Discrepancies in estimated flood losses on paddy production: Application of damage models on historical flood records of the Northwest States of Peninsular Malaysia

Abstract

Information of flood damage to crops production is essential for guiding risk-based decisions in reducing future adverse impacts of floods. For paddy, its susceptibility to floods is one of the factors that may influence the loss of paddy’s production. To date, there have been limited studies that have been undertaken to examine in detail how different damage functions (with and without a susceptibility index) influence flood damage estimates of paddy using past recorded flood information. This study attempts to examine flood damage functions of different forms in two conditions: as their stand-alone forms and when being applied for damage and risk estimations. Furthermore, recorded revenues from the past were used to investigate the effects of paddy’s susceptibility to floods on revenues. Historical flood evidence and revenues between 1987 and 2021 occurred on paddy granaries under the Muda Agricultural Development Authority’s (MADA) monitoring located in Perlis and Kedah states of Peninsular Malaysia and were used in this study. Application of three damage functions reveals that the exclusion of susceptibility index from the damage calculation results in significantly overestimations of losses, with a standard deviation reaching as high as 38 and overestimations up to four times that of the function with susceptibility index. The high estimates could hinder the acceptance of risk-based flood assessment (and its results) in flood alleviation decision-making. Furthermore, as the percentage of flooded area increases, the revenue loss increases, indicating the effects of floods on harvested paddy quality. This further highlights the potential role of the susceptibility index in the damage function.