Analysis of Rainfall-Flood Severity Relations in Small Ungauged Catchments

Abstract

As extreme floods occur frequently in recent years due to global climate changes, an increase in sudden local flooding of great volume and short duration is becoming the significant danger and loss of life and property in the Korean Peninsula as well as most parts of the world. Since such a local flood rises quite quickly with little or no advance warning to prevent flood damage, this study has developed a new flash flood index for the use in small ungauged catchments. The flash flood index is obtained by relative severity factors estimated in ratios for hydrograph characteristics of each flood event to those of the highest recorded maximum flood. Flood runoff hydrographs for the two selected small ungauged basins are generated from a rainfall-runoff model for the annual maximum rainfall series of long-term observed data. The aim of this study is to present the best-fit regression equation with the high coefficient of determination between the flash flood index and rainfall characteristics to provide the basis database for forecasting a local flood severity directly from rainfall data in small ungauged catchments. The regression results in this study show that the proposed flash flood index has a very high relation to a certain rainfall pattern for both study basins. It is therefore expected that the regression equations between the new flash flood index and rainfall characteristics can provide better understanding of the hydrologic behavior of local flash flooding using rainfall patterns in small ungauged catchments.

An Assessment of Flooding Risk Using Flash Flood Index in North Korea - Focus on Imjin Basin -

“…, 모의된 유출 수문곡선의 홍수반응시간을 제외한 상승부경사와 홍수량 비를 이용하여 산정한 돌발홍수지수를 기존 3개의 상대심 도로 산정한 돌발홍수지수와 비교하였다 (Kim et al, 2012 (Dury, 1961;Williams, 1978;Leopold, 1994 비해 13, 38, 31, 43, 45 소유역은 각각 67.1, 70.5, 72.4, 73.2, 72.3 포인트로 평균 돌발홍수지수 대 비 편차가 3.9, 7.4, 9.3, 10.1, 9.1 포인트 높았고, 평균을 기 준으로 6.2, 11.7, 14.7, 16.0, 14.5 …”

Development of a New Flood Index for Local Flood Severity Predictions

“…, 과거 강우자료 를 이용하여 각 빈도별 지속시간별 확률강우량에 대한 유 출수문곡선을 바탕으로 돌발홍수지수를 산정하고 돌발홍 수지수-지속시간-빈도 관계곡선을 제시하였으며 (Kim et al, 2010), 모의된 유출수문곡선의 홍수반응시간을 제외 한 상승부경사와 홍수량비를 이용하여 산정한 돌발홍수 지수를 기존 3개의 상대심도로 산정한 돌발홍수지수와 비 교하였다 (Kim et al, 2012 (Williams, 1978). 이러한 강턱유량은 현장자료를 이용하여 결정할 수 있으나, 현장에서 강턱유량이나 수심의 구별이 어려운 관계로 특정 재현기간별 유량으로 산정하는 연구들이 많이 수행되어 왔다 (Dury, 1961;Williams, 1978;Leopold, 1994).…”