ISSN : 0971-7447

NATURAL HAZARDS IN AN ECOLOGICALLY FRAGILE MOUNTAIN TERRAIN : A CASE FOR THE PINDAR BASIN OF UTTARANCHAL HIMALAYA

Vishwambhar Prasad Sati

Associate Professor and Head, Department of Geography

Eritrea Institute of Technology, P. O. Box 11370

Asmara, Eritrea, N. E. Africa

INTRODUCTION

The characteristics of hazards have a pulsating nature as slow acting and infrequent in source area, intense and catastrophic in other (Haque, 1997). The Pindar basin located in the center of Himalayan Mountain system, which is hazard prone and very sensitive in term of stability of landforms. Cloudbursts and landslides are the common phenomena. The history of cloudburst and consequently flashflood, landslides and landslips depicts that every year heavy rainfall occurred during the monsoon period and the entire region is affected. The major tributaries of the Pindar are worst affected due to cloudburst and landslides that occurs mostly along the course of the perennial streams and roadsides.

The entire basin is ecologically fragile, unstable and less rigid from the originating point to its confluence as it is also with the case of Himalayan Mountain System. The characteristic features of the basin, in terms of fragility, are more pronouns to discuss in the way that lowering the environmental conditions in both, highly elevated reaches and low-lying areas. The process of upliftment of mountain peaks and deepening of the river valleys is continued due to tectonic forces active throughout the basin resulting instability and disturbances in the landmasses. The natural hazards, both terrestrial (earthquakes) and atmospheric hazards (cloudburst, landslides and flush floods), can be seen everywhere. However, the impact of natural hazards increases with increasing elevation. (Swaminathan, 1991; Khoshoo, 1992; Dhar, 1993; Rajgopalan, 1993; Ramakrishnan et al., 1994; Rao, 1994; Qasim, 1995; Joshi, 1996; Valdiya, 1997).

Along with the process of development, in terms of construction of roads and dams using highly explosive measures, the rocks become more fragile and after heavy rainfall, the loosed materials of the rocks wash away and finally the process of landslides and mass movement takes place. In order to describe about the frequency and intensity of the hazards in the basin, it is observed that they are more devastating, intense and frequent. Out of these phenomena, cloudbursts followed by landslides are more prominent along with high frequencies.

The basin is tectonically more sensible and falls under the severe seismic prone region. Already, severe earthquakes have been taken place. The situation is grim in the area and there are about eight cases in the entire basin where due to landslides, many villages were devastated.

1. GEOGRAPHICAL LOCATION

The Pindar basin comprising of 1826.0 km² extends from 30^o N to 30^o 18’N latitude and 79^o 13’ E to 80^o E longitude. It represents the eastern part of the Garhwal Himalaya with elevation ranging between 800 m to 6800 m. River Pindar originates from the ‘Pindari Glacier’ in district Bageshwar (32 km) and flowing an approximate 124 km with its numerous tributaries, confluences into the Alaknanda River at Karanprayag in Chamoli district. The watersheds of the Ram Ganga in the south, the Saryu in the east, the Nandakini in the north and the Alaknanda in the northwest delimit it giving it a distinct socio-geographical identity. The nature of slope is very steep ranging from 60⁰ to 90^0. Somewhere, it is more than 90⁰. Mostly, the landslides are caused either by natural phenomenon or human-induced activities.

2. METHODOLOGY

The study is mainly based upon the collection of primary data. Case studies of two cloudburst-hit areas and various landslides zones have been done in order to facilitate an interpretation of natural hazards. Observations are done after field visits of the entire basin.

3. NATURAL HAZARDS IN THE PINDAR BASIN

As it is already mentioned that the basin is more prone to natural hazards ranging from cloudburst to landslide, rock-fall, flush flood and mass movement, case studies of cloudburst hit areas and landslides zones were done in the following manner:

3.1 Cloudburst

Cloud burst is natural calamity-a-crucial problem, not only because it depletes the natural resources of pivotal importance to the people of the region but also affects adversely in numerous ways. Like deforestation by biotic means, cloud burst is also a major factor contributing to a variety of other environmental problems, which include landslides, floods, soil erosion, loss of human and animal lives, loss of property, siltation and sedimentation, habitat destruction and some times species extinction (Sati and Maikhuri, 1992).

