Impacts of future climate change on urban flood volumes in Hohhot in northern China: benefits of climate change mitigation and adaptations

Abstract

Abstract. As China becomes increasingly urbanised, flooding has become a regular occurrence in its major cities. Assessing the effects of future climate change on urban flood volumes is crucial to informing better management of such disasters given the severity of the devastating impacts of flooding (e.g. the 2016 flooding events across China). Although recent studies have investigated the impacts of future climate change on urban flooding, the effects of both climate change mitigation and adaptation have rarely been accounted for together in a consistent framework. In this study, we assess the benefits of mitigating climate change by reducing greenhouse gas (GHG) emissions and locally adapting to climate change by modifying drainage systems to reduce urban flooding under various climate change scenarios through a case study conducted in northern China. The urban drainage model – Storm Water Management Model – was used to simulate urban flood volumes using current and two adapted drainage systems (i.e. pipe enlargement and low-impact development, LID), driven by bias-corrected meteorological forcing from five general circulation models in the Coupled Model Intercomparison Project Phase 5 archive. Results indicate that urban flood volume is projected to increase by 52 % over 2020–2040 compared to the volume in 1971–2000 under the business-as-usual scenario (i.e. Representative Concentration Pathway (RCP) 8.5). The magnitudes of urban flood volumes are found to increase nonlinearly with changes in precipitation intensity. On average, the projected flood volume under RCP 2.6 is 13 % less than that under RCP 8.5, demonstrating the benefits of global-scale climate change mitigation efforts in reducing local urban flood volumes. Comparison of reduced flood volumes between climate change mitigation and local adaptation (by improving drainage systems) scenarios suggests that local adaptation is more effective than climate change mitigation in reducing future flood volumes. This has broad implications for the research community relative to drainage system design and modelling in a changing environment. This study highlights the importance of accounting for local adaptation when coping with future urban floods.

Technical note: Laboratory modelling of urban flooding: strengths and challenges of distorted scale models

“…Flood losses are particularly severe in urban environments, and urban flood risk is expected to further increase over the 21st century (Chen et al, 2015;Hettiarachchi et al, 2018;Lehmann et al, 2015;Mallakpour and Villarini, 2015). In response, concepts such as water-sensitive urban design, low impact development and the sponge city model are rapidly developing (Gaines, 2016;Liu, 2016;Zhou et al, 2018). However, the design and sizing of measures aiming at enhancing urban flood protection require accurate tools for risk modelling and scenario analysis (Wright, 2014).…”

“…Existing lab studies representing urban flooding at the district level provide data on street discharges and water depths (Finaud-Guyot et al, 2018) and, in some cases, also surface flow measurements (LaRocque et al, 2013). Few studies report point velocity measurements for urban flooding at the district level (Güney et al, 2014;Park et al, 2013;Smith et al, 2016;Zhou et al, 2016), while detailed velocity measurements are generally available only for more local analyses (e.g. at the level of a single manhole; Martins et al, 2018).…”

Increase in flood risk resulting from climate change in a developed urban watershed – the role of storm temporal patterns

“…Although there are an increasing number of catchment/basin-scale and urban modeling studies that have been performed (Cameron, 2006;Graham et al, 2007;Leander et al, 2008;Zhou et al, 2018;Zope et al, 2016), there is a lack of a detailed studies that look at assessing future flood damage in a developed environment (Seneviratne et al, 2012). The majority of past studies focus on either the hydrologic modeling component or the rainfall intensity aspect and mostly overlook the crucial detail of rainfall patterns.…”

Quantifying the Uncertainty Related to Climate Change in the Assessment of Urban Flooding—A Case Study

“…Huong and Pathirana [11] used a 1-D/2-D coupled urban drainage/flooding model (SWMM-Brezo) model to estimate the changes in flood hazard in the city of Can Tho (Vietnam) in some future climate scenarios. Zhou et al [12] investigated the performance of a drainage system in Hohhot (northern China) in different climate scenarios, exploring the role of mitigation and adaptation measures in reducing urban flood. In Brazil, da Silva et al [13] used updated intensity-duration-frequency (IDF) curves to analyze the effects of climate change on an urban drainage system.…”