Impacts of future climate change on urban flood risks: benefits of climate mitigation and adaptations

Abstract

Abstract. As China is urbanized, flooding has become a regular feature in major cities. Assessing potential urban flood risks under climate change has become crucial for better managing such risks given the severity of the devastating disasters (e.g., the current 2016 flooding across China). Although the impacts of future climate change on urban flood risks have been investigated in many existing studies, the effects of both climate mitigation and adaptations have rarely been accounted for in a consistent framework. In this study, we assess the benefits of (1) avoided greenhouse gas (GHG) emissions and (2) adapting drainage systems on urban flood risks within the context of global warming through a case study in the Northern China. The urban drainage model, Storm Water Management Model (SWMM), was employed to simulate urban floods under current conditions and two feasible adaptation scenarios (i.e., pipe enlargement and low impact development), driven by bias-corrected meteorological forcing from five general circulation models (GCMs) in the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive Based on the results, the volume of urban floods is projected to increase by 52 % in the period of 2020–2040 when compared to that in 1971–2000 under the business-as-usual scenario (i.e., Representative Concentration Pathways (RCP) 8.5). The magnitudes of urban floods are found to increase nonlinearly with changes in precipitation intensity, and highest risks associated with floods with smaller return periods below 10 years are identified. Despite the high level of uncertainty, it is obvious that avoided greenhouse emissions will be beneficial in terms of reducing risks associated with urban floods. On average, the magnitude of projected urban floods under RCP 2.6 is 13 % less than that under RCP8.5, demonstrating the importance of global-scale efforts on GHG emission reduction in regulating local to regional hydrometeorological responses. Moreover, the two feasible adaptation scenarios are shown to be able to further reduce risk associated with floods effectively. This study highlights the importance of accounting for local climate adaptation efforts in assessing urban flood risks under a changing climate.

Evaluating the Effects of Low Impact Development Practices on Urban Flooding under Different Rainfall Intensities

“…Comparison of some Low Impact Development (LID) practices [19]. Compared with traditional flood control measures, LID practices are more flexible in response to climate change, which is a very important aspect for government decision-makers [36]. Also, it is considered to be a pivotal approach to sustainable urban development.…”

Increase in urban flood risk resulting from climate change – The role of storm temporal patterns

“…This seems contrary to prevailing scientific thought (Milly et al, 2007) and can lead to inadequacies of future stormwater infrastructure as there is evidence to believe that warmer temperatures are forcing intensification of temporal patterns and an increase in variability (Mamo, 2015). Several previous studies have examined the sensitivity of urban catchments to changes in intensity and temporal patterns with peak runoff rates and volumes modelled (Lambourne and Stephenson, 1987;Mamo, 2015;Nguyen et al, 2010;Zhou et al, 2016). For example, Lambourne and Stephenson (1987) presented a Hydrol.…”

“…In particular, flooding in Uttarakhand and Kashmir, which was caused by extreme rainfall coupled with inadequate stormsewer design, is blamed for 580 and 200 deaths respectively (Bisht et al, 2016). China has also experienced a devastating flood season in 2016 (Zhou et al, 2016) with the rapid increase in urbanization. Even with better planned and mature urban cities, Europe and North America are not immune to flooding in urban areas (Ashley et al, 2005;Feyen et al, 2009;Smith et al, 2016).…”

“…Flood risk assessment and communication depend on flood risk mapping, for which flood inundation areas are needed (Merz et al, 2010). Urban catchments are typically complex and need to capture the response of the system along with the interactions of the various components of the stormwater infrastructure (Zoppou, 2001) 2007;Leander et al, 2008;Zhou et al, 2016;Zope et al, 2016). However, there is a lack of a detailed study that looks at assessing future flood damage in a developed environment (Seneviratne et al, 2012).…”

“…comparative model study to look at the impact of temporal patterns on peak discharge rates and volumes. However, these studies largely ignored the detailed hydraulic conveyance aspects of storage ponds, sewers, culverts, and flow control structures, with the exception of (Zhou et al, 2016), which play an important role in how the flow rates generated during runoff move through and impact on the built environment.…”