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Catastrophic flood and forest cover change in the Huong river
basin, Central Vietnam: a gap between common
perception and facts
Phong Tran, Ph.DCollege of Economics, Hue University
Asian Symposium on Disaster Impact and AssessmentHue - August
25-27 2010
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Outline♦Research problems♦Research questions♦Research location
and conceptual framework♦Results♦Conclusions
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Research problems♦ Increasing impacts of natural
disaster in Viet Nam♦ Problems of traditional disaster
risk reduction approach and planning in the face of climate
change impacts
♦ Deforestation is often blamed as a main cause of flood in the
lowland
010002000300040005000600070008000
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Total Loss Caused by Natural Disasters (Bil. VND)(Source CCFSC,
2005)
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Research Questions– What are linkages between flood in the
lowland
and forest cover in the upland?– What are the gaps between flood
management
and forest management policies and practices at local level?
– How local knowledge and community participation can be
utilized to sustainably reduce disaster risks?
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Research location: Thua Thien Hue♦ Most disaster prone areas
of Vietnam♦ The province has an area
of 5,053 square km ♦ The estimated population
is 1,150,000 in 2006♦ Infrastructure and industry
lies in the coastal plain♦ Most of the population
lives within 25 km of the coast
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Huong river basin
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Research location
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Research methodologies
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Disaster trends
Year
2010200019901980197019601950
Ave
rage
mon
thly
pre
cipi
tatio
n (m
m) i
n flo
od s
easo
n
700
600
500
400
300
200
100
Average monthly precipitation in rainy season (Aug-Dec) from
1960 to 2004
02468
1012141618
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Number of major disasters from 1804 to 1945
Number of major disasters from 1975 to 1999
Disaster frequency by month in Thua Thien Hue Province
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Disaster trends (Cont.)
02468
101214161820
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2002
2003
2004
2005
0
100
200
300
400
500
600
700
Number of days above alarm level II Flood level at Kim Long
(cm)
Linear (Flood level at Kim Long (cm)) Linear (Number of days
above alarm level II)
Day Cm
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Disaster trends (Cont.)♦Frequency and severity are
increasing♦Disasters last longer and unpredictable, e.g. flood
1999♦The flood/storm season comes earlier than before♦Local
climate has been affected by global climate
change (1996, 1997)♦Climate change may have contributed to a
rise in
intensity and frequency of adverse metrological phenomena
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Remote sensing images
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Forest cover change in uplands
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Forest cover change in uplands (cont.)
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Rainfall and discharge
0
200
400
600
800
1000
1200
1400
1 12 23 34 45 56 67 78 89 100
111
122
133
144
155
166
177
188
199
210
221
232
243
Rainfall (mm/day) Discharge (m3/s)
♦ 78% of discharge variance was accounted for by the rainfall♦
No correlation b/w runoff coefficient and catastrophic flood
levels
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Causes of catastrophic flood
♦As evidence from spatial and temporal data analysis– 71% due to
climate
change/variability– Infrastructure
development in lowlands
– Negligible impacts of forest cover change
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Observation of uplanders
Observation of upland people on flood and biodiversity♦ Flood
increasing♦ Biodiversity (quantity/quality decreasing)
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Perception of upland people on the impact of deforestation
Deforestation causes: flooding, soil erosion, flash flood,
reduce water in summer
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Perception of people on the cause of catastrophic flooding
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Findings from data analysis♦ In the Huong river basin
– Forest plays negligible role in decreasing catastrophic
large-scale flood.
– Most catastrophic floods were caused by climate variability,
and by the development of main roads and dyke infrastructures in
the lowlands rather than by land-use changes in the uplands
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Key findings from social survey♦Many forest management programs
and policies
rely on the forest-catastrophic flood linkages♦Reduce the
accessibility of upland people to natural
resources♦ Indigenous practices have been ignored♦Local
management systems have been disrupted♦The main agriculture land
has been moved to the
vulnerable areas
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The Gap…♦Common perceptions and scientific evidences in
case of catastrophic floods♦The same coping mechanisms for
normal floods
and catastrophic floods♦Lack of disaster consideration in
environment
programs♦The traditional methods of flood risk mitigation
are
ineffective to deal with catastrophic floods
Catastrophic flood and forest cover change in the Huong river
basin, Central Vietnam: a gap between common perception and facts
OutlineResearch problemsResearch QuestionsResearch location: Thua
Thien HueHuong river basinResearch locationResearch
methodologiesDisaster trendsDisaster trends (Cont.)Disaster trends
(Cont.)Remote sensing imagesForest cover change in uplandsForest
cover change in uplands (cont.)Rainfall and dischargeCauses of
catastrophic floodObservation of uplandersPerception of upland
people on the impact of deforestationPerception of people on the
cause of catastrophic floodingFindings from data analysisKey
findings from social surveyThe Gap…