According to Beyond the Rainbow, the shortage of water along the main road to Navajo Mountain forced the 1928 trip into the depths of Nitsin Canyon, and their first night was at Inscription House. In view of his many 1927 photographs of Betatakin, it is surprising that Hanks took no photographs of Inscription House. It turns out that the arroyo cutting near Inscription House in Nitsin Canyon is quite similar to what occurred in Tsegi Canyon some 30 km to the east, both in the beginning of incision (some time after 1927/1928) and its magnitude (as much as 20 m). So to document the incision in Nitsin Canyon, we include here a ca. 1927 photograph by Phillip Johnston (NAU.PH.413.75), a 1951 photograph by Tad Nichols (NAU.PH.184.108.40.206.10, and 2016 images from Google Earth (Goog-lepeats!). As was the case at the Tsegi Canyon camera station, there is no incision discernible in the ca. 1927 image, but there is clear evidence of incision in the 1951 image (the dark shadow of the channel wall at the base of Inscription House). In the Google Earth images, arroyo incision near the center of the alluvial valley is ~20 m.
The National Park Service has this to say about arroyo cutting at Inscription House:
“Since the 1930s, erosion had been visible in the wash below Inscription House. In the early 1940s, the wash eroded at the rate of about twenty feet per annum.
“By 1944, it was “positively dangerous” to reach Inscription House.
“In 1949, the ferocity of the flow of water caused a number of burials from the cave at Inscription House to wash out toward Lake Meade. Brewer found bones and high quality pottery in the wash after a heavy spring rain, prompting him to call for better protective measures against creeping erosion.”