 6 Regular monitoring should be done in the area and the outlets of the polythene pipe that are placed for crossing users group should be strengthened. the irrigation water via landslide portion. 4. The debris flow from the upper part of the landslide Based on the above should be controlled by providing structural and non recommendations structural measures. for all the sites, the 5. Grazing and farming should be strictly prohibited in the "Landslide section" landslide area. and "Rehabilitation 6. Additional catch drains in the middle and bottom part of Section" of DWIDP the landslide area are necessary to control gully erosion. should follow up 7. It is recommended to construct sufficient horizontal the recommended drains to reduce the existing pore water pressure. activities in these 8. Maintenance of the existing structures are very necessary. sites.

Recommendations for Matatirtha site: 1. One additional catch drain is necessary at the

downstream area along with the strengthening of the Photo 2: Vertical existing catch drain. Boring Hole no. 2 at 2. The waterway of the nearby stream should be fully Chalnakhel Landslide maintained. The encroachment activity in the stream Model site

Photo 3: Present Situation of Okharpauwa Landslide ( Kathmandu-TrishuliRoad )

Photo 1: Mitigation Measures at Kathmandu-Naubise Road Sector Photo 4: Site Visit at Matatirtha Rehabilitation Site 9 DWIDP BULLETIN 2005 - 2006 APPLICATION OF “SABO SOIL CEMENT METHOD” FOR WATER INDUCED DISASTER MITIGATION

– Mr. Sundar Prasad Sharma – Mr. Shree Hari Regmi – Mr. Toshiya Takeshi Assist. Soil Conservation Officers, DWIDP Overseer, DWIDP JICA Expert, DMSP-FU

ABSTRACT Water-induced disaster is one of the worst disaster among all natural disasters in Nepal. It causes huge loss of life, dwellings, development infrastructures, agricultural lands, cattle and environmental degradation annually, which in turn cause economic retardation and deterioration in the state of health and hygiene of the people. Considering the socio-economic and geo- physical parameters of Nepal, sabo soil cement method has latent value as a structural countermeasure for the disaster mitigation. Generally, sabo works are carried out in mountainous areas where construction cost increases and the construction efficiency tends to be degraded because transportation of construction materials is restricted. So, the fundamental principle of the sabo soil cement method is to utilize site generated soil effectively. This paper highlights the concepts, features and construction methods of sabo soil cement applicable for sediment related disaster mitigation in the country. 1. Background various public works in addition to Sabo works. Research Generally, Sabo works are carried out in mountainous areas works on Soil-Cement method is underway in Japan. where construction cost such as excavated soil disposal cost, etc. increases and the construction efficiency tends to be 2. What is Sabo Soil Cement? degraded because transportation of concrete and other The Sabo soil cement is developed for effective utilize the construction materials is restricted. Furthermore, there are site-generated soil for constructing sabo structures (Check problems in dumping surplus soil, noise, environmental dams, revetments etc.). pollution etc. The Sabo soil cement is made-up by agitating and mixing Sabo1 dams and revetments have being constructed using site-generated soil, cement, cement milk etc at the works techniques called “CSG2 method”, “INSEM3 method” and site, and is the general term for the material utilized for “Sabo CSG method” (collectively called INSEM Method) constructing Sabo structures and associated secondary and “ISM4 method” in Sabo sites of various places in Japan. structures as well as for soil stabilization. These methods are generally named as the “Sabo Soil Site-generated soil + Agitating & Sabo Soil Cement”. Cement Mixing Cement The main objective of the methods is to effectively utilize site generated soil, and since the amount of soil carried out of 3. Concept of Sabo Soil Cement construction sites can be reduced, cost can be reduced, Sabo Soil Cement have been developed as the material that loads to environment can be alleviated, and in addition, can achieve a wide range of quality fit for various methods without using formworks are also possible, and construction conditions at the site, unlike rigid ordinary execution of works can be simplified and the term of works concrete. Though the quality varies by the cement content, can be shortened, and as a result, the exposure period of excavated surface can be shortened, thereby contributing to High

safe execution of works. Large

Concrete Soil These methods have been confirmed to be effective in Material

Japan. SABO Technical Center (STC), Sabo Frontier Sabo Soil Sabo Cement Soil Cement Cost

Consideration,

Foundation, and Advanced Construction Technology Center Total X-section Soil and Kyoto University have been positively involved with Sabo Concrete Material works and data-bases are available in these institutions. Environmental

The Sabo Soil Cement is assumed to be suited for various Low High Low High Material quality (strength etc.) Sabo works in developing countries from view points of Material quality (strength etc.) workability and cost. Moreover, it can also be applied to Figure 1: Image illustration of material quality and advantages of Sabo soil cement 10 DWIDP BULLETIN 2005 - 2006 the water content, the grain size distribution of soil, etc., it Item Description can be utilized as the material intermediate of soil and Scope Primarily gravity -type concrete structure in the ground Applicable ground Soil containing cobble stones and gravels concrete. A desire construction method can be selected in Max. agitatable aggregate Gmax = 300 mm terms of the required function, site condition, labour and Kind of cement used - Cement content 150- 350 kg/m 3 time for construction work. ”Strong but low in cost” can be Agitation thickness of one layer Max. H = 1 m by twin header pursued. Agitation and mixing time 3 min/m 3 2 Compressive strength (age: 28 days) 3? ó 28 ? 21 N/mm 4. Methods of Sabo Soil Cement Quality control Aggregate moisture content - Water-cement ratio of concrete 60% To utilize site-generated soil, four methods have been developed so far, namely: 6. Examples of INSEM method (Japanese case): To control debris flow, several sabo dams have been I. Method for building structures by agitating and mixing constructed using INSEM methods in Japan. Environmental with twin Header (ISM Method) (recycling), Aesthetic (stone pitching on the surface of the dam), 1. ISM method economic (uses of cement, sand, gravel (CSG) method) and (Note: To date, ISM method has been adopted for ergonomic (work safety and easy) factors have been considered subsurface section and foundation of Sabo structures such for the construction of the dam. Cost of construction has been as Sabo dams, groundsills, riverbed girdles, etc.) reduced considerably up to 30% compared to that of concrete II. Method for building structures by compacting with dam (Fujigawa Sabo Office, Kofu). vibrating rollers (INSEM Method) Examples Genbu Sabo Nishi-Ohtori Hirogawara 2. INSEM Dam (Iwate) River Sabo Dam Sabo Dam Method INSEM INSEM INSEM method Applicable position Wing, sub -dam Main dam Inside Apron 3. CSG method Unit cement content 80 kg/m3 50 kg/m3 130 kg/m3 4. Sabo CSG Unit water content 124 kg/m3 Not used 140 kg/m3 method Target strength 0.48 KN/mm2 0.15 N/mm2 6 N/mm2 (Note: To date, Gmax 150 mm 40 mm 80 mm INSEM method has been adopted whole or parts of sabo structures such as sabo dams, groundsills, revetments etc.) Figure 2: Construction Procedure by ISM (In- These methods situ mixing) Method (Concept is to prepare are used to materials at the site) construct structures and stabilize soil by agitating and mixing site- Fig 4: River-bed materials for soil-cement generated soil with cement with no gradation control except removal of large cobbles.

5. Features of ISM method An example of features of ISM method is given below: Figure 3: Construction Procedure by INSEM (In-situ stabilized excavation materials) Method (Concept is not to remove soil from the site) Fig 5: Soil-cement structure 11 DWIDP BULLETIN 2005 - 2006

Fig 9: Check dam in January 2006 7.1 Structural Design Structural design of the soil cement checkdam is given below: Fig 6: Soil-cement structure

0.5m 2.5m

5 m 2 m 2 m 3m

1.5 m 0.5m

8 m

Plan

5 m A 2m 2m

Fig 7: Sabo dam in Fujigawa (2004) 3.3.5 7. Soil-ccement Experiment (Nepalese case): 3m To control a torrent in Girubari Sabo Model Site (Chormara, 2m Nawalparasi) an experiment has been done by constructing a check dam in 2004 before rainy season. The method 5 m 1 AA’ combines soil- cement with gabion work. Front Elevation

Application position Foundation and Apron 2.5m 1.5m Unit cement content 80 kg/m3 3.5m Gabion work Unit water content Not used 1:0.8 1:0.8 Target strength 6 N/mm2 3m Soil Cement Gmax 150 mm 4m X-Section A-A’

7.2 Work Execution Back-hoe machine have been used for soil excavation, agitation, mixing and compaction of the site generated materials with cement. The processes can be summarized as following diagram.

Excavation, Temporary storage, removal of large stones

Agitation and mixing

Compacting by back-hoe and wheel Fig 8: Check dam in January 2006 Backfilling 12 DWIDP BULLETIN 2005 - 2006

– Reduced use of construction machinery and transportation – Suppressed noises, vibrations and gas emission • Total cost reduction – By 53% compared with Stone masonry – By 16% compared with Gabion work • Uses of local resources (material, labor)

9. Conclusion Generally, the principles of sabo soil cement for sediment control measures adopted in Japan are also applicable in Nepal. It is not necessarily limited to sabo works but can also be used to various other construction works. But there are some bottle-necks that hinder to select and apply the method particularly, lack of sufficient data, equipments and expertise on Fig 10: Agitation, mixing and compacting of soil-cement at foundation the field. 7.3 Characteristics of site-ggenerated material The figure below shows the estimated gradation Soil Cement method is still in micro-level research in Nepal. characteristics of site-generated material (aggregate) used for This method can be applied where there is no clay particle and Soil-Cement method in Girubari Sabo Model Site, Chormara, organic matter in river bed material. Research on effectiveness Nawalparasi. Fine aggregate smaller than 5 mm accounts for of different types of design and different site condition the greater part, with 30%. Other gradations are contained considering the environment and ergonomic (work safety and about 5-20%. 40- 80 mm are relatively many and 150- 300 work easy) aspects is necessary. Information sharing in research mm are slightly less. Workability reduces with larger findings of different national and international organizations aggregates. will be very beneficial. Possible Application Areas of the Soil-Cement are River Training Fig 11:Grain Size Distribution Works (Revetments, Spur dykes etc.), Sabo dams (Check dams, (Check dam construction work using soil-cement in Girubari Sabo Model Aprons etc.), Retaining Walls, Foundation treatment and Site, Chormara, Nawalparasi- 2004) Emergency rehabilitation works. Notes 40

30 • If site generated soil contain large quantity of cohesive soil, fine aggregate, or organic matter, increased amount of 20

sizes (%) cement is necessary. 10 • Usually, the stone size (Gmax) is up to about ½ the

Percentage by particle particle by Percentage 0 thickness of one layer, or less than 150 mm in diameter ? 5 5-10 10-20 20-40 40-80 80-150 (depend on the method used e.g. up to 300 mm can be Normal size classification of seive opening (mm) adopted if agitating and mixing is done by using machine). • It is an effective means when structures are constructed by Comment: Experiment of Soil-cement in Girubari Sabo Model Site local people without using large machinery. is the combined methods of the ISM and INSEM in terms of • It has benefit of effective utilization of collapse soil. machine used (back-hoe) and applied in the portion of the structure (foundation of check dam and apron). • It has been constructed at lower cost compared with concrete (even gabion) structures. 8. Advantages of Sabo Soil Cement References: The advantages of sabo soil cement are listed below: 1. Prof. Takahisa Mizuyama, Kyoto University & The Society for • Reduced amount of soil carried out Study of Sabo Soil Cement, Utilization Guidelines for Sabo • Improved safety Soil Cement. 2002 – Versatile use of machinery 2. S.P. Sharma, Report on Training Programme on – Reduced number of workers Bioengineering for Hillslope Stabilization in Japan. 2004 – Reduced time for work completion 3. Field Data- Soil Cement Works in Girubari Sabo Model • Contribution to the recycling based society Site, Nawalparasi (unpublished). 2004 – Recycled site-generated soils 4. Sharma, S.P., Sabo Soil Cement Mehtod for Water Induced Disaster Mitigation, paper presented in 16th General – Required no new banking sites Course Training organized by Department of Water Induced – Reduced amount of external construction materials Disaster Prevention, Kathmandu, 2 January 2006. Visit of the President of Ehime University Dr. KOMATSU Masayuki, Dsc, President of National University Corporation: Ehime University, Japan, visited the Department of Water Induced Disaster Prevention on May 29, 2006. 13 DWIDP BULLETIN 2005 - 2006

Water-induced Disaster Mortality of Nepal

– Mr. Prakash Man Shrestha Engineer, DWIDP

ABSTRACT Nepal is a water induced disaster prone country. The water-induced disasters occur every year mostly during the monsoon period. The mortality due to water-induced disaster in Nepal is significant and the effect is much more pronounced due to its recurrence every year. Nepal has the history of water-induced disasters claiming more than one thousand lives in a year, that is in the year 1993. This Term Paper presents the mortality due to water-induced disasters in Nepal, its history, causes and the mitigative measures, plans, policies and strategies.

