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Assessment of Loss of Life Due to Dam Failure Floods Considering Population Distribution andEvacuation〇Jiaqi PENG, Takahiro SAYAMA, Jianmin ZHANG

Introduction
The dam failure is considered a low probability, highPopulation change per unit hour was calculated using

consequence event. Although the frequency of dam

the number of end and start orders for shared bikes andfailures has decreased since the 21st century, the risk ofthe percentage of the population using them. Since thedam failure still exists. Loss of life (LOL) is the mostpopulation changes are not significant in some timesevere consequence of dam failure floods. Assessing

intervals, a day was divided into three intervals:

potential losses can provide scientific guidance fornighttime, commuting, and working time. The

response in dam emergencies.

population distribution was downscaled to a 100m grid

The LOL due to dam failure is influenced by various

size using building vector data, point-of-interest (POI)

uncertainties. Researchers currently strive to consider

data, and nighttime lighting data.

as many uncertainties as possible. However, the impact

The dam failure LOL assessment modelof the spatial-temporal distribution of the population on
the results of life losses still needs further investigation.

The dam failure LOL formation consists of thefollowing six processes (Figure 2).

This study established a population distribution(1) Generation of population at risk (PAR). The

model and a LOL assessment model. By calculating thenumber of PAR is determined by the inundation

spatial-temporal changes in life losses during different

extent and the spatial and temporal population

periods and warning times, the study can provide

distribution, which directly affects the LOL results.

evacuation guidance for decision-makers.
The population distribution model
The population distribution model (Figure 1) isestablished based on multi-source data.

(2) Transmission of warnings. Warnings are spreadamong the population in the downstream throughradio, social media etc., with a transmission timeof Ttran. The time between the issuance of thewarning and the occurrence of the dam failure is
the warning lead time, Twar.
(3) Evacuation preparation process. After receiving
the warning, people need time to make decisions
on whether, when, where, and how to evacuate.
This part of the time is called the reaction time Tres.
(4) Vertical evacuation process. When conditions are
not suitable for horizontal evacuation, peoplechoose vertical evacuation, i.e., moving verticallyupwards inside buildings. People are safe if theFigure 1 Population distribution calculation modelbuilding can be stabilized during flooding. Thepercentage

ofpopulation

choosesverticalevacuation is R. The percentage of population
successfully evacuates vertically is Rveva.
(5) Horizontalevacuation

process.

Horizontal

evacuation means the population moves to shelters.

(b) Clear(a) Fuzzy

The success of horizontal evacuation depends onwhether the available time (flood arrival time

Figure 3 Comparison of LOL at two levels of(Tarri), rise time (Trise), etc.) is greater than theunderstanding

required time (Teva). The percentage of successful
horizontal evacuation is Rheva.

(2) LOL assessment
The value of loss of life varies significantly when

(6) Loss of life formation. The PAR who did not

dam failure occurs at different times of the day.

successfully evacuate is called the exposed

Since people's reaction ability at night is lower than

population Pexp, who may lose their lives. LOL isthat in daytime, a longer Twar is needed for people

calculated by the formula.

to react. Meanwhile, for the dam site similar to

LOL = PAR  R (1 − Rheva ) + (1 − R ) (1 − Rveva ) FM (1)Where FM is the mortality rate.

Zipingpu, the downstream is the non-central areaof the city, due to the population activities, i.e.,
going to the central city to work during the day andreturning home at night, the number of people inthe downstream at night is more than that in thedaytime, so it should be more concerned about thesafety of the dam at night.

Figure 2 The process of dam break LOL formation
Result(a)(b)

Taking the case of Zipingpu Dam in Sichuan
Province, China, the most severe condition isconsidered. HEC-RAS is used to calculate the dam
failure flood evolution process.
(1) Comparison of results(c)

The results of this study were compared with theFigure 4 LOL at different Twar during different time (a)Li-Zhou method, which is the recommendednight time, (b) commuting, (c) working time

method of calculation LOL for Chinese dams.

Conclusion

Under two levels of understanding and three WTThis study models the spatial- temporal distribution(time between warning issuance and floodingof the PAR based on multi-source data and analyzes thereaching the PAR) scenarios, the results of this

impact of differences in population distribution undermodel are within the Li-Zhou method resultnighttime, commuting, and work hours on the LOL ofintervals, or the results are higher than the Li-Zhou

dam failures. The results provide the latest Twar andmethod when the level of understanding is clear.

suggest that managers should pay more attention to thedam status at night.