Edgar McGregor

Edgar McGregor is a climatology senior at San Jose State University. He has collected litter from Eaton Canyon and other natural areas for over 1,400 days. Edgar's climate activist #EarthCleanUp account on Twitter has over 35,000 followers.

Utilizing Bigcone Douglas-Fir Log Locations And Aerial Imagery To Measure Historical Flood Magnitude In Eaton Canyon

Abstract

Over one hundred large Bigcone Douglas-Fir (Pseudotsuga macrocarpa) logs are scattered among the desert-like fields of sand, cacti, and boulders in the wash portion of Eaton Canyon on the south face of the San Gabriel Mountains. As no specimens of this species grow within a 2-mile radius, these logs are quite conspicuous. In this study, we will attempt to reconstruct historical flash floods in Eaton using aerial imagery. Then, we will back up that method by comparing results with Bigcone Douglas-Fir log locations. The first step, however, is to prove that these logs were indeed delivered to the wash from higher elevations by major flash floods.

This study finds that major debris flows are in fact responsible for placing these logs in the wash portion of the canyon. However, because of differences in magnitude of each flood as well as changes in topography between floods, this study also finds that not all log locations are the result of the same flood. This study has been able to determine which logs have moved as recently as 2021 and which logs have sat stationary for over half a century. In addition, this study has been able to determine how many acres of Eaton Canyons’ wash were destroyed during each of the most recent large floods.

Introduction

Eaton Canyon experiences rapidly changing climatological and ecological changes between its wide elevation range. Elevations between 4,500′ and 6,100′ in the canyon consist of conifer forests full of Bigcone Douglas-Firs, Canyon Oaks, Coulter Pines, and even the occasional California Incense Cedar. Meanwhile, elevations between 900′ and 3,000′ in Eaton Canyon can be very hot and dry, with well draining soil, chaparral ecosystems, and medium sized trees huddled in canyons. Eaton Canyon is also an exceptionally steep mountain face, with elevations rising several thousand feet in a matter of 3 miles. The 6-square mile canyon averages over 100″ of snow each winter at one end and can experience 6 straight months with an average high >90°F at the other end. Owing to their size, shape, and length, the vast majority of logs in the wash should be the Bigcone Douglas Fir, a resilient conifer native to the region that dominates the conifer forest above. At lower elevations, Eaton Canyon’s only primary native trees, the Western Sycamore, the Coast Live Oak, and the White Alder, do not have any of the characteristics that these logs show.

Methodology

To demonstrate that these logs were transported by flash floods, we designed three specific tests that can be conclusively attributed to such events. These tests are as follows:

  1. Log Distribution: If flash flooding was indeed responsible, there should be a higher concentration of logs in wider sections of the wash, with a noticeable scarcity in narrower sections where deeper and faster-moving waters would carry logs away.
  2. Log Condition: All logs should be completely devoid of branches, consistent with the forceful removal of limbs during transit via high flow events. 
  3. Species-Specific Evidence: Bigcone Douglas-Fir logs should be completely absent in areas not affected by major flooding in past decades, indicating that their presence in historical flood zones can only be due to the floods themselves.


Over the past 5 years, we’ve carefully mapped out and cataloged 108 individual non-native logs scattered throughout Eaton Canyons’ wash between the Chuck Ballard Memorial Bridge and the New York Bridge. (Figure 1) While some of these logs are out in the open and easy to spot, others are partially buried, deep inside bushes, or in rather inaccessible locations. The largest log on this list has a diameter of 57 inches, while the longest is 31 feet. In order for a log to be considered in this list, it must have a diameter of at least 8″. (Figure 2) Once the mapping of these logs was completed and our maps were analyzed, the first two tests should be answerable.

