Abstract
Drainage networks are essential compartments in an urban infrastructure system for the efficient collection and prompt drainage of flood water. In addition to the advances in numerical techniques on urban flood simulation, the topological characteristics of urban drainage networks and their impacts on flooding have not been investigated thoroughly despite their importance. This study evaluated the urban drainage networks in Seoul, South Korea, in terms of the network configuration and its implication for peak flows and flood mitigation. Gibbs’ model was used to analyze the network configuration of 31 urban catchments with various slope ranges. The results showed that urban drainage networks can be less efficient than river in nature in terms of the drainage time, which is counter-intuitive. On the other hand, the analysis showed that efficient networks have risks of flood concentration and, hence, increase potential flood risks. This study showed that efficient networks tend to have higher peak flows at the outlet and vice versa. Therefore, an alternative drainage network layout, which is less efficient and more sinuous, was introduced and it resulted in reduced peak flows and flooding. This result shows managing a proper drainage network layout can contribute to flood mitigation in urban catchments.
Highlights
In 2010 and 2011, the metropolitan city of Seoul, South Korea suffered from floods that the city had not experienced before
The flood damage in 2011 was caused by heavy rainfall; more than 200 mm fell over a six hour periods on 27 July in Gangnam areas, which have a high-density of assets and population in the southeastern part of Seoul
The heavy rainfall in 2011 at the Gangnam area was equivalent to the rainfall-amount of a 50 year-return period, which was slightly greater than the design standards, resulting in flooding of more than four square kilometers of the city’s heart near Gangnam subway station [1]
Summary
In 2010 and 2011, the metropolitan city of Seoul, South Korea suffered from floods that the city had not experienced before. Since the flood in 1990, the city government has invested heavily to reinforce the levees and pumping stations primarily to prevent a similar flood. In contrast to their predecessors, the floods in 2010 and 2011 were both caused by local heavy rainstorm converged on very small areas rather than by flooding from the Han River. The heavy rainfall in 2011 at the Gangnam area was equivalent to the rainfall-amount of a 50 year-return period, which was slightly greater than the design standards, resulting in flooding of more than four square kilometers of the city’s heart near Gangnam subway station [1]
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