- Power Decay: used when a user-provided DEM is input for project topography
- Exponential Decay: used when a pre-loaded Topographic Index (TI) file is input for project topography
The exponential decay routine was part of the original TOPMODEL-based development of i-Tree Hydro. The power decay routine was added as described in Wang et al. 2006.Both the ExponentialDecay and PowerDecay modes can work with DEM data. Jun Wang found the PowerDecay seems to generate results that better match urban hydrology. ExponentialDecay matches the original TOPMODEL theory and the TI values are more intuitive.
In Hydro+, UnifiedHydroConfig.xml allows for either infiltration subroutine to be used based on the <Infiltration> parameter tag, which can have values of "PowerDecay" or "ExponentialDecay", as in:
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