3-4 hours is a good rule of thumb. But, after looking at a LOT of visuals last fall when I was trying to work out a correlation, I would have to say it varies quite a bit.

Take Saturday for instance, plus 9 inches correlates to about 3.31 on the Edgemont gauge. If you look at the Edgemont readings, the closest reading to that level was at 07:43. The visual was plus 9 inches at 09:30, so it looks like in that case it only took 2 hours for the water to get to the bridge gauge.

For the next reading of 6 inches, that is roughly 3.05 on the Edgemont gauge, and that would have occured for Edgemont about halfway between the 09:07 and 10:03 readings, call it 09:30. The visual for 6 inches was at 11:00, just 90 minutes for the water to get down.

Take the next reading of 4-4.5 inches, which should correlate to about 2.9 on the Edgemont gauge. Closest time for that would have been the 11:05 reading. The visual was at 14:20, so it took 3 hours and 15 minutes for that water to come down to the bridge.

The next reading was 2 inches, which should correlate to about 2.7 on the Edgemont gauge. Closest time for that would have been the 13:26 reading. The visual was at 17:00, so it took 3 hours and 35 minutes for that water to come down to the bridge.

If you look at the two Sunday readings, you get more of the picture. First reading was 0, which is approximately 2.52 on the Edgemont gauge. There isn't a reading that matches this well, but if it dropped linearly between the readings on either side of 2.52, that level would have been about 10:00. The reading was at 13:00, so it took that water 3 hours to come down to the bridge.

The next reading is minus 1 which corresponds to about 2.43 at Edgemont, which would have happened around the 13:26 reading. The visual was at 17:30, so that water took about 4 hours to get to the bridge.

Have a headache yet? Now, this assumes that everyone took readings perfectly and times were all reported with perfect accuracy. We know that is never completely the case, but even so, you can see how the time to the bridge varies even with this one rain event. Now, consider that other rain events will react differently and you canget a picture how the time varies. At the peak of the bubble and for higher water it will go faster down to the bridge (1-2hours). Once past the bubble, 3-4 hours to get to the bridge gauge is a good estimate. There is also more fluctuation in the reading once you get past 6 inches. In the realm that I boat Wilson at (plus 3 and below) the gauge is usually within an inch. Get up past 6 inches and the error is more like plus or minus 3 inches. I bet a lot of that error could be worked out if someone could sit at the gauge and take photos of the gauge every 5 minutes over a weekend sometime when we had a rain event. Not likely to happen, but it would be helpful. The correlation used is a linear correlation, and I suspect that at some point the linearity breaks down, but it is hard to say when. The

I remember this time last year before the Edgemont gauge worked when the virtual was off of Watauga and it would sometimes show Wilson @ zero when it was 11 inches or vice versa. This new gauge is a phenomenal improvement over what we used to have. I am personally greatful to everyone who posts visuals with times. I am also really greatful to both Chris G. who put up the correlation I worked out on SYOTR.org and to Chris B. who combined visuals I collected with his own data to put a virtual gauge up at boatingbeta.com. I use both of those pages to help me make informed decisions about whether or not to make the 4 hour drive to Wilson, knowing I won't get skunked like I used to last year.

Sorry to be so long

Garrick