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
Outline♦Research problems♦Research questions♦Research location and conceptual framework♦Results♦Conclusions
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)
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?
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
Huong river basin
Research location
Research methodologies
Disaster trends
Year
2010200019901980197019601950
Ave
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mon
thly
pre
cipi
tatio
n (m
m) i
n flo
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easo
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700
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Average monthly precipitation in rainy season (Aug-Dec) from 1960 to 2004
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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
Disaster trends (Cont.)
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101214161820
1977
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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
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
Remote sensing images
Forest cover change in uplands
Forest cover change in uplands (cont.)
Rainfall and discharge
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1400
1 12 23 34 45 56 67 78 89 100
111
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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
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
Observation of uplanders
Observation of upland people on flood and biodiversity♦ Flood increasing♦ Biodiversity (quantity/quality decreasing)
Perception of upland people on the impact of deforestation
Deforestation causes: flooding, soil erosion, flash flood,
reduce water in summer
Perception of people on the cause of catastrophic flooding
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
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
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…