This is the second part of the article on remote sensing and GIS dealing with the applications of remote sensing and GIS in civil engineering. The previous article was aimed at letting you know 'what remote sensing and GIS means'. Because only after knowing that, we can learn about their applications in civil engineering.
Regional
Planning and Site Investigations
|
Site
investigations in general require topographic and geologic
considerations. Remote sensing data permits such an assessment. In case
of dam site investigation, information on topography is essential.
Geological consideration involves the different soil and rock types and
physical properties.
|
In
selecting river-crossing sites for bridges and pipelines, an important
consideration is the stability of slopes leading down to and up from the
water crossing. Such slopes include riverbanks, terrace faces and valley
wall. History of river erosion and sedimentation would give clues needed
for locating the sites where scour is likely to occur. High spatial
resolution satellite data with stereo vision capability can facilitate
depth perception in the above said investigations and also for regional
planning of large commercial airports, harbors, industrial towns and
recreational sites. The hydro geological and geomorphologic information
along with geological structures derived from satellite data are very
useful in sitting the ground – water bore holes.
|
Terrain
Mapping and Analysis
|
Assessment
of the performance of the terrain for specific developmental activities
can be made through terrain evaluation. For this, terrain information
can be acquired from RS data and by generating the Digital Terrain Model
(DTM). A DTM is an ordered array of numbers representing the spatial
distribution of terrain characteristics stored in a computer so as to
enable the determination of any quantitative data pertaining to terrain.
DTMs facilities investigation of a number of alternative horizontal and
vertical alignments of canals, roads, pipelines or corridors for any
such applications. In engineering construction like dam, the knowledge
of material comprising the terrain is essential for proper planning,
location, construction and maintenance of engineering facilities. For
computation of hydro graph parameters like peak runoff rate, time of
concentration and time to peak, the height and slope information derived
from Digital Elevation Model (DEM) are useful.
|
The
information on regional engineering soils is essential for general
planning and site evaluation purposes. High spatial resolution satellite
data can be analyzed to delineate various landforms, mapping of soil
classes of significance to engineering construction, delineation of
landforms – engineering, soil relationships and grouping of landforms
with various physio graphic setting or terrain associations.
|
Remote
sensing based inventory of construction material such as boulders,
quarry rock, sand – clay mixtures etc., would help to locate suitable
sites of construction materials for building up of water resources
engineering projects like dams, bridges, etc., across the rivers.
|
Water
Resources Engineering
|
By
analyzing multidate RS data, it would be possible to monitor the effects
of dam construction. Remotely sensed data of pre and post dam
construction can reveal the forest and other land at different water
levels. This would also help in preliminary investigation of finding
suitable areas for human resettlement.
|
To
study the feasibility of inter basin transfer of surplus flood flows, RS
data can be cost effective. In large area reconnaissance studies,
various technically feasible and economically viable alternatives in
locating surplus flow diversion routes to water deficient basins can be
arrived at. Also, reservoir sites to store the surplus flows in these
basins could be identified. Such projects of large dimensions require
considerations of land use / land cover, soil and geological mapping,
terrain evaluation, construction material inventory etc. the latter are
derived from satellite remote sensing data of particular resolution
depending upon the scale on which such information is required.
|
The
water storage built in through reservoirs, tanks, etc., are often
reduced due to sedimentation. Remotely sensed data can be used to
monitor the water bodies over time and assess the silting condition. In
case of gauged reservoirs of medium to large sizes, RS data can provide
an assessment of sediment volume and reduction in the capacity of
sediment volume and reduction in the capacity of the reservoir. In case
of small water bodies such as tanks, it is possible to come out with a
list of problematic tanks with symptoms of heavy siltation and loss of
water holding capacity. The condition of tank bunds, fore shore
encroachment, etc., also can be analysed with the help of high spatial
resolution RS data.
|
Characterization
of water bodies in terms of geological, geomorphological, hydro
geological, soil and land use / land cover parameters carried out using
RS data enables conservation of land and water resources. The RS based
input integrated with ground based information through GIS is useful for
broad reconnaissance level interpretation of land capability, irrigation
suitability, potential land use, water harvesting areas, monitoring the
effects of soil and water conservation measures, estimation of run off
and sediment yields and monitoring land use change including land
degradation.
|
The
commercial areas of irrigation projects are fed by different sources of
irrigation like reservoir, tanks, ponds and wells. Assessment of command
areas and crops would be highly useful in water release policy or
conjunctive use of water in the overall project command area. Satellite
data has been advantageously used to obtain such information on surface
irrigation projects.
|
In
case of floods, appropriate flood management work has to be executed to
reduce the damages and utilize the floodwaters. For this purpose
satellite RS provides comprehensive, reliable and timely information (multidate)
on flood inundated and drainage congested areas, extent of damage to
crops, structure etc., river configuration, silt deposits and vulnerable
areas of bank erosion. Flood mapping and damage assessment, using
satellite data, is being done in India for more than two decades.
|
Satellite
derived snow cover assessment is being extensively used as an important
input in snow melt runoff prediction models to assist in multi purpose
reservoir operations. Seasonal snow melt inflow forecasts for Bhakra
reservoir in Sutlej basin are being operationally issued every year with
the accuracy better than 90% to Bhakra Beas Management Board.
|
Town
Planning And Urban Development
|
The
unprecedented growth of urbanization in India has given rise to problems
of housing, sanitation, power, water supply, disposal of effluents and
environmental pollution. Systematic mapping and periodic monitoring of
urban land use is therefore necessary for proper planning, management
and policy making (with the help of RS and GIS optimal master plan for
development and management of urban settlements can be prepared).
|
For
sustainable development of urban agglomeration, optimal urban land use
plans and resources development models need to be generated by
integrating the information on natural resources, demographic and socio
– economic data in a GIS domain with the currently available satellite
data.
|
Transportation
Network Analysis
|
With
the help of high spatial resolution data, mapping of road and rail
network can be accomplished. This facilitates in deciding optimal
routing for transport of construction materials. Even, identification of
village roads is possible in certain cases.
|
Landslide
Studies
|
Landslides
are the most common and recurring hazards in mountainous areas causing
enormous loss of life and property every year. The parameters that
contribute directly or indirectly include litho logy and structure,
landform, slope, aspect, relief, vegetation cover, climatic and human
activities. Information on these aspects can be collected and integrated
for preparing a landslide hazard zone map that can be done through RS
and GIS.
|
