Hi, Elizabeth! Thank you so much for bringing your question to us. The
attractions at Disney's Blizzard Beach Water Park are divided into three areas: Green Slope, Red Slope, and Purple Slope. The Chair Lift that you mentioned can be used to access the Green Slope attractions found at the top of Mt. Gushmore. These attractions are Summit Plummet, Teamboat Springs, and Slush Gusher. Runoff Rapids is a Red Slope attraction and its entrance is found at the back part of Mt. Gushmore. I did a bit of research to see if there was an alternate entrance you could possibly use, but unfortunately, I discovered that the only way to reach the three water slides of Runoff Rapids is to climb the stairs that lead up the back part of Mt. Gushmore. Also, the tubes that Guests use during the ride must be picked up at the base of attraction and carried to the peak.
I have a few ideas for you that may possibly help. You mentioned your difficulty with stairs. If you are able to climb them but it may take a bit of time, feel free to take as long as you need to climb those stairs. You are more than welcome to take a few at a time until you reach the top. I am wondering if you will be visiting alone or with friends or family. Runoff Rapids does feature two flumes that allow for double-seated tubes to be used. Perhaps another member of your party could carry the tube and you could experience the attraction together.
Even though the Chair Lift does not help you gain access to Runoff Rapids, be sure to still hop aboard at some point. It gives a great view of the park as you head to the peak, and I know you'll love Teamboat Springs. My older daughter insists on us riding it over and over again when we visit!
Please stop by and let us know if you have any further questions as you continue to plan your visit, Elizabeth.
Brandy B.