Storm of July 26, 2007
In the Area of Indian Springs Road
West of Phoenix International Raceway

The storm depicted above occurred on July 26, 2007 from approximately 16:45 through 18:00
MST, with the majority of rain falling in a 1-hour period. It formed in a moist and unstable
environment over the northern Estrella Mountains and moved very little after its formation. The
colored grid above represents rainfall estimates from weather radar that are adjusted using
FCDMC raingage data. The raingage at Avondale Blvd. and the Gila River (black dot on the
map) recorded 0.36 inches (9mm). The colored scale on the left is in millimeters of rain. The
heavy black lines are watershed boundaries for washes that I have labeled 1, 2 and 3. On the
evening of July 26, a pickup truck driven by a teenager, carrying four younger siblings, slid off
Indian Springs Road due to floodwaters from Wash #1 and flipped over near the western-most
PIR parking lots. All were rescued and there were no serious injuries. It appears from news
video that the driver lost control of the vehicle due to speed and hydroplaning rather that from
the depth of flow.

This map is a zoom of the previous map, with a topographic background and the estimated
rainfall amounts in inches labeled on the grid cells. This map suggests that Watershed #1, above
Wash #1, received that highest rainfall amounts over the greatest area. In this area of the County
the 100-year, 1-hour rainfall is 2.09 inches and the 500-year, 1-hour rainfall is 2.63 inches.
Much of the areas of watersheds 1 and 2 received rainfall comparable to these magnitudes.

These are aerial photos of the wash crossings. Wash #3 below is west of washes 1 and 2 above.
The striped areas east of Wash #1 are the western parking areas for PIR.

These photos show the crossing point of Wash #1 with Indian Springs Road. The four culverts
were likely overtopped during the event of 7/26/07, and water flowed over the road from south to
north. There is not much of a swale at the crossing so the water was likely less that 1 foot deep,
but the flooded area was likely much wider than the culverts or the wash itself.

These photos show the crossing point of Wash #2 with Indian Springs Road. The six culverts
were likely overtopped during the event of 7/26/07, and water flowed over the road from south to
north. Again, there is not much of a swale at the crossing so the water was likely less that 1 foot
deep, but the flooded area was likely much wider than the culverts or the wash itself.

These two photos of Wash #3 show a more dangerous condition for vehicles than exists at either
Wash # 1 or 2. There are no culverts, and a pronounced swale can easily allow for crossing
depths of 2 to 3 feet. Had the storm been centered over the watershed feeding this crossing, a
life-threatening condition would have surely developed.