Coastal Vulnerability Index

The Coastal Vulnerability Index (CVI) is a scientific tool used to assess the relative vulnerability of coastal areas to natural hazards such as sea-level rise, coastal erosion, storm surges, and flooding. It combines multiple physical, geological, and environmental parameters to provide a composite measure of how susceptible a stretch of coastline is to the impacts of climate change and oceanographic processes.
The CVI helps policymakers, planners, and environmental managers identify high-risk coastal zones, enabling targeted adaptation and mitigation strategies for sustainable coastal management.

Concept and Purpose

The concept of the Coastal Vulnerability Index was originally developed by the U.S. Geological Survey (USGS) in the 1990s to evaluate the potential impact of sea-level rise along the U.S. coastlines. Since then, the methodology has been widely adopted and adapted globally, including in India, for coastal risk assessments.
The primary purpose of the CVI is to:

• Quantify and map the relative vulnerability of different coastal segments.
• Integrate physical and environmental factors that influence coastal stability.
• Support disaster management and coastal zone planning.
• Assist in formulating climate adaptation policies and coastal protection measures.

Parameters Used in Coastal Vulnerability Index

The Coastal Vulnerability Index integrates both natural and anthropogenic factors. While specific parameters may vary by study, the most commonly used variables include:

1. Geomorphology:
   • Type and structure of the coast (e.g., rocky, sandy, deltaic, or mangrove).
   • Determines inherent resistance to erosion and flooding.
2. Coastal Slope:
   • Influences the potential inland extent of flooding and storm surges.
   • Gentle slopes are more vulnerable than steep ones.
3. Relative Sea-Level Change:
   • Rate of sea-level rise or subsidence due to natural or human causes.
4. Shoreline Change Rate:
   • Historical rate of erosion or accretion over time, derived from satellite or survey data.
5. Tidal Range:
   • The vertical difference between high and low tide; higher tidal ranges generally reduce vulnerability by dissipating wave energy.
6. Wave and Wind Energy:
   • Determines the intensity of coastal dynamics and potential erosional forces.
7. Coastal Elevation:
   • Low-lying areas are more prone to inundation and salinity intrusion.
8. Land Use and Population Density:
   • Human settlements, infrastructure, and land use patterns influence socio-economic vulnerability.

Methodology

The CVI is computed by assigning numerical rankings to each selected parameter based on their relative contribution to vulnerability.

Steps in CVI Calculation:

1. Data Collection:
   • Gather data on each variable using remote sensing, field surveys, and existing databases.
2. Classification and Scoring:
   • Each variable is categorised (for example, from very low to very high vulnerability) and assigned a score, typically on a scale of 1 to 5.
3. Index Calculation:
   • The Coastal Vulnerability Index (CVI) is calculated as the square root of the product of ranked variables divided by the number of variables:

     CVI=(a×b×c×d×e×f)nCVI = \sqrt{\frac{(a \times b \times c \times d \times e \times f)}{n}}CVI=n(a×b×c×d×e×f)​​
     where a, b, c, d, e, f represent parameter scores and n is the number of variables.

4. Zonation and Mapping:
   • The computed CVI values are categorised into vulnerability classes:
     • Very Low
     • Low
     • Moderate
     • High
     • Very High
   • These are then represented spatially through GIS-based maps.

Application of CVI in India

India has a coastline of about 7,516 kilometres, stretching across 13 coastal states and Union Territories. This vast coastal area supports major population centres, industries, ports, and ecosystems but is increasingly threatened by climate change, cyclones, and sea-level rise.
To assess coastal risks, several national institutions have adopted the CVI framework.

1. Indian National Centre for Ocean Information Services (INCOIS):

• INCOIS, under the Ministry of Earth Sciences, developed a national-scale CVI to identify vulnerable coastal stretches of India.
• The Indian CVI integrates parameters such as coastal geomorphology, shoreline change rate, mean tidal range, significant wave height, and sea-level rise.
• The output provides a vulnerability ranking map for each coastal segment (typically 1 km grid resolution).

2. State-Level Assessments:

• Coastal vulnerability assessments have been carried out for states such as Tamil Nadu, Odisha, Kerala, Gujarat, and West Bengal.
• For example, the Odisha coast, with its low-lying deltas and frequent cyclones, ranks as one of the most vulnerable coastal zones in India.

3. Coastal Regulation Zone (CRZ) and Disaster Planning:

• CVI data supports the formulation of Coastal Regulation Zone (CRZ) guidelines.
• It also helps in disaster risk reduction planning under the National Cyclone Risk Mitigation Project (NCRMP).

Findings and Insights from India’s CVI Studies

• Approximately 40% of India’s coastline is under moderate to very high vulnerability.
• Highly vulnerable regions include the Sundarbans (West Bengal), Puri–Paradip coast (Odisha), Mumbai–Konkan coast (Maharashtra), Kanyakumari (Tamil Nadu), and Kutch–Saurashtra coast (Gujarat).
• Coastal regions with deltaic formations, mangrove loss, and rapid urbanisation face the greatest risks.
• The western coast (Arabian Sea) generally shows lower vulnerability compared to the eastern coast (Bay of Bengal), which is more prone to cyclones and storm surges.

Importance of the Coastal Vulnerability Index

1. Disaster Risk Reduction:
   • Identifies areas most at risk from sea-level rise, erosion, and storm surges.
   • Helps prioritise coastal protection measures.
2. Planning and Policy:
   • Assists in integrated coastal zone management (ICZM).
   • Informs urban planners and policymakers for sustainable infrastructure development.
3. Climate Adaptation:
   • Supports climate resilience planning for coastal communities.
   • Guides relocation or reinforcement of critical infrastructure.
4. Biodiversity Conservation:
   • Helps protect sensitive coastal ecosystems such as mangroves, coral reefs, and estuaries.
5. Public Awareness and Education:
   • Provides a visual and quantitative tool for communicating climate risks to the public and stakeholders.

Limitations of CVI

• Simplified Representation: The index provides relative vulnerability but may not capture dynamic interactions between physical, ecological, and socio-economic factors.
• Data Gaps: Accuracy depends on the availability and quality of long-term datasets on shoreline change, sea-level rise, and geomorphology.
• Temporal Variation: The CVI typically uses static data and may not reflect real-time changes or sudden extreme events.
• Socio-economic Exclusion: Many CVI models focus mainly on physical parameters, overlooking human adaptability and resilience.

Enhancements and Future Directions

To make the CVI more comprehensive and useful for decision-making, ongoing research focuses on:

• Incorporating socio-economic vulnerability indices (SEVI) to assess community resilience.
• Using remote sensing, LiDAR, and AI-based modelling for high-resolution coastal mapping.
• Integrating CVI with climate projections and hydrodynamic models to simulate future scenarios.
• Developing dynamic CVI frameworks that update periodically based on new data.