Rapid Assessment for Resilient Recovery and ... - GFDRR

characteristics in one area can have adverse impacts on other areas a considerable
distance away.
To avoid this situation, and also to provide the government with a comprehensive
understanding of flood behavior in the basin, there is an urgent need for comprehensive
modeling of the entire basin, and of the northern mountain catchments from which the
basin’s rivers originate. Having such a model available, with real time connections to rainfall
levels, river height, dam operations and other critical inputs, would enable all agencies,
developers, urban planners, etc, to have access to and share a common hydraulic
information source for the entire basin. This would enable the impacts of proposed
developments to be assessed for their wide impact, rather than for their very limited impact
as presently appears to be the case. This initiative is reported on in more detail in the Flood
Control, Drainage and Irrigation section of this report.
Providing for climate change impacts
It is now widely accepted that climate change will result in more such events as the recent
flood, and also more periods of dry weather than is the case now. Climate change mitigation
needs to become a standard input into the design of infrastructure that interacts with rainfall
data and river flows. This should be considered as part of the basin modeling referred to
above. Some studies of climate change impacts have been undertaken, and should be
referred to. 90
Develop hazard mapping
In conjunction with the hydraulic model development referred to above, the entire river basin
should be mapped from the perspective of hazard vulnerability. Given the nature of the
basin, this would focus largely on flood-related hazards, but would also take into account
other hazards to which the basin might be subject.
Consider development of strategic road sub-networks
For a flood of this magnitude, perhaps 1 in 50 or 100 years to be determined, it is not
always possible to maintain the entire road network in a flood free condition, at an
acceptable cost. An alternative is to identify critical links in the network that are to be
flood-free, and designed and constructed to be so, and to allow the remainder of the
network to be inundated from time to time. This remainder would be designed to withstand
inundation more effectively than present designs so, for example by including floodways
– depressed sections of road, suitably protected against flow damage – to allow water to
dissipate more quickly than is the case at present. Some portions of these less critical roads
can be constructed higher than others, so that they can become places of refuge for people,
livestock, implements, etc, to allow them to avoid the impact of the flooding on their usual
locations.
Consider alternative pavement structures for road sections likely to be inundated
A very substantial portion of the damage to the road network, particularly the national network
that carries heavy traffic, is failure of the pavement structure due to inundation-caused
90 A Master Plan on the Climate Change of Thailand: An Energy and Food Crisis, Chulalongkorn University, 2010
112 THAI FLOOD 2011 RAPID ASSESSMENT FOR RESILIENT RECOVERY AND RECONSTRUCTION PLANNING