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Design, install and maintain protection systems in ways that don’t ultimately exacerbate risk.

Flood protection systems in the Tarai currently reduce short-term risk while increasing long-term risk. Embankments need to be designed considering sedimentation rates, the possibility of safe failure, and accounting for the increasing trend in rainfall intensities that has been observed over the past two decades, by adding safety marings. They also need to be designed in ways that will not attract undesired development near or on the protection structure that undermines the protection level (i.e., embankment roads, agricultural activity on dams, etc.), and for longer lifespans – beyond 25 years – and allow financing and staffing for maintenance, control, and lifecycle management. The presence of embankments and their ability to prevent low-intensity flooding, together with poor land use regulation, can lead to a false sense of security and increased development in adjacent areas; this is known as the ‘levee effect.’ Furthermore, it is unlikely that this development will be built to withstand floods. The likely embankment failures will then be catastrophic, as was the case in the Koshi embankment breach in 2008. Protection systems need to be designed to give space to the river. This means allowing rivers to flood, keeping key assets outside of the flood zone, and protecting lives within the flood zone.

PERC Reports