A series of small earth movements occurred along the slopes of State Route 87 at about mile marker 224 (between the Bush Highway and Route 188) throughout the winter of 2007‐2008, culminating with a landslide on Friday, 21 March 2008. This landslide buckled the southbound lanes, displaced the northbound lanes, and closed the highway for nearly a week. The mass movements occurred on slopes that were constructed with re‐vegetated, laid back slopes; soil nail walls; and rip rap‐lined channels. However, our reconnaissance mapping indicates that most, if not all, of the slope movements are located within a much larger, older landslide adjacent to, and cut by, SR‐87. No specific trigger for the landslides was immediately apparent, although a combination of factors (e.g., precipitation, groundwater levels, etc.) may have contributed to conditions for the slope failure. Headscarps of various types of landslides are present along both sides of the highway. Results from our preliminary investigation indicate that up to three other paleo‐landslides may be present in the immediate vicinity. The full extent and nature of these landslides are unknown and require further investigation to evaluate their potential to be reactivated and risk they pose to the highway.

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.

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.

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.

During the mid-part of the last decade, when the population growth rate was at its highest, the Phoenix area experienced rapid development and urban sprawl. The result has been an intensification of the Urban Heat Island effect. In this edition of Decades, author Sally Wittlinger discusses this uncomfortable consequence of urbanization.

In a desert city such as Phoenix, summertime heat is a way of life, but how much does the built environment contribute to the intensity of the heat on a summer night? In urbanized Phoenix, nights don’t cool down as much as in the surrounding rural areas and on more and more summer nights, the official Phoenix temperature fails to drop below 90 degrees. Climate plays a huge role in the comfort and quality of life of residents, with numerous implications for tourism, energy demand, water use, and the vulnerability of low-income families.

Both the effect of climate change on our future water supply and the size of the population that will need to share in that supply are uncertainties that water planners must consider when making decisions regarding our future. We have options, but we have to be sure that we use water efficiently to meet our urban, agricultural, and environmental needs. This Policy Points offers a clear, succinct overview of the status of Arizona’s water supply and what the current drought really means for water availability.

As Arizona’s population continues to grow, so does the need for electricity. Retail sales of electricity in Arizona have increased along with the population, although sales per person have declined since peaking in 2007, a sign of decreased use and increased efficiency. As we progress in the twenty-first century, action must be taken to increase the sustainability of our energy resources by continuing to conserve and by shifting to the greater use of energy from renewable sources. In addition, we must work to mitigate climate change by reducing greenhouse gas emissions.