Decide on a method for calculating runoff

[mmcfarland]

TR55 paper expects CN to be averaged from the entire area of interest and used in the runoff equation. Previous Azavea implementation averages the runoff results per tile. Barry Evans is developing a simple water quality routine that could co-opt some routines in TR55 but would be more accurate if the runoff was calculated by aggregating on Land Cover type within the whole area, and then using that volume to model known pollutant loads for that type of land. Neither method is necessarily more difficult to code, but there is a potential downside to deviating from the published paper.

[rcheetham]

The modifications (over the default, classic TR-55 methodology) in the Scala/Flex code are due to a need to compute ET, runoff and infiltration when BMP modifications are made in the landscape, for example, with a green roof, clustered housing, bioswales, changes to tilling patterns, etc. These effects are not really included in the classic TR-55 methodology and modifications were developed by Michelle Adams and Steve Benz to enable BMP support.