Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 18, 171-183, 2018
https://doi.org/10.5194/nhess-18-171-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Jan 2018
Development of a precipitation–area curve for warning criteria of short-duration flash flood
Deg-Hyo Bae1, Moon-Hwan Lee1, and Sung-Keun Moon2 1Department of Civil and Environmental Engineering, Sejong University, Seoul, 05006, South Korea
2Water Resources Research Division, Water Resources & Environment Research Group, Rural Research Institute, Korea Rural Community Corporation, Ansan-si, Gyeonggi-do, 15634, South Korea
Abstract. This paper presents quantitative criteria for flash flood warning that can be used to rapidly assess flash flood occurrence based on only rainfall estimates. This study was conducted for 200 small mountainous sub-catchments of the Han River basin in South Korea because South Korea has recently suffered many flash flood events. The quantitative criteria are calculated based on flash flood guidance (FFG), which is defined as the depth of rainfall of a given duration required to cause frequent flooding (1–2-year return period) at the outlet of a small stream basin and is estimated using threshold runoff (TR) and antecedent soil moisture conditions in all sub-basins. The soil moisture conditions were estimated during the flooding season, i.e., July, August and September, over 7 years (2002–2009) using the Sejong University Rainfall Runoff (SURR) model. A ROC (receiver operating characteristic) analysis was used to obtain optimum rainfall values and a generalized precipitation–area (PA) curve was developed for flash flood warning thresholds. The threshold function was derived as a PA curve because the precipitation threshold with a short duration is more closely related to basin area than any other variables. For a brief description of the PA curve, generalized thresholds for flash flood warnings can be suggested for rainfall rates of 42, 32 and 20 mm h−1 in sub-basins with areas of 22–40, 40–100 and > 100 km2, respectively. The proposed PA curve was validated based on observed flash flood events in different sub-basins. Flash flood occurrences were captured for 9 out of 12 events. This result can be used instead of FFG to identify brief flash flood (less than 1 h), and it can provide warning information to decision-makers or citizens that is relatively simple, clear and immediate.

Citation: Bae, D.-H., Lee, M.-H., and Moon, S.-K.: Development of a precipitation–area curve for warning criteria of short-duration flash flood, Nat. Hazards Earth Syst. Sci., 18, 171-183, https://doi.org/10.5194/nhess-18-171-2018, 2018.
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Short summary
Recently, flash floods at some regions have occurred with very short duration less than 1 h. It is necessary to develop the criteria for deciding intuitively the flash flood occurrence with short duration. This article proposes quantitative criteria for flash flood warning that can be used to rapidly assess flash flood occurrence based on only rainfall estimates. The key advantage of this method is possible to issue flash flood warnings without running the entire hydrometeorological model.
Recently, flash floods at some regions have occurred with very short duration less than 1 h. It...
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