A case study on estimating the flood severity using flood hydrographs for small ungauged catchments in Korea

• Main Author: Hyun Il Choi
• Format: Article
• Language: English
• Published: Maejo University 2013-02-01
• Series: Maejo International Journal of Science and Technology
• Subjects: flood hazard index; flood severity; run-off hydrograph; rainfall run-off model
• Online Access: http://www.mijst.mju.ac.th/vol7/94-106.pdf

Local floods with rapid run-off and debris flow have posed a great potential threat of danger to life and property in recent years. Previous studies have examined the flash flood index determined by the characteristics of observed flood hydrographs such as rising limb, peak discharge and time to peak. To estimate the flood severity for small watersheds in Korea where the observed hydrograph is usually not available, this study proposes a flood hazard index (FHI) based on hydrographs generated from a rainfall run-off model for the annual maximum rainfall series of long-term observed data. The FHI is obtained by summing the relative severity factors measured by the ratios of characteristics of each flood to the highest recorded maximum value and implemented for two selected small ungauged basins in Korea. This study also presents regression equations between FHI and rainfall characteristics to predict the severity of flooding in small catchments. A stronger relation between FHI and maximum rainfall over a short interval demonstrates that heavy or excessive rainfall in a short period of time can cause a serious local flood in small watersheds.