GoWaterfalling’s page on Memorial Falls in Munising says:
MNA Memorial Falls is in Munising, off of H-58. Some of the locals refer to this waterfalls as “Twin Falls”. This is a very seasonal waterfall and is often dry. However when the water is flowing, which may only be after a good rain or when the snow is melting, you will be treated to a very pretty gorge with two waterfalls in it. MNA Memorial Falls is owned by the Michigan Nature Association and it is open to the public.
…Two streams empty into this gorge, but the second one likely only has water after or during a good rain. One very interesting feature of this gorge is a “window” in the walls between the two falls. You can crawl through this window, or just walk around it. You can see each of the waterfalls through this window.
Another nice thing about this waterfall is its proximity to Tannery Falls. The trail from Nestor streets forks just before it descends into the gorge. The trail to the right leads to the base of the falls. The trail to the left leads to H-58, about 100 feet away from the stairway to Tannery Falls, so you can visit both falls on the same hike.
In the winter both of these falls turn into ice columns that are tackled by the ice climbers. Despite their low volume of water, each of these falls manages to produce a very impressive column. Every winter Munising hosts an ice climbing festival. After the festival the ice columns look like they have been attacked by woodpeckers. There are many other interesting ice formations to see in the area.