Introduction
Coastal shorelines are dynamic and highly vulnerable to erosion and accretion caused by hydrodynamic, tectonic, geomorphic, and climate forcing, including tsunamis, cyclones, flooding, storm surges, wave action, wind and tide changes, and sea level variations. In addition to natural coastal processes, coastal resources are constantly under stress due to anthropogenic activities, such as industrialization, port construction, beach sand mining, garbage dumping, urbanization, trade, tourism, and recreational activities, which significantly impact the shoreline and result in damage to natural ecosystems.
Regular monitoring and assessment of shoreline changes are crucial to understanding their impacts on coastal ecosystems and communities. Implementing appropriate coastal management strategies, such as beach nourishment, dune restoration, and erosion control measures, can help mitigate the negative effects of shoreline changes. It is also important to adopt sustainable land use practices that balance economic development with resource conservation and responsible use.
The South Andaman region, located in the seismically active zone, is particularly vulnerable to tsunamis due to its location. Effective tsunami preparedness and resilience measures, including implementing early-warning systems, raising public awareness, and strengthening infrastructure resilience, are crucial for this region. Incorporating ecosystem-based approaches, such as preserving and restoring natural coastal land, can also contribute to reducing tsunami vulnerability.
Coastal Geomorphology and Hazard Assessment
The South Andaman region, with an area of approximately 1262 km² and a 413 km coastline, is the southernmost island of the Great Andaman. The region’s topography is influenced by tectonic activity and weathering processes, resulting in a diverse landscape of hills, valleys, beaches, mangroves, and coral reefs.
The East Andaman Thrust, also called the East Boundary Thrust, is a linear or curvilinear ~500 km long fault zone and is the locus of ongoing convergent and crustal deformation along the Sunda–Andaman plate boundary. This structure is pivotal in creating accretionary prisms within the outer-arc ridge of the Andaman and Nicobar subduction zones.
The coastal plains in South Andaman are dynamic and prone to tsunamis due to their location and active plate boundary. The region has experienced significant devastation and losses during the 2004 Indian Ocean tsunami, which triggered massive destruction of the coastal ecosystem.
To assess the vulnerability of the South Andaman region, we have computed the tsunami arrival times, run-up heights, and inundation extent along the coastline using the General Bathymetry Chart of the Ocean (GEBCO) data and the TUNAMI-N2 numerical model. The results indicate that the tsunami waves arrived in the region between 27 and 58 minutes, with run-up heights ranging from 1 to 13 meters and inundation distances reaching up to 950 meters in some locations.
The 2004 Sumatra earthquake-generated tsunami caused significant damage to the coastal areas of South Andaman, including the stagnation of tsunami water in agricultural lands, damage to bridges and houses, and widespread erosion and accretion of the shoreline.
Shoreline and Land Use–Land Cover Changes
To understand the dynamic changes in the coastal region, we have analyzed the shoreline and land use–land cover (LULC) changes in the South Andaman region using multi-temporal Landsat satellite data from 2004, 2005, and 2022. The analysis was conducted using the USGS Digital Shoreline Analysis System (DSAS) to estimate the shoreline change rates, and supervised classification techniques were applied to detect LULC changes.
The shoreline change analysis revealed a combination of erosion and accretion patterns in different zones of the South Andaman region. During the 2004-2005 period, which was directly impacted by the tsunami, the maximum erosion rates ranged from -23.9 to -24.71 m/yr, while the maximum accretion rates were around 6.54 m/yr. In the subsequent 2005-2022 period, the erosion rates decreased, ranging from -4.56 to -19.87 m/yr, and the accretion rates were up to 9.77 m/yr.
The LULC analysis showed significant changes in the region from 2004 to 2022. The built-up area increased from 7.38% in 2004 to 11.11% in 2022, while the forested area decreased from 66.46% to 51.10% during the same period. Cropland coverage decreased from 22.12% in 2004 to 17.15% in 2022, and the inundation areas, which increased from 3.29% in 2004 to 27.65% in 2005 due to the tsunami, had decreased to 9.08% by 2022.
These changes in shoreline and LULC are closely linked to the region’s geomorphology, coastal processes, and socioeconomic factors, as well as the impacts of the 2004 tsunami. The increase in built-up areas and the decline in natural ecosystems like forests and croplands have implications for the region’s vulnerability to future natural disasters and the sustainability of its coastal resources.
Implications for Disaster Resilience and Sustainable Development
The South Andaman region is highly vulnerable to tsunamis due to its location in the seismically active zone. The 2004 tsunami had a significant impact on the region, causing extensive damage to infrastructure, agriculture, and natural ecosystems. The region has experienced a rapid increase in population, tourism, and economic development since the tsunami, which has led to further changes in land use and increased the exposure of the population and assets to potential future disasters.
The increase in built-up areas and the decline in natural ecosystems like forests and croplands have implications for the region’s vulnerability to future natural disasters. The loss of natural coastal barriers, such as mangroves and coral reefs, can reduce the region’s resilience to coastal hazards, including tsunamis, storm surges, and sea-level rise.
Effective disaster preparedness and resilience measures are crucial for the South Andaman region. This includes implementing early-warning systems, strengthening infrastructure resilience, and promoting ecosystem-based approaches to disaster risk reduction. Engaging local communities, stakeholders, and indigenous knowledge holders in decision-making processes and promoting capacity-building initiatives are also critical for ensuring the sustainable development of the region.
Sustainable land use practices that balance economic development with resource conservation and responsible use are essential for the South Andaman region. This involves promoting eco-friendly tourism, protecting sensitive ecosystems like mangroves and coral reefs, and implementing land use planning that considers the carrying capacity and vulnerability of the region.
Conclusion
The South Andaman region has experienced significant shoreline and land use–land cover changes, driven by both natural processes and human activities. The region’s vulnerability to tsunamis and other coastal hazards has increased due to the expansion of built-up areas, the decline in natural ecosystems, and the growing population and economic development.
Effective monitoring and management of shoreline and land use changes, as well as the implementation of comprehensive disaster preparedness and resilience measures, are crucial for the sustainable development of the South Andaman region. By balancing economic growth with environmental conservation and disaster risk reduction, the region can enhance its resilience and ensure the long-term well-being of its communities and natural resources.
The insights and recommendations provided in this article can inform policymakers, coastal managers, and local stakeholders in their efforts to develop and implement effective strategies for the South Andaman region. By addressing the complex interplay between coastal processes, land use changes, and disaster risk, the region can move towards a more sustainable and resilient future.