1. Background Global Status of Water-iinduced Disasters Water-induced Disasters are the most destructive natural disaster The occurrence of large floods in the world has increased in among other natural disasters. Floods, landslides and debris flows recent years. According to the International Red Cross, between are widely considered as water-induced disasters. They are vicious 1973 and 1997, the number of global flood victims was 66 forms of natural phenomenon that have changed over time and million on an annual basis1. Flood victims account for the that have stricken repeatedly. Flood damage is aggravated by the largest group of victims suffering from natural calamities, fact that quick flood flow in land in the upper basin is flood flow including earthquakes and droughts. Viewed in terms of over land that has been altered for land use, by the fact that annual average of five-year periods, one can see that from populations are accelerating rapidly, by the fact that accumulation 1973 to 1977, the number of flood victims was 19 million, and concentration of assets and population is occurring in from 1988 to 1997, there were 111 million, and from 1993 to dangerous areas, and by the fact that there is a reduction of 1997 there were 131 million - a large increase1. drainage area caused by urbanization. In addition, it is expected that floods will increase in danger as a result of global warming, In the last 15 years, about 561,000 people have died in which is increasing the sea level, and as a result of the occurrence natural disasters. Only 4% of these individuals were from of abnormal climates. Thus, the mortality due water-induced advanced countries. Half of the victims were flood victims, and disasters are increasing in recent years. Asia has been hardest hit. Asia is a large landmass and is home to a large number of people, most of who live in coastal Southeast Asia, in words of Volker, is “a region with copious areas- areas that are dangerous in terms of flooding. rainfall, large rivers and a high population density”. The population is concentrated in the lower river valleys and deltas Table 1: Comparision of death casualties by Water Induced where lowland rice, the staple diet is produced. Therefore river Disasters in Nepal and World. flooding and high rainfall play an important role in agricultural Year Nepal World % Of the World water supply. The annual average per capita volume of water 1994 49 6683 0.73 % is 4000 m (in 1983), which is below world average and about 1995 246 9642 2. 55 % 1996 262 8438 3.10 % equal to that of Europe. The intimate relationship between man 1997 87 7759 1.12 % and rivers in Southeast Asia is due both to these facts and to the 1998 273 10676 2.56 % warm climate”. Volker described the large rivers in the region 1999 209 34717 0.60 % like the Irrawaddy, the Chho Phraya and the Mekong to have 2000 173 7429 2.33 % “gentle floods” (also the Ganges and Brahmaputra/ Yamuna) 2001 196 5370 3.64 % and the small rivers flash floods. The Red River in the northern 2002 441 5503 8.01 % 2 2003 232 4750 4.88 % part of Vietnman also has flash floods . Total 2168 100967 2.15 %

Nepal has more than 6000 small and big rivers with combined In addition, earthquake, tropical storms and cyclones occur total length of 45,000 km and having total drainage area of frequently. Between 1985 and 1990, Asian accounted for 77% 191,000 square km. They discharge more than 200 Billion of the deaths and 90% of those who lost their homes reside in Cubic meter of water annually. The abundance of water Asia. Asia is also accounted for 45% of the economic damage resources hold great potentiality for the development of recorded as a result of disasters in the world.1 hydropower, irrigation facilities, navigation, water for domestic and industrial uses. On the other hand, the swollen rivers in th each year monsoon cause heavy human casualties, and In the 20 century, “man-made environments” increased at an enormous damage to physical properties. explosive pace. This means that now any additional increases in economic and man made activities are dangerous. When people migrate to cities and coastal areas, they increasingly 14 DWIDP BULLETIN 2005 - 2006 become much weaker in their ability to deal with various kinds Status of Water-iinduced Disasters in Nepal natural disasters, specially water-induced disasters. Geomorphologic features of Nepal are very fragile. The constant tectonic action of varying degrees, together with varied intensity of Status of Water-iinduced Disasters in Asia weather conditions has adverse effect on the stability of earth’s Mekong River System is one of the important river system surface and river courses. The physiography of earth is changing causing floods in Asia. The 4800 km-long Mekong River slowly due to its own tectonic action and universal planetary (Catchment Area, 795,000 km2) originates in China, and flows action. Such activities are more pronounced in Asia (Oceania) through Myanmar, Lao PDR, Thailand and Caomoida before and South America. Among these, the Himalayan region and ending in the Mekong Delta of Vietnam. Tonle Sap Lake north some pockets of Oceania are most active. The major part of the of Phnom Penh, Cambodia rises and inundates due to the Himalayas lies in Nepal. Thus, the Himalayan region of Nepal can backflow from the swelled Mekong River. Mention has been be considered as one of the severest water-induced hazard zones made of the “gentle floods” in the major rivers such as the of the world. Furthermore, heavy precipitation, high wetness and Irrawaddy and the Mekong, characterized by the gradual rise steepness of watersheds and river channels contribute to flood (and fall) of the water levels and the consequent over-bank magnitudes of varying degrees. In general terms, the middle Hills flows and inundation, as a result of long-term seasonal rainfall are prone to landslides and the Terai to floods. Thus, floods and (the monsoons for days and weeks) over the extensive landslides are most frequent natural disasters in Nepal. These catchments with mountains, valleys and floodplains. High tides disasters occur almost every year in one part of the country or affecting the lower reaches add to the maximum flood levels. another. Although the hydrograph peaks are not very sharp, these floods can contribute most of the annual flood volumes of the basin. The Terai region of Nepal, occupying 17 percent of the country’s area and accommodating nearly half of the country’s The occurrence of tropical cyclones such as in the typhoon population, is very important for its agricultural land and monsoon sub-region may bring about an intensification of the human resources. The majority of the flood-affected prevailing monsoon, producing sharper hydrograph peaks over communities in Nepal inhabit the land along the marginalized short periods (hours). In the case of the Philippines, aside from the rivers, which are rain-fed and originate in the southern faces of warm-moist southwest monsoon and the typhoons of the summer the Siwalik and Churiya ranges. months, and the drier-cooler northeast monsoon and cold frontal systems of the winter months, the thunderstorms associated with Besides floods and the Inter-tropical Convergence Zone (ITCZ) are also flood landslides other producing weather events. As a consequence, flash floods with disasters like fires, duration of few minutes to one or two hours, may also occur epidemics, without warning in small but steep areas in the upper portions of avalanches, watersheds, or else in poorly drained urbanized areas. earthquakes, windstorms, Deaths and significant economic losses result from the floods in hailstorms, lightings, Asia. Table 2 shows Year 2000 Population, Number of Deaths glacier lake outburst and Economic Losses due to Water-induced Disasters in Asia floods and droughts including Nepal: also occur in Nepal. These disasters cause Fig. Water-induced Disaster Map of Nepal Table 2: Death Casualties (1990-2000) due to Water-induced Disasters in Asia the loss of thousands of human lives and destruction of physical properties worth billions of Death Casualties due Year 2000 Economic Losses due rupees each year. The earthquake of 1934, 1980 and the floods of S. to Water-induced Country Population to Water-induced No. Disasters July 1993 were the most devastating natural disasters of recent years. (Millions) Disasters (US $) (1990 – 2000) These caused not only heavy loss of human lives and properties, but 1 Bangladesh 137.439 1929 3204.000 also adversely affected the development process of the country. 2 Cambodia 13.104 1075 118.542 3 China 1282.437 19353 78288.847 Table 3: Death Casualities, Affected families etc due to Water- 4 India 1008.937 15846 4604.620 5 Indonesia 212.092 1289 248.652 induced Disasters in Nepal in Different years Unit Year 6 Korea R.P. 46.740 898 2234.800 Description 7 Lao P.D.R. 5.279 55 22.828 1994 1995 1996 1997 1998 1999 2000 8 Malaysia 22.218 47 3.606 Dead/Missing Nos. 49 203 258 83 273 193 173 9 Myanmar 47.749 2676 252.300 Injured Nos. 35 62 73 21 80 92 162 Affected families Nos. 3826 28973 37096 5648 33549 9424 24900 10 Nepal 22.7 3106 143.057 Animal Losses Nos. 256 3150 1548 103 982 460 1017 11 Papua N.G. 4.809 72 2.500 Houses Nos. 894 22251 28432 1790 13990 3807 6886 12 Philippines 75.653 1128 213.038 destroyed 13 Sri Lanka 18.924 97 283.010 Cattle Sheds Nos. 19 252 684 137 1244 128 540 14 Thailand 62.806 1041 3054.778 destroyed 15 Vietnam 78.137 2850 1558.570 Land losses Ha. 1143 38768 6846.6 939.01 326.89 182.40 888.90 Total estimated NRs. (Source: “Asian and Pacific Water Issues in the World Water Context”, the 673.71 1428.0 11859.8 94.5 1969.26 373.12 114.14 losses (in millions) author inserted the data of Nepal). Source: Ministry of Home Affairs. 15 DWIDP BULLETIN 2005 - 2006

Table 4: Districtwise Disaster Mortality of Nepal Death due to Water -induced Disasters Population Mortality (per S.No. District Development Region 1993 1994 1995 1996 1997 1998 1999 2000 2001 Average (2001) 10 Lakhs) 1 MANANG Western Region 0 0 15 0 0 0 1 0 0 1.778 9,587 185.436 2 SARLAHI Central Region 687 0 0 0 0 4 1 0 0 76.889 635,701 120.951 3 MAKAWANPUR Central Region 247 0 0 1 0 5 5 3 0 29.000 392,604 73.866 4 DOLAKHA Central Region 8 3 1 38 0 0 0 8 15 8.111 204,229 39.716 5 SANKHUWASABHA Eastern Region 0 2 2 0 7 4 7 5 24 5.667 159,203 35.594 6 SINDHUPALCHOWK Central Region 0 0 14 61 1 9 5 0 7 10.778 305,857 35.238 7 SYANGJA Western Region 0 0 15 3 4 55 7 1 3 9.778 317,320 30.814 8 DHADHING Central Region 24 0 0 6 3 4 22 2 32 10.333 338,658 30.513 9 KHOTANG Eastern Region 3 0 58 6 2 3 4 0 0 8.444 281,385 30.010 10 OKHALDHUNGA Eastern Region 30 0 3 3 0 2 1 0 3 4.667 156,702 29.781 11 BAGLUNG Western Region 1 0 14 10 0 18 4 1 18 7.333 268,937 27.268 12 SINDHULI Central Region 53 4 2 0 0 1 5 3 0 7.556 279,821 27.001 13 TAPLEJUNG Eastern Region 28 0 0 0 2 0 2 0 0 3.556 134,698 26.396 14 RAUTAHAT Central Region 111 0 0 1 0 3 1 0 3 13.222 545,132 24.255 15 PYUTHAN Mid-western Region 0 2 0 10 4 25 0 4 0 5.000 212,484 23.531 16 BHOJPUR Eastern Region 0 0 0 34 5 2 1 0 0 4.667 203,018 22.986 17 SOLUKHUMBU Eastern Region 5 0 3 0 0 3 3 4 3 2.333 107,686 21.668 18 BAJURA Far-western Region 0 1 0 0 1 1 6 9 3 2.333 108,781 21.450 19 PANCHTHAR Eastern Region 22 0 5 5 1 1 2 1 1 4.222 202,056 20.896 20 LAMJUNG Western Region 0 0 15 0 0 0 3 7 5 3.333 177,149 18.817 21 DARCHULA Far-western Region 0 0 0 0 1 8 6 5 0 2.222 121,996 18.216 22 ILAM Eastern Region 0 8 0 0 23 6 1 7 1 5.111 282,806 18.073 23 MUSTANG Western Region 0 0 0 0 0 1 0 0 1 0.222 14,981 14.834 24 KALIKOT Mid-western Region 0 5 0 5 2 0 2 0 0 1.556 105,580 14.733 25 JAJARKOT Mid-western Region 0 0 0 3 3 2 1 7 1 1.889 134,868 14.005 26 ARGHAKHANCHI Western Region 2 0 3 0 0 1 2 8 10 2.889 208,391 13.863 27 GULMI Western Region 2 4 2 1 0 14 0 1 12 4.000 296,654 13.484 28 KABHAREPA LANCHOWK Central Region 20 0 0 3 0 0 19 3 0 5.000 385,672 12.964 29 PALPA Western Region 10 0 6 2 1 11 1 0 0 3.444 268,558 12.826 30 TANAHUN Western Region 2 0 9 0 0 2 8 15 0 4.000 315,237 12.689 31 DOLPA Mid-western Region 0 0 0 2 1 0 0 0 0 0.333 29,545 11.282 32 RUKUM Mid-western Region 0 1 2 2 2 0 0 12 0 2.111 188,438 11.203 33 UDAYAPUR Central Region 1 0 6 4 0 0 11 5 2 3.222 287,689 11.200 34 CHITAWAN Central Region 24 0 0 0 2 0 20 0 1 5.222 472,048 11.063 35 ROLPA Mid-western Region 0 4 1 2 3 4 1 5 0 2.222 210,004 10.582 36 BAJHANG Far-western Region 1 0 0 1 3 5 0 5 0 1.667 167,026 9.978 37 KASKI Western Region 1 4 2 5 0 3 3 7 6 3.444 380,527 9.052 38 DAILEKH Far-western Region 0 2 2 3 0 0 0 4 6 1.889 225,201 8.388 39 DOTI Far-western Region 7 1 0 2 0 2 0 3 0 1.667 207,066 8.049 40 RAMECHHAP Central Region 5 2 0 0 2 3 1 0 2 1.667 212,408 7.847 41 LALITPUR Central Region 15 0 0 2 0 4 1 0 0 2.444 337,785 7.237 42 GORKHA Western Region 0 0 0 0 0 2 13 1 2 2.000 288,134 6.941 43 SALYAN Mid-western Region 6 0 5 2 0 0 0 0 0 1.444 213,500 6.766 44 HUMLA Mid-western Region 0 0 0 0 0 1 0 1 0 0.222 40,549 5.480 45 MUGU Mid-western Region 0 0 0 1 0 1 0 0 0 0.222 43,937 5.058 46 RASUWA Central Region 1 0 0 0 0 1 0 0 0 0.222 44,731 4.968 47 PARBAT Western Region 0 0 2 3 0 0 0 2 0 0.778 157,826 4.928 48 TERHATHUM Eastern Region 0 3 0 0 0 1 0 0 1 0.556 113,111 4.912 49 BAITADI Far-western Region 0 0 0 1 0 5 0 4 0 1.111 234,418 4.740 50 RUPANDEHI Western Region 0 0 1 6 0 18 4 0 0 3.222 708,419 4.548 51 ACCHAM Far-western Region 0 0 0 2 0 5 2 0 0 1.000 231,258 4.324 52 NUWAKOT Central Region 0 2 0 2 0 5 0 0 0 1.000 288,478 3.466 53 DHANKUTA Eastern Region 0 0 0 0 0 1 3 1 0 0.556 166,479 3.337 54 KATHMANDU Central Region 2 0 0 0 4 6 12 7 1 3.556 1,081,845 3.287 55 DANG Mid-western Region 0 0 0 1 1 3 0 4 4 1.444 462,380 3.124 56 BARDIYA Mid-western Region 0 0 7 1 0 1 0 0 0 1.000 382,649 2.613 57 KAPILVASTU Western Region 0 0 0 0 0 4 0 7 0 1.222 481,976 2.536 58 MAHOTTARI Central Region 8 0 2 0 0 1 1 0 0 1.333 553,481 2.409 59 KANCHANPUR Far-western Region 0 1 0 0 0 2 3 2 0 0.889 377,899 2.352 60 MORANG Eastern Region 0 0 0 9 0 4 1 1 1 1.778 843,220 2.108 61 JHAPA Eastern Region 0 0 0 5 0 1 5 0 2 1.444 688,109 2.099 62 NAWALPARASI Western Region 0 0 2 1 0 0 2 2 3 1.111 562,870 1.974 63 DADELDHURA Far-western Region 0 0 0 0 0 2 0 0 0 0.222 126,162 1.761 64 KAILALI Far-western Region 2 0 1 3 0 1 1 0 0 0.889 616,697 1.441 65 JUMLA Mid-western Region 0 0 0 0 0 0 0 1 0 0.111 89,427 1.242 66 SURKHET Mid-western Region 0 0 0 0 0 0 1 2 0 0.333 288,527 1.155 67 BANKE Mid-western Region 2 0 0 0 0 1 0 0 1 0.444 385,840 1.152 68 MYAGDI Western Region 0 0 1 0 0 0 0 0 0 0.111 114,447 0.971 69 SIRAHA Central Region 0 0 2 0 0 1 0 1 0 0.444 572,399 0.776 70 PARSA Central Region 2 0 0 0 0 0 0 1 0.375 497,219 0.754 71 SUNSARI Eastern Region 0 0 0 3 0 0 1 0 0 0.444 625,633 0.710 72 DHANUSHA Central Region 0 0 0 1 0 0 2 0 1 0.444 671,364 0.662 73 BARA Central Region 2 0 0 0 0 0 0 1 0 0.333 559,135 0.596 74 BHAKTAPUR Central Region 0 0 0 0 0 0 0 1 0 0.111 225,461 0.493 75 SAPTARI Central Region 0 0 0 0 0 1 0 0 0.125 570,282 0.219 Total 1334 49 203 256 78 273 209 173 176 305.722 23,201,350 16 DWIDP BULLETIN 2005 - 2006

