Efficient Hazard Assessment for Pluvial Floods in Urban Environments: A Benchmarking Case Study for the City of Berlin, Germany

Omar Seleem,Maik Heistermann,Axel Bronstert

doi:10.3390/w13182476

Abstract

The presence of impermeable surfaces in urban areas hinders natural drainage and directs the surface runoff to storm drainage systems with finite capacity, which makes these areas prone to pluvial flooding. The occurrence of pluvial flooding depends on the existence of minimal areas for surface runoff generation and concentration. Detailed hydrologic and hydrodynamic simulations are computationally expensive and require intensive resources. This study compared and evaluated the performance of two simplified methods to identify urban pluvial flood-prone areas, namely the fill–spill–merge (FSM) method and the topographic wetness index (TWI) method and used the TELEMAC-2D hydrodynamic numerical model for benchmarking and validation. The FSM method uses common GIS operations to identify flood-prone depressions from a high-resolution digital elevation model (DEM). The TWI method employs the maximum likelihood method (MLE) to probabilistically calibrate a TWI threshold (τ) based on the inundation maps from a 2D hydrodynamic model for a given spatial window (W) within the urban area. We found that the FSM method clearly outperforms the TWI method both conceptually and effectively in terms of model performance.

Highlights

ZeleňákováPluvial flooding causes massive human and economic losses [1,2]
We compared the output of the two methods, FSM and topographic wetness index (TWI), with the output from the TELEMAC-2D model and considered the latter as a true reference
Method, and unstructured triangular mesh for TELEMAC-2D model), we considered pixels with a simulated water depth (h) higher than 0.10 m as flooded for both the FSM method and the TWI method for comparing and evaluating the performance of the two methods

Summary

Introduction

Pluvial flooding causes massive human and economic losses [1,2]. They are considered as an omnipresent hazard both in urban and rural areas, e.g., [3,4]. It is challenging to predict pluvial floods as they could strike areas with no flood records with little warning time They have no defined flood plains such as rivers and seashores [8]. They depend on how well the storm drainage system and the associated infrastructure respond to a sudden precipitation storm. The European Flood Directive widely implements flood hazard maps for rivers and coastal areas, but corresponding efforts are scarce for pluvial flooding [8,12,13]

Objectives

Methods

Results

Conclusion