JES,
I am not sure its slope related, but volume related. And, it doesn't take a lot of volume for cart or mower wheels to cause a rut, which backs up more water, which causes a bigger damp area, etc.
Steeper slopes cause even more erosion during grow in, esp. depending on the soil, so they are a problem then, even though after grow in 3-4% wouldn't stay wet. In clay, 2% stays wet, in my experience.
With fabric netting and sodding reducing erosion, I think overall, you are right, we can use less fw catch basins at about the same cost.
As to draining right into a creek, generally that's a no no. The water would be piped to a man made wetland or dry detention area to make it sit for a while to settle out contaminants. Studies show that most input wash off occurs in something like the first inch of rain. Then, after a few inches (depending on soil, slopes, etc.) the inputs get diluted enough as to not worry about them (or at least they meet minimum EPA guidelines) So, those detention areas are sized to hold a 1-2.25" rain before they can overflow into the creek.
Matthew,
Now that is a great question and one I ponder often. Of course, the higher the greens fee the quicker the return. More importantly, its the high dollar courses that usually host golf outings and in addition to getting those played on time (assuming an afternoon shotgun follows) there is the image factor of having too many outings rained out that affects ability to book them later on.
Basically I size pipes and basins so water will not stand more than two-three days in a 100 year storm. I do this because if water sits in August heat longer than that, most turfs won't survive. If a 100 year storm is 9" in 24 hours, then I design for 3-4.5" in a day, or about .25"-.5" per hour which also drains most every day storms right away. Usually a one year storm is over an inch in an hour and a two year storm is usually over 2" an hour, depending on region, of course.
Environmental reggies actually favor ponding water around every catch basin for a bit to settle out inputs, so draining faster than that is sometimes not allowed anyway.
So, my drain design criteria usually delays play at least a few times a year, unless the owner has decided to spend more on pipe. Even for revenue and image sake, I don't find it pays to drain much more than a one year storm immediately. I think anyone recogizes that there will be a delay once or so per year on average. Two years would be tops.
So, you can do the math of losing three golf outings a year. 144 players at whatever per head. As to regular play, if it rains 60 days a year in your climate, and you figure by pure chance a third of those would be in the 8 night time hours where they wouldn't affect play, you would have to deal with rain 40 days as an operator, and only a few of those would require down time after the rain to allow puddling to subside.
Back in the old days, I used to drain courses for a ten year storm, but found that other gca's could build courses so much cheaper than mine that I was losing business.