• TUNE USHA

Articles written in Journal of Earth System Science

• Spectral characteristics of coral reef benthic compositions in Gulf of Mannar

Spectral characteristics of nine coral species (Acropora Nobilis, Acropora Hyacinthus, Acropora Varibalis, Favia Speciosa, Favia Stelligera, Porites Lobdata, Porites sp., Pocillopora Domicornis and branched dead corals), two seagrass species (Zosteraceae and Posidoniaceae), two sand benthic communities (sand mixed with coral rubble and carbonate sand), reef vegetation and sea moss were recorded using RAMSES-TriOS Hyperspectral radiometer from Mandapam group of islands, Gulf of Mannar, India. Based on the reflectance features, coral reef benthic compositions were categorized as brown mode and blue mode. Brown mode of corals was identified by a triple peaked pattern exhibiting local maxima or shoulders near 575, 600 and 650 nm. The blue modes of corals were identified by a plateau-like shape between 600 and 650 nm. The non-coral benthic compositions such as seagrass and sea moss can be identified by a peak between 550 and 560 nm. Results exhibited that, most of the coral reef benthic compositions falling under either blue mode or brown mode of corals and the patterns of spectral signatures exhibited in this region are matching with existing global signatures.

$\bf{Highlights}$

$\bullet$ This study attempts to analyse the spectral characteristics of nine different coral reef species species (Acropora Nobilis, Acropora Hyacinthus, Acropora Varibalis, Favia Speciosa, Favia Stelligera, Porites Lobdata, Porites sp., Pocillopora Domicornis and Branched dead corals) along with several of its associated benthic compositions two seagrass species (Zosteraceae and Posidoniaceae), two sand benthic communities (sand mixed with coral rubble and Carbonate sand), reef vegetation and sea moss recorded from various islands of Gulf of Mannar, India

$\bullet$ Results revealed that several coral species either fall under the broad category of Brown mode or Blue mode. Brown mode of corals was identified by a triple peaked pattern exhibiting local maxima or shoulders near 575, 600 and 650 nm. The blue modes of corals were identified by a plateau-like shape between 600 and 650 nm. The non-coral species such as seagrass and sea moss can be identified by a peak between 550 and 560 nm.

$\bullet$ It can also be noted that, irrespective of water column conditions; (i) all the coral reef benthic compositions tend to have its reflectance minimum around 674 nm (This phenomenon is due to the strong absorption of chlorophyll in that portion of EMR). (ii) Influence of water column can be seen in the rise of magnitude in the longer wavelengths of EMR for the measurements recorded based on exposed condition.

$\bullet$ Results exhibited that, most of the coral reef benthic compositions falling under either Blue mode or Brown mode of corals and the patterns of spectral signatures exhibited in this region are matching with existing global signatures.

• Flood impact assessment using field investigations and post-flood survey

Kerala, located in the southwest part of India experienced heavy flooding during 2018. A post-flood field survey was conducted by National Centre for Coastal Research (NCCR), Chennai to study the flood. The survey was conducted using in-situ measurement and fed to NCCR-Geo surveyor app. The app is indigenous and transfers the data including flood depth and geo-tagged photos to NCCR server. The survey also focuses on the peoples experience at the time of flood of central and southern parts of Kerala with a total of 206 respondent data. The district-wise survey results are presented. From the study, it was concluded that Pampa River basin and Periyar River basin were severely affected and respondents reported sudden rise in the water levels in locations near to the river banks. Major river banks of the state overflowed and destroyed houses, roads, etc. The field survey points towards long term solutions including advanced flood warning system to create an effective mitigation and preparedness plan to reduce the risk from the fury of future floods and for a resilient community.

$\bf{Highlights}$

$\bullet$ The post-flood field survey was conducted for Kerala floods of 2018. A team from NCCR visited the flood affected central and southern parts of Kerala.

$\bullet$ NCCR Geo-Surveyor app built in-house was used for the survey. A Geo-tagged image together with the flood depth is stored in transferred online into the NCCR server.

$\bullet$ Presented the district-wise field survey result in the paper. It was noticed that the flood intensified and affected millions due to unscientific way of dam operations, which affected infrastructure and lives of many living on the banks of the river.

$\bullet$ Kerala need to consider long-term solutions like early flood warning systems, conservation of environment and proper engineered constructions near to the river banks.

• Journal of Earth System Science

Volume 131, 2022
All articles
Continuous Article Publishing mode

• Editorial Note on Continuous Article Publication

Posted on July 25, 2019