1
Majurmarg-60 Panipokhari, Maharajgunj, Kathmandu ,
Nepal
2 Department
of Mines and Geology, Lainchaur, Kathmandu , Nepal
Abstract
Influx
of people from the villages to the cities to look for the jobs, education,
business, health care etc. are the main causes of fast growing and haphazard
expansion of cities in Nepal. Rapid population growth, uncontrolled
urbanization, haphazard development of infrastructures and their poor
management and unsystematic exploitation of natural resources are the major
causes of natural and human induced disasters and environmental degradation in
urban areas. Scarcity of treated water for drinking and poor sanitation
resulted frequent outbreak of communicable diseases that endangering public
health. Construction of non-engineered houses and use of low quality
construction materials without following the National Building Code are the
major causes of collapse of residential buildings even in the earthquake tremor
of low intensity.
Department
of Mines and Geology has already prepared Engineering and Environmental
Geological Maps (1:50,000/ 1:25,000 scale) of fast growing cities like
Katmandu, Pokhara, Butwal, Hetauda, Dharan, Biratnagar, Bhairahawa, Lumbini and
Birendranagar with a view to provide basic geo-scientific information required
for urban planning, infrastructure development planning, land use planning,
environment protection and disaster mitigation. These maps furnishes data on
geology, topography, land use pattern, settlement and industrial areas, natural
resources, infrastructures, water sources,
sanitary landfill sites, natural heritage etc. Areas endangered by
natural hazards are marked by standard symbols and the risk for human lives,
properties and infrastructures are identified and categorized as high, medium
and low hazard/ risk. All geologically related environmental issues are
identified.
The
engineers, planners, decision makers and donors who are involved in
infrastructure development works, disaster management and environment
improvement projects can integrate available geo-scientific information and
make multiple use of these maps to locate geologically safe ground and
environmentally sound areas for new settlement, selection of suitable waste
disposal site, industrial area development and also look for construction
material required for development works in urban areas to minimize the risk of
hazard and protect the natural environment.
Introduction
Department
of Mines and Geology (DMG) has started to prepare Engineering and Environmental
Geological Maps of major and fast growing cities under the Nepal/ German
Technical Cooperation since 1986. It has published first such map of Kathmandu Valley
and Pokhara Valley Pokhara Sub-Metropolitan City
The
prime objective to prepare Engineering and Environmental Geological map of fast
growing cities was to provide basic as well as specific information on ground
stability condition of the soils/ sediments/ rocks present in the area and
explain their engineering properties and provide geoscientific information
required for a better land use and urban development planning and
infrastructure development planning; identify hazardous/ risk areas and
recommend precautionary measures; identify various types of natural resources
available in the area and geological sites of natural heritage; locate drinking
water sources, recharge areas and their quality; identify all types of
pollutants responsible for water, air and ground pollution; and recommend
suitable measures for environment protection
The
methodology applied to prepare such maps is literature review at the initial stage
that includes review of existing reports, maps, research papers and collection
of existing data on geology, geomorphology, hydrogeology, engineering geology,
seismicity, hazards and environmental studies. Aerial Photos and Landsat Images
are interpreted and additional information has been incorporated in the maps. It
is followed by field visits/ ground survey, geological and hydrogeological
investigations and checking all types of sediments/ soils and the rock types
and their engineering properties. SPT and Grain size analysis were performed to
supplement the existing data. All these data are transformed into digital
database using GIS in ARC/INFO format and processed using Window driven ArcView
software. Cartographic works are done with the help of FreeHand program. Maps
are produced in multicolor line works using special plotter. Legends and
indexes are prepared in a format that is easily understandable even by non-geologist.
GIS with ARC/INFO is applied for all types of data storage, data processing and
plotting of the coloured map. All such GIS data layers are documented in standardized
form and preserved. In the map the colours for different geological units are selected
according to the standard international practice as practicable. The colours together
with letter symbols are applied for each lithological unit to make easy to
readers. Similarly standard graphic symbols and patterns are expressed in the
map as far as possible and practicable. Topographic contour lines, drainage
patterns and all other features are taken from existing digital data of topographic
maps (Toposheets at 1:25,000/ 1:50,000 scale). Rivers, lakes, roads, foot
tracks, height points, historical monuments, cultural heritage, settlements,
hospitals, open grounds, etc. are indicated by standard symbols.