Cloudburst is more devastating and foremost natural phenomenon in this region. It occurs in the highly elevated regions, mostly in the water parting areas. These areas are densely covered by forests, mostly coniferous, but are more instable. Due to dense forest cover and high elevation, rainfall is more intense and occurs in violent form. Along with heavy rainfall, instability of the land and violent nature of stream flowing through the gorges, the process of landslide gets violent, often resulting to hazards and disasters. The basin receives heavy downpour during the three months of rainy season. The average rainfall is about 300 to 400 cm per year. Because, the slopes are very steep, therefore, the major streams and their tributaries flow through deep dissected valleys. Due to high slope gradient and high velocity of running water, the soil erosion is high and, simultaneously, it is cutting both the edges of the slopes. The Pindar river itself becomes violent during the rainy seasons and flows above the danger marks. Many times there are flash floods in the river due to high rainfall. These flash floods were observed first during 1772 and later on in 1992, 1995 and 2002.

Case study of cloudbursts-hit areas

The case studies of two cloudbursts hit areas in the basin are as follows:

(a) Gadanigarh Tragedy

This tragedy occurred when “Danda of Khankrakhet” received intense rainfall followed by repeated cloudburst in the north slopes (59^o) of alpine meadows of Khankrakhet, which is characterized by dense forest of Deodar and Surain. As a result, trees got dislocated in 55^o to 56^o slopes after formation of holes and gullies. In the confluence point of three gullies, land scar was formed at 51^o, which measured 40/30/10 m. Along with the formation of land scar, debris eroded by gullies were accumulated and a small lake was formed. Due to mass wasting, bedrock has been exposed at many places along the stream. During this process, a huge quantity of water along with debris accumulated in more than eleven places along the stream. The last and disastrous reservoir was formed 800 m. above the Maiduni village. The stream flows in the of gorge from the originating point and has confluenced with Khainoli stream near Gadini Bazar, where it turned violent, resulting in huge loss of property of Dadni Bazar as well as loss of cultivated land.

Gadini Bazar (near south slope of Gadini village) is situated in the left flank of Ming Gadhera, a tributary of Pindar River in the middle catchments. The market is located at 78^o 23’ E and 30^o 5’ N. Ming Gadhera is fed by the Khankrakhet (at parting of Pindar and Ramganga rivers) flowing approximately 9 km, with its major tributary Khainoli Gad inlet in the Pindar River near Ming Gadhera Market. This catchment extends between 79^o 20’ E to 79^o 25’ E and 30^o 2’ N to 30^o 38’ N.

Due to this natural calamity, the whole Gadini Bazar has collapsed, in which 18 shops, 13 water mills, one panchakki, two flour mills, 100 m canal and approximately 85 huge trees and seven bridges were included. Fourteen people lost their lives on that ill-fated night. 20 ha of cultivated land (irrigated) located on both the sides of the stream have been fully washed away.

(b) Kaiwar Gadhera Tragedy

Devastated cloudburst occurred on the ‘Patihi’ hills, in the northwest slope of Kaiwer Gadhera in the middle of the Pindar River (Sati, 1993). A three-meter broad gully was formed on the top of the hill, which became violent being 30-50 m broad on the middle course and caused heavy damage of property and lives.