The next step in this study is to locate the dates and impacted zones of the canyon’s largest debris flow events. Our team noticed that when large floods occurred in the canyon, significant scarring left the landscape with a much higher albedo, indicative of the loss of all vegetation and the exposure of white granite rock, gravel, and sand. Utilizing aerial and satellite imagery courtesy of HistoricAerials.com, several different major flash flood events were made apparent. The most recent significant flood to have struck the canyon occurred in the winter of 2005, with satellite imagery in August 2005 showing much less vegetation in the wash compared to the year prior. (Figure 3) According to the Clear Creek RAWS (CEKC1) station near Mount Wilson, 23.26″ of rain fell during the 96 hours stretch ending at 5:00 am on January 11, 2005. (Figure 4) The nearly two feet of rain in just four days coincides with local recount as to when the major flood occurred. The mapping technique concluded that 31.6 acres of the wash were destroyed by fast moving water and boulders. Once we concluded a major flood last occurred in 2005, the team overlayed a map of the log locations with a map of where the flood is thought to have impacted the canyon. (Figure 5) Of the 108 logs cataloged, only 76 logs were inside the boundaries impacted by the 2005 flood. The other 32 logs, some of which more than 250 feet removed from any location in which the 2005 flood touched, needed a further explanation.

Further analysis through aerial imagery and weather data concluded that the winter of 1980 was also responsible for a major ecosystem-disturbing flood in Eaton Canyon. This time, nearly 20″ of rain fell at the weather station in Pasadena over a period of 8 days. This is more than twice the amount of rain that fell in the four-day period in 2005, though it fell in a longer time span. The Clear Creek RAWS station was not yet operational in 1980 to record this event, though upper portions of Eaton Canyon likely saw 30.00″ – 40.00″ of rain. Albedo mapping of the canyon floor resulted in an estimated 48.5 acres of the wash ecosystem being destroyed by the flood, about 38% more land than the 2005 flood. (Figure 6) After overlaying log location data, 29 of the 32 unexplained logs were located in the areas severely impacted by the 1980 flood. Three additional logs, however, stubbornly remained outside both the reconstructed 1980 and 2005 flood zones.

Using satellite imagery, historical photographs, and stories from locals once again, a third flood identified in 1969 that destroyed 43.0 acres explained the final three logs position within the wash. An interactive view of each flood zone may be found here.

Conclusion

By applying the three previously outlined tests against real-world observations, this study conclusively proves that these Bigcone Douglas-Fir logs were transported by major flood events before being deposited throughout the wash. A mapping of all logs in the canyon showed a much higher density of logs in areas where the wash is wide versus areas where the wash is more narrow. (Figure 7) A physical analysis of all logs also shows absolutely no branches or anomalous outcroppings within each log’s shape, consistent with the forceful and destructive nature of major debris flows. (Figure 8) Finally, aerial mapping of historic flood plains using significant changes in albedo perfectly matches with where logs are located within the lower canyon, with none of the 108 logs cataloged occurring outside known flood zones. (Figure 9)

Results and Discussion

This study has successfully reconstructed past flooding events using both aerial imagery and Bigcone Douglas-Fir log locations. We find that the 1969, 1980, and 2005 floods destroyed 43.0, 48.5, and 31.6 acres of Eaton Canyon’s wash respectively. This shows that although the 1969 flood gets lots of attention due to its destruction of the El Dorado Inn, the 1980 flood was actually larger and more impactful for the local ecosystem. The mapping of these debris flows also shows that just because one particular area was left untouched by a large flood does not mean it is safe from a less severe one. The team found that while the logs are fairly well distributed along the 2-mile long riverbed, there is a downward trend the further one gets away from the canyon mouth. Additionally, these maps show that the lower section of Eaton Wash beside the Eaton Canyon Nature Center has been drifting westward toward the parking lot with each successive flow. Most recently in 2005, the north end of main parking lot was nearly destroyed after fast moving flood water begin quickly eroding the embankment separating the parking lot from the wash, something the 1969 and 1980 floods couldn’t do. Local claims that the upper parking lot was destroying during one of the floods could not be confirmed using satellite imagery. Readers are encouraged to submit evidence should these claims be correct.

