The Little Colorado River (LCR) is a dynamic, unstable dry land river. It is a 356 mile meandering tributary of the Colorado River with erratic flows due to uneven snow melts and summer monsoons. The LCR has a total elevation drop of about 6,300 feet from its headwaters in the White Mountains to its confluence with the Colorado River.
Little Colorado River at the Winslow Levee
The complex hydrology of the LCR is a problem that first captured the attention of the United States government nearly a century ago. Since then, Navajo County and the City of Winslow have worked with federal and state partners to find a permanent solution.
LRC flooding has tormented Winslow and its environs for generations. The LRC’s channel form changes and the associated erosion poses an even-greater flood-related hazard than floodwater inundation. The river channel undergoes constant side to side migration and channel narrowing.
- Despite Arizona's arid climate, its all of rivers frequently flood as the result of three storm types:
- Winter frontal storms that cover large areas of the state and region (late November through mid-March);
- Dissipating Pacific Ocean tropical cyclones that move over the entire state (late summer and early fall); and
- Monsoon season convective thunderstorms (late June through mid-September).
These storms influence the type and duration of Arizona's flooding. Decaying tropical storms and winter frontal systems are generally slow-moving, low-pressure weather systems that produce regional floods. Monsoon thunderstorms bring flash floods which can occur within seconds to hours after the onset of rain. These are the deadliest because of the rapid increase in water levels and swift devastating flow.
In 2008, Navajo County partnered with USACE to conduct a Feasibility Study of how to best protect Winslow from LCR flooding. Navajo County is the local sponsor of this study and has paid 50% of its cost in cash and in-kind contributions. The total cost of the Little Colorado River at Winslow Levee Feasibility Study was $5.9M.
The 49-square-mile study area study evaluates structural and non-structural alternatives (such as reconstruction of portions of the existing Winslow Levee and Ruby Wash Diversion Levee, levee setbacks, flood warning system and elevation of residential structures, and river channel conveyance improvements) for managing flood risk for the majority of City of Winslow and portions of unincorporated Navajo County from the Clear Creek confluence downstream to the northern end of the existing Winslow Levee.
- Emergency Action Plan 2015 (PDF)
- Winslow Critical Facilities in Flood Plain (PDF)
- Background Information