There are a lot of variations of basic, first-order hydrology models to estimate runoff from rainfall with a few other parameters. From what I can tell, most very basic rainfall-runoff models use one of the following methods at their core: the SCS Curve Number method, the Rational method, and the Simple method. I'm trying to understand: how do these methods differ, and are there other methods used at the core of basic, first-order hydrology models?
From what I can tell, the SCS Curve Number method is only slightly different from the Rational method in that it uses a Curve Number (based on land use and soils) rather than a Runoff Coefficient (based on soil and basin slope). The two are both event-based models, at least in their initial design.
The Simple method appears to be a lot like the Rational method but the former is for estimating pollutant loading (using pollutant coefficients and runoff) while the latter is for estimating runoff (using runoff coefficients and rainfall). I could see the two being coupled, but they don't appear to have any redundancy in their use.
Considering the summary of my findings, can these methods be described together as "empirical models" given that they are all based on empirically derived coefficients (either Curve Number values, runoff coefficients, or pollutant coefficients)?