Future Work

Field biologists may want to investigate why these logs appear to show little to no signs of decay while sitting out in the desert. It is plausible that the necessary microbiology, including fungi and bacteria, needed to break down the logs does not exist in the hot, dry ecosystem in which these logs have been transported to. As a consequence, even the three logs identified to have not moved since 1969 (55 years since the writing of this study) show little sign of decay. (Figure 10)

An analysis of future flood potential using 3D-imagery, climate data, and historical risk should be conducted, especially in regards to the danger posed to Los Angeles County Parks and Recreation amenities such as the Nature Center by a quickly-changing creek route during extreme flow events.

Keywords: Bigcone Douglas Fir, flash flooding, Eaton Canyon, geomorphology, hydrology, sediment transport, arid environment, log preservation, heavy rainfall, debris flow, compartmentalization, desert, alluvial fan, scarp.

Charts and Figures

Figure 1: A sample map of the location of all Bigcone Douglas-Fir logs in Eaton Canyon between the Chuck Ballard Memorial Bridge and the New York Bridge.
Figure 2: This log, while still a Bigcone Douglas-Fir, is too small to be considered on the list as its diameter is <8.0″. It is more likely to be a branch and not a trunk.

Figure 3: A comparison of the canyon wash between the summers of 2004 and 2005 shows a heavy loss of vegetation as well as a change in the creek route. Note that the wash encroached on the upper parking lot, along with the loss of a large oak that once served to reduce erosion.

Figure 4: Clear Creek RAWS reporting nearly 24.00″ between January 7th and January 11th, 2005.
Figure 5: The 2005 flood zone (orange) only explains 76 of the 108 logs within the wash. 32 other logs (green and purple dots) exist outside the known 2005 flood zone and therefore need further explanation
Figure 6: Overlaying the 1980 flood zone with all logs explains why 29 of the 32 remaining logs were in the wash despite being outside the 2005 flood zone. The final 3 logs below the Midwick gate (purple dots) were outside the 1980 flood zone still, but inside the 1969 flood zone.
Figure 7: An analysis of the canyon floor width with log location shows that in areas where the wash is more narrow, deeper and faster moving water would prevent logs from settling into place. In areas where the wash was wider, shallow and slower moving water would allow logs to get caught on boulders, trees, or other debris.
Figure 8: A Bigcone Douglas-Fir trunk with branches removed. Note the lack of compartmentalization, a natural process in which trees that have lost their limbs will attempt to cover up the wounded area to prevent the spread of disease. This is an indication the branches were ripped off after the tree died, likely during transit from the upper canyon to the wash during the debris flow.
Figure 9: A comparison between flood zones and other sections of the park show absolutely no Bigcone Douglas-Fir logs in areas that have not experienced flooding from the main wash in recorded history. The map also shows some areas spared by the massive 1980 flood were eventually destroyed in the smaller 2005 flood.
Figure 10: This log, which is confirmed to have not moved since 1969, shows little to no evidence of decaying. The log was possibly burned in the October 1993 Kinneloa Fire, but definitely burned in the February 2018 Midwick Fire.

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10 Astounding Photographic Vantage Points In Eaton Canyon

With the improvement of mobile phone cameras, our ability to capture Eaton Canyon in all its glory has vastly improved. MyEatonCanyon.com maintains a photo gallery of some of the best views we’ve seen in the canyon so far. However, when searching up Eaton Canyon online, there is an overwhelming number of photographs of one single feature; the waterfall. As gorgeous as it is, there is so much more to Eaton Canyon that goes under appreciated.

