FastFlood Docs
FastFlood Method
Method outline
The FastFlood method uses a series of recent innovations in fast flow routing and flood estimation. The steps of the method are the following:
- Hydrocorrection of terrain
- Coastal inundation
- Flow network determination
- Steady state discharge
- Correction for partial steady-state
- Flow pressure correction
The a-temporal nature of the model (only predicting peak flood heights) comes from its usage of steady-state principles. This means a flow state is found where for each location, in and outflow are equal. This equates to the flow state on a landscape after a rainfall event of infinite duration. In reality, a steady state is rarely reached, so a correction is applied. This correction works by estimating the catchment properties (length, avarage travel distance, average velocities, slope etc..) for each location. From these, the actual peak throughflow in a partial steady state is estimated. Because of the a-temporal nature, the model features sensitivity to the usual parameters (elevation model quality, Mannings surface roughness coefficient, infiltration rates) and, just as any other physically-based model, required calibration and validation.
In many of these steps, the fast sweeping algorithm has been adapted for optimal routing and spatial processing of data. The infiltration currently employs a fixed-rate infiltration that is substracted from the precipitation. In an upcoming version, the Green and Ampt model will be employed in an analytically integreated manner.
Details
For more details, please see the paper concerning the method on EarthArxiv (full article under peer review).