IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002
USE OF IRS DATA FOR IDENTIFICATION OF SUBMERGED VECETATION
IN THE CHILKA LAGOON
S. R. Pal and P. K. Mohanty"
Department of Marine Sciences,
Berhampur University, Berhampur 760 007, Orissa, India
<pratap_mohanty @yahoo.com>
KEYWORDS: Vegetation, Identification, Spectral, IRS, Image.
ABSTRACT:
Studies on the spatio-temporal variability of submerged vegetation in Chilka lagoon have been carried
out using IRS-1B LISS-1 data as well as synchronous ground truth observations in different seasons.
The weighted index scheme called, Benthic Biomass Index and Yellow Substance Index have been used
to delineate the submerged vegetation in the lagoon. The validity of the index has been assessed by
statistical analyses considering the seasonal variability of radiance characteristics of the submerged
vegetation in different LISS-1 bands. Areas of submerged vegetation at different periods of study have
been estimated which show significant seasonal and interannual variability.
1. INTRODUCTION
The Chilka (N 19°28'-19°54*, E 85% 06°-85° 35")
is a shallow coastal lagoon on the east coast of algal bed down to 12m depth in the very
Indian (Fig. 1) and has been under constant transparent water of the Molene archipelago
environmental stress due to heavy siltation, (France) using band-1 and band-2 of HRV sensor
luxuriant weed growth and reduction in salinity, of SPOT. Tassan (1992) used TM data and
depth and fish yield. In recent years, compelling developed an algorithm for identification of
evidence has been accumulating which indicates benthic algae in the Venice lagoon which showed
that macrophyte growth and decay are the major high degree of correspondence with in-situ
causes of sedimentation in the Chilka at the observations.
present state of its transformation. Studies have
indicated that the vegetation is growing at an hg) UE SE SR EX
alarming rate (Pal and Mohanty, 2002) and thus a TA. x Kalkpayschat uan J |"
needs immediate attention. The submerged o ¢
vegetation in particular, expedites the siltation Mumbai _AThika Lagoon Bhargavi fc
"E : i NORTHERN
process, stabilizes the sediment bed and checks SECTOR
the flushing action of the riverine sediment from
the lagoon to the sea and allows the lagoon to fill = Repas Paire oo 7 ARAKHAKUDA |_|
in both by inorganic and organic sediment Barakul SECTOR AE. 3718
deposit. Therefore, the study on submerged Natabfa ) ey t da rou
vegetation and its spatio-temporal variability in VR.
Chilka has assumed utmost significance and is the S ai = Now Mouth
main objective of the present investigation. SF BAY
However, change detection of submerged E BENGAL
vegetation in Chilka is not an easy exercise and
may pose severe problems due to significant 19 7 d 19KM 5
spatial and temporal variability of submerged POR ambhd m = x12
vegetation, presence of other vegetation types
such as emergent and floating and wide Figure 1: Location map of Chilka Lagoon
variability of lagoon turbidity. Further, opening
of the new mouth on September 23, 2000 has
significantly changed the status of vegetation
coverage in Chilka lagoon. Therefore it is of
much interest to compare the status of vegetation
in the pre and post mouth opening scenarios. In
* Corresponding author
386
this endeavor, remote sensing can play an
important role as compared to other conventional
methods. Ben Moussa et al. (1989) identified
Therefore, it is believed that IRS-1B LISS-1 data
having ground resolution 72.5 m and spectral
characteristics (Table 1) matching other satellite
data would be useful in identifying benthic algae
in Chilka lagoon.
