Shailesh Nayak

Coastal Vulnerability Assessment for Orissa State, East Coast of India

Abstract Coastal areas of Orissa State in the northeastern part of the Indian peninsula are potentially vulnerable to accelerated erosion hazard. Along the 480-km coastline, most of the coastal areas, including tourist resorts, hotels, fishing villages, and towns, are already threatened by recurring storm flood events and severe coastal erosion. The coastal habitats, namely the largest rookeries in the world for olive Ridley sea turtles (the extensive sandy beaches of Gahirmatha and Rushikulya), Asias largest brackish water lagoon (the “Chilika”), extensive mangrove cover of Bhitarkanika (the wildlife sanctuary), the estuarine systems, and deltaic plains are no exception. .The present study therefore is an attempt to develop a coastal vulnerability index (CVI) for the maritime state of Orissa using eight relative risk variables. Most of these parameters are dynamic in nature and require a large amount of data from different sources. In some cases, the base data is from remote sensing satellites; for others it is either from long-term in situ measurements or from numerical models. Zones of vulnerability to coastal natural hazards of different magnitude (high, medium, and low) are identified and shown on a map. In earlier studies, tidal range was assumed to include both permanent and episodic inundation hazards. However, the mean of the long-term tidal records tends to dampen the effect of episodic inundation hazards such as tsunamis. For this reason, in the present study, tsunami run-up has been considered as an additional physical process parameter to calculate the CVI. Coastal regional elevation has also been considered as an additional important variable. This is the first such study that has been undertaken for a part of the Indian coastline. The map prepared for the Orissa coast under this study can be used by the state and district administration involved in the disaster mitigation and management plan.

Surface chlorophyll a estimation in the Arabian Sea using IRS-P4 Ocean Colour Monitor (OCM) satellite data

The IRS-P4 satellite launched on 26 May 1999 by Indian Space Research Organisation (ISRO) carried an Ocean Colour Monitor (OCM) payload, primarily designed to measure ocean colour, the spectral variations of waterleaving radiance that can be related to the concentration of phytoplankton pigments, coloured dissolved organic matter and suspended particulate matter. Remote sensing data obtained from IRS-P4 OCM sensor is processed for the removal of atmospheric effects of Rayleigh and aerosol scattering to derive normalized water-leaving radiance in visible channels of 412, 443, 490, 512 and 555 nm. Ocean chlorophyll-2 (OC2) global bio-optical algorithm was used to convert normalized water-leaving radiance data to chlorophyll a concentration. For quantitative accuracy assessment, OCM-derived chlorophyll a concentration values were compared to the in situ measurements of chlorophyll a, conducted during ORV Sagar Kanya SK-149c ship cruise during 15-27 November 1999 in Arabian Sea. In general OCM-derived chlorophyll a showed a good correlation ( r 2 =0.90, N = 8, RMS=0.125 mgm -3 ) with measured chlorophyll values.

Himalayan glacier retreat using IRS 1C PAN stereo data

A merged image of nadir viewing PAN and LISS III data of 2000 and PAN stereo data of 2000–2001 from Indian Remote Sensing satellite (IRS)‐1C covering Gangotri glacier was interpreted to identify its snout or terminus and to measure the retreat of this glacier with respect to the position of snout in a topographical map of 1962. Elevations from the map and DEM generated from stereo data were compared to determine the thickness of the glacier ice across the section of retreat prior to year 1962. The annual retreat of the glacier at the end of the ablation season during the year 2000–2001 was measured using PAN orthoimages.

Fishery forecast using OCM chlorophyll concentration and AVHRR SST: validation results off Gujarat coast, India

Satellite sensor data analysis, generation of fishery forecast, validation procedure, feedback analysis and results of validation experiments are discussed in this Letter. Indian Remote Sensing Satellite (IRS-P4) Ocean Colour Monitor (OCM) derived chlorophyll concentration and National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) derived sea surface temperature (SST) images were integrated to generate a fishery forecast. The matching chlorophyll and SST features were selected to suggest potential fishing zones (PFZs). Actual fishing using trawlers in the suggested PFZs was carried out to validate the fishery forecast. The feedback in terms of CPUE (catch per unit effort) was analysed to evaluate the technique. The CPUEs were categorized based on mean (µ) and standard deviation (SD). The categorized catch points were plotted on images. High fish catch points were found in the vicinity of matching features. About 80 per cent of observations in 50–100 m depth zone and 68 per cent of observations in 30–50 m depth zone were found positive. At some locations an abrupt increase in CPUE in PFZs was observed.

Synergistic analysis of SeaWiFS chlorophyll concentration and NOAA-AVHRR SST features for exploring marine living resources

Near-synchronous Sea-viewing Wide Field-of-View Sensor (SeaWiFS) derived chlorophyll concentration and National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) derived sea surface temperature (SST) images were used to understand patterns, persistence and inter-relationship between ocean colour and thermal features. Different types of oceanic features were observed on chlorophyll concentration and SST images. An inverse relationship between chlorophyll concentration and SST features was observed. The features observed in the chlorophyll concentration images were well defined and appeared to contained more information than those on the SST images. The frontal zone positions on the chlorophyll concentration images coincided with temperature boundaries at some locations. This coincidence indicates that the physical and bio-chemical processes are closely coupled at these locations. High fish catch points were found in the vicinity of these features. A synergistic analysis of chlorophyll concentration and SST may increase our understanding of the inter-relationship between environmental variables for locating potential fishing grounds.