General Geology
In
most cases bedrocks are exposed mainly in the hillocks, river cut sections and hill
slopes around the valley. The valley is filled with the fluvio-lacustrine
sediments (in Kathmandu ), Glacio-fluvial
deposits (in Pokhara), as river fan deposits (in Dharan and Butwal) and fluvial
deposits (in Bhairahawa, Lumbini and Biratnagar) of Quaternary age. The
thickness of the valley fill sediments varies considerably (e.g. in Kathmandu from 78m to 549m, and in Bhairahawa >1000m).
General geology, geological structures, rock and soil types are identified, their
engineering properties are described briefly in the legend of the map (Fig.1). Some
active faults and thrusts identified in the field are drawn on the map. Geological
units/ formations like unconsolidated loose sediments (e.g. alluvial, colluvial
and residual soils) and consolidated sediments like young sedimentary deposits/
Formations and different types of bed rocks are identified and named on the
basis of their mineral content, grain size, texture, structure and genesis. All
geological units are separated from each other by standard colours, line
patterns and letter symbols. Field survey also enabled to map the old and
recent landslides and delineate the areas of potential instabilities on the
hill slopes that endangered the area. Geological traverses covered the hill
slopes, mountains, and the valley floor areas to furnish information on geology.
Engineering and Environmental Geological Map
The
Engineering and Environmental Geological Map (an example Fig.1) include
information/ data on geology (ground condition, soil/ rock types), topography,
slope, land use pattern, existing and proposed settlement areas, industrial
areas, natural resources, infrastructures
like existing road networks, airport,
water sources, water quality, waste disposal sites/ sanitary landfill sites
etc. However, detail studies specific to the site, structure and land use is
essential prior to make the final decision. Areas endangered and affected by
natural hazards with risk for human life, properties and infrastructures are
identified and categorized as high, medium and low hazard/ risk. Natural
resources like minerals, water, forests are identified. Natural heritage and
geologically related environmental issues are also identified. Areas prone to
various geo-hazards like landslides, land subsidence, sinkhole, block falls,
gully erosion, and flood are marked by standard symbols and hatched lines.
Urban
settlement areas and industrial areas are shown by inclined double cross
hatching and straight double cross hatching respectively on the map (Fig.1).
Cultural heritage and historical monuments like Temples
Fig.1: Engineering and Environmental
Geological map of Dharan Area (published by DMG in 2009).
geotechnical
properties are presented. The legend also helps to the map readers and users in
interpreting and deriving the various types of information. However, the map
and the information contained there in cannot replace the detail site
investigation procedure that is essential for the specific purpose of
infrastructure design and construction.
Geological Hazards and Related Environmental Problems
The
areas susceptible to different types of hazards and risks are identified on the
map. Geologically hazardous areas and type of hazards are indicated by standard
symbols. The degree of risk/ hazard is directly related to geology, sediment
composition, degree of compaction and cementing material, engineering
properties of the rock/ soil, topography, slope, climatic condition etc. Risk
and hazard pertinent to the hill slopes due to landslide, rock fall, and gully erosion
are indicated in the map. Similarly the areas susceptible to different degree
of liquefaction hazard and the areas prone to flood hazard, low bearing
capacity and different categories of subsidence hazards are also delineated. Common
geological hazards related to infrastructure development and environment are
identified and briefly described. Low bearing capacity areas are susceptible to
land subsidence and differential subsidence due to the presence of saturated sediments
like lacustrine soft clay, silty clay, black clay and peat. Soil tests (SPT and
grain size analysis) are performed to identify the low bearing capacity areas. Among
them Kalimati Formation and peat of Lukundole Formation (in Kathmandu )
are vulnerable to subsidence. In the map these areas are shown in inclined red
lines (hatchings). Over extraction of ground water in Kathmandu
has also made some area susceptible to ground subsidence. Heavy construction
works in such ground requires detail investigation of the ground and special
foundations like strip or mat or pile foundations require for specific type of
building construction.
