Rapid Assessment for Resilient Recovery and ... - GFDRR

2.5 Infrastructure Sectors
Summary
Flood Control, Drainage and Irrigation
The objective of this chapter is to provide a preliminary description of the flood event and
of the damage incurred to the flood control, drainage and irrigation infrastructure with a
special focus on the reconstruction needs likely to emerge once the relief phase is over.
It will provide the government with an initial assessment of short-, medium- and long-term
intervention needs.
The 2011 floods affected many parts of the hydraulic infrastructure. Floodwater damaged
the main dikes of the Chao Phraya River and the associated hydraulic structures including
the drainage and irrigation canals and small hydraulic structures. Major dike breaches
occurred in Nakhon Sawan, Chai Nat and Lop Buri provinces. Over 11 percent (about
213,000 ha) of the present irrigation and drainage areas (totaling about 12.2 million rai or
2 million ha) in the 26 assessed provinces has been damaged. The King’s dike, the Ring
dike and associated flood control structures were also damaged. The main and secondary
drainage pumping stations and the main waterways were also damaged due to heavy
siltation and clogging. The total damage to the flood control, drainage and irrigation
infrastructure is estimated to be THB 8.7 billion. This estimate does not include damage
to the on-farm irrigation and drainage infrastructure, which is included in the agriculture
chapter.
Component
Royal Irrigation Department
Maritime Dept.
Bangkok MA
TOTAL
Disaster Effects
Ownership
Damage Losses Total Public Private
7,723 7,723 7,723
242 242 242
750 750 750
8,715 8,715 8,715
Table 23: Total damage
in the flood control, drainage
and irrigation sector,
in Thai baht, millions
The needs for recovery and reconstruction are estimated at THB 43.1 billion.
The reconstruction strategy recommends immediate, short-term requirements as well as
several medium- and long-term activities. Short-term needs include restoring the existing
drainage capacity and irrigation supplies for the forthcoming dry season crops by completing
the ongoing efforts to close canal breaches, completing temporary repairs to structures,
de-silting canals, and strengthening vulnerable and damaged components of the dikes,
barrages and river training works. Most of these works do not require new designs; the
structures can be restored to their pre-flood condition. However, a design review based on
new modeling may be required for certain critical flood embankments such as the King’s
dike and the Ring dike (for the industrial parks), drainage canals and pumping
stations. This will require hydrological and river morphological analyses and design
reviews. There is no damage to the major dams in the north of the basin. However, there
is an urgent need to carry out dam safety reviews for three large dams and update the
reservoir operations procedures. From a public safety perspective, the dams need to be
76 THAI FLOOD 2011 RAPID ASSESSMENT FOR RESILIENT RECOVERY AND RECONSTRUCTION PLANNING