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Furthermore, the flood risk analysis
Figure 6: Runoff statistic measured at Nakhon Sawan
province (C.2), unit: m3/second.
should also include an analysis on the
probabilities of dike breaches, as well
as the influence of human interventions
(e.g. reservoir operations). A major
difference between this flood and other
severe flood events was that water
levels rose at a slow, steady rate, and
flood water persisted in some areas for
almost 70 days before receding. The
main cause of the flooding was the low
flow capacity of the river, which resulted
Source: RID
in river dikes overtopping and breaching
Figure 7: Runoff statistic measured at Nakhon Sawan
in many river arms. Also the river’s
province (C.2), unit: million m3
capacity decreases downstream, which
implies that spillage from the river
channel gradually occurs in the upstream
areas when a large-scale flood occurs.
Some questions were raised regarding
how the major reservoirs where operated.
But as the preceding sentences show,
there was simply much more water
upstream than the downstream channel
was able manage, and the surplus water
Source: RID
flows had nothing to do but flow across
country. Floods in Bangkok and surroundings were caused by: (i) high discharges from
the upstream Chao Phraya River, some of which reached as far as Bangkok via the flood
plains; (ii) releases from the main upstream reservoirs; (iii) high sea water levels in the
Gulf of Thailand; (iv) high intensity rainy in the city, exceeding the capacity of the drainage
network and; (v) the compounding of i to iv.
Sector Context
Accumulated Volume (Mcm)
Thailand’s water sector is complex, with many agencies involved, but without significant
coordination amongst them, or sufficient legislation to support the establishment of a single
agency with oversight of the sector as a whole. The result is fragmentation, resistance to
change and inefficiencies in the overall water resources management structure. This section
presents a brief overview of the sector’s legal framework and key players and issues
related to institutional arrangements. A more comprehensive analysis is provided in Annex 8.
Water Laws and the Policy Framework
Thailand has many water related laws, administered by over 30 departments in eight
ministries (Annex 8). There is no umbrella legislation to link these laws and codes, and
consequently there is no legislative backing for any organization to undertake integrated
water resources management. In practice, this leads to erratic and ad hoc engagement
between agencies. While many of these agencies are involved in managing the delivery of
water, there is no single agency that has overall responsibility for managing water resources
in an integrated manner. The absence of a modern, comprehensive water resources law
78 THAI FLOOD 2011 RAPID ASSESSMENT FOR RESILIENT RECOVERY AND RECONSTRUCTION PLANNING