Riparian dendrochronology: a method for determining flood histories of ungaged watersheds

Abstract

Examination of 106 crossdated tree-ring cores from the riparian zone of Pine Creek near Escalante, Utah, 10 cores from Bright Angel Creek, Grand Canyon, Arizona, 8 cores from South Taylor Creek, Zion National Park, Utah, and 5 cores from the Animas River near Silverton, Colorado, has yielded the following information: 1. Various riparian gymnosperm and angiosperm species crossdate with semi-arid site gymnosperms. 2. Tree growth is best correlated with snowpack water equivalent. 3. Flood damage to trees is manifested in growth suppression on root exposure or burial, in reaction wood on tilting, and in scarring. 4. Flood damage is very infrequent at Pine Creek from 1700 to 1880, more so from 1880 to 1909, and very frequent from 1909 to the present. (The town of Escalante was settled in 1875, and stocking of the range around Pine Creek reached a maximum shortly after 1900.) 5. Flood damage shows fairly constant frequency in the Bright Angel Creek watershed, which has seen little land use. 6. Flood damage on South Taylor Creek shows a marked increase in frequency between about 1900 and 1937 when the region was included in Zion National Monument, after which flood damage declined markedly in frequency.