3. Types of Water-iinduced Disasters in Nepal hectares of land with agricultutal crops was washed away. The The types of water-induced disaster events that occur in Nepal total value of losses is estimated to have been NRs. 68.19 can be classifies as follows: million. i. Normal floods due to regional precipitation over large areas; 4.5 Matatirtha Debris Flow ii. Debris flows due to mass movement of loose sediment and Kathmandu district witnessed a devastating water-induced boulders in the middle Hills and Siwalik (Churia) range; disaster in the early morning of 23 July 2002 at Matatirtha iii. Landslide and debris temporarily damming rivers. Causing VDC, Ward No. 2 claiming the lives of 16 people in a single devastating flood events after such dams are overtopped event. About 1,500m3 of debris was deposited up to 600m and broken; from landslide, 5 houses buried (16people died) by landslide, iv. Extreme events due to: 3 houses partially destroyed by debris flow, and about 1 ha • Glacier Lake Outburst Floods (GLOFs), which occur corn field flashed or eroded by debris flow. when the moraine damming the glacial lake suddenly collapses and releases large quantities of water resulting Conclusion in a high velocity surge, causing devastating floods and Water-induced disaster mortality in Nepal is quite significant. It debris transport downstream; occupies an important role in the mortality rate of Nepal • Sudden cloud-brust over a localized area due to a because of the nature of recurrence of such natural disasters “break” in the monsoon trough resulting in precipitation every year. Among all natural disasters water-induced disasters of 300 mm-500 mm within 24-48 hours; are the most destructive and recurrent disasters. Water-induced • Flash floods on the southern rivers originated from disasters are much more pronounced due to unscientific Siwalik. landuse, and increasing population pressure in the marginal v. The following factors also contribute to flooding of the lands. Global warming and climatic change due to Nepalese rivers: Greenhouse Effect is causing abnormal climates resulting • Drainage congestion caused by intervention in the flood Glacier Lake Outburst Floods (GLOF), flash floods, landslides, plains on the other side of the international border to the debris flows etc. south; • Continuously increasing sediment loads in the rivers; The occurrence of large floods has increased in recent years. • Ad hoc river control works that address the expedient According to International Red-cross, the global flood victims needs of the moment. from 1973 to 1997 numbered 66 millions. In last fifteen years 561,000 people had died in natural disasters. Half of them This landslide of Shravan Danda killed two person and injured were flood victims and almost 90 % were from developing two. It damaged 35 houses completely and 85 houses partially. countries. Debris was deposited in and around the area of Butwal Multiple Campus. The Misnistry of Water Resources released NRs. 1.5 Death casualties in Nepal since 1990 to 2000 figured to be million to control the landslide as well as to clear the debris. more than 3 thousands. The water-induced disaster of 1993 is The total losses from this disaster have been estimated to be the worst one in the history of water-induced disasters in Nepal NRs. 58.13 million. The government arranged settlements in claiming 1336 lives in the single year. Other remarkable water- Tamnagar for the affected families. In Rupandehi district as a induced disasters are Landslide and flood in Tatopani of whole, floods and landslides claimed the lives of 18 people, Myagdi district, Floods and landslides in Syanja district, and and 4 People were seriously wounded, 1,446 families were Floods and landslides in Rupandehi district. affected, 128 houses and 1 cattle shed were destroyed and 10 References 1. “Water Voice” Project Report – March 2003, The Secretariat of World Water Forum 2. Asian and Pacific Water Issues in the World Water Context – March 2003, The Collection of Papers of The Third World Water Forum. 3. Chhetri, M.B. et al “Mitigation and Management of Floods in Nepal” – May 2001, Ministry of Home Affairs. 4. “Water Resource Strategy Nepal” January 2002– Water and Energy Commission Secretariat (WECS). 5. Shrestha, P.M., “A Comparative Review of World Water- induced Disasters and Water-induced Disasters of Nepal”- Disaster Review 2004, DWIDP, Nepal. Photo: Matatirtha Debris Flow Disaster July 2002 17 DWIDP BULLETIN 2005 - 2006 ENGINEERING GEOLOGICAL STUDY AND STABILITY ANALYSIS OF SHRAWAN DANDA JYOTINAGAR LANDSLIDE WARD NO. 5, BUTWAL MUNICIPALITY, RUPANDEHI DISTRICT, WESTERN NEPAL

– Mr. Ashish Ratna Shakya, M.Sc. (Geology) – Dr. Vishnu Dangol Geologist Associate Professor, Tri-Chandra Campus Ghantaghar, Kathmandu

ABSTRACT

Shrawan Danda Hillslope at the northern part of Butwal in the Siwalik hill, often experiences mass movements during monsoon increasing threat of life and property of the people living at the base of the hill slope. Among many landslides of the Shrawan Danda area, two major landslides, Landslide L1 and Landslide L2 with greater potential risk for people living near the base of the slope (Jyotinagar) were studied in detail. Altogether twenty six samples from different parts of the Landslides were collected and engineering geological tests were carried out. The analysis of laboratory tests of these samples shows that the soil is coarse-grained with moisture content of 15%-20% and specific gravity ranging from 2.65- 2.69. Stability analysis of Landslide L1 was carried out using different methods that shows the factor of safety is less than one. The immediate cause of Landslide is incessant rainfall for two weeks, which infiltrated through wide-open tension cracks in the head of Landslide as well as coarse-grained colluvial soil. For mitigative measures, surface drains and horizontal drilled drains are recommended along with other measures. 1. INTRODUCTION old and recent landslide. The study area lies in the ward no. 5 of Butwal Municipality, Rupandehi district, western Nepal, on the southern slope of the Siwalik Hills. North and north-eastern parts of the Jyotinagar, from where Siwalik hill rises, frequently experiences mass movements, especially during the monsoon. The Butwal area exhibits relatively steep and rugged topography. The Tinau River is the main river flowing through Butwal (Fig. 1).

Fig. 1 Perspective 3D visualization of the study area with landslides. View approximately northwards. IRS pan scene taken in January 2000 were draped over DEM (Nepali, 2002). Fig. 2 Geological map of the study area (after Duvadi et al, 2002) 2. GEOLOGY OF THE STUDY AREA The Siwalik is divided into three formations: 1) Lower Siwalik The study area is characterised by thin-thick bedded, fine- to Formation, 2) Middle Siwalik Formation and 3) Upper medium-grained pale yellowish sandstone and variegated Siwalik Formation. The study area is the part of the Lower mudstone of Lower Siwalik Formation. Sandstone is Siwalik Formation. The Main Frontal Thrust (MFT) is a characterised by three sets of joints and both sandstone and prominent geological structure in the study area (Fig. 2). It is mudstone are highly weathered. Most of the area is covered by an active thrust which separates the Siwalik Group from the colluvial or residual of either debris collected after slope failure Quaternary sediments of terai plains. In Butwal, this thrust or weathering of sandstone and/or mudstone. passes at the toe of Shrawan Danda Hill (Rimal et al., 2001) so it must be one of the contributing factors to reactivate the 3. SHRAWAN DANDA JYOTINAGAR LANDSLIDE The Landslide occurred on the upper part of the ridge (Shrawan 18 DWIDP BULLETIN 2005 - 2006

The length of Landslide L1 is around 850 m and width is about 200 m (at the middle part of Landslide). However the main scarp with height from 2 m to 30 m (Photo 3) extends for more than 500 m around the hill. The length of Landslide L2 is about 350 m while the width is about 70 m. Major tension cracks about 0.5-1 m wide and greater than 4-5 m in depth could be seen on the head of Landslide L1 which extends for about 200 m (photo 4). Tension cracks could also be seen at the flanks of Landslides L1 and L2. Abandoned agricultural terraces could also be seen on the head of Landslide L1. Debris flow of Landslide L1 has made a fan of about 75 m wide at the foot of slope. Landslide L2 is enlarging. The Durga temple and the houses below this Landslide are in critical condition as further debris flow from Phot 1: View of the Shrawan Danda Hill with Landslides L1 and L2. View towards northeast Landslide L2 could harm these structures. The area covered Danda) (Photo 1) overlooking the Jyotinagar area of the by Landslide L1 is 67,040 m2 while that by L2 is 16,050 m2. Butwal. The first Landslide in the Jyotinagar occurred in 1st The expected volume of loose and movable sliding mass of 3 September, 1998 at approximately 8 p.m. The heavy rain on Landslide L1 is 12,04,800 m and that of Landslide L2 is 3 5th September and early in the morning of 6th September 1,60,500 m . triggered large volumes of further debris to flow from the landslide area. One person was killed and 35 homes were destroyed by the debris that spread out and deposited over a large flatter area (Photo 2). The heavy rain combined with the silt runoff from the landslide blocked much of the drainage system of the area and cause large scale flooding of nearby homes, Butwal Multiple Campus (Photo 1), and premises of four UMN related organizations (BTI, DCS, NHE, and BPC). The debris flow resulting from the landslide scoured a large gully along the line of small pre existing stream (DWIDP, 2001).

Photo 4: Tension crack a on the head of Landslide L1 (DWIDP, 2001).

