Abstract

Water diversion systems play crucial roles in assuaging flood risk by diverting and redistributing water within and among basins. For flood and drought assessments, including investigations of the effects of diversion systems on river discharge worldwide, the explicit inclusion of these systems into global hydrological models (GHMs) is essential. However, such representation remains in the pioneering stage because of complex canal operations and insufficient data. Therefore, we developed a regionalized canal operation scheme and implemented it in the H08 GHM for flood diversion in the Chao Phraya River Basin (CPRB), Thailand, which is a complex river network with several natural and man-made diversion canals and has been subject to severe flooding in the past, including recent years. Region-specific validation results revealed that the enhanced H08 model with the regionalized diversion scheme could effectively simulate the observed flood diversion pattern in the CPRB. Diverted water comprises approximately 49 % of the annual average river discharge in the CPRB. The simulations further confirmed that the presented canal scheme had the potential to reduce flood risk in the basin by significantly reducing the number of flooding days. A generalized canal scheme with simple input data settings was also constructed for future global applications, providing insights into the maximum level of discharge reduction achievable with diversion of nearly 57 % of the annual average river discharge of the CPRB. Overall, the enhanced H08 model with canal schemes can be adapted and applied to different contexts and regions, accounting for the characteristics of each river network by maintaining the basic principles unaltered.

Highlights

  • Floods are among the most severe natural hazards, and flooding occurs naturally when river discharge exceeds the channel carrying capacity

  • The generalized scheme has a reasonable effect on the flood risk reduction, considerably reducing the number of flooding days (Fig. 8); it can be regarded as the preliminary survey of future global applications using simple input data settings that can be derived from river discharge alone

  • We developed a flood diversion canal operation scheme for the Chao Phraya River Basin (CPRB), a complex river network in Thailand with 530 several natural and man-made diversion canals

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Summary

Introduction

Floods are among the most severe natural hazards, and flooding occurs naturally when river discharge exceeds the channel carrying capacity. Almost 13% of the global population (around one billion people) lives in floodplains (Di Baldassarre et al, 2013); this population are at risk of exposure to river flooding caused by extreme weather events (Alfieri et al, 2017). These flood issues have been addressed in many areas to a greater extent 35 through the construction of 16.7 million reservoirs with a storage volume of nearly 8000 km (Lehner et al, 2011), along with other flood mitigation measures such as retention areas, afforestation, diversion dams, flood channels, etc

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