Gauge Description:

(Also see Gauge FAQ)
Look for ½" of rain within 6 hours at rain gages in upper watershed (Roselle and above). Dry ground takes more rain but intense rain at any upstream gage can bring a delayed rise in the river as much as 12-24 hrs later. The USGS Roselle gauge is accessible either on-line or by phone at 1-573-546-2502. The Roselle gauge is correlated with the paddler's gauge on the footbridge (old highway D bridge) at the takeout for the Lower St. Francis in Silver Mines Recreation Area. The paddler's gauge is on a bridge pier with marks from 0 to 42 inches (top of the bridge). For levels up to the top of the bridge, the approximate conversion is
D-bridge (inches) = 15 * (Roselle – 3)
Levels over the bridge are marked on the road in 1-foot intervals as the road goes up the hill. For levels that are over the bridge, the approximate conversion is
D-bridge (feet over the bridge) = (5/4) * (Roselle – 6)
Since it is pretty much the “only game in town” for regional paddlers, the Upper St. Francis is boated over a wide range of levels.

 

Gauge FAQ:
1. The highway D bridge over the St. Francis is neither a low-water bridge nor is there a gauge on it. What gives?
The low-water bridge with the gauge is the old highway D bridge. In 1993, the highway department by-passed this bridge with a new, high bridge. The low-water bridge was blocked to vehicular traffic and left as a pedestrian walkway. Although technically incorrect, paddlers still refer to the old bridge with the gauge as "D-bridge."
2. How good are the conversion equations at giving actual (real-time) D-bridge values?
Generally within a few inches on D-bridge when Roselle range is 3 - 9 ft. and the river is not rapidly rising. For higher levels, the correlation is not as good but still works after a fashion. The gauge conversion seems to work best when there was general rainfall over the entire watershed.
3. Why don't D-bridge values as estimated from the conversion formulas agree better with actual values?
The Roselle gauge is at highway 72 bridge, more than 5 miles upstream from the paddler's gauge on D-bridge. In between the gauges are one major tributary (Stouts Creek) and two minor tributaries (Mud Creek and Turkey Creek). The correlation between the two gauges can be influenced by such things as a rapidly rising river, rainfall variance in the St. Francis and tributary watersheds, wintertime freezing conditions, summertime vegetation growth, and even a beaver dam in the downstream outflow of the pool where the Roselle gauge is located.
4. In the Gauge description section, it says that the top of D-bridge is 42 inches on the paddler's gauge but the table says 45 inches. So which is it?
The top of the bridge is actually 42 inches. It's given to be 45 inches in the table for simplicity since a one-foot change in the USGS gauge represents an approximate 15-inch change in the D-bridge gauge.
5. The conversion formula for “feet over the bridge” doesn't quite agree with the formula for “inches on the bridge.” Why is this?
Again, for simplicity. The “exact” formula should be (5/4)*(Roselle – 29/5). By using “6” instead of “29/5” we're underestimating the level by 3 inches. Precision isn't warranted here since both formulas were meant to give only approximate conversions anyway.

 

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