Urban drainage and flood modeling for municipal authorities
For city and district governments we model urban drainage networks, map pluvial flood hazard, and build web GIS dashboards that let planning and public-works staff track infrastructure performance without needing GIS specialists on staff.
A city with a flooding problem usually knows which streets flood. What it rarely has is a defensible basis for deciding which of fifteen sub-catchments to spend the drainage budget on first, and the political cost of getting that ranking wrong is high. That is a modeling question before it is an engineering one.
We build coupled drainage-network and overland-flow models — EPA SWMM for the pipe network, HEC-RAS 2D or openLISEM for surface flooding — calibrated against events the city already remembers. The output is a ranked list of where damage actually concentrates, which is usually not where complaints concentrate.
What makes this sector different
- Drainage asset records are often incomplete, out of date, or held across several departments in incompatible formats.
- Flooding is driven by the interaction of the pipe network and overland flow, so modeling either alone gives the wrong answer.
- Rainfall intensities used in the original network design are frequently decades old.
- Capital budgets force a ranking across sub-catchments, not just a yes/no on whether flooding occurs.
What we deliver
- Coupled EPA SWMM and 2D overland flow model of the urban catchment
- Pluvial flood hazard maps at 5, 25 and 100-year return periods, under current and projected rainfall
- Sub-catchment risk ranking with cost-per-hectare-protected to support budget phasing
- A web GIS dashboard, where useful, so planning staff can query results without GIS software
Common questions from municipal authorities
We do not have a complete drainage asset database. Can you still model our network?
Yes. Incomplete asset data is the normal starting point. We build the network from whatever records exist, fill gaps by inference from surface levels and connectivity, and flag every inferred reach in the model documentation so you know which parts of the result rest on assumption. Producing a usable asset database is often a valuable by-product of the study.
What is the difference between pluvial and fluvial flooding, and which do we have?
Fluvial flooding is a river overtopping its banks; pluvial flooding is rainfall overwhelming the drainage network before it ever reaches a river. Most cities have both, and they can coincide. Modeling only the river misses the flooding that causes most complaints, which is why we couple network and overland models rather than choosing one.
How long does an urban flood study take?
Typically six to twelve weeks for a mid-sized catchment, driven mostly by data availability rather than model runtime. Assembling and cleaning the drainage network is usually the long pole; the modeling itself is comparatively quick once the inputs are sound.