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GABM Risk Index for Assessing Natural Hazard Risks 

Bridges play an important role in our transportation infrastructure, facilitating the movement of people and goods across geographical obstacles such as rivers and valleys. However, they face significant challenges posed by natural hazards like floods, earthquakes, cyclones, and landslides. These hazards can result in severe damage, economic losses, and threats to human lives. To address this challenge, the concept of risk index has been developed to assess the vulnerability of bridges to natural hazards. It provides a quantitative measure of bridge vulnerability to natural hazards and aid in prioritising maintenance and repair efforts. Subsequently, mitigation measures are evaluated and implemented based on the results of these risk assessments.

Challenges Posed by Natural Hazards:

The importance of incorporating risk assessment into bridge management becomes evident when considering the devastating impact of natural disasters, such as earthquakes, floods, cyclones, and landslides. Recent climate change-related events have brought this issue to the forefront. For instance, a significant flood event in North India in mid-July 2023 resulted in numerous casualties, infrastructure damage, and disrupted transportation networks. Similar extreme weather events, including heavy rainfall, extreme temperatures, cyclonic weather, and hurricanes, are being witnessed worldwide.

Diverse Natural Hazards in India:

India faces a wide range of natural hazards, with cyclones frequently affecting its extensive coastal regions. Earthquakes, especially in the Himalayan region, pose another significant concern. To effectively address these threats, improved disaster management and mitigation measures are essential, especially given the increased frequency and severity of natural disasters in recent years, partly attributed to climate change and rapid urbanisation.

Proactive Bridge Management:

Most Bridge Management systems (BMS) currently in use are primarily reactive, responding only when signs of distress become apparent. To more effectively manage natural hazards and reduce their impact on bridges, a proactive approach is crucial. This approach involves identifying vulnerable areas and implementing suitable mitigation measures.

What is Risk Index and its Role?

A risk index is a quantitative measure used to assess and quantify the level of risk and vulnerability associated with a particular event, situation, or location. It typically combines various factors and variables to calculate a numerical value that represents the likelihood and severity of distress / damage due to a specific risk or hazard.

It is used to evaluate the susceptibility of bridges to natural hazards such as earthquakes, floods, cyclone, and landslides. This index considers factors such as the probability of the hazard occurring, the intensity of the hazard, the distance from the hazard’s epicentre, and the vulnerability of both the population and infrastructure in the area. By calculating a risk index, decision-makers can prioritise resources, budget and allocate funds for mitigation efforts, and make informed decisions to minimise the impact of natural disasters on critical infrastructure like bridges.

Application of Risk Index in Global Analytics for Bridge Management (GABM):

The Global Analytics for Bridge Management (GABM) framework incorporates risk index into its approach. This ranking of bridges based on their risk levels facilitates the identification of priority structures requiring immediate attention and targeted interventions. This scientific data-driven approach ensures the safety, sustainability, and resilience of bridge infrastructure, supporting effective decision-making to safeguard critical transportation networks.

Methodology for Assessing Natural Hazard Risks:

A comprehensive approach is employed to assess and mitigate the risks associated with natural hazards. This methodology includes understanding deterioration mechanisms, considering consequences, identifying hazard types, gathering historical data, and quantifying vulnerability factors. These steps provide a systematic framework for evaluating the risks posed by various natural hazards.

Risk Index Calculation:

The risk index is calculated by application of algorithm which involves vulnerability of the bridge and the risk associated with specific hazard for the region. This index serves as a tool to gauge the likelihood and severity of distress that a natural hazard can cause due to its occurrence at a specific location. It factors in various elements, including the probability of hazard occurrence, the intensity of the hazard, distance from its epicentre, and the vulnerability of both the population and infrastructure in that area.

Application and Proactive Risk Management:

The risk index has numerous applications, includes identifying vulnerability of the bridges in that area, prioritising proactive mitigation measures, and evaluating the effectiveness of emergency response plans. It enables informed decisions that initiate proactive measures to ensure the safety and longevity of bridge infrastructure.

Enhancing Bridge Sustainability:

Risk assessment plays an integral role in bridge sustainability by aiding in hazard identification and prioritisation. Additionally, implementing targeted mitigation measures and considering environmental, social, and economic factors further enhance bridge sustainability. These factors promote the long-term viability and resilience of bridge infrastructure.

Methodology for Assessing Natural Hazard Risks:

Risk index evaluation flow chart

To assess natural hazard risks comprehensively, a systematic and multidisciplinary methodology is employed, encompassing the following steps:

  • Understanding Deterioration Mechanisms: This step involves a thorough examination of deterioration mechanisms and how they magnify due to natural hazards. The goal is to identify preventive and maintenance measures.
  • Considering Consequences: Risk assessment involves evaluating the consequences of bridge failure, including its impact on transportation networks, economic losses, and potential harm to human life. Historical data and geographic information are utilized to gain insights into these consequences.
  • Identifying Hazard Types: India is prone to various natural hazards. Main focus in India is limited to earthquakes, floods, cyclones, and landslides. It is crucial to understand their prevalence and impact for effective mitigation.
  • Gathering Historical Data: Historical data on past natural events are collected to assess the likelihood and potential consequences of future events.
  • Quantifying Vulnerability: The vulnerability of bridges to each hazard is assessed, taking into account factors such as the likelihood of service disruption, the probability of extreme events, and the consequences of such disruptions. Weighted factors are assigned based on their importance in the assessment.

Methodology in GABM:

GABM uses a mathematical model to evaluate the risk index. Subsequently, bridge managers use this index to prioritise efforts and allocate resources accordingly. Higher risk index indicates a greater need for immediate attention and the implementation of mitigation measures.

GABM identifies hazards
GABM data collection

Proactive Risk Management and Enhancing Bridge Sustainability:

Utilising a risk index enables the implementation of proactive measures to ensure the safety and longevity of bridge infrastructure. Mitigation strategies focus on addressing vulnerabilities to specific hazards. While completely preventing damage from hazards is challenging, efforts are made to minimize their impact. Enhancing bridge sustainability also involves considering environmental, social, and economic factors, engaging local communities, and conducting life cycle cost analyses.


Risk index is important for proactive bridge management, especially in the face of increasing natural hazards driven by climate change. Integrating risk index within the framework of Global Analytics for Bridge Management (GABM) enhances bridge infrastructure resilience and ensures public safety. Future research can refine risk assessment models and address limitations for practical applicability. Ultimately, proactive risk management is essential to safeguard critical transportation networks in the face of unpredictable natural hazards.

More about the application of Risk assessment within Bridge Management is available on UNDRR website ( or


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