Edgar McGregor

For only the ninth time in 116 years of record keeping, back-to-back wetter than average winters have occured in this part of Southern California. The mood in mid-January 2024 was bleak as only 3.00″ of rain had fallen for the entire water year so far. However, as expected, the months of February and March can not and should not be counted out. After a behemoth atmospheric river and a series of moderate storms in February, the 2023-2024 water year is officially above average in Eaton Canyon as of March 2nd! The annual average rainfall is 19.60″. 

Despite the February 4-7, 2024 atmospheric river being so powerful in Los Angeles County, no appreciable flooding of any magnitude occurred in Eaton Wash. The over 8.00″ of rain that fell in the single storm was not even enough to move a log people had been using a bridge across the first crossing since winter 2023. The reason why was because rain rates failed to reach even 1.00″ / hr in the canyon, and with 30 years of vegetation growth since the last wildfire, soils were pretty capable of soaking everything up. 

Since 2019, the Oceanwide Plaza development in downtown Los Angeles has been in a stagnant state after the Chinese-owned company put the project on hold citing financial issues. Over the past 5 years, the 49-floor skyscrapers that tower over the Crypto Arena have sat empty, completely unused and abandoned. As reported by the Los Angeles Times, graffiti artists have been inspired in recent weeks to take over the project and tag every floor of the 3-building complex. It may be a coincidence, but now Eaton Canyon Natural Area has been hit by one of its biggest vandals in years.

After dark on Saturday, February 10, 2024, an unknown number of vandals walked Eaton Canyon and tagged nearly every sign, road blocker, map, and pole in sight. The vandals even spray-painted the driveway ground itself, several rocks below the Midwick gate, and boulders in the creek below the Pinecrest Gate. The cost of cleanup, including labor, will likely total in the hundreds of dollars. While graffitiing has been a problem for years in Eaton Canyon, this latest round featured graffiti in places that had never been tagged before, including several pieces of Los Angeles County Parks and Recreation property.

It is a misdemeanor to vandalize public property that causes damages of under $400. If caught and convicted, the perpetrators could face up to one year in county jail, a fine of $1,000, and an informal probation. Photographs of the graffiti will not be shown in order to discourage the act. The header photograph is of a different canyon in Southern California from 2020.

Fourteen, seven, eleven, and ten: This is how many inches of rain fell on Eaton Canyon over a 3-day period during the most cataclysmic storms of the century. In no fewer than 6 instances between 1943 and 2024, Eaton Wash has been completely reset, ordered, and renewed, giving rise to an entirely new park each time.

Between February 4-6, 2024, the San Gabriel Valley experienced 54 hours of continuous rainfall. In that time, a whopping 8.5″ of rain fell at Eaton Dam while over a foot of precipitation fell at Camp Hi-Hill behind Mount Wilson. The storm entered the top-10 list for rainiest 2-day period ever recorded in Pasadena, a list occupied almost exclusively with dates that saw catastrophic flooding in Eaton Canyon. This time, however, Eaton Canyon emerged essentially unscathed. No such flooding of any appreciable magnitude happened. In fact, not even the Mule Fat that lines the creek was messed with. How is such a thing even possible?

Rising 6,000′ over the nearby Pacific Ocean, Eaton Canyon has a long and complicated relationship with flash flooding. For millions of years since it’s formation, Eaton Canyon’s flash flooding has gotten worse as the Sierra Madre fault continues to push it’s upper peaks higher and higher into the sky, enhancing orographic lift. Being at the intersection of a semi-arid desert, mountains, a reverse fault, and an ocean that covers half the planet, this history is not surprising. Hiking through the wash will yield lots of interesting discoveries, including flash flood debris, 12-ton boulders, and Bigcone Douglas Fir logs sitting out in the shrublands.

In general, there are 4 primary ingredients needed for major flash flooding in Eaton Canyon. Listed from most to least important, they are as follows:

1. Torrential rain rates (>2.00″ / hr)
2. Burned landscapes
3. Waterlogged soils
4. High snow levels

During the February 4-6, 2024 atmospheric river, the two most important ingredients for flash flooding in Eaton Canyon were absent. It has been 30 years since the 1993 Kinneloa Fire, and with so much vegetation covering the canyon, rain had a chance to soak in before running off the steep mountain slopes. Additionally, rain rates peaked at just 0.96″ / hr during the storm system, unlike the December 14, 2021 event when rain rates peaked at 2.51″ / hr. While enormous amounts of precipitation fell and snow levels remained >5,000′ during most of the system, major flash flooding in Eaton Canyon did not occur.

---

That all being said, here are some notable changes to the canyon from this storm system:

At approximately 2:42 pm on Sunday, February 4, 2024, a Coast Live Oak tree near the east end of the Meadow Trail collapsed in two parts about 1 minute apart. Parts of the tree are still alive and located at 34.181256342951244, -118.09564831451077. The Coast Live Oak was weighed down by the rain having begun about 40 minutes prior, and several large branches collapsed. Nobody was hurt, though several people by the first crossing heard the tree fall.

Yet another rockfall occured along the Mount Wilson Toll Road below the Pinecrest Gate sometime between Sunday night and 11 am Monday. A second rockfall occured just below Henninger Flats.

Photo by Sandy Chang

A new swale built by Eaton Canyon Nature Center staff last summer performed well during the storm. It prevented runoff from the parking lot from eroding other trails or being lost to Eaton Creek.