The goal of this study is to develop a method for identifying potential post-fire debris flow hazard areas prior to the occurrence of wildfires, providing more time for local governments and emergency planners to develop and execute hazard mitigation strategies. This pilot study focuses on the communities of Pine and Strawberry, which are located in forested canyons at the base of the Mogollon Rim in north-central Arizona. Results from this project will provide local agencies, emergency planners and land managers more effective tools for prioritizing watershed treatment areas and implementing mitigation measures to alleviate potential impacts and threats from post-fire debris flows to infrastructure, human life, and property in a timely and cost-effective manner.

In order to begin to assess debris‐flow hazards along the Santa Catalina Mountains in Pima County, we mapped the extent and character of relatively young prehistoric debris‐flow deposits in detail at fifteen
canyon mouths. Mapping was conducted on a scale of 1:6,000 using aerial photographs, detailed
topography, and field relationships. Deposits were classified into relative age categories based on
topographic relationships, soil development and surface characteristics of the deposits. Ages of selected
debris‐flow deposits in four canyons – Soldier, Sabino, Finger Rock and Pima – were estimated using
radiocarbon (14C) and cosmogenic (10Be) isotope methods.

Evidence of past debris flows were found in all fifteen canyons. Relative age dating, corroborated by
10Be, indicates the largest and most extensive deposits in all canyons are late Pleistocene to early
Holocene in age. Events from 2006 show that some potential exists for debris flows to exit the mountain front into developed areas near canyon mouths.

This field trip guide was created for a Project WET conference held in Tucson, Arizona, June, 2007. This guide discusses the general geology of the Santa Catalina Mountains in Sabino Canyon, and points out evidence of the July 2006 floods and debris flows. There are stops in the first few miles of canyon, and towards the end of the tram road, where the most spectacular debris flows are located.

A brief reconnaissance (5-8 November 2008) of the Big Sandy Formation near Wikieup (on US Highway 93 in Mohave County, Arizona) was undertaken to reconcile a reported dominance of lacustrine beds (Sheppard and Gude, 1972, 1973) with the largely terrestrial mammalian fauna reported from the formation (MacFadden et al., 1979; Lindsay and Mead, 2005). The issue is resolved satisfactorily by appreciation that nearly all fossil localities occur in fluvial beds that intertongue with and grade laterally into the dominant lacustrine strata.

To provide insight into provenance relations for multiple mid-Oligocene to mid-Miocene subbasins
(typically half-grabens) dissected by erosion in uplands lying north of the Catalina core complex and west of the San Pedro trough, 136 outcrop counts were made of clast types in tilted conglomerates of the Cloudburst and San Manuel Formations and their lateral equivalents in exposures as far north as the Gila River near Kearny. Clast counts were not made for younger conglomerates of the post-mid-Miocene Quiburis Formation, which fills the San Pedro trough and onlaps flanking uplands (Dickinson, 1998), because Quiburis clast assemblages in all cases match bedrock sources exposed uphill on the modern landscape. By contrast, paleotopography during Cloudburst and San Manuel deposition can only be inferred from local paleocurrent indicators (clast imbrications; figure 39 of Dickinson, 1991, p. 70-71) and clast assemblages in tilted strata. Areas included in this study were the Guild Wash allochthon between the Tortolita and Suizo Mountains, the Star Flat allochthon on the east flank of the Black Mountains, the
Black Hills (west of Mammoth), Camp Grant Wash (and Putnam Wash) between the Black Mountains and the Black Hills, multiple drainages of the Tortilla Mountains (Eagle Wash, Jim Thomas Wash, Hackberry Wash, Indian Camp Wash), and Ripsey Wash on the west flank of the Tortilla Mountains (Figs. 1-4).