Scope of the LSM
The Life Safety Model (LSM) allows the loss of life and evacuation times to be assessed for a range of types of flood events including slow rising floods, dam and flood defence failures, tsunamis and flash floods. The LSM has been piloted on a number of historical floods including the Mapasset Dam disaster that occurred in France in 1959 and the Great North Sea Flood of 1953 that inundated Canvey Island in the Thames Estuary resulting in the deaths of 58 people. The LSM has recently been used to help to improve the emergency response of coastal communities in Canada to tsunamis and assist emergency planners in Lincolnshire in the UK.
The LSM models individual receptors (e.g. people and cars) and their dynamic interaction with the floodwater. It estimates deaths of people from drowning, exhaustion, the collapse of buildings collapse and vehicles being swept away. The LSM also provides estimates of the time that it will take for people to evacuate an area at risk.
For a given population at risk of flooding the LSM will:
- estimate the potential loss of life due to an extreme flood event
- produce a spectrum of virtual representations of how a flood emergency could evolve
- support emergency analysis activities which aim to support the development of mitigation strategies that could reduce the potential loss of life
- provide insight into the damage to structures, determine areas of greatest flood risk and help to establish the best locations for safe havens and refuges
LSM can also provide insight into the damage to structures, determine areas of greatest flood risk, and provide insight into the needs for timing of evacuation as the flood progresses.
Animated output of the LSM showing the 1953 Great North Sea flood on Canvey Island
Description of the LSM input and engine
Modelling the fate of a set of objects
The system models the fate of receptors, described by their position at each time step of the simulation. The LSM uses generalised event logic to determine the location of each person at each time step, whether they are aware of the danger, whether they are trying to find a refuge, what happens if they encounter the flood in terms of their survival. The LSM includes damage and loss functions for people, vehicles and buildings. These specify whether the receptor survives the flood or not. These functions describe the ability of the receptor to resist the impact from the flood wave, in terms of depth and velocity. There are number of loss functions. For example, there are instantaneous loss functions in cases where an individual person is swept away in fast-flowing water, or has sought refuge in a building that suddenly collapses or a people who have sought refuge can suffer cumulative loss if they are exposed to the flood water for a significant length of time as a result of hunger or cold.
Functionalities of the LSM
Developing the Life Safety Model as an agent-based simulator enables the model to represent a myriad of probable scenarios which could result from a flood event. Unknown variables such as the effectiveness of warnings, road capacity, and time varying population density can be tested in a range of scenarios. To provide this range of assessment, the Life Safety Model was developed to represent the following:
- the number of people that are killed or injured by an inundation
The time-varying properties of the flood in terms of its depth and velocity affect people's survival capacity, and also the speed at which they move. Should a person be caught in the floodwave their chance of survival depends on the velocity and depth of the flood at a particular point in time (i.e. above a certain threshold level people will be drowned or be swept away by the water). However, the effect of continuous exposure to water is also modelled with the effects of exposure also being represented in the number of fatalities - the movement of vehicles is modelled by a simple traffic model
This allows the effects of traffic jams and other bottlenecks to be taken into account when the evacuation time is estimated - the dynamic interaction of the flood wave with vehicles
If people are leaving the area at risk in a car the engine will stop once the vehicle has encountered a certain depth of water or if the combination of velocity and depth is high it would get swept away in the floodwater - the capacity of each building to withstanding the floodwater
Depending on the characteristics of the building and the flood, buildings can: suddenly collapse; fail progressively as a consequence of continuous exposure to the flood; or remain intact. - people being modelled as individuals and also as groups (e.g. families)
so they do not separate during an evacuation. The speed at which a group moves is influenced by every member of the group - the speed of the dissemination of flood warnings
People can receive warnings from a "warning centre" and also by "word of mouth" from other people who are aware of the impending flood wave - the evacuation of people along roads or footpaths, toward refuges is predetermined by the user
The refuges can be areas of high ground, buildings resilient to the flood wave with more than one storey or specially adapted shelters.
For more information, visit our publications page.
Description of the output and how they can be used
The Life Safety Model can be used to provide answers to questions such as:
Risks to people and evacuation issues
- How much time does the population have to evacuate before the flood wave arrives?
- Is it safer to try to evacuate the population or to advise them to ‘stay put’?
- How long would the population take to reach safety?
- Where are the safest evacuation routes located?
Emergency plans for floods and reservoirs
- How can I assess the effectiveness of my plan?
- Which elements should I add to my plan to conform to the government guideline?
- Which tools are available for enhancing my plan?
Examples of the application of the LSM can be found within EU projects such as FLOODsite and FIM-FRAME.