Table 8.

Table of Symbols.

No.	Symbol	Definition	Unit
1		Represents the unit-width flood discharge at the entrance of the underground space	m3/s/m
2		The surface water depth at the entrance	m
3		The total floodwater volume entering the underground space at cumulative time	m3
4		Width of the entrance staircase to the underground space	m
5		Surface water depth	m
6		The water depth of underground flooding	m
7		Area of the underground space	m²
8		The rising velocity of underground water levels	m/s
9		Surface water depth rise rate	m/s
10		Flooding Risk Awareness Time	min
11		Evacuation Awareness Communication Time	min
12		Walking Time on Flat Ground within the Underground Space	min
13		Time to Pass Through the Underground Entrance of the Evacuation Staircase	min
14		Time to Reach the Surface Exit via the Evacuation Staircase	min
15		The time required for evacuation during flood intrusion into underground spaces	min
16	P	Population density of the underground space	persons/m2
17	N	Effective flow coefficient	persons/min·m
18	B’	Width of the underground entrance of the evacuation staircase	m
		Walking distance	m
19		Distance of the staircase	–
		Effective flow coefficient (= 90)	–
	β	Assuming that the water depth on the surface of the staircase steps during escape is cm, at this time the impact factor	–
20		Walking speed on the staircase	m/min
21	Cv	Arameters including the coefficient of variation	–
22	Cs	Skewness coefficient	–
23	Kp	Frequency factor	–
24	n	The rainfall reduction coefficient	–