Rock Island is noted for its excellent park and play.
The entire run is probably just a mile in length, and contained between Great Falls Lake and Center Hill Lake.
The powerhouse releases water into the area where the two main playspots are. At the top of the next rapid is a nice series of surf waves with good eddies on the left. The river left eddy is interesting due to the "waterfall" that drops into it. This falls is actually shooting thru the cliff on river left. This water is coming from the backwaters of Great Falls Lake and the Collins River on the other side of the cliff.
At the bottom of the wavetrain is the infamous Rock Island rodeo hole. The hole is fairly friendly at 2000 cfs, and rather munchy at a full release of 3800 cfs. Most get intimidated around 7500. Beware catching the left eddy, as the left wall is undercut and the eddyline feeds right into it.
Depending on the lower lake levels there may be two or three more small rapids below the rodeo hole. The next rapid contains a wave that is surfable at higher flows, but just above a dangerously undercut wall.
Warning - much of the channel flows into this wall. Get swimmers right.
Walk back up or take out in Rock Island State Park 'boat launch'
After rains: Starting at the base of the dam there is a 20' shelf with 0, one, or several lines dependant on the flow.. Check with the locals for more detailed info. 4200 minimum for 'the spout'; other lines (Mill-side and swing-side) start up around 4800. The rapid below constricts the river and the 3 holes can be violent. The rock is sharp and unstable, watch for seives in the first rapid. At flows above 10,000 the holes wash but the right wall at the bottom becomes a concern. There must be water flowing over the dam for the falls section to be running.
Brave Wave Ledge / Undercut
If you swim, swim River RIGHT and keep swimming into the eddy below the hole. Brave Wave Ledge recently broke the leg of a swimmer and the rocks here are sharp and grabby. The Undercut below Brave Wave on the Left is especially hazardous because of the sharp limestone shelves that could pose entrapment hazard. Swim right - you can make the eddy every time.
2012-10-12 07:12:35 (2079 days ago)
From Boatertalk: Rock Island Info: Go to this website. http://www.tva.gov/river/lakeinfo/index.htm Look up Great Falls. 1 generator will provide a level of 1400 to 1800cfs. It's ok. Top wave is sweet, but no eddy service. The 'hole' is more of a small wave. Generally speaking, it's not worth a long drive for this level, but still fun. 2 generators will give you a level of 2900 to 3800. The lower end, the top wave is still good, and the hole is kicking. At the higher end, the top wave starts to flush, but others come in at the falls, and the hole is STOMPIN! Notice the upper lake level. When it reaches 803' or so with more water coming in, they start to spill. Top of the gates is 804'. Look for the message 'Great Falls is Spilling'. Levels around 5000 to 6000 are prime. Several spots to run the falls. I've been out there around 11000, but you gotta watch the back wash. Sieve City is a no joke rapid. It has this name for a reason. Sad to say that Brave Wave is no longer there. There are always unexplored waves and holes in the rapids leading down to the boat ramp in Rock Island State Park.
2010-05-27 01:04:52 (2948 days ago)
Although this site and boatingbeta list 2000 as the minimum, the main hole is still playable down to at least ~1300 (1 generator); it's not nearly as big or as impressive as at 2 generators, but there's still something there to be had.
2004-03-10 01:46:57 (5217 days ago)
Clay and I paddled Rock Island Dryway at 30,000 cfs today- BIG!
Date: Mar 08 2004, 0:16 GMT
Super fun high action- Steep drop at 30,000 cfs. Highest it has ever been run and quite
Glad Clay is here!
2003-08-26 12:56:55 (5414 days ago)
To help determine levels:
Rock Island is rain dependent after the lake drops. It usually will not run during late summer and fall. However this will depend on the rainfall for the season. During wet years Rock Island has been observed to run for a few hours daily into late August.
Whitewater event organizers may sometimes secure guaranteed flows from the TVA. check the event calendar to see when events might be scheduled. You can only find out the level the day prior after 6:00 pm by calling TVA or the power house. However if releases have been running consistently then it usually means flow can be counted on the next day. Be advised that no one can accurately predict flow until after 6:00pm the night before or unless there is a scheduled event.
Call the TVA at 1-800-238-2264, punch 4, then punch 36. Listen to the last available 8 hours of discharge, and then listen for the next days schedule. Two or more generators mean excellent boating. At 2000cfs and up you will find great play.
2003-04-17 23:52:39 (5545 days ago)
When Center Hill Resevoir (TVA page) is above 650. feet the hole is washed out. They have recently been holding Center Hill higher than they used to after periods of rain.