"The measuring and mathematical study of the shape of the earth's surface and the extents of its landforms is known as morphometry"
Several studies on morphometric analysis have been carried out in numerous basins of Kerala. Morphometric analysis of the Ithikkara river basin is studied using SRTM DEM by
There is a great demand for studying and assessing a drainage basin's physiographic features and hydrologic behaviour by utilizing geospatial datasets from various DEMs in recent years. As a result, there is a significant question about the accuracy and sensitivity of these datasets derived from various DEMs.The current study compares drainage features of the SRB derived from four different DEMs: ASTER 30 m, SRTM 90 m, CARTOSAT 30 m, and ALOS 30 m and Survey of India toposheet 1: 50000. and also calculate relative error percentages of DEM-derived morphometric parameters with toposheet.For the effective management of water resources of a basin, it is very crucial to know the water availability of that Basin. Hence groundwater potential zonation map was also created using the weighted overlay analysis. The reason for choosing this study location is that SRB is one of the minor river basins of the Kasaragod district, which has received less attention from other researchers. No literature regarding morphometry is available for reference in the SRB. So, it could be a primary guide for further study in the area to evaluate and manage the Basin's natural resources.
SRB is one of the minor river basins of Northern Kerala. It is geographically located between latitudes 12°31'41.26" N -12°45'15.98" N and longitude 74°55'26.73" E -75°20'55.74" E (
The major portion is enclosed by laterite overlying the peninsular gneiss in the study area. The laterite is a result of weathering of charnockite /Hornblende biotite gneiss. Small patches of syenite, dolerite, and recent tertiary/quarternary alluvial deposits like grit, sandstone, and clay with lignite intercalations are seen as part of the Warkalli formation at the mouth side of the river basin. Basic dykes are also present on the southeastern side of the study area. Some garnitiferous sillimanite gneiss/schist patches are located at the NW- SE side of the Basin. Granite intrusion is present on the southern side of the Basin. Patches of hornblende diopside granulite schist rocks are seen almost in the middle portion of the SRB.It has some lineaments, with NW-SE's primary trend (
Morphometric analysis was carried out in this study using toposheet and GIS methodologies (
Initially, morphometric parameters are calculated from the toposheet. After that, digital elevation models were downloaded from Earth explorer (SRTM 90 m and ASTER 30 m), the Earth data portal of NASA (ALOS PALSAR 30 m) and the BHUVAN (CARTOSAT 30 m) web portal of ISRO, respectively (
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Toposheet |
1:50000 scale |
Nakshe portal of SOI |
ALOS PALSAR DEM |
30m |
Earth data portal of NASA |
SRTM DEM |
90m |
USGS earth explorer |
CARTOSAT DEM |
30m |
Bhuvan web portal of ISRO |
ASTER DEM |
30m |
USGS earth explorer |
For generating a stream network from any DEM, specific steps must be followed in Arc GIS software. The initial step is finding the flow direction corresponding to individual cells. The next step is to determine the accumulated number of cells upstream, denoting watershed derived from fill DEM. The selection of threshold values is essential. Because of drainage density and stream frequency change with a threshold value. Then, stream identification was made based on the cells with a higher accumulation value than the threshold value. Stream order was measured using the hydrology option after generating streams using a typical threshold value for different DEMs (SRTM, ASTER, ALOS PALSAR and Cartosat). Finally, the generated stream was converted into a vector for further calculation with the help of the stream to feature option in the hydrology tool.
