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NETWORK SIMPLIFICATION1D/1D dual-drainage simulation
DEMs and Urban Flood Modelling
Dual-drainage concept (1D/1D and 1D/2D)Sewer system (manholes and pipes)Overland system (depressions and flow paths)
Overland system
1D overland flow modellingOverland system consists of nodes (ponds) and links (flow paths), generated using DEM.
2D overland flow modellingSurface divided into small elements (squares or irregular triangles), the flow equations (St. Venant) are based on terrain characteristics derived from the DEM.
Network simplification strategies
• Pruning: <10m; <300mm• Merging: similar hydraulic capacity - difference in
dimension of consecutive links <100mm• First strategy
– Simplifications are applied to the sewer network and the overland network simultaneously (1D/1D model)
• Second strategy– Simplifications are applied first to the sewer network and
then to the 1D/1D model network, i.e. including the overland flow network
Preliminary results: network simplification
Complete 1D/1D model(1D/1D)
Sewer system pruned and merged and complete overland model (1Dpm/1D)
Sewer system pruned and merged and overland model pruned and merged separately (1Dpm/1Dpm)
1D/1D model pruned and mergedtogether ((1D/1D)pm)
Fir
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Sec
ond
Str
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Preliminary results: simulation results and time reduction
Type of networkSimulation time
for rainfall A780 min
Reduction of the simulation time
1D1D 193 s -
(1D1D) pm 122 s 71s (-37%)
1Dpm1D 89 s 104s (-54%)
1Dpm1Dpm 44 s 149s (-72%)
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