Almost
all the low lands by the sides of the rivers are prone to flood hazards. It is common
in Terai Plain and some parts of mid valleys and dune valleys. Due to blockage
of natural flow of river water some parts of western Terai frequently get
flooded during monsoon season. Flood and landslide of 1993 in central Nepal Tribhvan
Highway Kathmandu and Hetauda were also affected by
this disaster. In the map river flood plain areas are shown by symbols/
hatchings. The land of such category is not suitable for settlement and
construction of heavy structures. However, such areas can be used for dry and
wet cultivation, green belts, development of open spaces for recreation etc.
Such area could be potential for ground water.
Landslide
and flood hazards are the common geogenic hazard in Nepal
Fig.2: Srawandanda Landslide Disaster destroyed 37 houses in Jyotinagar, Butwal (1998)
3(a) Before 1934 Earthquake
3(b) After
1934 Earthquake
Fig.3:
The
earthquake catalogue of Nepal Kathmandu valley.
Because
of location of Nepal in the
central part of the seismically active Himalayan belt almost all parts of Nepal Nepal Kathmandu is ranked as one of the
world's most vulnerable cities for an earthquake disaster (JICA, 2002). Almost
all the fast growing cities are located by the side of rivers on the valley
fill sediments or on alluvial fan deposits which are loose and saturated with
water as a result the chances of liquefaction during earthquake are very high. The
Kathmandu Valley Earthquake Risk Management Project (KVERMP, 1999) has
predicted that an Earthquake similar to that of 1934 would cause 40,000 deaths
and 95,000 serious injuries and almost 60% of the infrastructures will either
be damaged (40%) or destroyed (20%). Butwal, Dharan, Hetauda, Bharatpur, Birendranagar,
all are very near to Main Boundary Thrust (MBT) and Butwal and Dharan (Fig.1)
are also close to Main Frontal Thrust (MFT). Both thrusts (Fig1) are still
active, that is why the chances of EQ disaster are very high in these cities. Therefore,
buildings and other major constructions in all these fast growing cities must
strictly follow the National Building Code of Nepal (BCDP, 1994) and national EIA
guidelines in order to take into design consideration.
Sinkholes
and land subsidence hazard are common in almost all types of calcareous valley
fill sediments in Pokhara
Sub-Metropolitan City Seti River Seti River
Fig.4: Damaged
Fig.5: River Bank Scouring and damage of Protection walls in Tinau River, Butwal
Siltation and eutrophism is highly affected the Phewa Lake Phewa
Lake , Seti River
Natural Resources
Natural resources like Minerals, Water and Forest are specially dealt with during mapping. All the
existing mineral resources such as mines/ quarries of construction materials (limestone,
marble, diatomite, lignite, block stone, building stones etc.) and river gravels
(boulders, gravel, sand, silt, clay) are shown by standard cross hammer symbol
in combination with one or two letter acronyms indicating the different
commodities. Haphazard mining and over extraction of sediments in the river
course has resulted river bank collapse and flooding during monsoon and improper
location of stone crushing plants are deteriorating the environment. Sources of
surface water (e.g. rivers/ streams/ lakes/ ponds, springs) and ground water
are marked by standard symbols on the map and their quality determined after
chemical analysis are presented in the report. In many cases river and lake
water are contaminated once they inter into the city area due to direct
connection of sewerage drains and dumping of all types of waste material in the
river beds. Rivers of Kathmandu are highly polluted and water is not usable for
household uses at all. Forests are the areas
for soil and water conservation and they are delineated in the map by green
horizontal hatchings or by typical symbols occasionally with boundaries. Deforestation
by human encroachment is the common problem in almost all the near by
settlement areas. Therefore, restriction is imposed to cut the trees for wood
to construct houses, fodder, firewood etc. Once reforestation campaign is
lunched and the existing forests are converted to community forest
deforestation activities are fairly controlled in Nepal
Use of Engineering and Environmental
Geological Map in Infrastructure Development Planning and Its Limitation
The
Engineering and Environmental Geological map provides basic guidelines and deliver
the primary geoscientific information that are important and useful to the
planners, engineers, decision makers, managers, lecturers of Engineering and
Geotechnical Institutions, and other user. It serves as an important database required
for regional and urban planning, infrastructure development planning,
structural design, land use planning, disaster management, environment
protection, identification of sites for construction materials and drinking
water sources. However, detail studies specific to the structure and land use
is essential prior to make the final decision. It is also useful for obtaining
the general information about the present status of the land use pattern,
general classification of the ground condition for all types of civil
constructions, potential areas for natural resources, waste disposal sites, environmentally
degraded and hazardous land and other areas requiring protection measures.