The drainage layer calculates fundamental aspects like the number and length of streams, area, perimeter and length of the Basin. Then, the remaining parameters of morphometry were calculated with the help of formulas (
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Linear |
Stream order (u) |
Hierarchical rank |
Strahler |
Stream length (Lu) |
Total Length of Stream |
Horton |
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Mean stream length (Lsm) |
Lsm = Lu ÷ Nu |
Horton, |
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Stream length ratio (RL) |
Rl= Lu ÷ (Lu-1) |
Horton |
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Bifurcation ratio (Rb) |
Rb=Nu ÷ (Nu+ I) |
Schumm |
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Rho coefficient (ρ) |
ρ = RL ÷Rb |
Horton |
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Relief |
Relief ratio (Rh) |
Rh = Bh ÷Lb |
Schumm |
Ruggedness number (Rn) |
Rn = Bh X Dd |
Strahler |
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Areal |
Drainage density (Dd) |
Dd = L ÷ A |
Horton |
Stream frequency (Fs) |
Fs = N÷ A |
Horton |
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Drainage texture (T) |
T = Dd x Fs |
Smith |
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Form factor (Ff) |
Ff = A÷Lb2 |
Horton |
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Circulatory ratio (Rc) |
Rc=4×πA/P^2 |
Miller |
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Elongation ratio (Re) |
Re = |
Schumm |
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Length of overland flow (Lg) |
Lg=1÷(2Dd) |
Horton |
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Here Nu denotes total number of stream segments of order u, Nu+1is used for number of stream segments of next higher order, Lu-1 corresponds to length of stream segments of previous lower order, Lb, A and P is used for length, area and perimeter of the basin, value of
After calculating all the parameters of morphometry relative error percentage of basic parameters with respect to the toposheet was assessed.To manage the water resources of SRB, it is crucial to know water availability. Hence the groundwater potential map is generated using weightage overlay analysisin Arc GIS 10.3.1 software using different thematic layers(geology, geomorphology, drainage density, slope, lineament density and water level). The critical aspects of these thematic maps are described below. The ranks and weightages of parameters assigned for various classes of different layers are given in
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Geomorphology |
Toposheet SOI,1:50000 |
6 |
Denudational hills, Lower plateau |
2 |
Poor |
12 |
Flood Plain,Valley,Islands |
5 |
Very good |
15 |
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Young coastal plain |
4 |
Good |
24 |
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Lineament density (km/sq.km) |
Bhukosh web portal |
5 |
0-0.64 |
1 |
Very Poor |
5 |
0.65-1.3 |
3 |
Moderate |
15 |
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1.4-1.9 |
4 |
Good |
20 |
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2-2.5 |
5 |
Very good |
25 |
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Slope (Degree) |
Prepared from SRTM DEM |
3 |
0-5.38 |
5 |
Very good |
15 |
5.38-10.75 |
4 |
Good |
12 |
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10.76-16.13 |
3 |
Moderate |
9 |
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16.14-21.5 |
2 |
Poor |
6 |
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Geology |
Toposheet SOI,1:50000 |
4 |
Laterite, Grit, Sandstone with clay intercalations |
5 |
Very good |
20 |
Dolerite, Granite, Amphibolite, Basic dyke, Syenite |
1 |
Very Poor |
4 |
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Garnitiferous sillimanite gneiss/schist, Hornblende diopside granulite schist |
2 |
Poor |
8 |
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Biotite gneiss/Hornblende biotite gneiss |
3 |
Moderate |
12 |
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Drainage density (km/sq.km) |
Prepared from SRTM DEM |
2 |
1.13-1.87 |
4 |
Good |
8 |
1.87-2.60 |
3 |
Moderate |
6 |
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2.60-3.33 |
2 |
Poor |
4 |
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3.33-4.07 |
1 |
Very poor |
2 |
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Depth to water level (m) |
Collected from district ground water department, Kasaragod and Mangalore |
1 |
4.66-8.58 |
4 |
Good |
4 |
8.58-12.49 |
3 |
Moderate |
3 |
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12.49-16.4 |
2 |
Poor |
2 |
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16.4-20.32 |
1 |
Very poor |
1 |
The outcome of the drainage basin analysis of the Shiriya river is discussed below.
