What is flood modeling?

Flood modeling is the process of creating a computer representation of anticipated flooding at a location; estimating depth, velocity and other parameters. This information can then enable stormwater systems to be designed appropriately and infrastructure like bridges, roads or buildings to be built safely. It can also be used to test whether proposed flood protection/mitigation works like levees (dikes) or groynes will be effective.

A flood model incorporates information on:

  • Hydrology: river flow and/or runoff generated by rainfall
  • Topography: ranging from simple estimates of the width and depth of a channel to a full 2D surface (“digital elevation model”) taken from LiDAR or drone photogrammetry
  • Surface roughness, usually represented as a Manning’s or Colebrook-White value
  • Relevant infrastructure information: pipes, bridges, roads, etc.

Other information will also be included for certain purposes, such as evaporation rate, sediment erosion rate or contaminant loads.

The modeled flood can be a historical (observed) event, a forecasted event (used in real-time systems), or a synthetic event based on estimates of rainfall or flow frequency. The latter is most common; allowing the model to test what happens in a 1 in 100 year flood, for example.

Flood models can be developed in a wide range of free and commercial software, including but not limited to HEC-RAS, MIKE, Infoworks ICM, TUFLOW, Flood Modeller, Open Flows, SWMM (with its variants), JFlow, FLO-2D, ICPR, iRIC and 12d.