Yin ZHOU1,2, Jing'ai WANG1,2,3, Wei XU3,4, Yao ZHOU1,2 1School of Geography, Beijing Normal University, Beijing 100875, China; 2Key Laboratory of Regional Geography, Beijing Normal University, Beijing 100875, China; 3State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China; 4Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China

1. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Mapping the flood disaster risk of metropolitan
region in the Yangtze River Delta of China
Speaker ： Yin Zhou
Tutor ： Jing’ai Wang
Key Laboratory of Regional Geography Research
School of Geography, Beijing Normal University

2. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
OUTLINE
1. Introduction
2. Methodology and materials
3. Selection of Class Intervals
4. Result of Flood Risk Map
5. Conclusion and Discussion

3. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
1. Introduction
China is among the few countries in the world with a relatively
large variety of highly destructive natural disasters (Shi, 2011).
2 000 human lives
30 billion dollars

4. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
1. Introduction
The Yangtze River Delta, which is one of the most developed regions
in China, contributed to 17.6% of China’s overall GDP in 2010
In the past thirty years, 119 floods were recorded, which seriously
threaten the regional economic development.

5. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
1. Introduction
•Maps can reflect the spatial pattern of disasters clearly, and
contribute to better understanding of fundamental laws of disaster
system.
•The maps are needed urgently when disasters outbreak, and the
automatic mapping which enhances the mapping efficiency greatly
has become a research hotspot.
•The data classification is an important part for automatic
mapping.

6. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
1. Introduction
In risk mapping, most classification schemes that have been
proposed are based on the properties of the data's statistical
distribution without regard for the data's spatial distribution.
we should consider spatial regularity while selecting class
intervals.

7. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
2. Methodology and materials
The flood disaster risk in Yangtze River Delta is evaluated by
Hazard, Exposure and Vulnerability, that is
R = H ⊗ E ⊗V
The hazard formative factors consist of rainfall, frequency of rainfall,
terrain and water system. The exposure factors include property
density, population density and land use. The vulnerability factors
include physical vulnerability and the capacities for disaster
reduction.

8. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
•The selection of class intervals can strongly affect the visual
impression given by a map.
•When the number of classes is determined, class interval is the
only factor that affects the result of classification.
•Class intervals are determined by classification method

9. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
•The flood risk in the Yangtze River Delta Region is ranked to
five levels: high, relatively high, medium, relatively low and low.
•Equal intervals, geometric intervals, quantiles, natural breaks,
mean standard deviation are the most common methods for data
classification .

10. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
Terrain Distance from coastline Water influence Land use coverage

11. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
•Flood disaster is prone to the areas with lower elevation.
According to water level statistical data, Yangtze River Delta is
divided into four parts by elevation: 2m, 2~5m, 5~10m, ≥10m.
Elevation ＜ 2m 2~5m 5~10m ≥10m
Weight 0.50 0.30 0.15 0.05

12. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
Generally ， flood disasters occurs more frequently in the areas
that near the coast line in Yangtze River Delta.
Distance ＜ 40km 40~80km 80~120km ≥120m
Weight 0.45 0.35 0.15 0.05

13. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
The influence of water is mainly decided by river density and the
distance from the rivers.
Flood disasters often occur in the area that near the river.
And the influence caused by rivers is different, such as the
Yangtze River influences much stronger than small rivers.
Buffer distance/kilometers
first-order river Second-order river
Inner buffer Outer buffer Inner buffer Outer buffer
8 12 6 10

14. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
The property density is various with different types of land use
coverage. The exposure of land decreases by: urban land, rural
land, farmland, grassland, forest and water bodies.
Land use type urban rural farmland grassland forest water bodies
Exposure 0.30 0.25 0.22 0.10 0.08 0.05

15. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
The spatial correlation coefficient between flood disaster risk and
the constraint layers can be calculated out.
Flood Disaster Risk
Terrain 0.37357
Land use 0.34379
Water Influence 0.28514
Distance from Coastline 0.12683
Ri=0.37357*R1i+ 0.12683*R2i + 0.28514*R3i +0.34379*R4i

16. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Selection of Class Intervals
Mean
Classification Equal geometric Natural
Quantiles Standard
Method Intervals intervals Breaks
Deviation
correlation
0.56199 0.48921 0.53176 0.56804 0.52121
coefficient

17. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Result of Flood Risk Map

18. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China
Conclusion and Discussion
This article has realized the intelligent selection of classification
method of the flood disaster risk based on the constraint layer.
The constraint layers don’t include disaster prevention and
mitigation capacity, which are also very important to the disaster
risk pattern. Selecting proper factors to represent disaster
prevention and mitigation capacity and finding the spatial pattern
of those factors are the further work should be done.

19. Mapping the flood disaster risk of metropolitan region
in the Yangtze River Delta of China