The present study revealed that the Shiriya river is a sixth-order stream with a chiefly dendritic drainage pattern (
The total number of streams obtained from toposheet, PALSAR, SRTM, CARTO and ASTER DEM are 1759, 1723, 1730, 1722 and 1807, respectively (
Stream length and number of streams are directly proportional. A shorter stream indicates that the area has greater slopes and finer textures. Conversely, larger streams are characterized by flat or nearly flat areas
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Basin area A (Sq. km) |
620 |
623 |
614 |
614 |
634 |
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Perimeter P (km) |
157 |
176 |
145 |
175 |
176 |
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Basin length Lb (km) |
43.98 |
45.1 |
44.17 |
44.43 |
41.31 |
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stream order (u) |
Stream Number (Nu) |
|||||
1 |
1305 |
1338 |
1340 |
1327 |
1372 |
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2 |
351 |
292 |
300 |
289 |
322 |
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3 |
75 |
68 |
65 |
74 |
85 |
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4 |
21 |
19 |
19 |
25 |
21 |
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5 |
6 |
5 |
5 |
6 |
6 |
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6 |
1 |
1 |
1 |
1 |
1 |
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Total |
1759 |
1723 |
1730 |
1722 |
1807 |
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Stream Length (Lu) (km) |
||||||
1 |
726.95 |
614.54 |
579.01 |
617.52 |
655.89 |
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2 |
250.51 |
263.2 |
251.15 |
243.27 |
290.82 |
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3 |
126.6 |
155.8 |
143.3 |
155.1 |
170.4 |
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4 |
82.44 |
64.06 |
62.87 |
77.92 |
72.31 |
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5 |
58.37 |
45.42 |
46.05 |
40.99 |
39.65 |
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6 |
44.66 |
41.14 |
36.81 |
37.62 |
38.21 |
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Total |
1289.53 |
1184.2 |
1118.86 |
1172.44 |
1267.24 |
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Mean stream length (Lsm) |
0.73 |
0.69 |
0.65 |
0.69 |
0.7 |
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Stream Length Ratio (RL) |
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2nd/1st |
0.34 |
0.43 |
0.43 |
0.39 |
0.44 |
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3 rd/2nd |
0.5 |
0.59 |
0.57 |
0.64 |
0.58 |
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4th/3rd |
0.65 |
0.41 |
0.44 |
0.5 |
0.42 |
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5th/4th |
0.71 |
0.71 |
0.73 |
0.53 |
0.54 |
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5 th/6th |
0.76 |
0.9 |
0.79 |
0.92 |
0.96 |
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Mean stream length Ratio |
0.59 |
0.61 |
0.59 |
0.59 |
0.59 |
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Bifurcation Ratio (Rb) |
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1st/2nd |
3.72 |
4.58 |
4.47 |
4.59 |
4.26 |
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2nd/3rd |
4.68 |
4.29 |
4.61 |
3.9 |
3.79 |
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3rd/4th |
3.57 |
3.58 |
3.42 |
2.96 |
4.05 |
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4th/5th |
3.5 |
3.8 |
3.8 |
4.17 |
3.5 |
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5th/6th |
6 |
5 |
5 |
6 |
6 |
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Mean Bifurcation |
4.29 |
4.25 |
4.26 |
4.32 |
4.32 |
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Rho coefficient (ρ) |
0.14 |
0.14 |
0.14 |
0.14 |
0.14 |
It is the ratio between the overall length of a stream of a particular order (Lu) and the stream number (Nu) for that order. Lsm is a distinctive property of drainage networks and their components.
RL is the same for streams of all orders within a watershed. Any deviations from the constant value of the RL can be traced to differences in slope and topographical conditions
The geology and lithology control the Rb of a basin. Usually, it falls between 3.0 to 5.0. The watershed that had undergone less structural disturbance has lower values of Rb (less than 3), and the one that had undergone high structural disturbance has higher Rb values
The Rho values of the study area calculated from different sources (toposheet, PALSAR, SRTM, Cartosat and ASTER DEM) are similar (0.14). This value indicates that the SRB has less storage capacity during a flood.
