[Advanced] Differences in sub-routines for Infiltration Rate Decay

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[Advanced] Differences in sub-routines for Infiltration Rate Decay

Post by rcoville » Wed Mar 11, 2020 3:40 pm

In i-Tree Hydro there are two different routines available for estimating infiltration rate decay. The two different routines are listed below, along with the condition for which the i-Tree Hydro GUI would use each respective routine:
  • 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
Professor Ted Endreny noted the following difference in the two infiltration subroutines:
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.
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.

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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