I have been watching this for a little while, and if the river is not going strait up, try this;
http://waterdata.usgs.gov/mo/nwis/uv?07034000
add this;
http://waterdata.usgs.gov/mo/nwis/uv/?site_no=07035800&PARAmeter_cd=00065,63160,00060
divide that number by 2, then apply standard formula (number minus three, times fifteen)
this is usually very close when river gauge is not vertical.
however, depending on the day, the 2 gauges reset every half hour or every hour, and it is kind of cool to know that Roselle has hit bridge level, and Mill creek is barely above zero.
It was even more cool to be at D bridge a while back 9:15am -22 inches/ 10:15am -over the bridge. very cool to see.