4. ENGINEERING GEOLOGICAL STUDY OF SOILS OF SHRAWAN DANDA JYOTINAGAR LANDSLIDE For engineering geological study of soil samples, twenty two samples (surface to 1-2 ft depth) were collected from different locations: 13 samples from Landslide L1 and 9 samples from Landslide L2 (Fig. 3). Four undisturbed samples from Landslide L1 were also collected to determine the cohesion and frictional angle for stability analysis.

Photo 2: Debris fan at the toe of the Landslide L1 causing damages to many 4.1 Grain size analysis structures (Duvadi et al, 2001).).View towards northeast The grain size analysis of 26 different samples of both Landslides L1 and L2 show that all soil samples falls under the coarse-grained soil (Table 1) as soils selected for the grading bear more than 50% coarse portion after sieving. The fine portions were tested for consistency limits and thereafter the soils were classified according to the Unified Soil Classification System (USCS). Most of the soil samples fall under “Gravelly sands with some fines” (Table 1). see page 5

The fine portions of the coarse-grained soils were classified according to the plasticity chart and the fine portions fall under CL-ML for both Landslides (Fig.4a and Fig. 4b).

Photo 3: Main scarp of the landslide. View towards northeast 19 DWIDP BULLETIN 2005 - 2006

Table 1: Results of the grain size analysis S. no. Landslide Grain Size Analysis Description USCS Gravel Sand Fines D10 D30 D60 Cu Cc S1 L1 31.05 63.51 5.43 0.12 0.80 3.60 31.30 1.55 Gravelly sands with some fines SW-ML S2 L1 15.31 79.96 4.72 0.95 0.32 2.00 2.11 0.05 Gravelly sands with some fines SW S3 L1 20.14 76.36 3.49 0.12 0.40 2.20 19.13 0.63 Gravelly sands with some fines SW S4 L1 33.12 62.86 4.02 0.13 0.62 3.80 29.23 0.78 Gravelly sands with some fines SW S13 L1 36.70 59.78 3.52 0.21 1.50 4.20 20.49 2.61 Gravelly sands with some fines SW S14 L1 41.12 55.20 3.67 0.12 1.35 4.90 40.83 3.10 Gravelly sands with some fines SW S15 L1 40.40 56.75 2.85 0.15 1.30 4.80 32.00 2.35 Gravelly sands with some fines SW S16 L1 24.41 71.80 4.59 0.22 0.73 2.90 13.18 0.84 Gravelly sands with some fines SW S17 L1 38.27 60.82 0.90 0.62 2.00 4.60 7.42 1.40 Gravelly sands with some fines SW S18 L1 12.75 82.58 4.66 0.09 0.20 1.25 13.59 0.35 Gravelly sands with some fines SW S19 L1 38.51 55.45 6.04 0.10 1.00 4.30 43.00 2.33 Gravelly sands with some fines SW-ML D1 L1 19.42 76.92 3.66 0.10 0.30 2.00 20.00 0.45 Gravelly sands with some fines SW D2 L1 26.94 71.10 1.97 0.17 0.68 3.00 17.65 0.91 Gravelly sands with some fines SW D3 L1 25.77 71.63 2.59 0.12 0.55 3.00 25.00 0.84 Gravelly sands with some fines SW D4 L1 15.44 82.85 1.70 0.20 0.54 2.20 11.00 0.66 Gravelly sands with some fines SW S20 L1 24.42 70.13 5.44 0.09 0.20 2.20 25.88 0.20 Gravelly sands with some fines SW S21 L1 14.38 80.67 4.95 0.09 0.20 0.84 9.33 0.53 Gravelly sands with some fines SW S5 L2 19.76 79.20 1.04 0.20 0.49 2.10 10.50 0.57 Gravelly sands with some fines SW S6 L2 27.79 69.02 2.59 0.12 0.69 3.15 26.25 1.26 Gravelly sands with some fines SW S7 L2 49.29 48.33 2.37 0.25 2.20 6.00 24.00 3.23 Sandy gravels with some fines GW S8 L2 21.96 75.14 2.91 0.12 0.50 2.50 20.83 0.83 Gravelly sands with some fines SW S9 L2 27.31 68.79 3.90 0.12 0.90 3.20 26.67 2.11 Gravelly sands with some fines SW S10 L2 22.20 75.41 2.39 0.12 0.28 2.20 18.33 0.30 Gravelly sands with some fines SW S11 L2 23.70 72.99 3.31 0.12 0.52 2.70 23.48 0.85 Gravelly sands with some fines SW S12 L2 67.63 31.07 1.29 1.00 4.40 8.15 8.15 2.38 Sandy gravels with some fines GW S22 L2 33.93 61.01 5.05 0.13 0.95 4.80 36.92 1.45 Gravelly sands with some fines SW-CL percentages (Fig. 5).

4.3 Direct shear test. Direct shear test is a mean of obtaining shear strength of the soil samples. The shear stress required for failure (τ) is obtained for various values of normal stress (σ) to shear plane. Shear strength of a soil is the maximum resistance to shearing stress at failure on the failure plane. Coulomb has Fig. 5 Average moisture content of soils of Shrawan Danda Jyotinagar Landslide represented the shear strength of soil by the equation: τf + C + σn = Tanφ 4.2 Average moisture content of soils of Shrawan Danda Where, C=Cohesion, Jyotinagar Landslide. τf =Shear strength of soil, σn =Total normal stress on the Soil samples taken for moisture content determinations from failure plane, φ = Angle of internal (shearing) friction. various parts of Landslides L1 & L2 (Fig. 3) show that moisture content in the soil during their acquisition ranges from 15-20 Four undisturbed samples collected from different locations of 20 DWIDP BULLETIN 2005 - 2006

Landslide L1 (Fig. 3) were subjected to direct shear tests. Results exposed: 1) at the main scarp of Landslide L1, 2) at the toe of are presented in Table 2. rupture of Landslide L1 and 3) at the right side of Landslide L2 at Table 2: Results of the direct shear test about 300m elevation. The highly weathered sandstone of the S.No. Cohesion of soil Angle of internal friction Wet unit weight Lower Siwalik is characterized by three sets of distinct joint sets and (C') KN/m2 (φ) Degree (γ ) KN/m3 a bedding plane. The data relating to location of acquisition and D1 0.6 23° 21.5 orientation of discontinuities is given in the Table 5. D2 0.7 23° 17.5 D3 0.9 25° 18.0 Table 5: Location and orientation of discontinuities D4 0.7 23° 18.5 Location Orientation of discontinuities (dip direction/dip amount) Bedding plane Joint J1 Joint J2 Joint J3 Hillslope The direct shear tests show that soils bear low value of Landslide L1 at main scarp 13°/19° 132°/41° 336°/55° 230°/54° 206°/65° Landslide L1 toe of rupture 0°/22° 146°/60° 22°/56° 261°/55° 229°/58° cohesion (0.6 KN/m2-0.9 KN/m2) and the angle of At right side of Landslide L2 47°/24° 221°/56° 304°/41° - 228°/32° internal friction are between 23°-25°. Sample D1, D2 and at an elevation of 300m D4 have angle of internal friction of 23° whereas the sample D3 has angle of internal friction of 25°. The joint analyses 4.4 Specific gravity test. show that Specific gravity test of soil samples of Shrawan Danda Landslide there is were also conducted the results of which are tabulated in Table 3. probability Table 3: Results of specific gravity test S.no. Average Result S. no. Average Result S. no. Average Result sp. gr. sp. gr. sp. gr. S1 2.67 Sandy gravels S18 2.67 Sandy gravels S5 2.68 Sandy gravels S2 2.65 Sandy gravels S19 2.69 Sandy gravels S6 2.66 Sandy gravels S3 2.70 Sandy gravels S20 2.67 Sandy gravels S7 2.66 Gravelly sands S4 2.65 Sandy gravels S21 2.65 Sandy gravels S8 2.69 Sandy gravels S13 2.67 Sandy gravels D1 2.67 Sandy gravels S9 2.68 Sandy gravels S14 2.66 Sandy gravels D2 2.67 Sandy gravels S10 2.66 Sandy gravels S15 2.65 Sandy gravels D3 2.65 Sandy gravels S11 2.70 Sandy gravels S16 2.68 Sandy gravels D4 2.66 Sandy gravels S12 2.67 Gravelly sands S17 2.67 Sandy gravels S22 2.68 Sandy gravels

Specific gravity test of the soil samples show that the values of of wedge specific gravity range from 2.65 to 2.69. Even though soil type failure at the is sandy gravels the specific gravity is relatively high than main scarp standard this is because the sand and gravel size particles and at toe consists of fragments of mudstone also. of rupture of Landslide 4.5 The soil consistency test L1. Since The consistency test of the fine portions (i.e. soil sample passing the Shrawan through 425 micron) of the soils show that they are non-plastic Danda area to low plastic silt and clay (Table 4). is characterized by the Fig.6. Engineering Geological map of the landslides L1 and L2 Table 4: Summary of soil consistency test overlying of the colluvial soil over S. no. Landslide Atterberg Limit Description S. no. Landslide Atterberg Limit Description the highly weathered and highly LL PL PI LL PL PI jointed and fractured rocks of the S1 L1 21.50 20.38 1.12 ML D3 L1 N.P. N.P. N.P. - Lower Siwalik, it can be concluded S2 L1 24.30 17.20 7.10 ML D4 L1 N.P. N.P. N.P. - that there is also possibility of S3 L1 24.70 16.72 7.98 CL S20 L1 N.P. N.P. N.P. - failure of underlying highly S4 L1 19.50 17.36 2.14 ML S21 L1 N.P. N.P. N.P. - weathered rocks by dragging of S13 L1 26.50 20.24 6.26 ML S5 L2 41.20 16.28 24.92 CL S14 L1 24.70 18.00 6.70 ML S6 L2 24.00 19.77 4.23 ML overlying thick colluvial soil. S15 L1 18.20 20.37 0.00 - S7 L2 19.80 17.98 1.82 ML The engineering geological map S16 L1 27.70 18.93 8.77 CL S8 L2 24.10 14.35 9.75 CL of Landslides L1 and L2 prepared S17 L1 30.80 11.30 19.50 CL S9 L2 23.70 14.86 8.74 CL S18 L1 N.P. N.P. N.P. - S10 L2 21.10 15.72 5.38 CL thus consists of joint analyses of S19 L1 22.00 16.99 5.01 ML S11 L2 24.50 9.41 15.09 ML rocks at three different locations, D1 L1 18.00 N.P. 18.00 - S12 L2 26.70 4.35 22.35 CL soil depth (delineated from D2 L1 25.40 21.65 3.75 ML S22 L2 23.30 15.69 7.61 CL resistivity survey performed by DWIDP, 2001), soil 5. ENGINEERING GEOLOGICAL MAPPING classifications, engineering structures and other features For engineering geological mapping joint analyses at three (Fig. 6). locations of the study area were done where the rocks are 21 DWIDP BULLETIN 2005 - 2006

6. STABILITY ANALYSIS For the stability analysis of Landslide L1 profile of the landslide The numerical value of factor of safety is calculated in the slope was prepared from the topographic map. The sliding mass stability analysis. The ratio of the actual shear strength to the above a trial failure arc was divided into 11 vertical slices and shear stress at failure is the factor of safety. For the purpose of area was calculated by using standard grid (Fig. 7). slope stability analysis, all slopes whose stability is governed by failure of the soil mass overlying the bedrock is treated with soil Swedish circle method of stability analysis has shown that the slope stability analysis. The limit equilibrium method of analysis factor of safety is 0.9987 (less than one), which shows the is based on an assumed failure plane and assumption that landslide is unstable in the present condition. The Bishop Coulomb’s Failure Criterion is satisfied along the failure Analysis shows that the stability number is 1.031(above one), surface. Stress-strain relationship and in situ stresses are not thus the landslide is stable in dry soil condition. But Bishop considered and the deformation cannot be predicted by this Analysis on fully saturated condition shows that the stability method. The shear strength parameter such as cohesion (c) and number is 0.679 (less than one), which means, the landslide is angle of friction (F) used in most soil slope analysis are based unstable if the area is submerged in water. Fellenius analysis on either total stress or effective stress, which are obtained from shows that the factor of safety is 0.8785 (less than one), hence laboratory test or in situ direct shear test. landslide is in unstable condition.

