A Three-Parameter S-Shaped Function of Flood Return Period and Damage

Table 6

The grades of flood hazards and main strategies.

Grade	Return period	Flood damage	Turning point	Physical meaning	Main strategy
I		Small	Point A	Damage-arising point	Resistance strategy
II		Medium	Point A	Damage-arising point
			Point C	Damage transition point
III		Large	Point C	Damage transition point	Resilience strategy
			Point B	Damage-ceasing point
V		Larger	Point B	Damage-ceasing point