Examples of Applications
Conceptual examples
This approach paper demonstrates the concept of dynamic risk assessment using the following conceptual/hypothetical examples.
- Considering dynamic nature of variables
- Accounting interaction between dynamic variables
- Incorporating interaction of multiple hazards happening at a same place during the same time period
- Accounting cumulative risk of hazards over time
- Potential risk of a forecasted hazard condition
- Inclusion of dynamics in exposure and vulnerability.
Example 1: Dynamic nature of variables
The hazard and vulnerability characteristics can be better assessed by incorporating the temporal variations (dynamics) of the same variable, rather than considering the variables static over a cumulative time period. For instance, considering daily rainfall variation for 10 days period instead of cumulative 10 days rainfall, would provide a better information about the rainfall thresholds that could trigger flood in a region.
Example figure -1. Dynamic nature of rainfall variable causing floods
The impacts of a heavy downpour after five consecutive wet day and five consecutive dry day are entirely different. The heavy downpour after five consecutive wet day might result in flood, whereas not in the case of occurrence of heavy downpour after five consecutive dry day. Another example could be the heat waves, the health impacts vary when people experience very high temperature for one day and continuously high temperature on each day for a week.
Example 2: Interaction between dynamic variables
The interaction between multiple variables contributing to the risk could be considered. For example, the interaction between the rainfall and soil moisture condition decides the runoff conditions. In coastal areas, the combined interaction of rainfall amount, water level in the river, tide level, and soil moisture decides the flood risk. Similarly, the heavy downpour could cause differential impacts during the different stages of crops .
Example Figure-2. Interactions between dynamic variables resulting in floods and posing risk to crops.
The dynamic nature of variables that are key for assessing the risk of flood, landslide and drought hazards are discussed below, and it fits for both short term (e.g. day-to-day, weekly) and long term (e.g. monthly, seasonal) risk assessment.
Dynamic nature of variables and its interaction
A schematic diagram shows the risk assessment flow with the help of selected dynamic variables. The same could be used for assessing short and long term risk as well as to assess the past and potential future risk.
- For flood hazards, the rainfall condition received over a period of time in a region is critical to determine the saturation point of soil that leads to run-off. The vulnerability of exposed elements such as crops to the hazard depends on the sensitivity of crop stages.
- For landslides, characterizing prior rainfall condition, soil moisture, and land use (thresholds varies spatially) is critical to understand landslide risk.
- For drought, pre-existing rainfall and soil moisture conditions are important in causing stress to crops and affecting water levels. The impacts of drought in 2015-2016 is severe in many Asian countries due to the pre-existing drought condition in 2014-2015. Even after the consecutive two year drought was over, many places were facing impacts in 2016-2017, e.g. low ground water table as the recovery takes longer time after prolonged drought.
Example 3: Dynamic interaction of multiple hazards
The dynamic interaction of multiple hazards occurring simultaneously would pose a different level of risk. For example, the combination of cyclone, flood and landslide or earthquake and tsunami occurring in a region at the same time period would result in a different impacts on the exposed elements, when compared to these hazards occurring as isolated events.
Example Figure -3. Multiple interaction of hazards happening at the same time.
Example 4: Cumulative risk of hazards
The cumulative risk posed by the rainfall variability from short to long term period would be different than looking at the risk for each time slices. Therefore assessing the integrated risk of a hazard posed at various time scales will provide holistic understanding of risk to aid preparation of adaptation plans
Example figure 4.Dynamic risk of a hazard integrated from short to long term
The cumulative risk of various hazards happening at the same place over time would be very different than looking at the risk of hazard as an isolated event. For example, the cumulative risk of a place experiencing drought during the present year experiencing flood in the following year and cyclone during next to next year, would be much severe than looking at the impacts of each individual hazards.
Example 5: Potential risk of a forecasted hazard condition
With the help of past experiences, modelling the potential risk is possible with forecasted hazard variables. For example, assessing the possibility of flooding and its risk in an area is possible based on the likely daily rainfall forecast for days to months. Similarly, the potential risk to the crops could be modelled based on the predicted rainfall conditions during days to months in advance
Example figure 5. Dynamic risk of a forecasted hazard condition
Case of assessing potential risk of extreme events
Hazard: Typhoon Ketsana crossed central provinces of Cambodia by end of September 2009, brought heavy rainfall and resulted in heavy floods. It is to be noted that the hazard happened at the end of the wet season. The condition of rainfall and water level in the region before the Ketsana event is critical to characterize the hazard better. For instance, knowing the pre-existing conditions (How much is the water level in the rivers during the month of September? How much was the monthly rainfall received during the months of May, June, July and August?) would help to assess the potential risk for Ketsana forecast.
Exposure and Vulnerability: Approximately 50,000 hectares of rice crops accounted for complete damage in the central provinces of Cambodia. The cyclone hit during the critical crop stage i.e. harvesting stage of the rice crop. Knowing the crop stage would help estimating the risk posed by a hazard, for planning quick pre-disaster response action to minimize the negative impacts.
Example 6: Dynamics in exposure and vulnerability assessment
A conceptual approach of incorporating dynamics in exposure and vulnerability assessment has been proposed by Jurgilevich et al. 2017. Understanding the interaction of changing exposure and vulnerability at a location at a given point of time is particularly critical for strategies like adaptation planning to remain relevant in the long term future.
Dynamics in exposure and vulnerability assessment
Exposure
- Exposure as a manifestation of a hazard - Climatic projections, climate modelling, climate scenarios, sea level rise simulations, heat or flood inundation simulation
- Exposure as geographical location - Urban spatial scenario modelling, land use plans, land-use modelling
Vulnerability
- As threshold - Demographic projections, impact threshold simulation, simulation of hazard scenarios coupled with socioeconomic scenarios
- As pre-existing condition - Simulation of population growth, urban growth and development scenarios, indicators projected over time
- As an outcome - Urban development plans, simulation/discussion of adaptation measures, local development scenarios including external and internal change factors, scenarios for adaptation, socioeconomic growth scenarios, population growth scenarios, adaptation pathways
Source: Jurgilevich et al. 2017