Welcome to LifeSim
The U.S. Army Corps of Engineers (USACE) Life Loss Estimation software (LifeSim) is a spatially-distributed dynamic simulation modeling system for estimating potential life loss and direct economic damages from natural and dam and levee failure floods.
LifeSim accounts explicitly for the impact of warning issuance time; warning diffusion; the population at risk's (PAR's) protective action initiation; the PAR's evacuation potential; detailed flood dynamics; and loss of shelter on loss of life. An agent-based approach has been developed to track individuals throughout the warning and evacuation process. The software can be used to provide inputs for risk assessment and to explore options for improving the effectiveness of a dam owner's emergency plans or a local authority's response plans. While LifeSim was developed for dam and levee safety analyses, the software is not just limited to flood hazards. LifeSim can be applied to any type of hazard that can be converted into a time series of gridded data including fires, toxic gas, and hurricanes.
Monte Carlo sampling techniques are used in LifeSim to capture the natural variability of temporal uncertainty in the warning and evacuation process as well as the potential for life loss when put in threatening flood situations. Many model parameters can be defined with uncertainty in LifeSim, providing a means of capturing knowledge uncertainty. The natural variability and knowledge uncertainty parameters will vary offering a range of potential life loss and economic damage results.
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Knowledge uncertainty (epistemic uncertainty) random variables are not known exactly and exist when it is not possible to make an accurate estimate of the value of an input. A few examples are flood likelihood, hydraulic coefficients, and channel capacities.
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Natural variability (aleatoric uncertainty) random variables vary spatially or event-to-event and exist when the outcome of a natural process is random, or the natural process is so complex it seems random when viewed in isolation. A few examples are flood magnitude and forecasts.
A better understanding of the factors driving consequences are gained by reviewing the distribution of results as opposed to a single deterministic result. LifeSim can be used to provide inputs for risk assessment and to explore options for improving the effectiveness of a dam owner's emergency plans or a local authority's response plans.
Purpose
The main purpose of the LifeSim software is to help studies and their teams better understand the consequences of a flood event. Although flooding can lead to many types of severe consequences, the primary objective of the USACE Dam and Levee Safety program is to manage risk to the public who rely on those structures to keep them reasonably safe from flooding. Thus, reducing the risk associated with life loss is paramount.
LifeSim was developed to:
- Effectively support reduction of life-safety risks associated with flooding,
- Evaluate existing and residual risks against tolerable risk guidelines,
- Understand life-loss dynamics associated with floods, and
- Create or improve existing emergency action plans.
LifeSim provides a practical life loss estimation approach. The software is designed to facilitate:
- Entry of appropriate data into each of the individual simulation required components,
- The flexibility to apply new research as data inputs to the model,
- Review simulation results from a high level down to individual details, and
- View simulation results as map animations to help facilitate review of results and discussion with emergency managers.
LifeSim evaluates consequences to a study area, and the damageable elements are defined through the addition of user defined agricultural data, structure inventories, road networks and evacuation destinations. These damageable elements can be impacted by hydraulic parameters. Table provides a list of the consequences that the LifeSim software can estimate given the following the minimum requirements:
| Estimate | Minimum Requirements |
|---|---|
| Structure damage | To estimate structure damages, LifeSim requires a user-defined structure inventory, and the hydraulic information must include depth for the flood event. |
| Life loss | To estimate vehicle damages and life loss LifeSim requires a user-defined structure inventory with population for each structure provided. In addition, they hydraulic information must include maximum depth and arrival time for the flood event. Emergency planning zones (EPZs) are also required. |
| Indirect income and job losses (ECAM) | The basic requirements for estimating life loss are necessary for this estimate. In addition, the user must define the total supply of available labor and capital for the entire county (or counties) in the study area. |
| Agricultural losses | The basic requirements include importing gridded agricultural data, and the user-provided hydraulic information must contain agricultural arrival time and flood duration. |
Modeling System Assumptions and Limitations
Every modeling system has limitations due to the choices and assumptions made in the design and development of the software. The following list describes the assumptions and limitations inherent to three aspects of the LifeSim modeling system:
Evacuation Modeling
When modeling evacuations, LifeSim assumes that people will evacuate to whichever of the designated destinations can be reached in the shortest travel time. This assumption does not account for trip chaining, where an individual might go from work, to pick up a kid at school, go back home, and then evacuate.
- This is a simplifying assumption made inherent to LifeSim due to data limitations. Specifically, it is prohibitively difficult to predict atypical evacuation behavior to this level of detail.
Additionally, evacuation routes are limited to the user-provided road networks.
- LifeSim limits evacuation routes to the user-defined road network and assumes that vehicles adhere to the rules of the road.
- The reason for this assumption and limitation is a lack of available data. Road networks are readily available, but alternative paths – such as those that go through parks or empty lots – are not as accessible in a format understandable by LifeSim.
Hydrologic and Hydraulic Uncertainty Modeling
LifeSim does not provide means to account for hydrologic and hydraulic uncertainty. Each alternative relies on a constant hydraulic scenario. Therefore, any analysis of hydraulic or hydrologic uncertainty must be performed outside of the LifeSim software before import.
Due to the event-based nature of LifeSim, hydraulic and hydrologic uncertainty would need to be run as separate alternatives and performed as a sensitivity analysis as part of the LifeSim study.
Modeling Life Loss
The following are three assumptions and limitations in the LifeSim modeling system when estimating life loss:
- In LifeSim, population data is linked directly to structures. Therefore, there is no direct accounting for transient or homeless population. Often, the data necessary to model transient or homeless population is not readily available. However, in a situation where the data was available, a modeler could take steps to account for homeless population by manually adding structure data points with assigned population values in locations where structures may not actually exist.
- When a simulation is computed, the road network is assumed empty prior to evacuation. The purpose of this assumption is to prevent double counting of the population both on roads and in structures.
- LifeSim does not account for indirect life loss, or life loss associated with the duration of flooding. This is a simplifying assumption made inherent to LifeSim due to limited resources and available data.