Rapid Assessment for Resilient Recovery and ... - GFDRR

Overall, Thailand relies almost entirely on its road sector for the effective operation of its
economy. While its existing institutions, with some uncertainty about the local level, are
capable of relatively rapidly restoring damaged infrastructure to its pre-flood condition,
there remain longer-term concerns about the gradual deterioration of the network due to
less than adequate maintenance funding. Should this situation continue, the network would
be progressively less able to resist damage from future events such as floods, necessitating
higher damage restoration costs than would otherwise be the case.
Damage and Losses
Damage
Table 34 summarizes the damage to the transport sector, by sub-sector, as a consequence
of the flood. As mentioned above, the damage is almost entirely to the road sector.
For the 26 provinces that are included within this needs assessment, the damage can be
broadly broken down as shown on the following page. The estimates of damage cost are
based on the respective agencies’ preliminary assessments of damage to their networks,
converted to costs for each damage site or activity using the agency’s standard unit costs
for each type of work required.
Roads
For both major areas that the flood has affected, the central and northeast plains, the
terrain is generally gently sloping. Rivers are wide and, in normal times, slow flowing. The
heavy rain in the mountains to the north resulted in much greater than average inflows into
the rivers that feed into the plains from the mountains. This flow exceeded the capacity of
the rivers, which resulted in very substantial flows across the land surrounding the rivers,
across which the region’s road networks have been constructed. In most cases, drainage
structures did not have the capacity to quickly pass the water under the roads, and the
roads were overtopped. Typical damage, broadly in order of frequency, is described
below. The damage types are common for all classes of road, from national highway to
local accesses.
• Pavement surface cracking, or otherwise failing, caused typically by traffic continuing
to use the road when a long period of inundation had reduced its strength substantially.
• Pavement loss, caused typically by a combination of traffic and rapid shallow flow
across the downstream lane of the road surface.
• Embankment erosion, typically on the downstream side of the road, caused by
shallow cross flow and, in some areas, wind-induced wave action.
• Damaged cross drainage structures, typically culverts, and adjacent slope protection.
• Incidental damage to traffic control facilities, such as signage, pavement markings,
railing, etc.
THAI FLOOD 2011 RAPID ASSESSMENT FOR RESILIENT RECOVERY AND RECONSTRUCTION PLANNING
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