Over a year ago, I began feeling a little worried after reading renowned Cal Tech semiologist Dr. Lucy Jones’ prediction about the catastrophic earthquake that is bound to strike Southern California one day – or as Angelenos refer to it, “The Big One”. I was specifically concerned about all of the surrounding dams located in the San Gabriel Valley holding back extraordinary amounts of water.

Photo: Big Dalton Dam – Library of Congress, HAER CAL, 19-GLENDO 1-11

When I first moved to California, my uncle and I drove to see the Morris Dam in Azusa. I told him that I had never seen a dam before; in northwest Louisiana water just runs about everywhere, filling up an impressive network of locks and bayous. After our tour of Morris Dam, I realized what an amazing engineering feat it was to build such an impressive structure between the mountains of the San Gabriel Valley.

Big Dalton Dam – Library of Congress, HAER CAL, 19-GLENDO 1-15

But it was the Big Dalton Dam in Glendora that really punched my paranoia button after investigating the dam’s history. Completed on September 11, 1928, Big Dalton Dam was recently seismically reinforced in 2014. The Northridge Earthquake was the catalyst for its repair. And so for a moment my worries were pacified…until I found a Los Angeles Times article online about the 250 acre Puddingstone Reservoir built in 1928. The reservoir needs major reassessment before the next rainy winter season.

Located within the Frank G. Bonelli Regional Park – an impressive 1,957 acre county park located within the city of San Dimas, California – the Puddingstone Dam isn’t as fancy as the Morris Dam, but one of the three dams features a whopping 147 foot high earth and rock-filled structure. The dam system has created a massive artificial lake stocked with bass.

The dam at Puddingstone Reservoir has leaked before, but was repaired. It seems to hold up after periodic storm drain discharges into it from the Live Oak Wash, Walnut Creek Wash, and the San Dimas Wash.

In November 2013, California’s Flood Future was distributed by Flood Safe California and the US Army Corps of Engineers. Puddingstone was listed as a resource with relevant risks, along with ill-fated Oroville Dam. In 2014, geophysical tests were conducted at Puddingstone, but since then it’s been all quiet. After the gravity of Oroville Dam’s partial collapse, I guess it was finally deemed time to take another look at our state’s other dams which have an average age of 70 years old, some with imminent risks.

Three of the ninety-three total dams require “comprehensive” assessment, according to the State of California – Division of Safety of Dams report: Pyramid Dam in Castaic, Cogswell in Devil’s Canyon, and finally, Puddingstone Dam in San Dimas. Local operators of Puddingstone, Bureau of Public Works will be expected to access the following features, per DSOD Supervising Engineer Daniel Meyersohn:

  • Drainage System
  • Retaining Wall
  • Geological Makeup of its Bedrock
  • Other elements (???)

Considering Puddingstone is an earth and rock-filled dam, I began wondering the ways in which landscape architects, horticulturalists, geologists, civil engineers, Los Angeles County of Public Works, and the local area water agencies could approach the redesign of its structure. One idea is to re-energize Walnut Creek, revitalizing the flow instead of maintaining a giant reservoir.

Could we, as a creative team, be the “other elements”?

My curiosity took me into the vaults here at AHBE Landscape Architects where I discovered a thoughtful report that included several additional proposals about what to do with the space and its historic buildings. The report was developed in conjunction with the Water Conservation Authority, Tzu Chi Foundation, Los Angeles County Parks, and the Los Angeles County Flood District (LACFD), as well as other area specialists. This concept plan looked specifically at the surrounding 60 acres within the Walnut Creek Habitat and Open Space in 2011 owned by the City of San Dimas and the Water Conservation Authority. Community, stakeholders, and property owners were acknowledged, while a vision was created for the surrounding area. The top request made by the community was to keep as much natural open space with local native plants, bird walk, and a trail network lined with educational signage.

Image: AHBE Landscape Architects

The 57 North and South Freeway lanes have a slight dip to it around the Via Verde exit, located nearly at the point of where one of the dams is located. That dip has been repaired at least once. Is there a river still running underground? Will the weight of vehicles driving above this section make the pillars slowly sink?

Walnut Creek naturally flows free for two miles without the concrete channels so prominently visible through San Dimas – ironically past the manmade flows of Raging Waters – and travels on through the San Gabriel Valley. What if the stream was reengineered to flow naturally from underneath the 57 Freeway into Walnut Creek Park past the Antonovich Trail? The original stands of Quercus agrifolia (Coast Live Oak) and Platanus racemosa (California Sycamore) are ready for regular irrigation for sure!



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  1. Karen scalzi #
    August 17, 2017

    My back yard is cinnamon creek which runs into Walnut Creek from the north side. It’s a dry creek until we get even a light rain and then it turns into a raging river that erodes the banks and sends a lot of debris down. The city many years ago out in coverts to stop the erosion but now refuses to maintain them even though all the area streets drain into it. Back in time before all the housing tracts overtook the area, the open spaces the area was a ranch and the open fields absorbed the water so there was a small creek vs a raging river.

    Liked by 1 person

  2. katharine rudnyk #
    August 18, 2017

    Hi! Karen, You may want to connect with your Los Angeles County Supervisor Kathyn Barger’s office to see if they can help address your situation. They may have contributed monies to build your channel and may have special interest in your situation. Otherwise, you may need to get an attorney to represent you with the help of an engineer to show danger to health, safety and welfare caused by the on-going erosion. Thank you for comment. I wish you the best, and I can only image the situation you face with the oncoming winter rainy season ahead of us.


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