Canyons are inherently risky. Flash floods occur without notice on sunny days. Technical skills & surrounding topography knowledge required yet does not eliminate risk.
MIA Exit's Scary!
Gear Used for Canyon: Rappelling and anchor gear, Ropes and or pull cords for rappels up to 165 feet, 40 feet of webbing for sling placement, and wet suits. Wet suits will be needed if the canyon is flowing. There are no swims in Boundary since the pools are no more than waist deep. But with the canyon flowing, you will be wet while rappelling down waterfalls and it does get chilly even in hot months. A 3mm full seems to be about right.
Boundary Canyon is an incredible treat. From the first rappel all the way through the technical section that canyon just puts a smile on your face, especially if water is running in it. Unfortunately the technical section is very short.
Water is available year round in Kolob Creek. There is also a spring that has been routed to a pipe on the roads along the MIA Exit. I am not sure if this runs year round but I suspect it does.
The approach to Boundary uses one of MANY old overgrown logging roads that create a maze in the wooded areas leading down to Boundary. The route described here is one of the few possible routes into Boundary. Keep this in mind when comparing notes from multiple sources of beta for this canyon. This route describes an approach, not necessarily the best approach.
Boundary can be rated an A or a C canyon depending on what time of year you go. Spring runoff can create significant flow or the canyon may be bone dry later in the year.
Before going down Boundary it is a good idea to check water flow from the Kolob Reservoir. Flows up around 10 to 15 CFS will make the trek from Boundary to the MIA Exit a little slower as you navigate the swift water. Lower CFS levels will make that section a casual walk down some of the narrows of Kolob Creek. You can check flow rates by calling the Washington County Water Conservancy District at 435-673-3617 and ask for the release rate of the Kolob Reservoir.
Boundary can hold a fair amount of snow so it may be a good idea to check with the Zion Back Country Desk to see if there had been any recent descents and ask about snow conditions.
After the technical section is a walk down the last part of Boundary which is quite beautiful as well. When Boundary joins Kolob Creek the routes continues down Kolob Creek 1.2 miles to the MIA Exit. There are two options for exiting, MIA Exit or continue down Kolob Creek to the Narrows then down the narrows to the Temple of Sinawava for an exit on the Zion Shuttles. Using the MIA Exit the route is done in a day. Exiting Via the Narrows the route is an overnight trip.
The MIA Exit has a reputation of being difficult to locate and a pain in the butt to climb out of. If you pay attention on the way down Kolob Creek, the MIA Exit is not too difficult to locate since it is the next major drainage on the right (west) downstream of Boundary Canyon. Locating this exit at night could prove very difficult though.
The MIA Exit definitely lives up to its name for being difficult. The MIA Exit starts out steep and eventually gets up to a saddle where you can view your route down then up another steep climb. The first steep climb is only a warm up for the second climb! The second climb up has about 600 feet of elevation gain over about 850 feet of horizontal distance. This does not sound too bad until you see what you will be climbing up! The route up is loose, sandy, steep and a lot of what you touch moves! You may find yourself questioning your sanity for depending on the root of a bush while you claw your way up. Allow about 2 or 2.5 hours to climb up the MIA Exit from Kolob Creek up to a dirt road. Once on the dirt road it will be an easy walk back to the car but you will need to pay attention to the maze of roads so you do not get lost.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.