Table 1. Comparative Study of the two cloudburst-hit areas

S. No.	Land features and nature of losses	Gadinigarh tragedy	Kaiwargadhera tragedy
1.	Name of hit area	Khankrakhet hill	Patidy hill
2.	Slope	59^o	80^o-85^o
3.	Height	2800 m (masl)	1700 m (masl)
4.	Lat. and Long.	79^o 23’E and 30^o 2’ N lat.	30^o8’47” N lat to 79^o22’56” E long
5.	Name of affected area	Gadini Bazar	Musudiyar
6.	Slope	21^o	30-35^o
7.	Height	1200 m (masl)	1450 m (masl)
8.	Lat. and Long.	78^o23’ E long and 30^o5’ N lat	30^o8’45”N lat and 79^o22’56” E long
9.	Distance between hit area and affected area	3 km downwards	1 km downwards
10.	Area of Reservoir	800m	200 m
	Losses of property and lives
11.	Agricultural land	20 ha (irrigated)	1 ha
12.	Houses	33	14
13.	Lives	14 (people)	25 (animals)
14.	Forest type in hit area	Devdar and surain forest	Pine forest

Sources: From the survey made by the author.

The affected area is located at east facing slope, 6 km away from Narainbagar service center and extended at 30^o8’46” N and 79^o22’56” E at the height of 1450 m from masl occupying about 8 ha land in the both slopes of a seasonal nala (stream). The affected part is located about 1 km downwards from the cloudburst-hit area. The hit area is located on slope 80^o to 85^o. at 30^o8’47” N and 79^o22’56” E at the height of 1700 m from masl. The local people are engaged with stone mining in this area. The entire region got heavy downpour for two days and there was about 2-diameter cave got formed. Due to heavy downpour, the cave broke and a gully got formed. The distance between affected and the hit area is about 1 km, which is covered by pine trees. Due to steep slope, the frequency of erosion repeated and a gully became bigger in shape and violent. In the downward part, which had almost gentle slope (30^o-35^o), a reservoir of water also got formed, which later broke and damaged 30-50 m land on the both slopes of the nala. Thundering also took place at the same night but its impact was negligible. There was huge debris flow along with stones of huge diameters, which swept away. Heavy loses of lives (animal) and property took place in which 12 buffaloes, 6 oxen and 7 cows died; 7 cowsheds and 2 houses were fully damaged and 3 houses were partially damaged along with crops and croplands. Table 1 shows the comparative study of the two cloudburst-hit areas.

3.2 Landslides

The landslide hazard has become a common feature in the mountain regions of the world (Singh, 1991). Its vulnerability is increasing with an alarming rate due to increasing anthropogenic activities (Singh and Pandey, 1995). The term landslide covers down slope movements of rocks and soil-debris that have become separated from the underlying stable part of the slope by a sheer zone or slip surface. The type of movement, which may include falling, sliding and flowing depends largely on the nature of geologic environment including material strength, slope configuration and pore water pressure (Smith, 1996). Jones (1992) claimed that landslides will become an increasingly disastrous hazard and will draw attention to several types of terrain where the greatest physical threat exists. Constructions of roads and engineering cuts of slopes, which according to Valdiya (1987) are about three to five meter high and four meter wide, produce sizeable volume of debris. Landslides can be seen everywhere in the basin but they are worst affected along the roadside and on the course of the perennial streams particularly of the Pindar river. Recently two major landslides, one in Narayanbagar and other in Harmony, are becoming more intensified. The table 2 provides a comparative description of these two landslides:

Table 2. Comparative studies of two landslides areas

Name of landslide areas	Narainbagar	Harmony
Length	200 m	400 m
Width	300 m	400 m
Elevation	1100 m (masl)	1120 m (masl)
Cause of slide	Left side erosion by Pindar	Headword erosion, slope failure
Consequences	1. Road block during rainy seasons even for more than a month 2. Downward movement of the area including settlements and a temple.	1. Road block during the rainy seasons even for a month 2. Mass movement of slope
Future consequences	The east portion of Kaiwar village may come under its influence	Complete failure of slope
Suitable measures	1. Diversion of road is impossible because there is no suitable site 2. River embankment is also impossible, because river flows in a narrow patch and violent in nature 3. Construction of bridge connecting Narainbagar village with the main road may help to reduce the intensity of landslide. One bridge is already constructed 4. Plantation of suitable species will definitely reduce the intensity of landslide	1. Diversion is possible but heavy investment is required 2. Slope embankment is possible but it is not only a solution 3. Construction of divergent road with taking care of all aspects related with fragility of slope in view 4. Plantation of suitable species will definitely reduce the intensity of landslide