4.6 Stability analysis of the Landslide L1 (along electrical 7. PREVENTIVE AND MITIGATIVE MEASURES FOR SHRAWAN profile G1-GG2) DANDA JYOTINAGAR LANDSLIDE Field evidence shows that the Shrawan Danda Jyotinagar 7.1 Preventive and mitigative measures Landslide is rotational slide. Failing mass is colluvial soil The foremost preventive works is the avoidance of landslide. overlying the highly jointed and highly weathered Siwalik Rocks Butwal Municipality Office attempted to relocate people whose (sandstone and mudstone) and the failure surface is about 8m- houses were destroyed in the landslide by distributing land at 30m below ground surface. Tamnagar (western part of Butwal). Those who were relocated are returning back claiming their land. Also those who were The stability of a finite slope can be investigated by a number requested to left place, whose houses are not yet destroyed, of methods. The most widely used methods of analysis of have not left yet. homogeneous, isotropic, finite slopes are: 7.2 Surface and shallow subsurface water drainage. • Swedish circular method or method of slices, Control work was initiated by Butwal Municipality Office by • Bishop's method and constructing surface drainage channel at the head of Landslide • Fellenius method L1 to divert water to nearest natural channel. But the drainage channel has not been properly constructed and managed. The base of the channel was filled with available colluvial coarse-

71º sediments from the head of the landslide. Also the channel lies just next to the main scarp, so, even though the drainage channel somewhat drains water out of the landslide area, due to the coarse-grained colluvial soil water can easily infiltrate through the soil and saturate the colluvial soil mass in one way NE 600m and also can pass through the slip surface in other way thus destabilizing the soil mass. So this kind of poorly constructed D1 1 and unmaintained drainage cannot provide sufficient drainage 2 500m of surface water. 56º 3 4 D2 Instead, series of drainage network of surface and shallow 48º 5 D3 subsurface drains consisting of main drain and tributary drains 400m 6 are suggested in head and at middle part (at an elevation of 41º 7 8 SW 9 425m) of Landslide L1. Catch drain is suggested at the crown 34º 10 11 D4 of Landslide L1 to collect and divert surface runoff during 300m 27º precipitation For Landslide L2 also shallow surface and 21º 15º 3º -2º 9º -8º subsurface drainage network is suggested. The design considerations of these drains are to be according to the 0m 50m 100m 150m 200m surface and subsurface water these drains have to carry during Test Sample D1 D2 D3 D4 Cohesion, c (KN/m2) 0.6 0.7 0.9 0.7 and after monsoon. Friction angle, φ 23º 23º 25º 23º Unit weight, γ (KN/m2) 21.5 17.5 18 18.5 7.3 Horizontal drilled drains Liquid limit, LL 18 25.4 – – Plastic Limit, PL NP 21.65 NP NP Horizontal drilled drains are proposed for Landslide L1 at an Plasticity Index, PI – 3.75 – – elevation of 450m where major seepages have been noticed. Toughness Index, TI 2.15 0.51 – – Flow Index, FI 8.3 7.39 – – Horizontal drill drains are constructed radially and about 5°- Natural Moisture Content NMC 19.76 16.64 19.56 19.30 10° to the horizontal with length varying within about 70-80 m. Fig. 7 Profile of the Landslide L1 along electrical profile G1-G2 The diameter of the holes is variable within 50-100 mm. After

22 DWIDP BULLETIN 2005 - 2006 drilling, the semi perforated HDP is installed in the whole length • The study area lies in the north-eastern part of the Butwal of drainage hole. The perforations in the pipe are made on the city, on Siwalik Hills, Western Nepal. The study area is upper half with 3mm diameter holes at the rate of 10-15 mm characterized by the presence of colluvial soil overlying the distance and in zigzag pattern. The pipe is wrapped with highly jointed and highly weathered Lower Siwalik rocks. suitable fixtures, and supported at the outlet. The drain outlet • Shrawan Danda Jyotinagar Landslide is rotational type of suitable support with cement masonry, concrete or gabion slide that occasionally reactivates during monsoon after structure, and the collected groundwater is discharged to the intense precipitation. Intense precipitation results in nearest drainage system (DOR, 2003). maximum infiltration through wide open tension cracks and colluvial soil. 7.4 Check dams and protection walls • The immediate cause of Shrawan Danda Jyotinagar Check dams are constructed to control gully erosion. Butwal Landslide in 1998 is incessant precipitation for nearly two Municipality Office and other agencies have constructed check weeks. Presently, the landslide possess huge amount of dams at different parts of Landslide L1 and Landslide L2. Most loose and potential sliding mass which is endangering the of check dams constructed in Landslide L1 are functioning while inhabitants of Jyotinagar and Laxminagar also. check dams constructed in landslide L2 at various locations are • The colluvial soil of the Shrawan Danda Landslide can be destroyed. So new check dams should be constructed at classified as coarse-grained soil, the fine portions of which previous and new locations to protect gully erosion. Protection possess low compressibility silt and clay. The Atterberg limit walls (gabion walls) are also constructed at the sides of gully in tests of fine portions of coarse grained soil show non-low some parts of Landslide L2 to prevent debris materials from plastic (Landslide L1) and low-moderately plastic (Landslide flowing outside of gully over the slope. New check dams should L2). Natural moisture content ranges between 15-20%. be constructed at elevation of 270m and around 250 m below Specific gravity of soil is between 2.65-2.69. Direct shear toe of Landslide L2 as here deep (2-3 m) and narrow gully is test shows friction angle of 23°-25° and cohesion of 0.7- developed. 0.9 KN/m2. • The depth of slip surface varies from 30-8 m and decreases 7.5 Catch wall towards the toe. The calculated factor of safety along the Catch wall functions to catch debris materials flowing from profile G1-G2 of Landslide L1 using Swedish circle, Bishop, hillslope before it reaches the inhabited areas. Catch wall is and Fellenius methods are 0.998, 1.061 and 0.8785 proposed at foot of Shrawan Danda Hillslope about 50m away respectively. Saturated condition for Bishop also shows the from toe (Rimal et al., 2001). But this method would be factor of safety of 0.751. exaggerating as there is no vacant land to construct catch wall. • For control works, surface, subsurface drainage and Acquiring the inhabited land for construction of catch wall horizontal drilled drains have to be constructed. would be very costly. Engineering structures like check dams and protection walls 7.6 Removing the existing debris and maintain the slope gradient have to be constructed. Grass plantation can be applied to Removing the existing debris and taking other steps such as protect soil erosion. Grading of slopes can be done to building a berm around he deposition area to encourage the reduce slope angle of the slope and overhanging blocks future debris to remain in that area. This option is expensive as have also to be removed. Tension cracks are to be sealed a lot of materials need to be removed, large earth berms need with suitable materials to prevent infiltration of surface and to be constructed, and the structure need to be maintained. rain water. There would be continuing danger that the deposition area is • For mitigative measures regular monitoring of groundwater not large enough, or that the berms are not high enough, and level fluctuations and measurement of slope movements that the debris will flow out of the area and damage adjacent have to be done. houses (BPC Hydroconsult, 1998). REFERENCES 7.7 Plantation of grasses and bamboos BPC Hydroconsult, United Mission to Nepal (1998). 1998 Butwal To control erosion by surface runoffs during precipitations Landside. Preliminary Geological Investigation, Technical Report grasses of definite species (suitable for the climate of that area) Department of Road, (2003). Guide to Road Slope Protection Works, and bamboos should be planted. Grasses (species not known) HMG, Ministry of Physical Planning and Works. could be seen planted at elevation of 400m where there are Duvadi, A. K.; Sikrikar, S. M.; Piya, B. and Rimal, L. N., (2002). seepages and soil is wet. But proper care and maintenance of “Engineering and Environmental Geological Investigations in those plants are not taken. Besides planting of grasses, old and Butwal area”, Journal of Nepal Geological Society, Vol. 27. pp dead trees should be removed. 151-158. DWIDP, (2001). Geological/Geophysical Investigation of Shrawan Besides these measures, installation of piezometers for Danda Jyotinagar Landslide in Butwal Municipality, Rupandehi monitoring of fluctuation of groundwater and moving peg District, Nepal. survey must be conducted for measurement of slope movement Nepali, D., (March 2002). Bivariate-Statistical Landslide Hazard so that assessment of the slope movement can be done Analysis of Butwal Area, Western Part of Nepal:: Stutgart. properly. Rimal, L. N., Sikrikar, S. M. and Sapkota, S. N., (Part 3-Geo-Hazards), (2001). Technical Report on Engineering and Environmental 8. CONCLUSIONS Geological of Butwal Area, Project 53, DMG/EGP Follow-up Bared on the above study following cucelusim can be drawn: Program, Unpublished Report, 18 p. (with map). 23 DWIDP BULLETIN 2005 - 2006 Trends in Human Life and Economic Losses from Landslides and Floods in Nepal

– Mr. Hari K. Shrestha Associate Professor, Nepal Engineering College

ABSTRACT Trends in Human life and economic losses from landslides and floods in Nepal are significant. The article intends to present the long term trends of disaster effects in Nepal

It is a well known fact that Nepal faces a variety of natural and decades, despite the Annual Human Life Loss from Lanaslides and Floods human activity induced disasters every year. In terms of human increase in technical 1400 life and economic losses, the landslides and floods are the know how and 1200 biggest natural disasters in Nepal. enormous money spent 1000 on disaster mitigation 800 Systematic data collection on the effects of disasters is a 600 measures. Figure 1 Average Loss: 324 per year relatively recent phenomenon in Nepal. The Ministry of Home 400 shows that in average, Affairs started compiling data on losses due to various types of 200 slightly more than 300 disasters since the last two decades. Based on the available 0 Nepalese die each year

data, it seems that the number of natural disasters like landslides 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 from landslides and and floods has increased in the last two decades due to various floods. A 10-years Fig. 1 Human Life loss in last two decades from reasons. The climate change effect is one of the reasons added average of the number of landslides and floods in Nepal on top of other existing natural reasons of disasters in Nepal. people dead from landslides and floods (Figure 2) does not Agencies in Disaster Mitigation impart much positive messages. Although there is a declining The Department of Water Induced Disaster Prevention (DWIDP) trend, the number of people dead continuously hovers above is responsible for various activities to reduce damages from 300. In fact, Figure 2 shows that after a declining trend from water induced disasters like landslides and floods. The Japanese 1993 to 2000, the number of people dead started rising at the Government funded Disaster Prevention Technical Center latter part of the graph. A sharp drop in 2003 in the 10-years (DPTC), which is the predecessor of DWIDP, initiated various average value, in Figure 2, resulted because the value of 1993 activities like river training, slope stabilization, and public has no effect on calculation of value for that year. awareness generation as part of its disaster mitigation programs. The records of Currently DWIDP is being assisted by Disaster Management 10 Years Running Average of People Dead economic loss from 500 Support Project (DMSP), which is another Japanese government 450 landslides and floods 400 funded program. DMSP has started creating a database of 350 portray equally gloomy 300 losses from water induced disasters in Nepal. 250 Declining trend resulted pictures. Figure 3 200 150 mostly due to very big The Disaster Unit of the United Nations Development indicates that in 100 number in 1993 50 Programme has conducted various activities in Nepal to average Nepal is 0 generate public awareness and for application of DisInventar, losing about 816 which is a comprehensive database of the effects of various million rupees every 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 types of disasters. year. A poor country Fig. 2 10-years running average of people dead from like Nepal which has to landslides and floods in Nepal The Department of Narcotics Control and Disaster Management rely on almost 60% of its annual budget on foreign aid and (DNCDM) under the Ministry of Home Affairs along with the loans can ill afford such a major loss of resources. Figure 3 also Central Natural Disaster Relief Committee (CNDRC) coordinate indicates that the frequency of years with economic losses relief activities with the Nepal Red Cross Society (NRCS), Nepal approaching 1000 million rupees is increasing at the latter part Police, Royal Nepal Army, and hospitals. The regional, district of the graph. The result of this rise in frequency can be seen in and local units of CNDRC, the District Administration Office, the the following figure. Village Development Committee and the district office of NRCS located in the disaster affected area play an important role in the Figure 4, which is a 10-years running average of the economic field level coordination of rescue and relief activities. Nepal losses from landslides and floods in Nepal, in fact indicates a very Police and Royal Nepal Army mainly conduct rescue operations. disturbing trend of a gradual rise in economic loss with the passing Nepal Red Cross Society conducts emergency relief operation, of each year. As in Fig. 2, the sharp decline in the 10-years average runs relief camps, and provides relief materials to the disaster value of 2003 resulted because the value of 1993 has no effect in victims. DNCDM and NRCS conduct training programs on the value average value of that year. From figures 1 to 4, it seems rescue and relief operations also. that all the works of disaster mitigation activities of various governmental and non-governmental organizations in Nepal in the Trends in Disaster Effects last two decades have gone in vain. A quick glance at the raw data of human life and economic loss seems to show that not much progress has been achieved in Or, is it? reducing the losses from landslides and floods in the last two Figures 1 through 4 are the graphical presentation of the raw 24 DWIDP BULLETIN 2005 - 2006

Annual Economic Loss (in million Rs.) data of the number of the consumer price index of Ecomonic Loss from Landslides and Floods 5000 people dead and the 2003, different trends in (as percentage of total annual national budget) 4500 30 4000 economic loss, without annual economical losses 25 3500 20 any standardization. emerge, compared to Figure 4. 15 3000 Average Loss: 788 10 2500 million per year The base lines of the The Figures 7a and 7b show 5 2000 0