In this article, we’re sharing the 10 best locations to take unique photographs of Eaton Canyon you might not find anywhere else. In many cases, these vantage points are unremarkable compared to the rest of the canyon for most of the year. However, when the timing, lighting, and colors are right, these spots have repeatedly produced incredible photographs time and again. Summer is typically the best time to get colorful landscape photographs in Eaton Canyon. Without further ado, here are our 10 favorites:

#10: The Fifteen Sisters

Located in Coyote Canyon, the fifteen sisters is a single Western Sycamore tree whose trunk has been buried by debris flows within the canyon. Western Sycamore trees carry the unique ability to turn part of their trunk meant to be above ground into part of the their root system should they be buried by flash floods. Western Sycamores are often only found close to sources of water, and you’d rarely if ever see one on a steep mountain slope. This single western Sycamore has branched into 15 different trunks all of which are roughly the same size. In my opinion, I have not captured the beatify of this tree well enough. The window of opportunity occurs near sunrise in late autumn when the tree is nearing peak color, specifically after a night of heavy rainfall with isolated fog draped over the hills above. Such a combination I’d imagine would produce a stunning photograph, but I have yet to be lucky.

The tree is located at: 34.18415694903343, -118.0975114636475

 

#9 The Colosseum 

Deep in Eaton Canyons’ mountain gorge is area I like the call “The Colosseum.” Here, Eaton Creek makes a full 180° turn just after passing the waterfall. This large bend has carved out a roughly 440 foot tall cliff that towers over the canyon. When approaching the turn from below, the mountain gives you the feeling of being in a colosseum. While the colors here pop best during solar noon, especially in May, June or July, the lack of shadows prevents one from really comprehending the colosseum. 

 

#8 The Canyon Mouth

Eaton Canyon spent quite some time with a rather unphotogenic canyon mouth following the 2005 flood. The flash flood destroyed all the White Alders next to the creek, and repairs to the Mount Wilson Toll road kept the scene from feeling exceptionally natural. However, a new generation of White Alders has since grown up and covered the (in my opinion) ugly parts. Now, the canyon mouth has a small forest at its base with steep, desert cliffs towering overhead. Here, the view is best in the low sun months of November, December, and January, especially when the Western Sycamores are nearing peak color. 

 

#7 The Subtropical Rainforest

Poison Oak is considered a climbing shrub, one that can be both a bush or a vine depending on what its environment will allow. Eaton Canyon is often a very dry place, but during certain times of the decade and in certain areas, the park can look much more like a subtropical rainforest.  Nowhere is this more prevalent than near the intersection of the Meadow Trail and the East Bank Trail within the L.A. County Natural Areas district. Inside a thicket of brush lies one of the largest Western Sycamores in Eaton Canyon wrapped in a huge poison oak vine climbing tens of feet into the air. We’ve seen poison oak climb trees, but nothing like this! This plant is truly reaching for the sky. As a result, the scene looks like something you’d find in the Santa Cruz mountains or the Amazon rainforest, not dry and dusty Eaton Canyon.

 

#6 Mount Markham From Eaton Saddle

Located at the top of the canyon, Mount Markham sticks up like a sore thumb to 5,745′ and serves as only of the only high elevation north-facing slope in Eaton Canyon. A pair of long, narrow rock fields on its northeast flank are a reminder to the trees that sit in rows in-between that they live on borrowed time. With over 100 inches of snow falling per winter, this scene has the potential to create incredible photographic opportunities. 

 

#5 Bigcone Douglas Fir Logs

If you’ve spent any time walking around Eaton Wash, you may have noticed huge tree logs sitting out in the desert far from any other tree. How did they get here? Well, these are Bigcone Douglas Fir logs that washed down during Eaton Canyon’s major flash floods over the past century. They are fantastic proxy data for telling us how large the floods in the canyon can get. There are over 100 of these logs scattered throughout the wash portion of the canyon, many of them making for some incredible photographs. Take a walk through the wash and look for one. Position yourself to add some mountains, rocks, and a nearby Yucca, and you’ve got yourself an incredible desert photograph!

The most impressive, however, are those above the fourth waterwall. These logs are only accessible via mountain climbing gear. Eaton Canyon actually qualifies as a slot canyon in some areas, one of the very few slot canyons in Southern California. These channels are so deep and narrow that Bigcone Douglas Fir logs floating down the canyon during major flood events can get wedged in-between the canyon walls where they remain indefinitely. 