Impact of the tsunami and earthquake of 26th December 2004 on the vital coastal ecosystems of the Andaman and Nicobar Islands assessed using RESOURCESAT AWiFS data

Tsunami waves struck the Indian coast on 26th December 2004 affecting the Andaman and Nicobar group of islands. A quick assessment of the status of the vital coastal ecosystems has been made using pre- and post-tsunami Advance Wide Field Sensor (AWiFS) data of Indian satellite RESOURCESAT with an accuracy of 87–90% and the Kappa ranging from 0.8696 to 0.9053. Among the coastal ecosystems the coral reefs have suffered the maximum with the Nicobar reefs (69% eroded and 29% degraded) bearing the brunt more than the Andaman reefs (54% eroded and 22% degraded). Significant improvement to the condition of the reef damaged due to backwash has been noted. About 41% of the Sentinel reef area has undergone significant improvement. The continuance of the erosion of the southwestern Andaman reefs is due to the impact of recurring earthquakes. The impact on mangroves of both the groups of islands has been due to uprooting as well as inundation of seawater and resulting stagnation. Changes are expected in community structure of mangroves as a result of tsunami.

Bifurcation of the East India Coastal Current east of Sri Lanka

The East India Coastal Current (EICC) flows equatorward during October–December carrying low salinity water from the Bay of Bengal en route. Using results from a high resolution ocean general circulation model, satellite altimeter data, Argo float profiles and ocean color images we show that the EICC bifurcates east of Sri Lanka. One part continues along the coast of Sri Lanka but the major part of the EICC, called here as the East Sri Lanka Jet (ESLJ) flows eastward into the Bay of Bengal. As a result of this bifurcation, there is offshore transport of chlorophyll a rich low salinity water from the coast of Sri Lanka. Altimeter data from 1993–2004 show that the bifurcation occurred every year except during the Indian Ocean Dipole (IOD) years of 1994 and 1997. The bifurcation occurs when an anticyclonic eddy that propagates westward ahead of a downwelling Rossby wave front impinges on the Sri Lanka coast. This new finding suggests that the main route of the low salinity water from the Bay of Bengal into the southeastern Arabian Sea may not be along the coast around Sri Lanka but through the Winter Monsoon Current.

Groundwater prospective zones in basaltic terrain using remote sensing

The study aims at investigating the relative role of landforms and lineaments as an integrated unit for the assessment of groundwater availability with an example of an area occurring in basaltic terrain. The article describes the use of remote sensing data for hydrogeomorphological mapping, zoning of the area into groundwater prospects and evaluation of zones by using well discharge data of handpumps located in the area. It has been found that the rocks, which are both, fractured and weathered, are more productive in groundwater discharge. The study shows that the lower elevation zones of micro-watersheds have better groundwater prospects.

Coastal morphology: a case study of the Gulf of Khambhat (Cambay)

Abstract Geomorphic processes greatly influence the industrial, commercial and recreational activities in the Gulf of Khambhat (Cambay). LANDSAT data with their synoptic and repetitive coverage have been used in studying the distribution of suspended sediments, currents and fronts and for mapping shoreline configuration and wetlands. Visual interpretation of LANDSAT Multispectral Scanner (MSS) band 6 and 7 images and diazo colour overlays was carried out for the above purpose. Colour density slicing was performed on all four MSS images for the qualitative estimation of suspended sediments. The observation of suspended sediments suggests that during the monsoon many sediments brought in by various rivers remain in suspension and start settling down with the onset of the winter season. Tides also play an important role in the movement of the suspended sediments and fronts. The concentration of the suspended sediments is high on the mainland side during the flood tide and in the centre of the Gulf during the...

Remote Sensing of suspended sediments along the Tamil Nadu coastal waters

Indian Remote Sensing satellite (IRS) 1A & 1B digital data in combination with field measurement were used to map distribution and concentration of suspended sediments along the Tamil Nadu coastal waters for monsoon and non-monsoon periods. Qualitative suspended sediment mapping was done for entire Tamil Nadu coast while quantitative studies were taken at two selected sites (eg. Tuticorin and Ennore). For qualitative mapping both monsoon (17-12-90) and non-monsoon (18-4-90) season data were analysed by level slicing technique and a qualitative scale was assigned to different sediment classes based on tonal variations. The suspended sediment concentration (SSC) samples were collected on April 15, 1992 and March 10, 1992 around Ennore and Tuticorin coastal waters respectively, synchronous to IRS-1A satellite overpass. This data was used for quantitative estimation of SSC using digital chromaticity technique. The study shows that the plumes of high suspended sediment concentration are contributed from the nearshore wetlands and river mouths and were finally dispersing towards Jaffna coast. Different classes of high to low SSC values ranging from less than 5 mg/L in offshore areas to 21 mg/L in nearshore of Tuticorin were also delineated. The dispersal pattern of the sediments on different is discussed.