ORIGINAL RESEARCH article
Front. Water
Sec. Water Resource Management
Flood Simulation and Risk Assessment in Urban Underground Spaces Based on 3D Laser Scanning: Capacity–Depth–Damage Curves and Computational Fluid Dynamics-Based Flood Response
Provisionally accepted
- 1Nanjing Hydraulic Research Institute, Nanjing, China
- 2Taihu Basin Authority, Taihu， Development，Research, China
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Urban underground spaces are rapidly expanding, but their low elevation, limited drainage capacity, and strong enclosure make them highly vulnerable to pluvial flooding. To elucidate how inundation dynamics in 3D underground spaces under extreme rainfall translate into actionable risk indicators (e.g., depth thresholds and arrival time), we propose and cross-validate a rainfall-informed capacity–depth–damage (C–D–D) curve method and a physics-based computational fluid dynamics (CFD) inundation model. The first approach is a rainfall-informed C–D–D curves method that rapidly maps net inflow to depth evolution and warning indicators (e.g., threshold depth and arrival time). The second approach is a 3D-geometry-resolved CFD inundation model that simulates spatially distributed depths/flows under prescribed inflow and drainage/outlet conditions, providing high-fidelity validation and hazard maps. A GeoSLAM handheld 3D Laser Scanning system was used to reconstruct as-built, modeling-ready 3D geometry of the underground space, addressing the common limitation of idealized layouts in prior evacuation-time assessments and enabling geometry-specific inundation and warning-threshold predictions. Using an underground parking garage in Tongzhou District, Beijing as a case study, we evaluated flood dynamics and risks under rainfall scenarios with annual exceedance probabilities of 1%, 2%, and 5%. Results show that stronger rainfall significantly advances critical water-depth thresholds and compresses evacuation windows; for example, under P = 1%, the 0.2 m alert occurs 1.5 hours earlier than under P = 2% and 5.3 hours earlier than under P = 5%. The two methods exhibit strong consistency in threshold timing (typically within 0–1 hour), while CFD resolves spatial heterogeneity and identifies medium-to-high risk zones earlier in the intrusion stage. This integrated framework supports rapid early warning, evacuation-window assessment, entrance protection, and drainage-capacity design. Novelty lies in (i) integrating handheld 3D Laser Scanning with a 'curve-first, CFD-refine' dual-model workflow, (ii) cross-validating fast C–D–D-based warning thresholds against geometry-resolved CFD dynamics, and (iii) delivering actionable time-to-threshold warnings and spatial risk maps for emergency planning.
Keywords: 3D laser scanning, Capacity–Depth–Damage (C–D–D)curve, Computational Fluid Dynamics (CFD), Flood inundation dynamics, Hydrodynamic model, Risk-response assessment, urban underground space
Received: 29 Dec 2025; Accepted: 12 Feb 2026.
Copyright: © 2026 Wang, Cai, Chu, Peng, Liu, Lin and Tang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Yan Wang
Zhao Cai
Li Tang
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