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

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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

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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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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…