This is the first in an ongoing series of stories that looks at the issue of stormwater management within Fountain Hills.

In the early 1990s a woman who had grown up as a young girl on the P-Bar Ranch in the 1950s, on what is now Fountain Hills, related to The Times stories of seeing cattle being tossed about as they were swept up in flash flooding on what is now Ashbrook Wash. The P-Bar Ranch house at the time was located on property that is now the parking lot at Fountain Hills High School. Ashbrook Wash runs right past the site.

Clearly flash flooding is nothing new to this area, however, the development of Fountain Hills has created new issues with more paved streets and housing development to spur runoff.

Part of the striking attraction of Fountain Hills is the undulating terrain with ridgelines stretching from the McDowell Mountains to the west and toward the Verde River to the east. The arroyos between the ridgelines make the pathways that carry water from as high at 3,000 feet down to the river basin about 2,000 feet below.

It is easy amid decades-long drought conditions to forget how powerful flash floods can be. Even looking at rainfall totals averaging around 10-inches a year in Fountain Hills does not seem like much on the surface, but records show that rainfall can come quickly and unexpected. Just last year as much as 12.44 inches of rain fell in a rain gauge in northwest Fountain Hills. A single storm on Aug. 13, 2021, produced nearly 1.5-inches of rainfall in just 15 minutes and 2.36 inches in just one hour at that rain gauge. Nearly half the year’s total fell in 72 hours – this is how dangerous flash flooding occurs, with water sweeping downstream from the higher elevations pushing tree limbs, rocks, debris and even vehicles out of the way.

Other than the occasional danger and inconvenience of such flooding, what is the financial cost? As this story is being written that data is still being collected by Town of Fountain Hills staff to provide to The Times. Those costs will be explored further in this series. One key example, however, is a storm in the fall of 2018 when flood waters raged through the washes and collected behind the dam at Golden Eagle Park. The result was up to 12 feet of water behind the dam and three to six feet of water on the recreational ballfields, the mud and debris damaging facilities and equipment.

The initial costs of clean-up and repairs to restore the park were reported at more than $600,000. There have been ongoing efforts to plan and construct the changes that will mitigate that amount of damage from a single storm in the future.

One caveat is that Golden Eagle Park and the areas behind the dam were designed as a detention basin for flood water to prevent damage to residential development downstream. As a designated detention basin, insurance was little help in covering those costs. That dam, by the way, is not far from the high school parking lot where the P-Bar Ranch was located – prior to the dam being constructed.

When development began in Fountain Hills McCulloch Properties was required by the Arizona Department of Water Resources to build flood control detention dams like the one at Golden Eagle Park. There are six others, including one at Fountain Lake itself (although that may be considered a retention dam for water storage).

The Maricopa County Flood Control District also takes the threat of flash flooding in this area seriously. The District has installed hundreds of ALERT monitoring stations across the county and higher elevations just outside the county. There are eight such ALERT sites within the Town of Fountain Hills as well as one along a wash just outside the northwest corner of the town boundary.

The rainfall data readers see in this article as well as other stories in the series is from the records of these monitoring stations.

Among the topics this series will explore are stormwater regulations from the state and federal governments, and a stormwater fee the Town established to offset the costs of the regulatory requirements (this fee is in limbo currently with questions about the Town’s right to collect the fee).

The Times will also look at ongoing projects to manage drainage from water shed to mitigate flooding potential to private property, as well as look to the future and potential projects to further manage flood control in Fountain Hills.