29 Sep 2022
29 Sep 2022
Status: this preprint is currently under review for the journal NHESS.

Uncovering Inundation Hotspots through a Normalized Flood Severity Index: Urban Flood Modelling Based on Open-Access Data in Ho Chi Minh City, Vietnam

Mazen Hoballah Jalloul1, Leon Scheiber1, Christian Jordan1, Jan Visscher1, Hong Quan Nguyen2,3, and Torsten Schlurmann1 Mazen Hoballah Jalloul et al.
  • 1Ludwig-Franzius-Institute of Hydraulic, Estuarine and Coastal Engineering, Leibniz University of Hannover, D-30167 Hannover, Germany
  • 2Institute for Circular Economy Development, Vietnam National University – Ho Chi Minh City, 700000 Ho Chi Minh City, Vietnam
  • 3Institute for Environment and Resources, Vietnam National University – Ho Chi Minh City, 700000 Ho Chi Minh City, Vietnam

Abstract. Hydro-numerical models offer an increasingly important tool to determine the adequacy and evaluate the effectiveness of potential flood protection measures. However, a significant obstacle in setting up hydro-numerical and associated flood damage models is the tedious and oftentimes prohibitively costly process of acquiring reliable input data, which particularly applies to coastal megacities in developing countries and emerging economies. To address this problem, this paper takes the example of Ho Chi Minh City, Vietnam, and proposes a new and comprehensive methodology for acquiring, processing, and applying the necessary open-access data (topography, bathymetry, tidal, river flow, and precipitation time series) to set up an urban surface run-off model. As a key novelty of the paper, a normalized flood severity index (NFSI) that combines flood depth and duration is proposed. The index serves as an indicator that helps uncover urban inundation hotspots with severe damage potential, drawing attention to specific districts or boroughs with special adaptation needs or emergency response measures. The approach is validated by comparison with more than 300 locally reported flood samples, which correspond to NFSI-processed inundation hotspots in over 73 % of all cases. These findings corroborate the robustness of the proposed index, which may significantly enhance the interpretation and trustworthiness of hydro-numerical assessments in the future. The proposed approach and developed indicators are generic and may be replicated and adopted in other coastal megacities.

Mazen Hoballah Jalloul et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-238', Anonymous Referee #1, 12 Oct 2022
  • RC2: 'Comment on nhess-2022-238', Anonymous Referee #2, 09 Nov 2022

Mazen Hoballah Jalloul et al.

Mazen Hoballah Jalloul et al.


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Short summary
Urban floods have caused a growing amount of damage during the last decades, esp. in low-elevation coastal zones like Ho Chi Minh City, Vietnam. This study presents a numerical model that simulates local flood depths and durations exclusively based on open-access data. Subsequently, a novel and easy-to-apply indicator, the Normalized Flood Severity Index, is introduced, combining both parameters to uncover local inundation hotspots. This approach can be replicated in any other coastal megacity.