Flooding time nomograph for urban river flood prediction: Case study of Dorim stream basin, Seoul

Abstract

Global climate change is intensifying flood damage in urban rivers. Notably, most small and medium-sized urban rivers have a brief concentration period and are highly vulnerable to sudden heavy rains that lead to a rapid increase in water levels. Therefore, rapid flood forecasting must be performed through accurate flood occurrence and timing prediction. In this study, a flooding time nomograph (FTN) was proposed to predict the flood occurrence time according to rainfall conditions, such as intensity, time distribution, and duration. In addition, rainfall-runoff simulations were performed by establishing different virtual rainfall scenarios using Huff's quartile rainfall time distribution. The simulation results were used to formulate the relationship between the rainfall intensity and flood occurrence time to generate the FTN. The applicability of this tool was verified through a comparison with the observed flood occurrence time for an actual rainfall event, which was highly accurate in the target watershed, with a correlation coefficient >0.8 and Nash-Sutcliffe efficiency >0.6. Therefore, the proposed FTN can be used to reasonably predict the occurrence of floods and the time of flood occurrence using only predicted rainfall information. K E Y W O R D S flood, flood forecasting and warning, flooding time nomograph, rainfall-runoff model, urban stream 1 | INTRODUCTION Extreme weather events caused by global climate change are frequent worldwide. According to the 6th evaluation report published by the Intergovernmental Panel on Climate Change (IPCC), the surface temperature has sharply increased since the fifth evaluation report, with the highest temperatures observed since 1850, and extreme climate change, unprecedented in modern human history, is occurring (IPCC, 2021). To examine the heavy rainfall characteristics of major urban areas in Korea, Yoon et al. (2016) performed quantile regression analyses by applying various classification criteria for extreme precipitation to eight major cities in Korea.According to the Mann-Kendall test and Sen test results, the annual top 10th maximum precipitation has increased by 3.1%-15.0% on average over the past 30 years . At present, the temperature is

Assessing future urban flood hazard: A comprehensive approach to estimating the implications of future rainfall scenarios

“…The Dorim river basin was selected as the target basin for this study, which includes the most flood vulnerable area among the 34 urban areas where flooding is likely to occur in Seoul (Moon, Yoon, Lee, et al, 2023). Figure 1 shows geographic information about the study area.…”

The growing strength of the ‘Journal of Flood Risk Management’ community

“…When considering the improvements of predictions, Moon et al (2023) use nomographs to consider future flooding of an urban river. Sahraei et al, 2022 use a GIS‐based multi‐criteria decision‐making approach for large ungauged watersheds, focusing on susceptibility when having little access to data: an interesting hybrid method that seemingly outperforms some previous methods when compared with known historic maps.…”