1500 data have changed in that there are clear and 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 1000 the last two decades. consistent declining trends in Year 500 0 The population of the average annual Fig. 6 Declining trend of ratio of economic Nepal has increased economical losses in Nepal loss from landslides and floods in Nepal 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 tremendously in the from landslides and floods. The Fig. 3 Annual Economic loss from landslides and floods in Nepal last twenty years. The rate of decline is higher in Figure 7a than is Figure 7b because population of 2002 in of the lingering effect of the 1993 disaster in Figure 7b. Nepal is 50% more than the population in 1982. A loss of 300 people out of 15 million populations is not the same as a loss Five Years Running Average of Economic Loss 10 Years Running Average of Economic Loss (in 2003 market price, adjusted for inflation) (in 2003 market price, adjusted for inflation) of the same number of people out of 25 million. The economic 4000 3000 3500 2500 activities of Nepal in 2002, in terms of the total annual budget, 3000 2000 2500 rupees) are 900% more than the economic activities of 1982. The Rupees) 2000 1500 on i l on on l i l 1500 mi

mi 1000 n

average market price of 1982 is much lower than in 2003; if i n i 1000 ( ( 500 500 adjusted for the current market price, the cost of disaster events 0 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 in 1980s will be higher and hence will show a different trend in a 1987 1989 1991 1993 1995 1997 1999 2001 2003 b economic loss. Figures 1 through 4 however ignore these Fig. 7 Declining trends in economic loss, when adjusted for average annual inflation rate changes. The declining trends shown in figures 5, 6 and 7 can be 10 Years Running Average of Economic Loss Consideration of the interpreted as accomplishments of various organizations 1200 changes in the base involved in pre- and post- disaster mitigation activities in Nepal. 1000 lines of the data paints 800 Cause of Declining Trend of Losses upees) r Increasing trend despite completely different 600

on The declining trends in the ratio of human life and economic loss i l l very big loss in 1993. pictures. When the mi 400

n will result if (a) there is a reduction in the number of landslide i Big drop in 2003 due to ( number of persons 200 lack of effect from 1993. and flooding events, (b) there is reduction in disaster data dead from landslides 0 collection, and (c) the population density and economic and floods, compared 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 activities decline in the landslide prone areas. to the number of Fig 4 10-years running average of economic loss from persons living at that The basic natural causes of landslides and floods in Nepal, landslides and floods in Nepal time is plotted against namely the earthquakes, weak geo-logy, steep topography time, the linear regression shows an unmistakable declining and intense monsoonal rainfalls, have not changed very trend (Figure 5). In a study conducted from the data from 1990 much in the last two decades, and are not going to change to 1998, Nepal ranked third (35), behind Bangladesh (135) and significantly any time soon. Out of these natural causes, Afghanistan (62) in the annual number of persons dead from rainfall pattern is one factor that can change relatively various disasters per million living people in mountainous Asian rapidly. A check of last 15 years’ data of 24-hours maximum countries (N. Khanal, M. Chaudhari and T. Li, Risk, Vulnerability precipitation, which is one of the leading causes of landslides and Sustainable Development in Mountainous Areas of Asia, and floods in Nepal, of some meteorological stations located Asia High Summit, 2002). in the hilly areas indicated a rising trend in the frequency of high intensity rainfall events (Figure 8). Human activities such Number of People Dead (per million living people) The total annual budget of from Landslides and Floods as deforestation, rock and sand mining that initiate soil Nepal in 1983 was about 80 erosion, gully formation and eventually trigger landslides are 9187 million rupees. In the 60 on the rise along with rapid population increase and 40 same year the total consequent growing demand for food and settlement areas. 20 economical loss from 0 More infrastructures, like roads, communication towers, landslides and floods in

1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 transmission lines, schools and houses, are being built in Nepal was 2400 million Year mountainous terrains of Nepal in the last two decades. Very rupees, a whopping 26% of Fig. 5 Declining trend of ratio of human life little consideration for slope stability is given during the budget. The highest loss from landslides and floods in Nepal infrastructure development. Obviously the numbers of ever recorded economic landslide and floods disaster events in Nepal are increasing. loss from landslides and floods in Nepal is in 1993, when the total loss amounted to 4904 million. However, that was less Fig 8: Rising Trend in the frequency of high intensity of rainfall events. (a, b, c, d and e) than 16% of that year’s total annual budget. An economic loss of 2400 million rupees in 2004 budget would be roughly about y = 1.6738x + 90.31 y = 1.6576x + 89.61 2.3% of the budget. The linear regression line in Figure 6 300 300 indicates that there is a definite declining trend in the ratio of 250 250 economic losses from landslides and floods compared to the 200 200 economic activities of the nation. 150 150 100 100 Based on various information sources, the average inflation rate 50 50 in Nepal is 8.3% in 1970-1979, 9% in 1980-1989, 8.6% in 0 0 1990-1999 and 3.2% in 2000-2003. When the annual b

a 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 economical losses from landslides and floods are adjusted for 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 25 DWIDP BULLETIN 2005 - 2006

y = 2.6059x + 120.4 y = 1.7074x + 170.18 figures 2, 5, 6 and 7 above. A gradual increase in 10-years 300 300 average of economic loss (Figure 4) resulted from the fact that 250 250 no adjustment was made on the data for the average annual 200 200 inflation rate in Nepal. When the adjustment was made, the 150 150 100 100 results clearly indicated that there is a definite declining trend in 50 50 the annual economical loss as well. In fact, in a developing 0 0 country like Nepal, a gradual increase in economical losses d from landslides and floods is to be expected as more and more 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

c 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 developmental activities are being carried out in geologically unstable areas. The declining trends in both the ratio of people y = 1.1515x + 127.53 300 Table: Figures 8(a) to 8 (e) show 24 -hrs. max. dead and economical losses despite significant increases in 250 precipitation in the stations given below. population density and economic activities in landslide prone 200 Index No St. Name District areas can be considered at least a partial success in disaster 150 1038 Dhunibesi Dhading mitigation activities. Undoubtedly, experts may argue on the 0809 Gorkha Gorkha 100 0902 Rampur Chitawan significance and the reason of the declining trends shown 50 0804 Pokhara Kaski above. The volume of data is insufficient to make strong 0 0815 Khairenitar Tanahun statements on the trends, and a few major disasters in the near e 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 future, if they are to occur, may change the trends. However, based on the observation of the available data, the author believes that we are obaserving the Good Case Scenario. CNDRC has significantly improved its disaster data collection Future data may prove, or disprove, the statement. mechanism in the last two decades.?The relatively better access Not a Time to Relax to remote areas, compared to two decades ago, ensures that the Letting the guards down, however, would be a disaster. It is not declining trends of ratio of human life and economic loss with a time to relax yet. An annual loss of more than 300 human time are not due to reduction in data collection. lives from landslides and floods is an unacceptable standard. A The Ministry of Population and Environment data indicates that resource constrained country like Nepal can ill afford an annual the population density (persons per square kilometer) has loss of around 800 million rupees. The performance of line increased in the landslide prone areas of Nepal in the last two agencies and other organizations involved in disaster mitigation decades, from 25 to 33 in the mountain areas and from 117 to must be improved. Increase in the rate of the declining trend of 167 in the hilly areas. With the rise in population density there proportion of human life and economic loss cannot be expected has been consequent rise in economic activities. The rapid rise without better efforts from all the concerned parties because in the number of micro-hydro projects in hilly areas of Nepal various natural and human factors are progressing that can tip increased economic activities. So, the declining trends in ratio of the balance and reverse the declining trends in the ratio of human life and economic loss are not due to lessened human life and economic losses. population density or lowering of economic activities in the hilly The Department of Hydrology and Meteorology’s study show terrains. that there is rising trend in the average air temperature of Nepal. So, what is the cause of the declining trend in the ratio of human The effect of global climate change seems to be contributing to life and economic loss in Nepal in the last twenty years? Let us this rising trend in temperature. An increase of a few degrees of look at the three possible reasons. The first possible reason may air temperature can spell a major disaster from rapid snow melt be called a Bad Case Scenario; if the number of disaster events and glacier regression in the Himalayan mountains of Nepal. and the consequent losses remain relatively constant and the As indicated in the National Action Plan on Disaster population and budget gradually increases with time, the Management in Nepal-1996 (NAP), well coordinated and declining trend as shown in figures 5 and 6 will result without continuous efforts should be made towards pre- and post- any improvements in disaster mitigation activities. The second disaster activities to prevent the declining trend from reversing. possible reason is the Worst Case Scenario; if the rate of Implementation of NAP’s programs would be a major step in the disastrous landslides and floods events and the consequent right direction. damages are increasing, but the rate of increase in population and budget figure is even higher, then we will still see the The importance of public awareness enhancement (PAE) in declining trends as shown in figures 5, 6 and 7. If this is indeed reducing the effects of disasters cannot be over emphasized. The the case, then all the disaster mitigation attempts in Nepal can concerned governmental, non-governmental, academic and be considered a total failure. The third possible reason is a social organizations should make concerted effort for PAE. Good Case Scenario. In this case, the continuous efforts of Thousands of lower secondary and high schools spread across DPTC, DWIDP, DMSP, CNDRC, NRCS, UNDP, the mass media Nepal can play crucial role in PAE efforts. The mass media like and other organizations (non-governmental, academic, social) radio, television and newspapers should me made a regular part in enhancing public awareness are silently making an effect. of PAE to accelerate the declining trend of ratio of human life Inclusion of information on landslides and other types of and economic loss. disasters in school textbooks, however limited, are affecting the way people react to disasters. People living in vulnerable areas The author is an Associate Professor at Nepal Engineering are getting the lessons. As people become more aware of the College, Changunarayan VDC-9, Bhaktapur, Nepal. This paper potential risk of disaster, they make provision for escaping from is based on a presentation made during Second International its consequence, which results in declining trends shown in Seminar on Disaster Mitigation in Nepal, Kathmandu, in November 2004. 26 DWIDP BULLETIN 2005 - 2006 Rapid Environment Impact Assessment in Disaster In the Context of Nepal

Ms.Amrita Sharma President, Center For Disaster and Environmental Management

ABSTRACT An Event beyond the immediate means of the affected population to cope and which threatens lives or immediate well - being is DISASTER. Rapid Response in disaster is most important to minimize the further loss. Those who respond to disaster have little time for in depth research and are not likely to be environmental specialist. The REA is based on the concept that identifying and incorporating environmental issues in to the early stages of disaster response will make relief activities more effective and lay a foundation for a more comprehensive and speedy rehabilitation and recovery. So, relevance of REA on effective response is suggested for identifying framing and prioritizing environmental issues in such ways as to allow the negative impacts to be minimized or avoided during the immediate response to a disaster. This paper explains the need, relevance as well as process of REA in Disaster. Key Words: Disaster, REA, Response, Environmental Issues.

Background affected regions. Consequences may be long term and may even Nepal is a land locked and predominantly mountainous and irreversibly affect economic and social structure of environment. hilly country sandwiched between China in the North and India There are a number of factors, which may positively or negatively in the South, east and west. With an area of 147181sq.Km the influence the severity of environmental impacts during and country extends about 885 Km in the east-west direction and an following a disaster. These factors are related to the spatial, social average approximate width of 193Km in the north-South and economic conditions under which the disaster survivors live direction. The Vast altitudinal Variation within a short span of and indicate environmental impact issues, which may need to be about 193 Km ranging from 60m to 8848m above the sea addressed as part of the disaster response. Identifying the level makes the country an abundant storehouse of bio-diversity and ecological niches with diverse climatic zones. With this geographic diversity and varied climatic conditions Nepal is prone to various types of Natural and Manmade disasters such as Floods, Landslide, fires, earthquakes, epidemics, windstorms, hailstorms, Lightening, avalanches. The Country is especially prone to hydrological hazards and seismic activity owing to the topography and young geology. Water induced disasters like Landslides, floods, Debris flow, Sedimentation flows and GLOFs are frequent occurrences that cause heavy loss of Human lives and Physical properties worth billions of rupees each year.

In most of the disaster situation rescue relief works are mostly Photo 2: Flood at Sumari, Makwanpur important. Disasters have a major impact on the living condition, economic performance and environmental assets and services of importance of these factors aids in determining which relief activities to avoid or to use to mitigate negative environmental impacts, and where these interventions should be targeted.

There is a strong link between environmental damage and disasters. Identifying, evaluating and responding to critical environmental issues during a disaster are key to effective disaster relief and recovery operations. In normal, non-disaster, situations an environmental impact assessment (EIA) can be used to identify possible environmental impacts and mitigation measures. Most governments and humanitarian assistance organizations specifically allow for not doing an EIA in emergencies, recognizing that a full EIA would considerably slow emergency assistance. Although REA is not applied in the context of Nepal till date, its importance in mitigating the environmental impacts and Photo 1: Disaster due to Flood at Aambhanjyang VDC, Makwanpur consequent disaster should not be neglected. 27 DWIDP BULLETIN 2005 - 2006

3. Provide simple steps for analyzing this information to identify important issues and,

Review procurement decisions to reduce the potential negative environmental impacts of emergency assistance.

The REA is designed for use during the critical disaster response period, from when a warning of a disaster is first received until conditions have stabilized, normally within 120 days after a trigger event. It is conducted in two level assessment , organizational and community. REA does not replace a formal EIA. Rather, it fills the gap between the start of a disaster and when the formal EIA process can be initiated Data collected and data collection systems established through a REA can Photo 3: Flood Affecting Drinking Water Supply Pipe provide important inputs into an EIA. Rapid Environmental Impact Assessment (REA) Rapid Environmental Impact Assessment (REA) fills a gap in the range of tools available to assess environmental impacts during disasters. The REA is designed to provide input on environmental conditions in disaster situations in a way, which is convenient for the fast moving, time compressed operational environment faced in responding to a disaster. The REA is one of several initiatives to improve the linkages between sustainable environmental management and disaster response.