Sources: Compiled by the author

Major landslides in the basin

The landslides in the basin are mostly found in the course of the river Pindar or along the roads. The landslides, which are found along the roads, are more problematic because of roadblocks during the rainy season. The major landslides along the Pindar river are as follows:

(a) Simli Landslide

A landslide is developing on the way to Gwaldom and Gairsain, two kilometer away from Simli service center. There is a bifurcation of road - one goes to Gairsain and other to Gwaldom. There was a small gully developed due to a small perennial stream and in a course of time it took a big shape, attenuated by expansion of roads. Now every year, particularly during the rainy seasons, landslides occur and block roads creating problem for transportation.

(b) Narainbagar Landslide

Narainbagar is a small service center located in two small pockets. One is known Tharalibagar and other is the main service center. In between the two pockets, a landslide zone occurred, which appeared after 1996 due to left side erosion by the Pindar river. There is also a perennial spring. In the recent years, violent landslides occur almost every year. The length of landslide is about 200 m and its width is about 300 m. The settlements on the head of the affected area are now on the verge of getting devastated.

(c) Harmony Landslide

It is one of the biggest landslides of the basin on the course of the Pindar river. It is about 400 m in length and 400 m in width. The slope gradient is 50⁰ to 75⁰ having loose soil. The landslide occurs due to headword erosion and slope failure.

Causes of landslides

The followings are the causes of landslides in this ecologically fragile mountain terrain:

Instability of terrain, because the process of deepening river valleys and uplifting of mountain peaks are continued.
Human induced activities such as construction of terraced agricultural fields, mass felling of trees for fuel, fodder, furniture and other needs and also for construction of roads.
Unscientific measures used for construction of roads such as blasting, cutting of fragile slope, etc.
Heavy downpour and repetition of cloudburst at a time and within a limited geographical area.
Steep slopes and high velocity of running water.
Overgrazing and consequently soil erosion.
Construction of settlement on the instable slopes.
Practice of quarrying.

Consequences of landslides

Heavy losses of lives and property.
Land instability.
Blocking of roads and transportation.
Severe future consequences as a form of mass wasting and sweeping away of settlements and agricultural land.
Stream blocking in the first stage, construction of reservoir and breaking of reservoir and consequently flash floods.

3.3 Rock fall

Rock falls can be seen along the sides of the main road in the basin. The major causes of rock fall are construction of road using explosive materials, instability of rocks, steep slope and high velocity of stream water. During rainy seasons, when heavy rainfall occurs, the soil surrounding the rocks flows along with water due to high run off; consequently, the boulders looses its stability and due to high slope gradient, they fall downwards causing heavy losses. Sometimes they fall upon the settlements, located in the valleys.

3.4 Mass movement

Mass movement, at a large scale, generally occurs due to slope failure and instability of land. The instability of the basin, which is tectonic prone, causes mass movement. Table 3 shows average proportion of natural hazards in the Pindar basin.

Table 3. Average proportion of natural hazards in the basin*

Nature of hazards	Proportion in percent
	Main stream	Tributaries
Cloudburst	50	60
Landslide	30	25
Rock fall	15	10
Mass wasting	03	05
Draught	Nil	Nil
Avalanches	02	Nil

* These figures are estimation by the author after long experience and observation of the region

3.5 Deforestation

Deforestation is also a factor as tree roots add strength to a hill slope by vertically anchoring the soil to rock beneath and laterally reinforcing the slope across zones of instability and weakness (Swanston, 1997). Haigh, (1984) estimated that in general, excavation of one tree destroys 500 trees on the slope. Though, it is man-induced, it becomes natural and results in landslides, landslips and rock falls. This has been seen in the entire basin. This basin is rich in the natural vegetation reservoir and its diversity. The types of plants vary from subtropical to temperate along with vast alpine meadows. Out of the total vegetal cover about 75% is occupied by coniferous forest, in which pine forest dominates.