The
planners, decision makers, engineers involved in infrastructure development
works, environment improvement project workers and disaster management
specialists can make multiple use of these maps especially to locate
geologically safe ground and environmentally sound areas for new settlement,
industrial area development, sanitary landfill site, sewage treatment plant,
recreation centers and public parks, cultivated land, and also look for
construction materials required for development activities.
It
is a reconnaissance type map which is prepared at regional scale (1: 50, 000 or
1:25,000) with a view to give regional picture. As a result, it has some
limitation as specific details such as bearing capacity of the soil (sediments)
of the particular site, geological age of individual units and location of all
active faults etc. could not be included at this stage. Regular upgrading of
the map with additional information and printing of revised version (new
edition) is necessary.
Most of the low lands are suitable for paddy and
sloping dry lands for wheat, maize, millet crops, fruit farms, tea garden, reserved
forest etc. Agricultural/ cultivated lands are not delineated in the map. Protected
forest areas are well demarcated with symbols and boundary lines. Except
temporary sites existing, abandonment and proposed sanitary landfill/ waste
disposal sites are shown in the map by standard symbols. Only low permeable
areas such as fine grained silty clay, clayey silt and peat bed and old clay
mine burrows are suitable sites for waste disposal. Detail site investigation
specific to waste disposal is required for final selection.
Open spaces like public parks, playing grounds and
recreation centers are very important places for relief operation in case of
any natural calamities like earthquake, flood and other emergency situations. Therefore,
due importance is given to such areas and delineated in the map. Location of
general utility service stations for electricity, water supply, ropeways, road
networks, airport, fuel storage sites, hospitals, police stations, army camps
etc. are marked in the map so that one can easily located the place to get
services. Cultural heritage and historical monuments like Temples
Geo-Environment and Pollution
Improper locations of some industries like cement
factory in Hetauda; brick kilns, stone crushing plant and stone quarries in Kathmandu
valley; stone crushing plants in Butwal and along the road sides; carpet, garment,
leather factories (Fig.6) and chemical industries within the core city area are
the main sources of air, water and ground pollution. Similarly discharge of
municipal waste, industrial effluents and toxic chemicals directly into the
river, and haphazard dumping of solid waste by the side of the river/ flood
plain (Fig.7), direct connection of sewerage drains to the rivers etc. have
created river water pollution in most of the cities in Nepal
Fig.6: Industrial
effluents from leather factory, Fig.7: Haphazard dumping of
Municipal waste in
a source of Pollution in Biratnagar Bagmati
Riverbed, at Kathmandu
9. Conclusion and Recommendation
The
Engineering and Environmental geological Maps of fast growing cities in Nepal
The
map also provides the basic information on the soil/ rock types, their
engineering geological properties, ground condition and it can be used for
preliminary planning of foundation type for different constructions/
structures. It also depicts the hazardous areas such as landslides, flood,
sinkholes and land subsidence prone areas, low bearing capacity areas etc. that
makes aware of Planners, Engineers and others to plan and design the
structures.