The REA is based on the concept that identifying and incorporating environmental issues into the early stages of a disaster response will make relief activities more effective and lay a foundation for a more comprehensive and speedy rehabilitation and recovery. The process and structure of the Photo 5: Flood Affecting livelihood of the vilagers REA recognize that those who respond to disasters have little time for in depth research and are not likely to be Recommendation and Conclusion environmental specialists. Although the REA has been developed as a good practice in disaster in many countries of the world, its application in Nepal is almost in zero. For the several factors as to identify the extent of disaster, Survivors displacement, resource availability, self- sufficiency, sustainability, social solidarity REA process will cooperate the crucial role in Preparedness, Relief, Recovery and Rehabilitation process of Disaster Management.

Reference: Guidelines for Rapid Environmental Impact Assessment In Disasters(2004),inter Works LLC. For CARE International with USAID. Poudyal Chhetri,M.B.P (2001),A Practitioner’s View of Disaster Management in Nepal: Organization , system, Problem and Photo 4: Community Affected by Flood in Makwanpur Prospects. Paper presented at an international Seminar on Water Induced Disaster, November Katmandu A completed REA identifies critical environmental issues. Some issues arise from conditions existing before the disaster. Others are Poudyal Chhetri, M.B.P & Bhattrai .D (2001), Mitigation and new to the location or population experiencing the disaster. The Management of Floods in Nepal: MOHA, His Majesty’s nature and impact of environmental issues will change during and Government of Nepal. after the disaster and new issues may arise. For these reasons, the Miller G.T (2002): Living in the Environment, California, output from an REA is not a static assessment but one to be Wadsworth Publishing Company reviewed and revised throughout the post-disaster period. IUCN-The World Conservation Union, Caring for the Earth: A REA Process: Strategy for sustainable Living. Gland Switzerland, October 1. The REA process helps to: 1991 2. Collect information needed to assess environmental impacts,

28 DWIDP BULLETIN 2005 - 2006 A SUSTAINABLE WAY OF CONTROLLING DEBRIS FLOWS AND LANDSLIDES ALONG MUGLING-NARAYANGARH ROAD

– Dr. Surendra Prasad Joshi Engineer, MNWIDPP/DWIDP

ABSTRACT The cloud outburst occurred on 30th July 2003 has damaged Narayangarh Mugling Road tremendously creating 213 instabilities and blocking the road for six days. Among these instabilities approximately 50% of total damage was due to debris flow, 40% slope/embankment failure and 10% was due to toe cutting, road subsidence, wall failure, bridge/culvert damage and others. To stabilize the road Department of Road (DoR) has worked intensively cleaning accumulated debris, constructing breast walls, retaining walls, Check dams, toe walls and other necessary structures along the road corridor. However, there are still chances of debris flow from the cross drainages due to the existence of huge active landslides in their catchments. Mugling Narayangarh Water Induced Disaster Prevention Project (MNWIDPP) has established under Department of Water Induced Disaster Prevention (DWIDP) to control these debris flows by treating necessary measures in the catchment area. This paper highlights the progress made by the DoR and DWIDP to stabilize the road in a sustainable manner after the devastating cloud outburst of 2003. KEYWORDS: Debris Flow, Landslide, Check dams, Retaining walls, Toe walls, Mugling Narayangarh Road, Trishuli River. 1. BACKGROUND Lower Nuwakot group of the Nawakot complex. This group Narayangarh-Mugling Road is one of the busiest strategic consists mainly following formations: roads of Nepal, which connects the Terai Plains with the Capital • Kuncha formation near Mugling with highly weathered and other central mountainous districts. This road section is phyllite and metasandstone. very important to transport foods, commercial and industrial • Fagfog quartzite (about 500m band) goods, fuel etc to the Kathmandu valley, where nearly two • Dandagaon phyllites made up of grey feeble phyllites million people live. • Nourpul formation, which extensively distributed in this However, this road sector was severely damaged by the sector, made up of about 100m band of purebesi quartzite intensive rainfall occurred on 30th July 2003, which have in the base and followed by slates, phyllites and quartzites. created numerous landslides, slope failures, rock falls and • Dhading dolomite represented by grey dolomites debris flows killing several people and live stocks. An inventory • Benighat slates represented by highly cleaved study conducted by DoR just after the disaster has noted 213 carbonaceous slates Siwaliks instabilities in the road, which has washed out 1480m • Dun valley gravels embankment, 9 slab culverts and 2 bridges and damaged 8675m pavement and 494m retaining walls, blocking the road The unstable parts of the road (from Ch 16.4 Km to 33.0 Km) traffic for weeks. Numerous debris flows, slope failures within pass through Nourpul formation. Among them the most the watershed areas of the cross-drains deposited huge volume vulnerable part from Ch 22.5 Km to 25.0 Km lies in fault zone of debris on the road. The debris flow from upstream brought between Nourpul formation and Dandagaon phyllites. The by the Trishuli River and as well as from opposite bank gullies rocks in this area are moderately weathered and highly has aggravated toe cutting by the River especially in Simaltal fractured phyllites and quartzites. area. As a result of the blockage the blockage many essential goods became shortage in the capital as well as in the central 2.2 Meteorological Effect part of the country. Realizing the seriousness of the problem On 30th July 2003 the cloud outburst was occurred around and its impact in future socio-economic situation, the then Kabilas VDC, which was concentrated mainly in south face of HMG of Nepal allocated necessary budget to the Department the ridge of the VDC i.e. in Dashdhunga, in north face i.e. in of Road to rehabilitate Narayangarh-Mugling Road corridor. Bhorle, Ghumaune and Simaltal villages. The 24-hr rainfall Considering that the rehabilitation works just along the road recorded at that day in Bharatpur and Devghat were 346mm corridor can not protect the road from debris flows and and 446mm respectively. landslides in a sustainable way, and therefore feeling the necessary of slope stabilization works in the catchments of the 2.3 Hydrology of this Area drainages, beyond on the slopes upstream of the corridor and Trishuli River is the largest tributary of Narayani River with at toes along the Trishuli river bank, Mugling Narayangarh catchment area of 19700 Sq. Km. There is a Hydrological Water Induced Disaster Prevention Project (MNWIDPP) was station in Narayani River at Devghat with Catchment area of launched under Department of Water Induced Disaster 31300 Sq. Km, which has hydrological records from 1963 to Prevention with grant assistance of Japanese Government in FY till now. In this station the maximum instantaneous discharge 2004/05. Analyzing the causes of blockage of the road and has been recorded as 14900 Cumecs in August 1999 and implementation works carried out by Central Division Road minimum instantaneous discharge have been recorded as 156 Office No.8 and MNWIDPP, some recommendations are made Cumecs in 1984. Therefore, the maximum instantaneous in this paper for stabilizing the road in a sustainable manner. discharge is approximately 100 times more than the minimum instantaneous discharge. According to the flood frequency 2. CAUSES OF THE PROBLEM analysis 50 years flood was occurred in 1999. If the maximum 2.1 Regional Geological Causes instantaneous discharge of the Narayani River is divided in The rocks of Mugling-Narayangarh Road sector belongs to Kaligandaki and Trishuli River according to their catchment 29 DWIDP BULLETIN 2005 - 2006

areas, the maximum instantaneous discharge of the Trishuli CDRO-88 after the 2003 Disaster River is about 9400 Cumecs. It was learned from the local S.N. Structure Chainage inquiry that the high flood level in the Trishuli River during the 1 Breast wall 8+930, 12+040, 15+360, 16+990, 17+115, 18+850, 30th July, 2003 flood was about 1.5m higher than during a. Gabion 20+350, 26+710, 30+550, 31+475, 31+810 1993 flood, i. e. the highest flood level villagers have known. b. Masonry 8+660, 13+035, 18+750, 18+790, 19+580, 20+350, 20+800, 21+130, 21+925, 24+000, 24+600, 26+710, 3. PROGRESS MADE IN THE REHABILITATION WORKS: 30+550 Central Division Road Office No.8 (CDRO) is playing major 2 Retaining wall role for rehabilitating this road corridor. Since the time, when a. Gabion 9+500, 14+300, 18+696, 20+350, 20+850, 21+080, major disaster was occurred in July 2003, this office has 21+642, 21+850, 20+800, 27+280 cleared 199,529 cu. m. of debris mass coming from up hill b. Masonry 11+620, 15+060, 17+850, 18+355, 18+415, 21+175, sides and cross drainages. The location of debris flow and 21+850, 23+423, 23+570, 11+650, 17+050, 24+850, 27+160, 27+280, 28+080, 31+ 630, 31+810, 32+550 disturbed days are presented in Table 1. The maximum debris flow was occurred in the gully of Mohore Khola Ch. 21+560 wc. R. C. C. 21+040, 29+325 and followed by gullies of Ch. 23+760, Khahare Khola (Ch. 3 Toe wall 11+300) and Gaighat Khoal (Ch. 18+460). a. Concrete toe wall 16+850, 17+850, 19+450, 24+000 b. Masonry toe wall 23+785, 32+475 Table 1. Location and volume of debris flow and disturbed days c. Gabion Toe wall 26+250, 32+475 4 Catch pit wall 15+060, 24+750, 25+070, 27+070, 29+825, 30+456, Contractors E/W Machinery work, hr Volume, 31+400 S.N. Chainage 3 Days 3 Total work volume, m Loader Excavator m 5 Check dam 11+100, 15+060, 16+950, 17+295, 17+560, 18+460, 1 8+000 - 24 - 1 1560 1560 a. Gabion 20+200, 20+800, 21+130, 21+560, 22+150, 23+080, 2 11+300 21075 10.5 9 3 1762 22837 23+550, 23+780, 24+400, 24+750, 25+070, 26+960, 3 16+800 - 5 325 325 27+070, 27+160, 27+200, 27+545, 27+600, 27+860, 4 16+900 1243 - - - - 1243 29+825, 30+456, 30+890, 31+400, 32+890, 34+090 5 17+300 245 - - - - 245 b. Masonry 15+930, 30+890 6 17+560 1003 15 3 975 1978 6 Gabion Guide wall 11+300, 19+450, 18+460 7 18+460 10093 38 21 10 4990 15089 8 19+900 283.5 283.5 7 Gabion spur 11+300 9 20+550 373 - - - - 373 8 R.C.C. Anchor wall 17+115, 24+600, 31+875, 31+890 10 20+800 148 20 2 1300 1448 (Source: CDRO 8, FY 2004/05) 11 20+815 6324 - - - - 6324 12 20+855 1560 - - - - 160 Presently, the road seems to be stable near the road corridor 13 21+100 7599 7599 and it is black topped. However, there are still possibilities of 14 21+560 43938 134 63.5 28 16330 60268 disturbing the road traffic by debris flows from the cross drains 15 21+640 2117 2117 because there are numerous active landslides in the catchment 16 23+070 128 - - - - 128 area and also some slope failures and toe cuttings in the road 17 23+515 360 360 alignment. Therefore, Mungling Narayangarh Water Induced 18 23+550 707 4 - - 260 967 Disaster Prevention Project has given priority to study the causes 19 23+760 2932 251.7 80.5 25 26023 28955 of landslides in the catchments of the cross drainages along the 20 23+770 23 3.5 5 1915 1915 21 23+775 8015 8015 road and design the remedial measures to prevent debris flows. 22 23+800 1715 35 12 2275 3990 Joint meetings were held between the CDRO and MNWIDPP 23 23+900 25 1625 1650 on 4th January 2005 and 24th November 2005. The first 24 24+400 1194 16.5 3 11 1432.5 2626 meeting has pointed out the most critical five gullies to be 25 24+740 3671 16.75 8 1089 4760 controlled in the priority basis. These gullies are located at 26 24+750 2402 2402 Chainages 23+760, 30+890, 18+460, 21+560 and 27 24+880 169 169 24+740 respectively. The project has studied these gullies and 28 24+920 875 875 constructed necessary remedial measures to control debris 29 25+025 173 173 flows. Similarly, the second meeting has given importance to 30 26+700 378 378 control debris flows in seven cross drainages (in Ch. 15+030, 31 27+060 3663 3663 32 27+160 1778 1778 15+900, 15+940, 16+940, 20+800, 24+370 and 33 27+545 450 450 30+500), to trim the hanging slope in Ch. 13+600, to control 34 27+850 3522 3522 landslides in Ch. 24+025, 22+000 and 27+200 by 35 27+860 701 701 constructing horizontal drains. Like wise this meeting has also 36 29+500 1596 1596 recommended to construct necessary down hill structures in the 37 30+460 325 325 drains of Ch. 20+800, 21+560, 24+600, 27+160 to 38 30+890 654 29 15 1885 2539 protect the road from washing away, to control rock falling in 39 31+400 2232 1.5 1 97.5 2329 Ch. 31+400 and to stabilize the landslide of Ch. 17+125. 40 31+890 3231 3231 41 32+400 6.5 422 422 4. CAUSES OF DEBRIS FLOWS OF MAJOR DRAINS AND ITS 42 34+090 139 139 REMEDIAL MEASURES MNWIDPP has studied most vulnerable gullies of the road and In addition to the debris clearance works, total 809 m long found the causes of the debris flows and analyzing the causes breast wall, 538 m long retaining walls, 42 Nos. of check dams implemented some civil and bio-engineering measures. in 33 streams, 104m long guide walls, 1 spur, 4 anchor walls, 7 catch pitch on the road and 269 m long toe walls in the left 4.1 Gully at Ch. 23+760 bank of the Trishuli River are constructed in different locations Causes: The central gully is about 30m long and 15m wide made of the road as shown in Table 2. up of debris deposit of weathered white phyllite. The upper part is made up of weathered slate. At the mouth of western gully, a thin Table 2. Major slope stabilization structures constructed by foliated phyllite and sandstone are exposed. The gully is narrow 30 DWIDP BULLETIN 2005 - 2006

