Editorial: Journal of Flood Risk Management: Volume 17, Issue 3

Researching and managing flooding in the urban context

When I began my academic career around 25 years ago much of the focus of the research focused on understanding risk in quite a narrow set of flood circumstances namely large inland rivers, high coastal risks and, to some extent, rapid onset flood events. Focus on more traditional floodplain events dominated considerations of flood risk and was, in part, reflective of the management priorities and technical abilities of the time. Considerations of food production and managing the areas where risk to life was highest, dominated the discourse of flood risk management and academics studying it.

I have been privileged to observe the evolution of flood risk research and the acknowledgement that other types of flooding are important and can have equally devastating impacts on individuals and communities. The flood risk research community has evolved to pioneer consideration of a much wider range of flood types, and this Journal as been at the forefront of these advancements. As well as continuing to improve knowledge and insight into many aspects of the ‘traditional’ flood types mentioned above: fluvial and coastal; The Journal of Flood Risk Management now regularly publishes (and welcomes) research into other types of risk such as groundwater or surface water flooding (e.g. see amongst others Allocca et al., 2022; Birch et al., 2021, Fathy et al., 2021), which have become more mainstream within the flood risk research community. In this editorial, I specifically want to reflect on the concept of Urban flood risk management, which continues to emerge as an important area of flood research and draw attention to several contributions to the current Issue of this Journal (Volume 17, Issue 3, June 2024) which have focussed on urban flood risk.

Whilst all flood risk is complex, considerations of urban flood risk raise particular challenges. Urban areas often have rapidly changing physical and social environments with higher population densities, more mobile, diverse, and less cohesive communities. There is often a complex interplay between the natural and built environment which impacts upon how easy it is to understand and model urban flood risk. For instance, the built environment may display complicated flood routing patterns and interaction with drainage solutions. Many areas display a lack of maintenance of storm sewers and SUDS which although are suggested as solutions may ultimately limit the ability to prevent flooding in an urban catchment. Finally, management options may be limited by factors such as the lack of space, the legacy of past interventions and challenges with flood forecasting and prediction, particularly when considering the potential impact of climate change on rainfall intensity.

This Issue offers valuable insights into the understanding, assessment, and/or management of flood risk in the urban context. Darnkachatarn and Kajitani (2024) in their research concerning the long-term flood exposure of Bangkok Metropolitan area highlight the need and challenge of assessing flood risk in a dynamic urban context. Highlighting the critical link between urban development and increasing flood vulnerability and population exposure, their research demonstrated how urban risk in their case continued to grow irrespective of the experience of flooding. They highlighted how knowledge of urban land use and land cover changes is critical to not only having an up-to-date assessment of risk, but how important this is for short term response, social and economic impacts, and recovery from flooding events. Their assessment also highlighted that policies to prevent urbanisation in at risk areas was failing and that stronger approaches to prevention are essential to prevent urban risk from increasing.

Whereas Darnkachatarn and Kajitani (2024) considered past land use and land cover change and its impact on flood risk, Moon et al. (2024) offer an approach to assessing future urban flood hazards. This is particularly important with the rapidly dynamic changes within the urban environment. Presenting the case of Seoul, Korea they used the GCM-based climate change scenarios to quantify changes in flood hazard and runoff characteristics. Identifying a process for estimating future runoff and potential mitigation effects, their work offers the ability to assess potential interventions and characterise changes to flood hazards in the complex urban environment.

In their case from the Wuding River Basin (China) Lai et al. (2024) focus on flash flooding events in the urban context and specifically on sedimentation hazards in hilly cities. This research offers a 2D hydro-sediment-morphological model to complement the usual depth and inundation area approaches and provide a more comprehensive view of hazards whereby flash flooding events create channel erosion and threaten bank stability in a hilly context.

In their contribution to this issue, Bayón et al. (2024) recognise the complexity of the urban environment and the interplay between the environment and floodwaters during flooding. Their post-flood photograph analysis of sixty-three floods (from 46 countries) highlights the contribution of solid load within the flood waters. They have classified and defined the presence and frequency of urban flood drifters (UFDs) within the flooding landscape, highlighting the importance of vehicles as well as urban and household furniture, offering a stability diagram for urban planners to assess the presence of potentially unstable urban elements. This offers a timely contribution to the development of resilient urban spaces as for the first time it classifies and characterises potential hazardous objects.

Rathnasiri et al. (2024) highlight the challenge of maximising opportunities of using large datasets associated with the built environment for flood resilience. Through their research they identify not only the difficulties in the use of these data, but also strategies for overcoming these challenges. Their research offers an insight into how data management processes need to evolve alongside the technology for gathering data to best harness and exploit opportunities for more effective decision-making in the urban context.

Finally, I would like to acknowledge the support and commitment the Journal receives from all our peer reviewers, who take the time to read and make valuable comments on the manuscripts we receive. As research considering different types of flooding has widened alongside the consideration of risk in these more complex urban environments as a journal, we also need to diversity our reviewer base so please contact the journal office (journals@ciwem.org) if you wish to become a reviewer.

Sally Priest,
Associate Editor
Flood Hazard Research Centre, Middlesex University

References
Allocca, V., Coda, S., Calcaterra, D., & De Vita, P. (2022). Groundwater rebound and flooding in the Naples' periurban area (Italy). Journal of Flood Risk Management, 15(2), e12775. https://doi.org/10.1111/jfr3.12775

Bayón, A., Valero, D., & Franca, M. J. (2024). Urban flood drifters (UFD): Identification, classification and characterisation. Journal of Flood Risk Management, e13002. https://doi.org/10.1111/jfr3.13002

Birch, C.E., Rabb, B.L., Böing, S.J., et al. Enhanced surface water flood forecasts: User-led development and testing. J Flood Risk Management. 2021; 14:e12691. https://doi.org/10.1111/jfr3.12691

Darnkachatarn, S., & Kajitani, Y. (2024). Long-term flood exposure assessment using satellite-based land use change detection and inundation simulation: A 30-year case study of the Bangkok Metropolitan Region. Journal of Flood Risk Management, e12997. https://doi.org/10.1111/jfr3.12997

Fathy, I., Ahmed, A., Abd-Elhamid, H.F. Integrated management of surface water and groundwater to mitigate flood risks and water scarcity in arid and semi-arid regions. J Flood Risk Management. 2021; 14:e12720. https://doi.org/10.1111/jfr3.12720

Lai, R., Li, J., Wang, P., Guo, Y., Xu, L., Zhang, X., Wang, M., & Zhang, X. (2024). Cumulative sedimentation hazard map of urban areas subject to hyperconcentrated flash flood: A case study of Suide County in the Wuding River basin, China. Journal of Flood Risk Management, e12996. https://doi.org/10.1111/jfr3.12996

Moon, H.-T., Yoon, S.-K., Kim, J.-S., & Moon, Y.-I. (2024). Assessing future urban flood hazard: A comprehensive approach to estimating the implications of future rainfall scenarios. Journal of Flood Risk Management, e13000. https://doi.org/10.1111/jfr3.13000

Rathnasiri, P., Adeniyi, O., & Thurairajah, N. (2024). Overcoming data utilization challenges for built environment flood resilience: Strategies and best practices. Journal of Flood Risk Management, e12986. https://doi.org/10.1111/jfr3.12986