It is recommended to integrate all available
geoscientific information and make multiple uses for the development activities
in the fast developing urban areas to minimize the risk of hazard and protect
the natural environment. Specific types of
foundations for civil construction in different types of sediments/ soil are also
recommended.
The Government/ Municipalities must enforce the
National Building Code of Nepal (BCDP, 1994) and strictly follow the national
EIA guidelines in all types of construction and other development works in the
city areas. It is a part of pre-disaster preparedness.
Natural resources, Historical monuments and Cultural
heritage are the important wealth of the country and valuable culture must be
protected from the environmental degradation.
All the industries and industrial areas/ industries,
brick kiln, stone crushing plants which are located in core city or close to
the settlements must be shifted far away from the city area and waste disposal
sites near the airport must be closed to avoid pollution and possible birds
strike problems.
Acknowledgement
The
authors are grateful to Mr. S.P. Mahato, Acting Director General, DMG for
giving permission to get all the related information and necessary reference
materials from DMG library to prepare the paper. The authors wish to
acknowledge Ms. Afia Akhtar, Convener, International Conference on Geoscience
for Global Development (GeoDev) and Director General, Geological Survey of
Bangladesh, and all the Members of the Organizing Committee for providing free
Registration (accommodation and local transport) to participate in the
Conference; and Nepal Academy of Science and Technology (NAST) for providing
partial fund to Mr. Kaphle for his international Travel (Kathmandu - Dhaka -
Kathmandu) to attend the Conference and present this paper.
References
BCDP (1994): Nepal
National Building
Code and Seismic Hazard Mapping and Risk Assessment for Nepal Nepal ; prepared
by BWI, SILT, and TEAC, Golder Associates, URR, Kathmandu .
DMG
(1998); Engineering and Environmental Geological maps of Kathmandu
Valley , and Pokhara Valley Germany
DMG
(2008), Engineering and Environmental Geological Map of Butwal Area; Published
by DMG.
DMG
(2009) Engineering and Environmental Geological Map of Dharan Area; Published
by DMG.
Japan
International Co-operation Agency (JICA, 2002); the study on earthquake
disaster mitigation in the Kathmandu valley,
Kingdom of Nepal Nepal
Kaphle,
K.P. and Joshi, P.R. (1998), Report on Engineering and Environmental Geological
Map of Kathmandu Valley; DMG unpub.
report. 38p.
Kaphle,
K.P. and Koiral, A. (1998), Report on Engineering and Environmental Geological
Map of Pokhara Valley
Kaphle,
K.P. and Jnawali, B.M (2002) Environmental Geological Assessment of Butwal
Municipality Area and its Surroundings,
Western Nepal ; Proceedings of 4th South Asia
Geological Congress (GEOSAS-VI), pp417- 428.
Kaphle,
K.P. (1998) Report on Environmental Geological Assessment of new infrastructure
development in Pokhara Valley. DMG
Unpub. report 43p.
Kaphle,
K.P. and Nakarmi, M. (1997): Comprehensive Database (Basic Information) on Disaster
Management Capabilities in Nepal Nepal
KVERMP,
(1999), The Kathmandu Valley Earthquake Risk Management Action Plan; A product
of Kathmandu Valley Earthquake
Risk Management Project implemented by NSET-Nepal and Geohazard International, USA (GHI), 37p. unpublished report.
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BCPR (2004), Reducing disaster risk: a challenge for development; A global
report of UNDP, 146p.
WDR (World Disaster Report - 2005), International
Federation of Red Cross and Red Crescent Societies, 251p.
Figure Caption
Fig.1:
Engineering and Environmental Geological map of Dharan Municipality
Fig.2: Srawandada
Landslide Disaster destroyed 37 houses in Jyotinagar, Butwal (1998)
Fig.3: Bhaktapur Durbar Square
Fig.4: Damaged
Highway Bridge
over Seti River
Fig.5: River
bank scouring and damage of protection walls in Tinau River
Fig.6:
Industrial effluents from leather factory, a source of Pollution in Biratnagar
Fig.7: Haphazard dumping of Municipal waste in Bagmati
Riverbed at Kathmandu
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