(about 6 m wide) and 7m deep. In this gully metasandstone and Remedial Measures: There is one existing gabion check dams phyllite are observed in the bed and banks. The intensive rainfall constructed by DoR near the road, which has trapped huge of July 2003 has eroded the bed of the gullies, which has triggered amount of debris, but these check dams are being gradually to slide down the colluvial deposits. The gully formation is started damaged by the sediments. MNWIDPP has constructed 3 to 4 from the lower part, which is gradually extended toward uphill. meters heights 10 check dams, 5 retaining walls to control debris flow towards the road. These check dams will reduce the Remedial measures: There are two gabion check dams flow velocity and accumulate huge mass of debris and prevent constructed by the CDRO, which has accumulated huge mass the toe cutting in the active slope failures. In addition to these of debris. However, these structures are not sufficient to stabilize civil structures, bio-engineering measures are also being this gully. Therefore, the project has constructed 17 check carried out in the active landslides. This stream seems to be dams and 1 retaining wall in FY 2062/63, to reduce gradient stable; however, it is also necessary to study upper parts of the of the gully and stabilize the gully banks. The construction of stream. additional 5 check dams and implementation of bio- engineering works are going on. Now toe of the banks are 4.4 Gully at Ch. 24+740 more stable than before and gradually stabilizing the gully sides Causes: This gully is located in Bangesal VDC, which indicates and bed of the gully. that the whole area is located in creeping zone. Although there were some instabilities in this gully before monsoon 2003, most 4.2 Gully at Ch. 30+890 of the landslides during that disaster period. The debris flow Causes: This is a newly found gully, which was originated only reoccurred also in summer 2004. At present the landslide area in July 2003. The surrounding of the gully is represented by covers about 20000 Sq. m with 650m long and 75m wide. This unconsolidated colluvial deposits probably during large gully can be divided in major four geological parts: (1) rocky landslide event in the past. The colluvial deposit is 2 to 5 m area, (2) recent debris deposit, (3) colluvial deposit and (4) thick and made from matrix of angular rock fragments and fine residual soil. Among them colluvial deposit has covered about grained and coarse grained materials. The bed rock is exposed 70% of the total area. The rocks are weathered phyllites and only near the road and on the bank of the Trishuli River. At first quartzites. The phyllites are green blue grey when fresh and red small gully was developed in the lower steep slope, which was in weathered condition. The quartzites are impure, micaceous further expanded laterally and progressively towards the upper of greenish grey colour and regularly interbeded with phyllite. moderate slope reaching the ridge area. The main cause of the The colluvial deposit is composed of boulders, gravels and gully erosion is due to the concentrated rainfall in the colluvial clayey silt. Generally, the thickness of the colluvial deposit is deposit. high and reaches upto 6m. Remedial Measures: In the lower wider landslide a 26m height Remedial Measures: Two gabion check dams are constructed cascade and 4 check dams are constructed to safely discharge by the CDRO near the road, which are controlling the debris the rain water storm, slide mass was trimmed and bio- flow to some extent, but these structures are not sufficient to engineering measures like brush layering, grass plantation and stabilize the landslides of the gully, because major landslides bamboo plantation are carried out in this area. In the upper are located far from the road. Therefore, MNWIDPP has gully 18 small check dams are constructed to control gully constructed additional 7 check dams, sub surface drainage and erosion and stabilize the banks. In addition to bamboo, tree one 30 m height cascade. In addition to the civil engineering and grass plantations and brush layering works were also measures other bio engineering measures like; brush layering, carried out in both sides of the gully. Presently the gully is almost grass, shrub, tree, bamboo plantations and palisades are also stabilized. However, some bamboo plantations in the up hill proposed to control the surface erosion in this area. As per the gully and cascade structure in valley side of the road are initial results of 2006 monsoon the check structures are still not needed to fully stabilize this gully. sufficient and need more structures to fully stabilize the landslide. 4.3 Debris Flow in Gaighat Khola (Ch. 18+460) Causes: Three types of failures have been observed in this 4.5 Debris Flow in Khahare Khola (Ch.11+300) stream, these are (1) Rock sliding from right side hill slope, (2) About 160000 cu m of debris was deposited in the vicinity of sliding of colluvial deposits and (3) bed erosion in alluvial the road area by the Khahare Khola in July 2003, damaging deposits. 30 m long bridge of the highway, washing two houses and trucks, blocking the road for several days. In the upstream area The bedrock in this stream is dominated by thin to medium the debris flow has eroded the toe of the banks creating several bedded, fine to medium grained, moderately weathered highly landslides on both banks of the river. As a result huge mass of jointed phyllites with quartzite and intercalation with carbonate debris material are deposited in the lower part of the river beds. The carbonate beds are alterating with phyllite and are clogging the opening of the bridge. usually dolomitic, often siliceous. The runoff water of the hill slope infiltrates into the fractured rock mass increasing the Cause: The Main Boundary Thrust crosses through the pore-water pressure, which has reduced the shear strength of catchment of the Khahare Khola. The upper area falls mainly rock mass and eventually sliding down in the stream. within Lesser Himalayan Metasediment, while lower portion is Moreover, the torrent flow in this steam erodes toe of right bank filled with recent alluvials and debris deposit underlain by Lower hill slope, located in the concave side, which has also triggered Siwalik Tertiary rocks consisting of sandstone mudstone and to slide down the fractured rock mass and residual top soil. siltstone alterations. The banks of the river are made up of Medium to steep hill slopes are covered by 0.5m to 2.0m thick rounded to sub rounded boulders, cobbles and pebbles in a colluvial deposits with silty gravel and boulders. Such surfacial sandy matrix. The boulders are occasionally large up to 3-5m deposits tend to slide down during heavy rainfall due to shear diameter. failure. The alluvial materials deposited on the bed of the khola, containing sub rounded gravels and boulders mixed with Remedial Measures: Seven sabo dams are proposed to silt, are transporting down stream in the form of debris flow accumulate the debris flow and control the toe erosion on the during torrent flow. banks of the river. Among them two concrete sabo dams with 50m 31 (Source: CDRO 8, FY 2004/05) DWIDP BULLETIN 2005 - 2006

long and 5m height area constructed in 2006. In addition to these Table 4. Existing Toe walls in the Trishuli River four spurs are also recommended to divert the flow from the S.N. CH. Structures L H eroding bank. After controlling the debris flow channelization 1 15+030 CM Retaining wall 36.50 6.50 works is proposed near the road head. After construction of the 2 16+900 Gabion Mattress civil structures necessary bio engineering works are to be done to prevent the sheet erosion. 3 17+125 Temporary gabion wall and Anchor 24.30 4.60 4 17+830 Gabion wall 17.00 5.00 4.6 Other Cross Drains studied by MNWIDPP 5 18+700 Gabion wall 10.00 4.00 MNWIDPP has also studied other major and minor cross drains 6 20+350 Gabion retaining wall 8.00 4.00 along the road, which are vulnerable to debris flow on the road 7 20+800 Gabion check dam and recommended for check dams, surface & subsurface 8 21+080 Gabion retaining wall 13.00 5.00 drains, cascades, retaining walls construction and for bio- 9 21+770 CM Retaining wall 5.00 5.00 engineering works. The short-coming of the studies are 10 21+995 Gabion and masonry retaining wall 10.00 4.00 presented in Table. 3. 11 23+500 Construction of safety parapet wall 12 24+600 Gabion wall and gabion mattress 22.00 5.00 Table 3. Problems, Causes and Remedial measures of other 13 26+250 Gabion toe wall 41.00 3.00 vulnerable drains 14 26+960 Gabion check dam 17.00 5.00 Solution 15 27+070 CM Retaining wall 28.00 5.30 S/N Location Problem Cause Remarks Completed To be done 16 27+160 Gabion wall 17.50 5.00 Ch. Landslides and Check dam Almost 17 27+280 CM Retaining wall/ Gabion cascade/ 1 Debris Flow Bio-Eng. 23+500 steep gradient -9 Nos. stable Gabion Mattress Ch. Landslides and Check dam C. dam -2 18 29+325 RCC Retaining wall 15.00 4.50 2 Debris Flow Fairly stable 23+250 steep gradient -4 Nos. Bio-Eng. Ch. Landslides and Check dam C. dam-7 Still 3 Debris Flow 24+300 steep gradient -3 Nos. Bio-Eng.w Unstable Although these structures are functioning well there are still Retain wall - Ch. Down hill Cascade- others vulnerable points that needs some river training works, 4 Scouring by debris 3 Fairly stable 24+600 scoring 30m Bio-Eng. which are shown in Table 5. C. dam-4 Ch. Huge landslide & (DoR-2) C. dam-3 Still Table 5. Endangering points on the Road by the Trishuli River 5 Debris Flow 21+560 rock falls Cute-2 Bio-Eng. Unstable (Dor-1) S/N Chainage Site Condition Severity Proposed structure's Debris Flow & C. dam-9 Rock fall, landslide & C. dam-3 6 Ch. 20+800 Down hill (DoR-3) Still Unstable Length, m Height, m Steep gradient Bio-Eng. scouring 1 15+915 Gravel +Sand Moderate 15 4 Landslides and steep Check dam - C. dam-3 7 Ch. 16+950 Debris Flow Fairly stable 2 17+530 Gravel +Sand Moderate 20 4 gradient 4 Nos. Bio-Eng. Slope 3 18+221 Gravel +Sand High 25 4 Uphill toe cutting by 8 Ch. 13+600 Landslide Brest wall -1 trimming Fairly stable 4 20+699 Gravel +Sand High 20 4 human being Bio-Eng. 5 23+932 Gravel +Sand Moderate 20 4 9 Ch. Debris Landslides and Check Check Still 27+160 Flow steep gradient dam-2 dam-11, Unstable 6 26+165 Gravel +Sand High 22 4 Surface 7 27+071 Boulder +Gravel Very High 30 5 drains, 8 29+905 Gravel +Sand Very High 35 5 Bio.-Eng. 9 17+125 Boulder +Gravel Very High 55 4 10 Ch. Debris Landslides and C. dam-7 Unstable 10 18+980 Boulder +Grave Very High 75 5.5 27+070 Flow steep gradient Bio-Eng. 11 Ch. Debris Landslides and C. dam-5 Unstable 11 23+070 Boulder +Gravel Very High 62 4.5 26+965 Flow steep gradient Bio-Eng. 12 24+600 Boulder +Gravel Very Hig h 70 4 12 Ch. Debris Landslides and C. dam-5 Unstable 13 21+900 Boulder +Gravel Very High 83 4 17+295 Flow steep gradient Subsurfa ce drain Bio-Eng. 5 . RECOMMENDATIONS 13 Ch. Debris Landslides and C. dam-5 Unstable This road was severely damaged by the cloud outburst 17+560 Flow steep gradient Bio-Eng. occurred on 30th July 2003 causing the instabilities at 213 places. Most of the instabilities near the road corridor were Apart from above mentioned studied vulnerable gullies, the already stabilized by the civil and bio-engineering measures project has to study other cross drains, which are still disturbing carried out by Central Division Road Office No. 8. Although the road during monsoon season. These locations are in Das the road seems stable near the road corridor and the road Khola, Jugedi Khola (Ch. 10+550) and in other minor drains is black topped, there are still many places, which are of Ch. 11+650, 11+932, 13+542, 15+000, 15+185, endangered by debris flows and uphill and down hill 15+380, 15+868, 15+965, 20+212, 20+264, 20+770 landslides. The landslides found in the gullies of Ch. and 24+860. 23+760, 24+740, 21+560, 18+420, 11+300, 23+500, 23+250 are very active, where MNWIDPP has 4.7 Toe Cutting by the Trishuli River already carried out immediate rehabilitation works. Among 36 Km road, 25km stretch passes through the left bank However, there are still many gullies which need immediate of the Trishuli River. This river is cutting the banks in most of the river training and soil conservation works. Furthermore, meandering points and in the confluence points of opposite prevention of toe cutting along the Trishuli River is very side tributaries. To control toe cutting and to prevent the important to stabilize the landslides in the valley side of the landslides in the valley sides of the road, the Department of road. In conclusion the stabilization of landslides in the Road has constructed several toe walls at different locations as catchments of the gullies and streams are very important for shown in Table 4. sustainable rehabilitation of Narayangarh Mugling Road. 32