This photograph by William Hunt shows one of those logs suspended 20-25 feet above the canyon floor. Note the people for scale. As I understand it, this log is between waterfalls #4 and #5. 

 

#4 Meteorology

Every now and again, nature puts on an incredible show of weather for visitors to Eaton Canyon. Monsoon thunderstorms, Santa Ana winds, blizzards, flash flooding, wildfires, cloud formations, rain shafts, and even rainbows have made an appearance in the canyon in recent years. Each one has its own unique challenges for photographers, but with a fair bit of luck and the right timing, simply astounding moments can forever be preserved. 

 

#3 Change

There will come a day in the not so distant future where nearly everything in Eaton Canyon is forever changed. The whole park, from the course of the creek to the route of the main trail, will be mixed up and set anew. Aerial imagery and historic photographs of Eaton Canyon show that the wondrous park has always been in a constant state of change, with flash flooding, human encroachment, wildfires, fault lines, and landslides all switching the park into a new version of itself. Nothing is safe from the tides of change. As a result, any photograph of Eaton Canyon that adequately captures it in its present state can serve as a good memory.

 

#2 The Garden Of Eden

Most astounding in July, the Garden of Eden is one of my most favorite locations in Eaton Canyon to photograph. The combination of desert, forest, cliffs, sky, and color all come together to produce a masterpiece. Unlike other photographs, five major color groups are present in this location, with reds, greens, blues, greys, and browns all being prominent. The vantage point is located right on the connector trail between the Midwick Entrance and the Eaton Canyon Trail at 34.18552027558575, -118.10156651797024. 

It embodies Eaton Canyon’s diversity unlike any other location. It is a view that isn’t always pretty, especially when skies are overcast. However, like with many other images on this list, the right time and lighting can make it simply mesmerizing. 

 

#1 The Aquatic World

Unphotographable in a single shot, the aquatic world of Eaton Canyon is the most marvelous yet ignored place in Eaton Canyon. Only visible in late spring after a wetter than average winter, the underwater portion of the canyon offers stunning views of algae, cliffs, waterfalls, miniature mountains, and wildlife. Underwater cameras set to slow motion capture the beauty best, and a certain level of zen can be achieved here too.

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Eaton Canyon Flooded With Tens Of Thousands Of Visitors Over Memorial Day Weekend

Since the debacle in 2020, even the mere thought of Memorial Day Weekend has struck fear in the minds of daily visitors to Eaton Canyon. Each year, this specific weekend sees the highest influx of Angelinos drawn by the holiday, the onset of summer, favorable weather, and high creek flows. The combination of COVID-19 and TikTok has allowed the canyon to surge in popularity across Southern California, with the main waterfall frequently being a top result when one searches “Waterfalls in Los Angeles.” On top of that, Eaton Canyon is one of the most centrally located and accessible waterfalls within Los Angeles County, the most populous county in the United States.

As a consequence to all of this, approximately 35,000 to 50,000 people visited Eaton Canyon between Saturday morning, May 25th and Monday evening, May 27th, 2024. Only Memorial Day weekend 2020 itself was busier.

The mass influx of people into the canyon has led to multiple issues in the area, including excessive trash, graffiti, unlicensed vendors, illegal parking, and loud music. The busy weekend has renewed conversations among locals who want to do something about the Disneyland-type visitation levels, with calls for more sheriffs, more park rangers, a fee for entry, a towing company on stand-by, and even a return to the COVID-era reservation system. The Angeles National Forest does not consider the waterfall trail a real trail, and thus no forest rangers occupy the area.

Hopes are that visitation will drop in the canyon after Big Santa Anita Canyon, which has been closed since August 2020 due to the Bobcat Fire and the 2023 floods, will reopen on June 1st.

Areas in red indicate areas taken up by hikers parking their cars on Monday, May 27, 2024 at approximately 10:30 am

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