H of the SRB obtained from SRTM DEM is 0.38 km, ASTER DEM has 0.39 km, PALSAR DEM shows 0.37 km, Cartosat DEM has 0.23km and 0.37 km from toposheet (
Rh depends upon the slope and geology of the Basin. Higher values of Rh link to the hilly region of the Basin, whereas lower values indicate the plain region. The Basin's relief ratio was obtained from toposheet-0.008, SRTM-0.009, PALSAR-0.008, Cartosat-0.005 and ASTER DEM-0.009 (
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Total relief (H) (km) |
0.37 |
0.44 |
0.35 |
0.33 |
0.39 |
Relief ratio (Rh) |
0.008 |
0.008 |
0.009 |
0.005 |
0.009 |
Ruggedness number (Rn) |
0.82 |
0.70 |
0.69 |
0.44 |
0.78 |
Drainage density (Dd) (kms/km2) |
2.23 |
1.9 |
1.82 |
1.91 |
1.99 |
Stream frequency (Fs) |
2.84 |
2.76 |
2.82 |
2.8 |
2.85 |
Drainage texture (Rt) |
6.33 |
5.24 |
5.13 |
5.35 |
5.67 |
Form factor (Rf) |
0.32 |
0.31 |
0.31 |
0.31 |
0.37 |
Circularity ratio (Rc) |
0.31 |
0.25 |
0.37 |
0.25 |
0.25 |
Elongation ratio (Re) |
0.60 |
0.62 |
0.63 |
0.63 |
0.68 |
Length of overland flow (Lg) |
0.22 |
0.26 |
0.27 |
0.26 |
0.25 |
The ruggedness number of the SRB derived from the different DEMs shows slight variation. The obtained values are 0.82, 0.70, 0.69, 0.44, 0.78 for toposheet, PALSAR, SRTM, CARTO, ASTER DEMS respectively. These results show that the region is less vulnerable to soil erosion.
Dd is an indirect indicator of groundwater potential associated with surface overflow and permeability. The region with high surface runoff will have a higher drainage density; thus, infiltration will be lower. Dd of the SRB is 2.23 km/km2 (Toposheet), 1.9 km/km2 (ALOS PALSAR), 1.82 km/km2 (SRTM), 1.91 km/km2 (Cartosat) and 1.99 km/km2 (ASTER). Drainage density less than 2 is grouped as low, 2-4 as moderate,4-6 as high and greater than 6 is treated as very high drainage density
The lithology, as well as texture, influences it. The Fs for the Basin derived from different sources (Toposheet, PALSAR, SRTM, Cartosat and ASTER DEM) are 2.84, 2.76, 2.82, 2.80 and 2.85 individually. The low Fs values of the SRB may be credited to moderate infiltration capacity and small relief.
T is controlled by the region's base rock, relief, and infiltration capability. Smith
An exactly circular basin has an Ff value of 0.7854. For elongated basins, Ff values will be smaller, and it experiences longer duration flows with lower peaks. The higher value of the Ff indicates shorter duration flows of the more prominent peak. The Ff of the study area varies around 0.32 (Toposheet) and 0.31(PALSAR, SRTM and Cartosat DEM). ASTER DEM shows a slightly higher value (0.37). This result specifies the elongated nature of the SRB with a smaller peak flow that lasts longer.
Range
Re fluctuates from 0.6 to 1.0 along with the climate and geology of the region. Using the elongation ratio, it is possible to classify watersheds as most elongated if the value is less than 0.5, elongated when the value is between 0.5 and 0.7, least elongated if Re is 0.7-0.8, oval when Re is 0.8-0.9 and circular if the value is between 0.9 and 1.0. The studied Basin has a range of Re value (0.60 to 0.68), indicating that the SRB is elongated (
Lg impacts the hydrologic and physiographic evolution of a watershed. Lg of the Shiriya river basin obtained from toposheet, PALSAR, SRTM, Cartosat, and ASTER DEMs are 0.22, 0.26, 0.27, 0.26 and 0.25, respectively. It shows that the SRB has a gentle slope that is less susceptible to erosion and is in a mature stage of geomorphic evolution.
