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IDENTIFICATION OF GEOMORPHIC SIGNATURES OF NEOTECTONIC ACTIVITY USING DEM IN THE
PRECAMBRIAN TERRAIN OF WESTERN GHATS, INDIA
K. S. Jayappa *, Vipin Joseph Markose, Nagaraju M.
Dept. of Marine Geology, Mangalore University
Mangalagangothri, Karnataka, India — 574 199
ksjayappa@yahoo.com
Working Group VIII/S
KEY WORDS: DEM, Geomorphology, GIS, Identification, Geology, Stream length gradient (SL) index
ABSTRACT:
To assess the relative tectonic activity classes, five geomorphic indices such as stream-gradient index (SL), drainage basin
asymmetry (Af), hypsometric integral (Hi), valley floor width — valley height ratio (Vf) and drainage basin shape (Bs) of ninety-
four sub-basins of Valapattanam river basin have been analysed by applying the standard formulae. Relative tectonic activity classes
(lat) obtained by the average (S/n) of different classes of geomorphic indices have been classified into three groups. Group I shows
high tectonic activity with values of S/n < 2; group II shows moderate tectonic activity with S/n > 2 to < 2.5; and group III shows
low tectonic activity with values of S/n > 2.5. Field evidences such as deep valleys, sudden changes in the river course and waterfalls
at fault planes clearly agree with the values and classes of tectonic geomorphic indices.
1. INTRODICTION
Digital Elevation Model (DEM) supported morphometric
analysis of landscape represents an active field of research in
many geomorphological applications which aim to model
surface processes. Landscapes in tectonically active areas result
from a complex integration of the effects of vertical and
horizontal motions of crustal blocks and erosion or deposition
by surface processes (Burbank and Anderson, 2001). As a
consequence, geomorphic investigation in regions of active
tectonics is a powerful tool for studies of tectonic
geomorphology (Azor et al., 2002). Significant improvement in
spatial and spectral resolutions of satellite data, image
processing techniques and advancement in computing resources
have enabled the geomorphologists to carry out more
quantitative and precise analysis of morphometric,
morphotectonic and geomorphic indices. In recent studies
related to morphotectonics, a mixture of geomorphologic and
morphometric analyses of landforms and topographic analyses
are utilized to obtain active tectonics (Della Seta et al., 2008).
Perez-Pena et al. (2010) have used geomorphic indices and
drainage pattern analysis for evaluating the Quaternary tectonic
activity in the Sierra Nevada mountain range of SE Spain.
Geomorphic indices computed by using GIS, are used for
evaluating the geomorphic anomalies and tectonic activity
(Dehbozorgi et al, 2010). Font et al. (2010) have used SL
analysis for detecting the impact of differential uplift on
drainage systems using DEM to understand landforms in
relation to the tectonics of Normandy intra plate area of NW
France. The objective of the preset study is to analyze various
geomorphic indices and their influence on neotectonic activity
of the Valapattanam river basin using SRTM DEM in GIS
environment.
2. STUDY AREA
The Valapattanam river basin extending from 14°59°49.46” to
15712°58.85” N latitudes and 74°17°2.32” to 74°36’46.35” E
* Corresponding author.
longitudes in Kannur district of northern Kerala, India forms the
study area (Figure 1). Valapattanam river originates in the
Brahmagiri Ghat reserve forest in Karnataka at an altitude of 900-
1350 m above mean sea level and drains into Kannur district of
Kerala state. Major tributaries of this river are the
Sreekantapuram river, Bavalipuzha, Venipuzha, and Aralam
puzha. The total drainage area of this river basin is 1867 sq.km.,
of which 546 sq.km is outside the Kerala state. The basin is
nearly level surface near the coast, undulating in the midland and
steep sided hills and mountain in the east. The basin forms the
Pre-Cambrian terrains of southern India occupied by hornbInde-
biotite gneisses and hornblende diopside granulite which
constitute the litho-units of migmatite complex.
3. METHDOLOGY
SRTM images were downloaded from GLCF website
(http://glcfumiacs.umd.edu) is used to extract the drainage
networks and sub-basins of the area. After creating the DEM,
errors such as sinks and peaks were removed using ‘fill sinks’
option available in ArcGIS hydro tools and created a Hydro
DEM. Flow direction i.e. the direction in which water will flow
out of the pixel to the eight surrounding pixels (Fairfield and
Leymarie, 1991) was calculated for each pixel using the Hydro
DEM as an input. In order to generate a drainage network, it is
necessary to determine the ultimate flow path of every cell on the
landscape grid. Flow accumulation was used to generate a
drainage network, based on the direction of flow of each cell. The
Stream Definition function takes a flow accumulation grid as
input and creates a Stream Grid for a user defined threshold of
50. This threshold value represents the minimum upstream
drainage area (threshold area) necessary to maintain a stream.
Using smaller threshold value will include more tributaries in
stream networks than using a larger threshold value. The stream
grid will have a value of ‘“1’’ for all the cells in the input grid
that have a value greater than the given threshold. All other cells
in the Stream Grid contain no data. Stream links, where streams
join together, were calculated using stream segmentation
