IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
  
  
  
2001 and srivastava et al 2000). Interestingly, huge landslides 
were created by earthquakes and or heavy rainfall resulted in 
the formation of large artificial lakes at these locations and 
subsequent flooding on the downstream side of the rivers. The 
Decision space tool has been used for two case studies namely, 
Landslide Hazard zonation (LHZ) Mapping & locating suitable 
water harvesting sites for Pithoragarh area, Uttaranchal and 
Alwar district in Rajasthan states respectively at ADRIN 
(Prasada Raju et al 1999; Prasada Raju et al 2001) 
2 DATA SOURCES 
Temporal satellite imagery comprising IRS-1C/1D PAN, LISS- 
III, IRS-1A/1B LISS-II and Radarsat imagery were used as 
primary source of inputs. Whereas SOI toposheets, Geology, 
Soil and other thematic maps were used as secondary data. 
Besides, media reports & Internet information used as collateral 
information. Satellite details like path, row and acquisition date 
and details about map sources, scale, year of publication etc., 
were also presented for each case study separately. 
3 METHODOLOGY 
Satellite data has been registered with 1:50,000 scale toposheets 
to generate geocode/georeferenced products and the same has 
been used for generation of thematic maps such as land use/ 
land cover, landslide-scars, hydrogeology, soil, lineaments 
/structural elements maps etc., Besides, thematic details such as 
road network, settlements, drainage and contour data (for 
generation of DEM's) etc., were extracted from SOI maps. 
Visual interpretation techniques were applied for delineation of 
various thematic layers. The output maps showing landslide 
hazard locations and suitable site locations of water harvesting 
structures etc., were prepared using satellite imagery through 
visual interpretation techniques by the domain experts. These 
maps later evaluated with (those) outputs maps derived using 
Decision Space and was found more than 90 per cent agreement 
between them. Hence, it is suggested that the Decision Space 
can plays an important role in locating favorable/ potential sites 
in water harvesting and landslide hazard (potential) zonation 
maps in cost and time effective manner. 
4 DISCUSSIONS 
In this paper, four case studies covering flooding, landslides 
and water harvesting structures were presented. Two studies 
focused on utilization of temporal satellite imagery in Landslide 
induced flash-floods over the Tsangpo and the Sutlej Rivers, 
while the third study dealing with the delineation of landslide 
(potential) hazard zones near Pithoragarh town, Uttaranchal 
state using Decision Space, and the fourth study emphasize the 
utility of Decision Space in locating the suitable water 
harvesting sites in a part of Alwar district, Rajasthan. The 
Decision Space developed by ADRIN has advantage over 
conventional GIS packages and in that Decision Space 
embodied with advanced computing modules like Analytical 
Hierarchy Process (AHP), Fuzzy Logic & Factor of Importance 
etc. It also incorporates the Experts knowledge/opinion while 
handling the complicated problems in an effective way. The 
Analytical Hierarchy Process (AHP) methodology embodied in 
the Decision Space has been selected for obvious advantages 
associated with the approach. The main advantage associated 
with the AHP method is that a complex problem under study 
will be resolved in simplified logical hierarchical steps (of 3 to 
4 levels and consist experts, parameters and categories). The 
relative importance of each parameter over others will be 
determined through pair-wise comparison of parameters at 
every time. Finally, each cell will be assigned a cumulative 
weightage and the size of the cell is depending upon the spatial 
resolution of the input data used. The output Landslide Hazard 
Zonation (LHZ) map consists 6-8 categories of hazard classes. 
Twelve (12) terrain related parameters such as lithology, slope, 
lineaments etc., were taken into consideration while delineating 
the landslide hazard zones. In another case study, the Decision 
Space was used for locating the suitable water harvesting sites 
in a part of Alwar district; Rajasthan. Subsequently a ground 
632 
truth study has been carried out and it was found that the water 
‘harvesting site locations derived using Decision Space were in 
full agreement with the local terrain conditions. As already 
mentioned, the main objective of the present study is to 
demonstrate the capabilities of Remotely sensed & Decision 
Support systems in monitoring the natural disasters such as 
floods, landslides and also resource inventories like locating 
suitable sites for water harvesting structures through pilot 
studies. 
4.1:A case Study of landslide induced flashflood in the 
Northeast India using temporal IRS-1C/1D Data 
4.1.1 Introduction: 
Incessant rains followed by flashflood on the Siang River 
during11-12 June 2000, as a resultant of overflow of the Tsangpo 
in Tibet, has claimed 26 lives and marooned 55 villages in 
Assam and Arunachal Pradesh states. Low-lying areas of the 
upper Siang district (across the Indo-Tibet border) in Arunachal 
Pradesh were completely cut off from the rest of the state. A 
hanging bridge recently built at a cost of Rs.50 crore by the 
General Reserve Engineering Force was washed away in Geling 
circle. Besides, infrastructure including communication network, 
bridges, power, and water supply lines was badly damaged. 
Floodwaters of the Siang River increased the water levels in the 
Brahmaputra and inundated a number of villages in upper and 
lower Assam. The ever-widening Brahmaputra River receives 
water from various tributaries of the mountainous Tsangpo 
flowing through Tibet. The recent flood was the result of a 
breach in an impounded artificial lake across the Yigongzangbu. 
River, in Tibet. A huge complex landslide originated in the 
valley of Zhamulongba stream, blocked the flow of 
Yigongzangbu River at 30°1440” N latitude and 96°58*15” E 
longitudes. The Yigongzangbu is a major tributary of Yarlung 
Zangbo (Brahmaputra) River and meets the later at the great “U” 
turn bend near Namcha Barwa. The landslides created a large 
impound of water body in the up streamside and subsequent dam 
breach resulted in the flashflood over the Tsangpo (Brahmaputra) 
river during 11-12 June 2000 in the states of Arunachal Pradesh 
and Assam. An attempt has been made here to locate and map 
the extent of landslide on the Yigongzangbu River, using 
temporal satellite imagery of IRS-1C/1D PAN data (pertaining 
pre as well as post landslide event). The flood extent was 
delineated and results of the same are presented (in Fig.1 & 
Table-1A and 1B). 
4.1.2 Data used: 
A) Satellite Imagery 
Satellite/sensor Path/row Acquisition date 
IRS-1C-PAN P112-R050 Feb 14, 1998 
IRS-1D-PAN P113-R050 May 05, 2000 
IRS-1C-PAN P112-R050 Jun 18, 2000 
IRS-1D-PAN P113-R050 Dec 16, 2000 
B) Maps: ONC & TPC maps on 1:10,00,000 & 1:5.00.000 scales 
C) Media Reports-Newspapers/TV coverage 
D) Website: www. Expediamaps.com 
4.1.3 Objectives of the study: 
The main objective of the study is to map/analyze the extent of 
damage caused due to landslide on April 2000 and its induced 
flashflood effect on the Yarlung Zangbo (Brahmaputra) river in 
the Northeastern India using temporal IRS imagery. : 
4.1.3A Zhamulongba River Basin Location: The Zhamulongba 
River basin is extended between 30°10’ to 30°14'40” N Latitudes 
and 94°56°30” to 95°00°30” E longitudes. It is a tributary of the 
Yigongzangbu River and located at a distance of some 350Km 
East of Lhasa (Fig.1) 
4.1.3B Landslide and its impact :On 9 April 2000, a huge 
complex landslide occurred in the valley of the Zhamulongba 
stream and about 300 Million cubic meters of displaced debris,