10
Tecnología y Ciencias del Agua
, vol. VIII, núm. 2, marzo-abril de 2017, pp. 5-18
Lee
et al
.,
Relationships between floods and social fragmentation: A case study of Chiayi, Taiwan
•
ISSN 2007-2422
Hsu, Yu, & Kuo, 2010). Coastal land subsidence
has continued unabated because most fish spe-
cies raised in coastal fish farms require more
than 80 percent fresh water, which is sourced
underground. Chen and Kuo (2000) analyzed
data from 1976 to 1996 and determined that sea-
levels on the Chiayi coast rose approximately
1.92cm/year during that period, exceeding the
global average. Ground subsidence has slowly
decreased since the government implemented
some control measures, and thus its contribu-
tion to rising sea-levels has also decreased.
Although whether climate change is the cause
of the rise in sea-level on the Chiayi coast cannot
be determined, the existence of the phenomenon
is undoubted. For example, the typhoon Min-
dulle attacked Taiwan in July, 2, 2004. Around
11,793 hectares of lands were flooded in Chiayi
County. In June 12, 2005, the extremely torren-
tial rain continued for several days, this area
was serous flooded including 8,261 hectares of
lands in Dongshi Township and 4,859 hectares
of lands in Budai Township.
Variables and data resources
This study conducts two analyses. First, this
study examines the historical trend of social
fragmentation at the township level in Chiayi
County by using longitudinal statistical data
from 1983 to 2011. Second, this study performs
overlay analyses of social fragmentation trends
and flood maps. Using the map of social frag-
mentation trend as the base map, this study
overlays a second layer, the flood map of Chiayi
County, under the condition of rainfall excee-
ding 500 mm daily. According to the Central
Weather Bureau of Ministry of Transportation
and Communications in Taiwan, the extremely
torrential rain means the accumulative rainfall
up to the threshold of 500 mm daily or above.
Thus, the rainfall threshold set to 500 mm daily.
Through this strategy, this study examines the
potential responsive capacity to major disasters
at the township level.
This study suggests that high migration from
rural areas manifests high social fragmenta-
tion. Accordingly, the rate of social increase is
assumed to be negatively related with social
fragmentation. On the other hand, marriage is
considered to be a crucial factor that increases
social integration in a social system (table 1).
To summarize, this study uses the rate of
social increase, crude divorce rate and crude
marriage rate to measure social fragmentation.
Longitudinal data for these three variables were
collected from the Department of Accounting
and Statistics of Chiayi County Government
from 1983 to 2011. To assess the responsive
capacity of a social system to natural hazards,
this study uses flood maps from Taiwan’s Water
Resources Agency for 2007 to 2011. The two data
Table 1. Variables and their relation to social fragmentation.
Construct
Variable
Relation to social
fragmentation
Data source
1
Social fragmentation
Rate of social
increase
2
Negative
Department of Accounting and Statistics, Chiayi
County Government (1983-2011)
3
Crude divorce
rate
4
Positive
Department of Accounting and Statistics, Chiayi
County Government (2000-2011)
Crude marriage
rate
5
Negative
Natural hazard risk Floods
-- --
Water Resources Agency, Ministry of Economic
Affairs (2007-2010)
Note: (1) Dapu Township has recently had extremely high social migration rates. To avoid confounding the index framework, this study excluded
data from Dapu; (2) social increase rate = (in-migration rate) – (out-migration rate); (3) the original data of the rate of social increase are absent
for 1988 and 1995; (4) crude divorce rate = (registered divorces/population of mid-year)*1 000 (5) Crude marriage rate = (registered marriages/
population of mid-year)*1 000.
