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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005

1D and 2D Modelling of Urban Drainage Systems using XP-SWMM and TUFLOW
B.C. Phillips1*, S.Yu2, G.R. Thompson3 and N. de Silva4 Director, Cardno Willing (NSW) Pty. Ltd., Level 3, 910 Pacific Highway, Gordon NSW 2072, Australia 2 Senior Hydro-Environmental Engineer, Cardno Willing (NSW) Pty. Ltd., Level 3,910 Pacific Highway, Gordon NSW 2072, Australia 3 Director, XP Software Pty. Ltd., PO Box 3064, Belconnen ACT 2617, Australia 4 Senior Engineer - Catchment Management, Fairfield City Council PO Box 21, Fairfield NSW 1860 *Corresponding author, e-mail: bphillips@cardno.com.au
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ABSTRACT
The release of a revised NSW Floodplain Management Manual in 2001 established a new direction for urban floodmanagement in NSW. This new direction was created by a redefinition of the floodplain as the area bounded by the PMF – this poses a challenge to estimate PMF flooding in highly urban areas and particularly in piped drainage areas; and the removal of the distinction between “mainstream flooding” and “local flooding” – this poses challenges in defining and mapping flood risk areas in residentialareas inundated by the PMF. At the same time the increasing collection of aerial laser scanning (ALS) across whole local government areas (LGAs) is providing detailed survey levels capable of supporting 2D terrain and hydrodynamic modelling and detailed floodplain mapping. This new direction and the increasing availability of ALS have ramifications for urban flood studies. The trend in NSW andelsewhere has been for the growing adoption of 2D models as the new benchmark for urban flood studies. As part of the on-going development of the XP-SWMM modeling system to enhance its functionality and its capability to model urban drainage systems the TUFLOW 2D hydrodynamic model is being incorporated as a layer into an XP-SWMM2D package. Two case studies that demonstrate the new 1D/2D modelingcapability of TUFLOW and XPSWMM2D are described. The first case study is of a reach of Prospect Creek in the City of Fairfield. A 2D and a combined 1D/2D models of the floodplain were assembled and run. A comparison of 1D, 1D/2D and 2D results is given. The second case study is of a local drainage subcatchment that demonstrates the interaction between the piped drainage system and 2D surface overlandflows. It is concluded that the 2D hydrodynamic modeling layer in the XP-SWMM package offers users new opportunities to undertake more detailed investigations of urban drainage systems and of urban waterways and floodplains. It also demonstrates the on-going evolution of the XP-SWMM package in response to the changing needs of stormwater managers.

KEYWORDS
1D/2D flood modelling, Drainage, Floodstudies, Overland flow, Urban flooding

Phillips, Yu, Thompson & de Silva

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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005

INTRODUCTION
The release of a revised NSW Floodplain Management Manual in 2001 established a new direction for urban flood management in NSW. This new direction was created by: (i) (ii) A redefinition of the floodplain asthe area bounded by the PMF – this poses a challenge to estimate PMF flooding in highly urban areas and particularly in piped drainage areas; Removal of the distinction between “mainstream flooding” and “local flooding” – this poses challenges in defining and mapping flood risk areas in residential areas inundated by the PMF;

At the same time the increasing collection of aerial laser scanning(ALS) across whole local government areas (LGAs) is providing detailed survey levels capable of supporting 2D terrain and hydrodynamic modelling and detailed floodplain mapping. This new direction and the increasing availability of ALS have ramifications for modelling systems used to characterize flooding in urban areas. The trend in NSW and elsewhere has been for the growing adoption of 2D models...