Kanchana Wijeratna, So Kazama, Kumudu Madhawa Kurugama, Janaka Bamunawala
Received 2 February, 2026
Accepted 26 April, 2026
Published online 24 June, 2026

Kanchana Wijeratna¹⁾, So Kazama¹⁾, Kumudu Madhawa Kurugama¹⁾, Janaka Bamunawala¹⁾

1) Department of Civil and Environmental Engineering, Tohoku University, Japan

Rapid flood inundation assessment is critical for anticipating disruptions to transportation networks and informing evacuation planning. This study evaluates a GIS-based flood simulation workflow in ArcGIS Pro by analyzing inundations associated with the Ditwah cyclone in the Kelani River Basin, Sri Lanka, with emphasis on road accessibility near the Kaduwela interchange. The simulation is forced by event-based rainfall and river discharge and represents inundation as a terrain-controlled surface flooding, rather than explicitly solving the shallow-water equations. The simulated inundation extents are validated against Copernicus Emergency Management Service satellite-derived flood maps by using spatial overlay analysis and the Critical Success Index (CSI). The results show moderate skill overall (CSI of 0.38), with better agreement in higher-elevation areas, and larger discrepancies across river-dominated zones. Simulated water-level time series reveal progressive loss of road accessibility and a limited evacuation window before key links become impassable. Although this model did not reproduce the exact timing of the flood, the method demonstrated its ability to reliably delineate inundation-prone zones, supporting rapid traffic management and evacuation planning during such hazards. In summary, this study demonstrates that integrating GIS-based flood simulation with satellite observations offers a practical tool for rapid transportation impact assessment during flood events.

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Copyright (c) 2026 The Author(s) CC-BY 4.0