The Santa Cruz River begins in the Basin and Range region of southern Arizona, then turns south on its way through a 35 mile loop of northern Mexico, before reentering the United States near Nogales, Arizona. The river basin covers approximately 8,600 square miles in Arizona, moving northwest through southern and central Arizona. The Alliance is focused on the lower section of the Santa Cruz River, from the Pima-Pinal County line to its terminus at the Gila River, 35 miles southwest of Phoenix.
According to the July, 2010, Santa Cruz River Data Collection Report (“the Report”), many studies have been conducted along the Santa Cruz River, but few have focused on the lower section within Pinal County. Once it enters Pinal County, the river is characterized by “lessening stream” behavior, where it disappears, “except in times of heavy storm flows when it has been known to destroy everything in its path.”
The river has a long history of producing catastrophic flows during major storms, resulting in severe damage to crops, farms, housing, communities, businesses, and infrastructure across the region. The report found that 34 major flood events have occurred on the river since the late 1800s, roughly one every 4 years, with 6 of the 7 largest flood events occurring in the last 50 years.
Damage from Santa Cruz River flooding has been widespread and devastating, including forced aerial evacuations, the loss of entire buildings, road and bridge closures, the destruction of dams, levees, dikes, high-pressure gas lines and crops, and severe erosion, channel migration, sedimentation and subsidence.
As destructive as previous floods were, the damage today from a major flood event would be much worse and could devastate the entire region. Previous floods occurred primarily when the region’s population was much smaller, and before Pinal County became one of the second fastest growing counties in the country, with a projected population of more than one million residents by 2030.
