Mekong River Commission

 

5.1 General Situation

The central and southern parts of Lao PDR were the most affected by floods in 2007, which were mainly associated with impacts of tropical storm 'Lekima'. The resultant national damage and loss exceeded that for 2006, particularly with respect to the rice crop. Elsewhere in the country the only events of note in 2007 were heavy rainfall during mid September in Luangnamtha Province and a local storm that caused some damage in Vientiane during April.

Figure 39. Lao PDR, local storms and fl ash flooding during 2007.

 

5.2 Tropical Storm 'Lekima'

Flash flooding and extensive flood inundation as a result of three days of heavy rainfall, locally in excess of 250 mm and widely above 150 mm, during the fi rst week of October principally affected the catchments of the Se Bang Hieng, Se Bang Fai and Se Done. At the Mahaxi streamgauge on the Se Bang Fai water levels rose almost 1 m above the danger level and the average depth of the consequent inundation was 1.5 m. Water levels on the Se Bang Hieng rose 7 m in less than 36 hours, causing very rapid inundation, typical of a fl ash flood situation. On the Se Done the river level increased by 13 m in the fi rst fi ve days of the month, while the Se Bang Fai rose by 10m. Figure 37 provides some photgraphs of the flooding.

Figure 40. Lao PDR, selected views of flood inundation in the Se Bang Hieng and Se Done river basin resulting from severe tropical
storm 'Lekima' during the first week of October.

 

5.3 Heavy rainfall in Luangnamtha Province

Between the 10th and 13th September, sustained heavy rainfall of up to 75 mm caused local flooding in Luangnamtha Province, disrupting road communication. The intensity of the storms caused a number of landslides in steep terrain, a number of which blocked roads. Agricultural damage, however, was not significant.

 

5.4 Storm in Vientiane

On the 29th April a highly localised storm occurred over Vientiane, associated with very high winds, with gusts of between 130 and 140 kilometres per hour. The overnight rainfall was 63 mm. However, there was little ponding of the runoff and what damage there was to property resulted from the high winds.

 

5.5 Damage and impacts

In Khammuane, Savannakhet and Saravane provinces the consequences of tropical storm ‘Lekima’ were that two people were killed and over 600 villages were affected in some way by the floodwater. Almost 160,000 ha of rice crop was damaged to some extent by prolonged submergence along with 30% of the planted vegetable crop. Full details of the damage are listed in Appendix II.

 

5.6 Lessons learnt

• The ponding of flood water in urban areas, particularly Vientiane, would be minimised if urban development were planned accordingly and the drainage infrastructure improved and maintained - though these improvements are ongoing.
• Prior to the incursion of the ‘Lekima’ tropical storm the Department of Meteorology and Hydrology did provide warnings to Khammouan, Savanakhet and Saravanh provinces. However, some delays occurred in the dissemination of the warnings due to a lack of telecommunication equipment at the local level.
• As in other developing countries, Lao PDR lacks a reserve budget for emergency responses so the relief effort took time. However, the capacity of local communities in coping with flood conditions largely proved to be effective.