Ground water potential map of SRB is shown in
The significant findings of the study are discussed below. The Basin is characterized by 6th order stream with a dendritic drainage pattern, which is elongated and less susceptible to soil erosion. The SRB has an intermediate texture and permeable homogenous geologic materials. The Basin has a gentle slope that is less susceptible to erosion and is in a mature stage of geomorphic evolution.
Many studies have been conducted in various basins regarding morphometric analysis from various data sources
This study also revealed that parameters derived from SRTM DEM match with the toposheet. Different DEMs used in the present study are more or less matched with the toposheet. Minor variation in drainage networks results because the flow direction grid is the primary determinant of drainage network derivation from DEMs. Variations in elevation and spatial resolution of the data may also impact the resultant networks.
To compare the five sets of data relative error percentage relative to the toposheet is calculated (
The SRB ground water potential zonation map is designed to the analysis of water resources of the region. It is evident from the map that there is a considerable water potential in the area of the basin where lineament density is high and drainage density is low. The spatial distribution map of depth to water level confirms it as well. Low depth to water level is seen in regions with high lineament density and vice versa. Average of ten years depth to waterlevel is considered in the present study.
This study aims to compare the morphometric parameters of the SRB based on the DEM type. This is an indirect method of determining the relative vertical accuracy of DEMs. Due to varied data collecting and processing methodologies for DEM creation, DEMs with identical spatial resolution can have distinct morphometric derivatives,which is understood from the study. The present investigation proposes that morphometric parameters(L2, L3, L5, Perimeter and Basin length) can be efficiently retrieved from SRTM DEM. The study concluded that the value of parameters derived from SRTM data is almost equal to that of parameters derived from the toposheet. SRTM DEM shows less relative error percentage with respect to toposheet. Hence, SRTM DEM data can be considered more suitable for the Shiriya River Basin morphometric analysis than other open-source DEMs employed in the present study. The SRB is morphometrically identified as sixth order, with a dendritic stream pattern. It is common in homogeneous terrain. Some structural or tectonic control in the SRB is clearly understood by the presence of lineaments and structural discontinuity. Elevation from different DEMs of the SRB indicates that it has low to moderate relief;as a result, there isn't much surface runoff. The Rn values of the SRB are 0.82, 0.70, 0.69, 0.44 and 0.78 for toposheet, PALSAR, SRTM, CARTO and ASTER DEMS respectively. The Rn values indicate the Basin's little runoff and high infiltration capacity. Dd of the SRB is 2.23 km/km2 (Toposheet), 1.9 km/km2 (ALOS PALSAR), 1.82 km/km2(SRTM), 1.91 km/km2 (Cartosat) and 1.99 km/km2 (ASTER). Drainage texture (T) of the watershed derived from Toposheet -6.33, PALSAR- 5.24, SRTM -5.13, CARTOSAT- 5.35 and ASTER DEM -5.67 are individually. The studied Basin has a Circularity ratio (Re) (0.60 to 0.68). All three parameters (Dd,T,Re) specify that the SRB is elongated with intermediate texture and permeable homogenous geologic materials. Hence the Basin has moderate infiltration capability, which has moderate groundwater potential. This result is also supported by the ground water potential zonation map. The output of the study can be very well used for the sustainable development of the SRB. Since no studies were available on the morphometry of the SRB, this work could be a primary guide for further study in the area.
Authors wish to gratefully acknowledge the Kerala State Council for Science, Technology, and the Environment (KSCSTE) for the financial support. The first writer also thankful for the Director, Research, Kannur University and the Principal, Government college Kasaragod and The HOD and research supervisor Department of Geology and research centre Government College Kasaragod.