So in the first step consider the basic data that you have and then analyse your past events and then go for simulation. SWAT is a model which gives you the possibility of simulating the discharge after each precipitation according to the characteristic of watershed and based on different method of calculations. In flood forecasting there is a chain of several issue have to be studied to get the acceptable result. In order to complete the answer on your question have to say first of all you have to declare what you want to do when you talk about the flood forecasting. Some of this may also be due to poor maintenance (see my researchgate report to prevent a small dam failure about 2013). It is obvious in SC and NC, the design calculations and mitigation measures used for many small dams was insufficient as evidenced by failures.

Cross checking good, and for dam failure considerations, I would recommend developing envelop curve for past flood data to estimate historic extremes to compare to. I would be very leary about relying only on the SCS CN method if other methods are available. There are some SC to NC differences also, and for example some drainage areas of the SC piedmont were more severely eroded and gullied than others, some coastal drainages have more wetlands and storage than others. The Feaster et al equations are also available for physiographic area, so that also could be considered if you did not want to use Streamstats. You might also want to compare the rainfall amount/intensity differences such as with Technical Paper 40 or updated version. The soils data is also available in Streamstats for site selected, so the CN numbers could be assigned for each drainage area evaluated.

You might select a few sites within a physiographic area in Streamstats that likely have varied drainage size, land use and imperveous areas to test some of your need.

Since you are in NC, you might try exploring the effect of imperveous areas in the SC physiographic areas using Streamstats, which now used the LiDAR topography and the equations developed by Feaster et al at USGS, which includes an imperveous element.

Hec ras 2d manual