Application and comparison of two different dual drainage models to assess urban flooding

Abstract

Two types of dual drainage models were set up to assess urban flooding for a study area in Germany: (1) a static model based on a conventional method in Germany; the overflow volumes of the manholes are gained by the sewer solver HYSTEM-EXTRAN. Using these water volumes and geographic information system (GIS) tools, an overland flow network, composed of flow paths and accumulated water in sinks, is produced, (2) a HYSTEM-EXTRAN 2D model; a two-dimensional (2D) overland flow module is coupled bi-directionally with HYSTEM-EXTRAN. The overland flow and the flow in the sewer system are simulated alternately.

Both models were supplied with a synthetic design rainfall and 25 extreme storms. After comparing the models and the results, a practical approach to assess urban flooding is proposed. In this approach the 2D model will compute the depth, extent, and propagation of floods only in the prone areas specified by the static model.

Keywords::

• urban drainage model
• dual drainage
• urban flooding
• HYSTEM-EXTRAN 2D
• GIS
• Germany

Acknowledgements

This research was carried out as part of a master thesis (Jahanbazi, 2012) at the Institute of Water Resources Management, Leibniz University of Hannover. The first author would like to thank her thesis supervisor Prof. H.-R. Verworn. We also thank the people at Water and Drainage Authority of Hamburg especially Dr. Hüffmeyer, and appreciate the very helpful comments of the anonymous reviewers.

Notes

^1. The term standalone is used to distinguish from the coupled simulation employed in the HYSTEM-EXTRAN 2D model.

^2. The terms sink and depression are used interchangeably in this paper.

^3. The DEM should represent the location of buildings as well.

^4. Arc Hydro is an ArcGIS add-on, which requires Spatial Analyst Extension.

^5. The mentioned flooding is understood as the case when the excess water leaves the street and invades public and/or private properties.