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DESCRIPTION
Seminar Session 15
Citation preview
Peak Discharge Estimates of Glacial Lake Outburst Floods
Dr. A K LohaniScientist FNational Institute of HydrologyRoorkee
THE STUDY AREA
DEM of the study area
Glacier mapping
Preparing inventory of glacial lakes
(Mapping of lakes, numbering in binary tree format, finding area, locations, elevetions etc.)
Identification of potentially dangerous lakes
Selecting most dangerous lake for final modeling(The potentially dangerous lakes are further assessed on the
basis of distance from outlet, volume, growth etc)
Finding GLOF simulation parameters for most dangerous lakes(Cross sections from lakes to outlet, several dam geometry parameters,
volume, dam break parameters, hydrological parameters)
MIKE-11 simulation of GLOF(Making the model and running it using extracted
parameters and collect the final result)
NDSI image
Overlay analysis with
glaciers
Proximity analysis with other lakes,
Area thresholding
Slope mapCreation of data base
(Preprocessing of satellite data, preparing drainage, slope and elevation maps)
MAPPING CLEAN-ICE GLACIERS
Clean-ice glaciers can be mapped automatically using
multispectral images using NDSI approach.
NDSI uses the high and low reflectance of snow in visible
(Green) and shortwave infrared (SWIR) region respectively
and it can also delineate and map the snow in mountain
shadows. The equation is given below:
NDSI = Visible band – SWIR band / visible band + SWIR band
Glaciers in the study area
)2()NIRGREEN()NIRGREEN(NDWI
GREEN is a band that encompasses reflected green light and NIR represents reflected near-infrared radiation
The selection of these wavelengths was done to : (1) maximize the typical reflectance of water features by using
green light wavelengths(2) minimize the low reflectance of NIR by water features; and (3) take advantage of the high reflectance of NIR by terrestrial
vegetation and soil features.
Normalized Difference Water Index
IDENTIFICATION OF GLACIAL LAKES
S. Number Lakes Class Lat-long Area (Sq. Km.)
Distance from the outlet (km)
1 140 Moraine dammed
27 54’ 53.26”88 12’ 04.89”
1.167 160.553
2 28 Moraine dammed
27 55’ 15.53”88 09’ 51.53”
0.689 165.496
3 27 Moraine dammed
27 53’ 44.32”88 11’ 33.33”
0.130 164.23
4 38 Moraine dammed
27 56’ 54.73”88 18’ 30.40”
0.279 151.814
5 41 Valley 27 56’ 46.32”88 20’ 02.47”
0.517 149.502
6 51 Moraine dammed
28 00’ 26.98”88 29’ 50.13”
0.380 155.366
7 21 Moraine dammed
27 51’ 14.76”88 14’ 40.23”
0.218 159.854
8 19 Moraine dammed
27 49’ 34.76”88 15’ 22.96”
0.372 161.673
9 17 Blocked 27 49’ 08.11”88 15’ 22.96”
0.100 161
Table: Most vulnerable lakes detected in the basin
10 8 Moraine dammed
27 32’ 01.48”88 05’ 15.33”
0.264 88.054
11 58 Moraine dammed
28 00’ 59.42”88 33’ 56.00”
0.201 150.304
12 59 Valley 28 00’ 32.65”88 34’ 33.65”
0.198 149.905
13 69 Moraine dammed
27 58’ 26.32”88 37’ 07.00”
0.559 145.051
14 70 Moraine dammed
27 57’ 36.55”88 39’ 05.07”
0.163 147.719
15 65 Moraine dammed
28 01’ 35.08”88 42’ 58.63”
1.044 166.982
16 63 Blocked 28 00’ 34.95”88 42’ 16.28”
0.805 169.569
17 61 Moraine dammed
27 59’ 34.95”88 49’ 18.78”
0.157 178.056
18 107 Moraine dammed
27 51’ 56.13”88 52’ 12.84”
0.150 132.789
Table: Most vulnerable lakes detected in the basin
Fig. : Area of the lake
Fig. : Graph showing distance from the outlet of various lakes
Fig. : Graph showing percantage change in area since 2009
Lake-140
Change in area
28.66%
Lake 140 Extent changes
Longitudinal
shift
Lateral shift Change in
area
303.66 m 66.03 m 28.66%
Lake Parameters
VolumeMm3
Depthm
Breach invert level
m
Breach formation
timehours
Breachwidth
m
4.293 37 28 3.9 76
GLOF Hydrograph at selected Site considering 50 m breach width with side slope 1:1
GLOF Hydrograph (including 100 year flood ordinates) at selected Site considering 72, 76 and 80 m breach width
with side slope 1:1
W72 W76
W80
Flood peak due to glacial lake outburst
Breach Depth Side SlopeTop
breach width
Flood at Lake Site
m3/s
Flood at Project
Sitem3/s
24 1.00 50 2611.14 1766.7124 1.00 72 5237.5 2376.224 1.00 76 5237.5 2482.824 1.00 80 5237.5 2604.9
CONCLUSION
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