In HEC-LifeSim, Alternatives represent complete evacuation simulation scenarios that combine all the main elements of the model: hydraulic events, structures (population), road networks, emergency planning zones, and destination points.
In other words, an alternative is a specific system configuration that you want to simulate. By creating multiple alternatives, you can compare the results of different scenarios and assess the impact of changes in conditions or evacuation strategies.
The alternatives allow you to simulate "what-if" scenarios. For example:
- Changing the population preparedness levels
- Adding or modifying destination points
- Varying the road network or flood magnitude
Results can be compared to evaluate evacuation times, life losses, and infrastructure impacts.
DEFINE INPUT DATA SOURCES
Creating alternatives in HEC-LifeSim requires selecting several key components:
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Hydraulic Event: Choose between Non-Failure (no dam breach) or Failure (dam breach) scenarios.
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Structure Inventory: The set of physical structures (buildings, bridges, critical facilities, etc.) included in the simulation.
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Emergency Planning Zone (EPZ): Select the population preparedness level, such as Minimally Prepared, Moderately Prepared, or Well Prepared.
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Road Network: The transportation network used for routing the evacuation, usually imported from GIS or OpenStreetMap.
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Destination Points: The safe locations or shelters to which the population will be routed during evacuation.
PUBLIC WARNING ISSUANCE
In the Public Warning Issuance tab:
The Imminent Hazard ID Time (Hours): This parameter defines the time it takes for the population to recognize an imminent hazard after the event begins. In other words, it indicates how quickly people become aware of the threat and are able to start evacuation.
The Uncertainty Type options are:
- None:
- No delay in hazard identification is considered.
- All agents perceive the hazard immediately.
- Used for “best case” scenarios with no perception delays.
- Triangular:
- Perception times follow a triangular distribution, defined by minimum, most likely, and maximum times.
- Allows you to model asymmetric variability, e.g., most people react around the most likely time, but some react much faster or slower.
- Normal:
- Perception times follow a normal (Gaussian) distribution.
- Most people perceive the hazard around the mean time, but some react earlier or later.
- Makes the simulation more realistic by introducing variability in response times.
- Uniform:
- All agents take the same fixed amount of time to perceive the hazard.
- Example: if set to 1 hour, everyone reacts exactly 1 hour after the event begins.
- Useful for simple or idealized scenarios.
Example:
Uncertainty Type: Uniform
Minimum: -1
Ma
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