In the area, the people have two dwelling, i.e., one in the lowland and the other in the highland. During summer they migrate seasonally to the higher reaches with their domestic animals for grazing and rearing animals. These higher reaches are known as Kharaks (alpine grassland). Almost three to four months they remain there and during winters, they return to lowland. Almost every family has a possession on these Kharaks. Due to this practice, forest depletion continually takes place. Furthermore, for firewood need, the people are still dependent on the forest. There are many instances in the basin where landslide occurs due to deforestation. Over burden on the forestland due to human search for cultivated land and construction of settlements caused forest depletion in the entire basin, which gave the birth to landslides and other natural catastrophes.

3.6 Flash floods and droughts

Flash floods are common along with cloudbursts and landslides. They generally occur on the course of the streams during the rainy seasons. Sometimes, they are violent and wash away the low-lying areas. Droughts generally takes place in the valley region, but their impacts are very less.

3.7 Earthquakes

As it is discussed, the basin falls in the tectonic belt and therefore, the tremors of earthquakes have been observed many times during the past. The two recent earthquakes, e.g., Uttarakashi in 1991 and Chamoli in 1998 were worst affecting.

4. VULNERABILITY POSITION OF THE PINDAR BASIN

The dangers lurking beneath the pristine and calm beauty of the basin are hardly apparent when one travels through the region. The natural disasters are in fact become common features that the people have been experiencing at a regular interval of 2-3 years. While there is the awareness of the dangers that the hazards could have in the mountains, recent trends of increased occurrence of the hazards have concerned the authorities and alarmed the villagers. The risk increases because of the increased population and unplanned settlements. It is easy to see why heavy rains cause so much destruction to life and property; the settlements are in a slope sometimes precariously perched over the only available flat land in the hills. Deforestation, as the local people understand, is linked to soil erosion and landslides but there is little they can do to prevent it.

CONCLUSION

Earthquakes, cloudbursts, landslides, flash floods, etc., are the disasters, which may not be stopped. But, the intensity of damage due to the occurrence of these phenomena can be reduced after adopting several measures. These measures are as follows:

It is very difficult to predict the actual occurrence of landslides. Yet there are certain signals like forecasted heavy rainfall. Seismic activity combined with landslide vulnerability can predict the estimated time and possible consequences. The community has to be trained to recognize the signals and act upon it.
A warning system to relay information about landslides could be placed in the settlements to help quick evacuation.
Public awareness programmes for people on causes and effects of landslides, climactic conditions that lead to landslides would be an extremely effective measure to prevent damages.
Preparation of landslides hazard maps for locating areas prone to slides could probably be the first step for mitigation and prevention of damage in landslides. For this, information related to past landslide events – the history, topography and bedrock data and aerial photographs could help in preparing the hazard maps.

5. Other important factors to be studied are water pressure, the climatic changes, soil types, etc. This may involve relocation of settlements of certain hazardous pockets. Restrictions may also be placed on building activity on the landslide areas.

6. Certain policy level interventions may be necessary for prevention of landslides. This would involve more investment in erosion control, maintenance of agricultural and forest land.

7. It may, on the basis of observations made above, be concluded that the cloudburst has triggered debris slides along the tension cracks and caused casualties and damages on the large scale in the catchment areas should not be allowed to be obstructed and house construction activities in the interior of hills regulated.

8. Since the whole of Himalayan region is declared earthquake prone, houses should be allowed to be built only in accordance with the earthquake resistant designs recommended by the Central Building Research Institute, Roorkee.

9. A safe distance from each side of the nala, according to the situation, should be left and no cultivated fields and houses made on the said distance.

10. All landslide affected zones should be left for natural stabilization and no human activities be allowed in such landslide affected weak slopes till they are fully stabilized in due course of time.

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